Update Cargo.toml

Add GitHub Actions workflow for build and test on every PR

.github/codeql/codeql-config.yml

@@ -0,0 +1,19 @@
+name: "Rust without tests"
+
+disable-default-queries: false
+
+queries:
+  - uses: security-extended
+  - uses: security-and-quality
+  - uses: ./.github/codeql/queries
+
+query-filters:
+  - exclude:
+      id:
+        - rust/unwrap-on-option
+        - rust/unwrap-on-result
+        - rust/expect-used
+
+analysis:
+  dataflow:
+    default-precision: high

.github/codeql/queries/common/ProductionOnly.qll

@@ -0,0 +1,20 @@
+import rust
+
+predicate isTestOnly(Item i) {
+  exists(ConditionalCompilation cc |
+    cc.getItem() = i and
+    cc.getCfg().toString() = "test"
+  )
+}
+
+predicate hasTestAttribute(Item i) {
+  exists(Attribute a |
+    a.getItem() = i and
+    a.getName() = "test"
+  )
+}
+
+predicate isProductionCode(Item i) {
+  not isTestOnly(i) and
+  not hasTestAttribute(i)
+}

.github/codeql/queries/qlpack.yml

@@ -0,0 +1,4 @@
+name: rust-production-only
+version: 0.0.1
+dependencies:
+  codeql/rust-all: "*"

.github/workflows/codeql.yml

@@ -0,0 +1,45 @@
+name: "CodeQL Advanced"
+
+on:
+  push:
+    branches: [ "*" ]
+  pull_request:
+    branches: [ "*" ]
+  schedule:
+    - cron: '0 0 * * 0'
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ${{ (matrix.language == 'swift' && 'macos-latest') || 'ubuntu-latest' }}
+
+    permissions:
+      security-events: write
+      packages: read
+      actions: read
+      contents: read
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: actions
+            build-mode: none
+          - language: rust
+            build-mode: none
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v4
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          config-file: .github/codeql/codeql-config.yml
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v4
+        with:
+          category: "/language:${{ matrix.language }}"

.github/workflows/rust.yml

@@ -2,9 +2,9 @@ name: Rust
 
 on:
   push:
-    branches: [ main ]
+    branches: [ "*" ]
   pull_request:
-    branches: [ main ]
+    branches: [ "*" ]
 
 env:
   CARGO_TERM_COLOR: always
@@ -42,5 +42,13 @@ jobs:
     - name: Build Release
       run: cargo build --release --verbose
 
+    - name: Run tests
+      run: cargo test --verbose
+
+# clippy dont fail on warnings because of active development of telemt 
+# and many warnings
+    - name: Run clippy
+      run: cargo clippy -- --cap-lints warn
+
     - name: Check for unused dependencies
       run: cargo udeps || true

.kilocode/rules-architect/AGENTS.md

@@ -0,0 +1,58 @@
+# Architect Mode Rules for Telemt
+
+## Architecture Overview
+
+```mermaid
+graph TB
+    subgraph Entry
+        Client[Clients] --> Listener[TCP/Unix Listener]
+    end
+    
+    subgraph Proxy Layer
+        Listener --> ClientHandler[ClientHandler]
+        ClientHandler --> Handshake[Handshake Validator]
+        Handshake --> |Valid| Relay[Relay Layer]
+        Handshake --> |Invalid| Masking[Masking/TLS Fronting]
+    end
+    
+    subgraph Transport
+        Relay --> MiddleProxy[Middle-End Proxy Pool]
+        Relay --> DirectRelay[Direct DC Relay]
+        MiddleProxy --> TelegramDC[Telegram DCs]
+        DirectRelay --> TelegramDC
+    end
+```
+
+## Module Dependencies
+- [`src/main.rs`](src/main.rs) - Entry point, spawns all async tasks
+- [`src/config/`](src/config/) - Configuration loading with auto-migration
+- [`src/error.rs`](src/error.rs) - Error types, must be used by all modules
+- [`src/crypto/`](src/crypto/) - AES, SHA, random number generation
+- [`src/protocol/`](src/protocol/) - MTProto constants, frame encoding, obfuscation
+- [`src/stream/`](src/stream/) - Stream wrappers, buffer pool, frame codecs
+- [`src/proxy/`](src/proxy/) - Client handling, handshake, relay logic
+- [`src/transport/`](src/transport/) - Upstream management, middle-proxy, SOCKS support
+- [`src/stats/`](src/stats/) - Statistics and replay protection
+- [`src/ip_tracker.rs`](src/ip_tracker.rs) - Per-user IP tracking
+
+## Key Architectural Constraints
+
+### Middle-End Proxy Mode
+- Requires public IP on interface OR 1:1 NAT with STUN probing
+- Uses separate `proxy-secret` from Telegram (NOT user secrets)
+- Falls back to direct mode automatically on STUN mismatch
+
+### TLS Fronting
+- Invalid handshakes are transparently proxied to `mask_host`
+- This is critical for DPI evasion - do not change this behavior
+- `mask_unix_sock` and `mask_host` are mutually exclusive
+
+### Stream Architecture
+- Buffer pool is shared globally via Arc - prevents allocation storms
+- Frame codecs implement tokio-util Encoder/Decoder traits
+- State machine in [`src/stream/state.rs`](src/stream/state.rs) manages stream transitions
+
+### Configuration Migration
+- [`ProxyConfig::load()`](src/config/mod.rs:641) mutates config in-place
+- New fields must have sensible defaults
+- DC203 override is auto-injected for CDN/media support

.kilocode/rules-code/AGENTS.md

@@ -0,0 +1,23 @@
+# Code Mode Rules for Telemt
+
+## Error Handling
+- Always use [`ProxyError`](src/error.rs:168) from [`src/error.rs`](src/error.rs) for proxy operations
+- [`HandshakeResult<T,R,W>`](src/error.rs:292) returns streams on bad client - these MUST be returned for masking, never dropped
+- Use [`Recoverable`](src/error.rs:110) trait to check if errors are retryable
+
+## Configuration Changes
+- [`ProxyConfig::load()`](src/config/mod.rs:641) auto-mutates config - new fields should have defaults
+- DC203 override is auto-injected if missing - do not remove this behavior
+- When adding config fields, add migration logic in [`ProxyConfig::load()`](src/config/mod.rs:641)
+
+## Crypto Code
+- [`SecureRandom`](src/crypto/random.rs) from [`src/crypto/random.rs`](src/crypto/random.rs) must be used for all crypto operations
+- Never use `rand::thread_rng()` directly - use the shared `Arc<SecureRandom>`
+
+## Stream Handling
+- Buffer pool [`BufferPool`](src/stream/buffer_pool.rs) is shared via Arc - always use it instead of allocating
+- Frame codecs in [`src/stream/frame_codec.rs`](src/stream/frame_codec.rs) implement tokio-util's Encoder/Decoder traits
+
+## Testing
+- Tests are inline in modules using `#[cfg(test)]`
+- Use `cargo test --lib <module_name>` to run tests for specific modules

.kilocode/rules-debug/AGENTS.md

@@ -0,0 +1,27 @@
+# Debug Mode Rules for Telemt
+
+## Logging
+- `RUST_LOG` environment variable takes absolute priority over all config log levels
+- Log levels: `trace`, `debug`, `info`, `warn`, `error`
+- Use `RUST_LOG=debug cargo run` for detailed operational logs
+- Use `RUST_LOG=trace cargo run` for full protocol-level debugging
+
+## Middle-End Proxy Debugging
+- Set `ME_DIAG=1` environment variable for high-precision cryptography diagnostics
+- STUN probe results are logged at startup - check for mismatch between local and reflected IP
+- If Middle-End fails, check `proxy_secret_path` points to valid file from https://core.telegram.org/getProxySecret
+
+## Connection Issues
+- DC connectivity is logged at startup with RTT measurements
+- If DC ping fails, check `dc_overrides` for custom addresses
+- Use `prefer_ipv6=false` in config if IPv6 is unreliable
+
+## TLS Fronting Issues
+- Invalid handshakes are proxied to `mask_host` - check this host is reachable
+- `mask_unix_sock` and `mask_host` are mutually exclusive - only one can be set
+- If `mask_unix_sock` is set, socket must exist before connections arrive
+
+## Common Errors
+- `ReplayAttack` - client replayed a handshake nonce, potential attack
+- `TimeSkew` - client clock is off, can disable with `ignore_time_skew=true`
+- `TgHandshakeTimeout` - upstream DC connection failed, check network

AGENTS.md

@@ -0,0 +1,40 @@
+# AGENTS.md
+
+** Use general system promt from AGENTS_SYSTEM_PROMT.md **
+** Additional techiques and architectury details are here **
+
+This file provides guidance to agents when working with code in this repository.
+
+## Build & Test Commands
+```bash
+cargo build --release          # Production build
+cargo test                     # Run all tests
+cargo test --lib error         # Run tests for specific module (error module)
+cargo bench --bench crypto_bench  # Run crypto benchmarks
+cargo clippy -- -D warnings    # Lint with clippy
+```
+
+## Project-Specific Conventions
+
+### Rust Edition
+- Uses **Rust edition 2024** (not 2021) - specified in Cargo.toml
+
+### Error Handling Pattern
+- Custom [`Recoverable`](src/error.rs:110) trait distinguishes recoverable vs fatal errors
+- [`HandshakeResult<T,R,W>`](src/error.rs:292) returns streams on bad client for masking - do not drop them
+- Always use [`ProxyError`](src/error.rs:168) from [`src/error.rs`](src/error.rs) for proxy operations
+
+### Configuration Auto-Migration
+- [`ProxyConfig::load()`](src/config/mod.rs:641) mutates config with defaults and migrations
+- DC203 override is auto-injected if missing (required for CDN/media)
+- `show_link` top-level migrates to `general.links.show`
+
+### Middle-End Proxy Requirements
+- Requires public IP on interface OR 1:1 NAT with STUN probing
+- Falls back to direct mode on STUN/interface mismatch unless `stun_iface_mismatch_ignore=true`
+- Proxy-secret from Telegram is separate from user secrets
+
+### TLS Fronting Behavior
+- Invalid handshakes are transparently proxied to `mask_host` for DPI evasion
+- `fake_cert_len` is randomized at startup (1024-4096 bytes)
+- `mask_unix_sock` and `mask_host` are mutually exclusive

AGENTS_SYSTEM_PROMT.md

@@ -0,0 +1,207 @@
+## System Prompt — Production Rust Codebase: Modification and Architecture Guidelines
+
+You are a senior Rust systems engineer acting as a strict code reviewer and implementation partner. Your responses are precise, minimal, and architecturally sound. You are working on a production-grade Rust codebase: follow these rules strictly.
+
+---
+
+### 0. Priority Resolution — Scope Control
+
+This section resolves conflicts between code quality enforcement and scope limitation.
+
+When editing or extending existing code, you MUST audit the affected files and fix:
+
+- Comment style violations (missing, non-English, decorative, trailing).
+- Missing or incorrect documentation on public items.
+- Comment placement issues (trailing comments → move above the code).
+
+These are **coordinated changes** — they are always in scope.
+
+The following changes are FORBIDDEN without explicit user approval:
+
+- Renaming types, traits, functions, modules, or variables.
+- Altering business logic, control flow, or data transformations.
+- Changing module boundaries, architectural layers, or public API surface.
+- Adding or removing functions, structs, enums, or trait implementations.
+- Fixing compiler warnings or removing unused code.
+
+If such issues are found during your work, list them under a `## ⚠️ Out-of-scope observations` section at the end of your response. Include file path, context, and a brief description. Do not apply these changes.
+
+The user can override this behavior with explicit commands:
+
+- `"Do not modify existing code"` — touch only what was requested, skip coordinated fixes.
+- `"Make minimal changes"` — no coordinated fixes, narrowest possible diff.
+- `"Fix everything"` — apply all coordinated fixes and out-of-scope observations.
+
+---
+
+### 1. Comments and Documentation
+
+- All comments MUST be written in English.
+- Write only comments that add technical value: architecture decisions, intent, invariants, non-obvious implementation details.
+- Place all comments on separate lines above the relevant code.
+- Use `///` doc-comments for public items. Use `//` for internal clarifications.
+
+Correct example:
+
+```rust
+// Handles MTProto client authentication and establishes encrypted session state.
+fn handle_authenticated_client(...) { ... }
+```
+
+Incorrect examples:
+
+```rust
+let x = 5; // set x to 5
+```
+
+```rust
+// This function does stuff
+fn do_stuff() { ... }
+```
+
+---
+
+### 2. File Size and Module Structure
+
+- Files MUST NOT exceed 350–550 lines.
+- If a file exceeds this limit, split it into submodules organized by responsibility (e.g., protocol, transport, state, handlers).
+- Parent modules MUST declare and describe their submodules.
+- Maintain clear architectural boundaries between modules.
+
+Correct example:
+
+```rust
+// Client connection handling logic.
+// Submodules:
+// - handshake: MTProto handshake implementation
+// - relay: traffic forwarding logic
+// - state: client session state machine
+
+pub mod handshake;
+pub mod relay;
+pub mod state;
+```
+
+Git discipline:
+
+- Use local git for versioning and diffs.
+- Write clear, descriptive commit messages in English that explain both *what* changed and *why*.
+
+---
+
+### 3. Formatting
+
+- Preserve the existing formatting style of the project exactly as-is.
+- Reformat code only when explicitly instructed to do so.
+- Do not run `cargo fmt` unless explicitly instructed.
+
+---
+
+### 4. Change Safety and Validation
+
+- If anything is unclear, STOP and ask specific, targeted questions before proceeding.
+- List exactly what is ambiguous and offer possible interpretations for the user to choose from.
+- Prefer clarification over assumptions. Do not guess intent, behavior, or missing requirements.
+- Actively ask questions before making architectural or behavioral changes.
+
+---
+
+### 5. Warnings and Unused Code
+
+- Leave all warnings, unused variables, functions, imports, and dead code untouched unless explicitly instructed to modify them.
+- These may be intentional or part of work-in-progress code.
+- `todo!()` and `unimplemented!()` are permitted and should not be removed or replaced unless explicitly instructed.
+
+---
+
+### 6. Architectural Integrity
+
+- Preserve existing architecture unless explicitly instructed to refactor.
+- Do not introduce hidden behavioral changes.
+- Do not introduce implicit refactors.
+- Keep changes minimal, isolated, and intentional.
+
+---
+
+### 7. When Modifying Code
+
+You MUST:
+
+- Maintain architectural consistency with the existing codebase.
+- Document non-obvious logic with comments that describe *why*, not *what*.
+- Limit changes strictly to the requested scope (plus coordinated fixes per Section 0).
+- Keep all existing symbol names unless renaming is explicitly requested.
+- Preserve global formatting as-is.
+
+You MUST NOT:
+
+- Use placeholders: no `// ... rest of code`, no `// implement here`, no `/* TODO */` stubs that replace existing working code. Write full, working implementation. If the implementation is unclear, ask first.
+- Refactor code outside the requested scope.
+- Make speculative improvements.
+
+Note: `todo!()` and `unimplemented!()` are allowed as idiomatic Rust markers for genuinely unfinished code paths.
+
+---
+
+### 8. Decision Process for Complex Changes
+
+When facing a non-trivial modification, follow this sequence:
+
+1. **Clarify**: Restate the task in one sentence to confirm understanding.
+2. **Assess impact**: Identify which modules, types, and invariants are affected.
+3. **Propose**: Describe the intended change before implementing it.
+4. **Implement**: Make the minimal, isolated change.
+5. **Verify**: Explain why the change preserves existing behavior and architectural integrity.
+
+---
+
+### 9. Context Awareness
+
+- When provided with partial code, assume the rest of the codebase exists and functions correctly unless stated otherwise.
+- Reference existing types, functions, and module structures by their actual names as shown in the provided code.
+- When the provided context is insufficient to make a safe change, request the missing context explicitly.
+
+---
+
+### 10. Response Format
+
+#### Language Policy
+
+- Code, comments, commit messages, documentation: **English**.
+- Reasoning and explanations in response text: **Russian**.
+
+#### Response Structure
+
+Your response MUST consist of two sections:
+
+**Section 1: `## Reasoning` (in Russian)**
+
+- What needs to be done and why.
+- Which files and modules are affected.
+- Architectural decisions and their rationale.
+- Potential risks or side effects.
+
+**Section 2: `## Changes`**
+
+- For each modified or created file: the filename on a separate line in backticks, followed by the code block.
+- For files **under 200 lines**: return the full file with all changes applied.
+- For files **over 200 lines**: return only the changed functions/blocks with at least 3 lines of surrounding context above and below. If the user requests the full file, provide it.
+- New files: full file content.
+- End with a suggested git commit message in English.
+
+#### Reporting Out-of-Scope Issues
+
+If during modification you discover issues outside the requested scope (potential bugs, unsafe code, architectural concerns, missing error handling, unused imports, dead code):
+
+- Do not fix them silently.
+- List them under `## ⚠️ Out-of-scope observations` at the end of your response.
+- Include: file path, line/function context, brief description of the issue, and severity estimate.
+
+#### Splitting Protocol
+
+If the response exceeds the output limit:
+
+1. End the current part with: **SPLIT: PART N — CONTINUE? (remaining: file_list)**
+2. List the files that will be provided in subsequent parts.
+3. Wait for user confirmation before continuing.
+4. No single file may be split across parts.

Cargo.lock

@@ -437,6 +437,12 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
 
+[[package]]
+name = "foldhash"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
+
 [[package]]
 name = "form_urlencoded"
 version = "1.2.2"
@@ -585,6 +591,25 @@ dependencies = [
  "wasip3",
 ]
 
+[[package]]
+name = "h2"
+version = "0.4.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f44da3a8150a6703ed5d34e164b875fd14c2cdab9af1252a9a1020bde2bdc54"
+dependencies = [
+ "atomic-waker",
+ "bytes",
+ "fnv",
+ "futures-core",
+ "futures-sink",
+ "http",
+ "indexmap",
+ "slab",
+ "tokio",
+ "tokio-util",
+ "tracing",
+]
+
 [[package]]
 name = "half"
 version = "2.7.1"
@@ -608,9 +633,7 @@ version = "0.15.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
 dependencies = [
- "allocator-api2",
- "equivalent",
- "foldhash",
+ "foldhash 0.1.5",
 ]
 
 [[package]]
@@ -618,6 +641,11 @@ name = "hashbrown"
 version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
+dependencies = [
+ "allocator-api2",
+ "equivalent",
+ "foldhash 0.2.0",
+]
 
 [[package]]
 name = "heck"
@@ -685,6 +713,12 @@ version = "1.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6dbf3de79e51f3d586ab4cb9d5c3e2c14aa28ed23d180cf89b4df0454a69cc87"
 
+[[package]]
+name = "httpdate"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df3b46402a9d5adb4c86a0cf463f42e19994e3ee891101b1841f30a545cb49a9"
+
 [[package]]
 name = "hyper"
 version = "1.8.1"
@@ -695,9 +729,11 @@ dependencies = [
  "bytes",
  "futures-channel",
  "futures-core",
+ "h2",
  "http",
  "http-body",
  "httparse",
+ "httpdate",
  "itoa",
  "pin-project-lite",
  "pin-utils",
@@ -999,11 +1035,11 @@ checksum = "5e5032e24019045c762d3c0f28f5b6b8bbf38563a65908389bf7978758920897"
 
 [[package]]
 name = "lru"
-version = "0.12.5"
+version = "0.16.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "234cf4f4a04dc1f57e24b96cc0cd600cf2af460d4161ac5ecdd0af8e1f3b2a38"
+checksum = "a1dc47f592c06f33f8e3aea9591776ec7c9f9e4124778ff8a3c3b87159f7e593"
 dependencies = [
- "hashbrown 0.15.5",
+ "hashbrown 0.16.1",
 ]
 
 [[package]]
@@ -1057,6 +1093,25 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "num-bigint"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5e44f723f1133c9deac646763579fdb3ac745e418f2a7af9cd0c431da1f20b9"
+dependencies = [
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.46"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7969661fd2958a5cb096e56c8e1ad0444ac2bbcd0061bd28660485a44879858f"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -1714,7 +1769,7 @@ dependencies = [
 
 [[package]]
 name = "telemt"
-version = "1.2.0"
+version = "3.0.0"
 dependencies = [
  "aes",
  "base64",
@@ -1729,9 +1784,15 @@ dependencies = [
  "futures",
  "hex",
  "hmac",
+ "http-body-util",
+ "httpdate",
+ "hyper",
+ "hyper-util",
  "libc",
  "lru",
  "md-5",
+ "num-bigint",
+ "num-traits",
  "parking_lot",
  "proptest",
  "rand",
@@ -1899,8 +1960,12 @@ checksum = "9ae9cec805b01e8fc3fd2fe289f89149a9b66dd16786abd8b19cfa7b48cb0098"
 dependencies = [
  "bytes",
  "futures-core",
+ "futures-io",
  "futures-sink",
+ "futures-util",
+ "hashbrown 0.15.5",
  "pin-project-lite",
+ "slab",
  "tokio",
 ]
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "telemt"
-version = "1.2.0"
+version = "3.0.1"
 edition = "2024"
 
 [dependencies]
@@ -9,7 +9,7 @@ libc = "0.2"
 
 # Async runtime
 tokio = { version = "1.42", features = ["full", "tracing"] }
-tokio-util = { version = "0.7", features = ["codec"] }
+tokio-util = { version = "0.7", features = ["full"] }
 
 # Crypto
 aes = "0.8"
@@ -37,7 +37,7 @@ tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 parking_lot = "0.12"
 dashmap = "5.5"
-lru = "0.12"
+lru = "0.16"
 rand = "0.9"
 chrono = { version = "0.4", features = ["serde"] }
 hex = "0.4"
@@ -45,9 +45,15 @@ base64 = "0.22"
 url = "2.5"
 regex = "1.11"
 crossbeam-queue = "0.3"
+num-bigint = "0.4"
+num-traits = "0.2"
 
 # HTTP
 reqwest = { version = "0.12", features = ["rustls-tls"], default-features = false }
+hyper = { version = "1", features = ["server", "http1"] }
+hyper-util = { version = "0.1", features = ["tokio", "server-auto"] }
+http-body-util = "0.1"
+httpdate = "1.0"
 
 [dev-dependencies]
 tokio-test = "0.4"
@@ -57,4 +63,4 @@ futures = "0.3"
 
 [[bench]]
 name = "crypto_bench"
-harness = false
+harness = false

Dockerfile

@@ -0,0 +1,43 @@
+# ==========================
+# Stage 1: Build
+# ==========================
+FROM rust:1.85-slim-bookworm AS builder
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    pkg-config \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /build
+
+COPY Cargo.toml Cargo.lock* ./
+RUN mkdir src && echo 'fn main() {}' > src/main.rs && \
+    cargo build --release 2>/dev/null || true && \
+    rm -rf src
+
+COPY . .
+RUN cargo build --release && strip target/release/telemt
+
+# ==========================
+# Stage 2: Runtime
+# ==========================
+FROM debian:bookworm-slim
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN useradd -r -s /usr/sbin/nologin telemt
+
+WORKDIR /app
+
+COPY --from=builder /build/target/release/telemt /app/telemt
+COPY config.toml /app/config.toml
+
+RUN chown -R telemt:telemt /app
+USER telemt
+
+EXPOSE 443
+EXPOSE 9090
+
+ENTRYPOINT ["/app/telemt"]
+CMD ["config.toml"]

README.md

@@ -2,27 +2,89 @@
 
 **Telemt** is a fast, secure, and feature-rich server written in Rust: it fully implements the official Telegram proxy algo and adds many production-ready improvements such as connection pooling, replay protection, detailed statistics, masking from "prying" eyes
 
-## Emergency
-**Важное сообщение для пользователей из России**
+## NEWS and EMERGENCY
+### ✈️ Telemt 3 is released!
+<table>
+<tr>
+<td width="50%" valign="top">
 
-Мы работаем над проектом с Нового года и сейчас готовим новый релиз - 1.2
+### 🇷🇺 RU
 
-В нём имплементируется поддержка Middle Proxy Protocol - основного терминатора для Ad Tag:
-работа над ним идёт с 6 ферваля, а уже 10 февраля произошли "громкие события"...
+15 февраля мы опубликовали `telemt 3` с поддержкой Middle-End Proxy, а значит:
 
-Если у вас есть компетенции в асинхронных сетевых приложениях - мы открыты к предложениям и pull requests
+- с функциональными медиа, в том числе с CDN/DC=203  
+- с Ad-tag — показывайте спонсорский канал и собирайте статистику через официального бота  
+- с новым подходом к безопасности и асинхронности  
+- с высокоточной диагностикой криптографии через `ME_DIAG`  
 
-**Important message for users from Russia**
+Для использования нужно:
 
-We've been working on the project since December 30 and are currently preparing a new release – 1.2
+1. Версия `telemt` ≥3.0.0
+2. Выполнение любого из наборов условий:
+   - публичный IP для исходящих соединений установлен на интерфейса инстанса с `telemt`
+     - ЛИБО
+   - вы используете NAT 1:1 + включили STUN-пробинг
+3. В конфиге, в секции `[general]` указать:
+```toml
+use_middle_proxy = true
+```
 
-It implements support for the Middle Proxy Protocol – the primary point for the Ad Tag:
-development on it started on February 6th, and by February 10th, "big activity" in Russia had already "taken place"...
+Если условия из пункта 1 не выполняются:
+1. Выключите ME-режим:
+   - установите `use_middle_proxy = false`
+     - ЛИБО
+   - Middle-End Proxy будет выключен автоматически по таймауту, но это займёт больше времени при запуске
+2. В конфиге, добавьте в конец:
+```toml
+[dc_overrides]
+"203" = "91.105.192.100:443"
+```
 
-If you have expertise in asynchronous network applications – we are open to ideas and pull requests!
+Если у вас есть компетенции в асинхронных сетевых приложениях, анализе трафика, реверс-инжиниринге или сетевых расследованиях — мы открыты к идеям и pull requests.
+
+</td>
+<td width="50%" valign="top">
+
+### 🇬🇧 EN
+
+On February 15, we released `telemt 3` with support for Middle-End Proxy, which means:
+
+- functional media, including CDN/DC=203  
+- Ad-tag support – promote a sponsored channel and collect statistics via Telegram bot  
+- new approach to security and asynchronicity  
+- high-precision cryptography diagnostics via `ME_DIAG`  
+
+To use this feature, the following requirements must be met:
+1. `telemt` version ≥ 3.0.0
+2. One of the following conditions satisfied:
+   - the instance running `telemt` has a public IP address assigned to its network interface for outbound connections  
+     - OR
+   - you are using 1:1 NAT and have STUN probing enabled  
+3. In the config file, under the `[general]` section, specify:
+```toml
+use_middle_proxy = true
+````
+
+If the conditions from step 1 are not satisfied:
+1. Disable Middle-End mode:
+   - set `use_middle_proxy = false`
+     - OR
+   - Middle-End Proxy will be disabled automatically after a timeout, but this will increase startup time
+
+2. In the config file, add the following at the end:
+```toml
+[dc_overrides]
+"203" = "91.105.192.100:443"
+```
+
+If you have expertise in asynchronous network applications, traffic analysis, reverse engineering, or network forensics — we welcome ideas, suggestions, and pull requests.
+
+</td>
+</tr>
+</table>
 
 # Features
-💥 The configuration structure has changed since version 1.1.0.0, change it in your environment!
+💥 The configuration structure has changed since version 1.1.0.0. change it in your environment!
 
 ⚓ Our implementation of **TLS-fronting** is one of the most deeply debugged, focused, advanced and *almost* **"behaviorally consistent to real"**:  we are confident we have it right - [see evidence on our validation and traces](#recognizability-for-dpi-and-crawler) 
 
@@ -44,7 +106,9 @@ If you have expertise in asynchronous network applications – we are open to id
   - [Telegram Calls](#telegram-calls-via-mtproxy)
   - [DPI](#how-does-dpi-see-mtproxy-tls)
   - [Whitelist on Network Level](#whitelist-on-ip)
+  - [Too many open files](#too-many-open-files)
 - [Build](#build)
+- [Docker](#docker)
 - [Why Rust?](#why-rust)
 
 ## Features
@@ -128,6 +192,7 @@ Type=simple
 WorkingDirectory=/bin
 ExecStart=/bin/telemt /etc/telemt.toml
 Restart=on-failure
+LimitNOFILE=65536
 
 [Install]
 WantedBy=multi-user.target
@@ -143,10 +208,6 @@ then Ctrl+X -> Y -> Enter to save
 ## Configuration
 ### Minimal Configuration for First Start
 ```toml
-# === UI ===
-# Users to show in the startup log (tg:// links)
-show_link = ["hello"]
-
 # === General Settings ===
 [general]
 prefer_ipv6 = false
@@ -170,11 +231,19 @@ listen_addr_ipv6 = "::"
 # Listen on multiple interfaces/IPs (overrides listen_addr_*)
 [[server.listeners]]
 ip = "0.0.0.0"
-# announce_ip = "1.2.3.4" # Optional: Public IP for tg:// links
+# announce = "my.hostname.tld" # Optional: hostname for tg:// links
+# OR
+# announce = "1.2.3.4" # Optional: Public IP for tg:// links
 
 [[server.listeners]]
 ip = "::"
 
+# Users to show in the startup log (tg:// links)
+[general.links]
+show = ["hello"] # Users to show in the startup log (tg:// links)
+# public_host = "proxy.example.com"  # Host (IP or domain) for tg:// links
+# public_port = 443                  # Port for tg:// links (default: server.port)
+
 # === Timeouts (in seconds) ===
 [timeouts]
 client_handshake = 15
@@ -188,6 +257,7 @@ tls_domain = "petrovich.ru"
 mask = true
 mask_port = 443
 # mask_host = "petrovich.ru" # Defaults to tls_domain if not set
+# mask_unix_sock = "/var/run/nginx.sock" # Unix socket (mutually exclusive with mask_host)
 fake_cert_len = 2048
 
 # === Access Control & Users ===
@@ -221,6 +291,10 @@ weight = 10
 # address = "127.0.0.1:9050"
 # enabled = false
 # weight = 1
+
+# === DC Address Overrides ===
+# [dc_overrides]
+# "203" = "91.105.192.100:443"
 ```
 ### Advanced
 #### Adtag
@@ -376,6 +450,23 @@ Keep-Alive: timeout=60
   - in China behind the Great Firewall
   - in Russia on mobile networks, less in wired networks
   - in Iran during "activity"
+### Too many open files
+- On a fresh Linux install the default open file limit is low; under load `telemt` may fail with `Accept error: Too many open files`
+- **Systemd**: add `LimitNOFILE=65536` to the `[Service]` section (already included in the example above)
+- **Docker**: add `--ulimit nofile=65536:65536` to your `docker run` command, or in `docker-compose.yml`:
+```yaml
+ulimits:
+  nofile:
+    soft: 65536
+    hard: 65536
+```
+- **System-wide** (optional): add to `/etc/security/limits.conf`:
+```
+*       soft    nofile  1048576
+*       hard    nofile  1048576
+root    soft    nofile  1048576
+root    hard    nofile  1048576
+```
 
 
 ## Build
@@ -394,9 +485,44 @@ chmod +x /bin/telemt
 telemt config.toml
 ```
 
+## Docker
+**Quick start (Docker Compose)**
+
+1. Edit `config.toml` in repo root (at least: port, users secrets, tls_domain)
+2. Start container:
+```bash
+docker compose up -d --build
+```
+3. Check logs:
+```bash
+docker compose logs -f telemt
+```
+4. Stop:
+```bash
+docker compose down
+```
+
+**Notes**
+- `docker-compose.yml` maps `./config.toml` to `/app/config.toml` (read-only)
+- By default it publishes `443:443` and runs with dropped capabilities (only `NET_BIND_SERVICE` is added)
+- If you really need host networking (usually only for some IPv6 setups) uncomment `network_mode: host`
+
+**Run without Compose**
+```bash
+docker build -t telemt:local .
+docker run --name telemt --restart unless-stopped \
+  -p 443:443 \
+  -e RUST_LOG=info \
+  -v "$PWD/config.toml:/app/config.toml:ro" \
+  --read-only \
+  --cap-drop ALL --cap-add NET_BIND_SERVICE \
+  --ulimit nofile=65536:65536 \
+  telemt:local
+```
+
 ## Why Rust?
 - Long-running reliability and idempotent behavior
-- Rust’s deterministic resource management - RAII 
+- Rust's deterministic resource management - RAII 
 - No garbage collector
 - Memory safety and reduced attack surface
 - Tokio's asynchronous architecture

config.toml

@@ -1,13 +1,9 @@
-# === UI ===
-# Users to show in the startup log (tg:// links)
-show_link = ["hello"]
-
 # === General Settings ===
 [general]
-prefer_ipv6 = false
+prefer_ipv6 = true
 fast_mode = true
 use_middle_proxy = true
-ad_tag = "00000000000000000000000000000000"
+#ad_tag = "00000000000000000000000000000000"
 
 # Log level: debug | verbose | normal | silent
 # Can be overridden with --silent or --log-level CLI flags
@@ -24,6 +20,8 @@ tls = true
 port = 443
 listen_addr_ipv4 = "0.0.0.0"
 listen_addr_ipv6 = "::"
+# listen_unix_sock = "/var/run/telemt.sock" # Unix socket
+# listen_unix_sock_perm = "0666" # Socket file permissions
 # metrics_port = 9090
 # metrics_whitelist = ["127.0.0.1", "::1"]
 
@@ -35,6 +33,12 @@ ip = "0.0.0.0"
 [[server.listeners]]
 ip = "::"
 
+# Users to show in the startup log (tg:// links)
+[general.links]
+show = ["hello"] # Users to show in the startup log (tg:// links)
+# public_host = "proxy.example.com"  # Host (IP or domain) for tg:// links
+# public_port = 443                  # Port for tg:// links (default: server.port)
+
 # === Timeouts (in seconds) ===
 [timeouts]
 client_handshake = 15
@@ -44,10 +48,11 @@ client_ack = 300
 
 # === Anti-Censorship & Masking ===
 [censorship]
-tls_domain = "google.ru"
+tls_domain = "petrovich.ru"
 mask = true
 mask_port = 443
 # mask_host = "petrovich.ru" # Defaults to tls_domain if not set
+# mask_unix_sock = "/var/run/nginx.sock" # Unix socket (mutually exclusive with mask_host)
 fake_cert_len = 2048
 
 # === Access Control & Users ===
@@ -63,6 +68,9 @@ hello = "00000000000000000000000000000000"
 # [access.user_max_tcp_conns]
 # hello = 50
 
+# [access.user_max_unique_ips]
+# hello = 5
+
 # [access.user_data_quota]
 # hello = 1073741824 # 1 GB
 
@@ -74,6 +82,10 @@ weight = 10
 
 # [[upstreams]]
 # type = "socks5"
-# address = "127.0.0.1:9050"
+# address = "127.0.0.1:1080"
 # enabled = false
-# weight = 1
+# weight = 1
+
+# === DC Address Overrides ===
+# [dc_overrides]
+# "203" = "91.105.192.100:443"

docker-compose.yml

@@ -0,0 +1,29 @@
+services:
+  telemt:
+    build: .
+    container_name: telemt
+    restart: unless-stopped
+    ports:
+      - "443:443"
+      - "9090:9090"
+    # Allow caching 'proxy-secret' in read-only container
+    working_dir: /run/telemt
+    volumes:
+      - ./config.toml:/run/telemt/config.toml:ro
+    tmpfs:
+      - /run/telemt:rw,mode=1777,size=1m
+    environment:
+      - RUST_LOG=info
+    # Uncomment this line if you want to use host network for IPv6, but bridge is default and usually better
+    # network_mode: host
+    cap_drop:
+      - ALL
+    cap_add:
+      - NET_BIND_SERVICE   # allow binding to port 443
+    read_only: true
+    security_opt:
+      - no-new-privileges:true
+    ulimits:
+      nofile:
+        soft: 65536
+        hard: 65536

src/config/mod.rs

@@ -1,32 +1,91 @@
 //! Configuration
 
-use std::collections::HashMap;
-use std::net::{IpAddr, SocketAddr};
-use std::path::Path;
+use crate::error::{ProxyError, Result};
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
-use crate::error::{ProxyError, Result};
+use serde::de::Deserializer;
+use std::collections::HashMap;
+use std::net::IpAddr;
+use std::path::Path;
+use tracing::warn;
 
 // ============= Helper Defaults =============
 
-fn default_true() -> bool { true }
-fn default_port() -> u16 { 443 }
-fn default_tls_domain() -> String { "www.google.com".to_string() }
-fn default_mask_port() -> u16 { 443 }
-fn default_replay_check_len() -> usize { 65536 }
-fn default_replay_window_secs() -> u64 { 1800 }
-fn default_handshake_timeout() -> u64 { 15 }
-fn default_connect_timeout() -> u64 { 10 }
-fn default_keepalive() -> u64 { 60 }
-fn default_ack_timeout() -> u64 { 300 }
-fn default_listen_addr() -> String { "0.0.0.0".to_string() }
-fn default_fake_cert_len() -> usize { 2048 }
-fn default_weight() -> u16 { 1 }
+fn default_true() -> bool {
+    true
+}
+fn default_port() -> u16 {
+    443
+}
+fn default_tls_domain() -> String {
+    "www.google.com".to_string()
+}
+fn default_mask_port() -> u16 {
+    443
+}
+fn default_replay_check_len() -> usize {
+    65536
+}
+fn default_replay_window_secs() -> u64 {
+    1800
+}
+fn default_handshake_timeout() -> u64 {
+    15
+}
+fn default_connect_timeout() -> u64 {
+    10
+}
+fn default_keepalive() -> u64 {
+    60
+}
+fn default_ack_timeout() -> u64 {
+    300
+}
+fn default_listen_addr() -> String {
+    "0.0.0.0".to_string()
+}
+fn default_fake_cert_len() -> usize {
+    2048
+}
+fn default_weight() -> u16 {
+    1
+}
 fn default_metrics_whitelist() -> Vec<IpAddr> {
-    vec![
-        "127.0.0.1".parse().unwrap(),
-        "::1".parse().unwrap(),
-    ]
+    vec!["127.0.0.1".parse().unwrap(), "::1".parse().unwrap()]
+}
+
+fn default_unknown_dc_log_path() -> Option<String> {
+    Some("unknown-dc.txt".to_string())
+}
+
+// ============= Custom Deserializers =============
+
+#[derive(Deserialize)]
+#[serde(untagged)]
+enum OneOrMany {
+    One(String),
+    Many(Vec<String>),
+}
+
+fn deserialize_dc_overrides<'de, D>(
+    deserializer: D,
+) -> std::result::Result<HashMap<String, Vec<String>>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let raw: HashMap<String, OneOrMany> = HashMap::deserialize(deserializer)?;
+    let mut out = HashMap::new();
+    for (dc, val) in raw {
+        let mut addrs = match val {
+            OneOrMany::One(s) => vec![s],
+            OneOrMany::Many(v) => v,
+        };
+        addrs.retain(|s| !s.trim().is_empty());
+        if !addrs.is_empty() {
+            out.insert(dc, addrs);
+        }
+    }
+    Ok(out)
 }
 
 // ============= Log Level =============
@@ -71,6 +130,50 @@ impl LogLevel {
     }
 }
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn dc_overrides_allow_string_and_array() {
+        let toml = r#"
+            [dc_overrides]
+            "201" = "149.154.175.50:443"
+            "202" = ["149.154.167.51:443", "149.154.175.100:443"]
+        "#;
+        let cfg: ProxyConfig = toml::from_str(toml).unwrap();
+        assert_eq!(cfg.dc_overrides["201"], vec!["149.154.175.50:443"]);
+        assert_eq!(
+            cfg.dc_overrides["202"],
+            vec!["149.154.167.51:443", "149.154.175.100:443"]
+        );
+    }
+
+    #[test]
+    fn dc_overrides_inject_dc203_default() {
+        let toml = r#"
+            [general]
+            use_middle_proxy = false
+
+            [censorship]
+            tls_domain = "example.com"
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_dc_override_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let cfg = ProxyConfig::load(&path).unwrap();
+        assert!(cfg
+            .dc_overrides
+            .get("203")
+            .map(|v| v.contains(&"91.105.192.100:443".to_string()))
+            .unwrap_or(false));
+        let _ = std::fs::remove_file(path);
+    }
+}
+
 impl std::fmt::Display for LogLevel {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
@@ -96,7 +199,11 @@ pub struct ProxyModes {
 
 impl Default for ProxyModes {
     fn default() -> Self {
-        Self { classic: true, secure: true, tls: true }
+        Self {
+            classic: true,
+            secure: true,
+            tls: true,
+        }
     }
 }
 
@@ -104,21 +211,72 @@ impl Default for ProxyModes {
 pub struct GeneralConfig {
     #[serde(default)]
     pub modes: ProxyModes,
-    
+
     #[serde(default)]
     pub prefer_ipv6: bool,
-    
+
     #[serde(default = "default_true")]
     pub fast_mode: bool,
-    
+
     #[serde(default)]
     pub use_middle_proxy: bool,
 
     #[serde(default)]
     pub ad_tag: Option<String>,
-    
+
+    /// Path to proxy-secret binary file (auto-downloaded if absent).
+    /// Infrastructure secret from https://core.telegram.org/getProxySecret
+    #[serde(default)]
+    pub proxy_secret_path: Option<String>,
+
+    /// Public IP override for middle-proxy NAT environments.
+    /// When set, this IP is used in ME key derivation and RPC_PROXY_REQ "our_addr".
+    #[serde(default)]
+    pub middle_proxy_nat_ip: Option<IpAddr>,
+
+    /// Enable STUN-based NAT probing to discover public IP:port for ME KDF.
+    #[serde(default)]
+    pub middle_proxy_nat_probe: bool,
+
+    /// Optional STUN server address (host:port) for NAT probing.
+    #[serde(default)]
+    pub middle_proxy_nat_stun: Option<String>,
+
+    /// Ignore STUN/interface IP mismatch (keep using Middle Proxy even if NAT detected).
+    #[serde(default)]
+    pub stun_iface_mismatch_ignore: bool,
+
+    /// Log unknown (non-standard) DC requests to a file (default: unknown-dc.txt). Set to null to disable.
+    #[serde(default = "default_unknown_dc_log_path")]
+    pub unknown_dc_log_path: Option<String>,
+
     #[serde(default)]
     pub log_level: LogLevel,
+
+    /// Disable colored output in logs (useful for files/systemd)
+    #[serde(default)]
+    pub disable_colors: bool,
+
+    /// [general.links] — proxy link generation overrides
+    #[serde(default)]
+    pub links: LinksConfig,
+}
+
+/// `[general.links]` — proxy link generation settings.
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct LinksConfig {
+    /// List of usernames whose tg:// links to display at startup.
+    /// `"*"` = all users, `["alice", "bob"]` = specific users.
+    #[serde(default)]
+    pub show: ShowLink,
+
+    /// Public hostname/IP for tg:// link generation (overrides detected IP).
+    #[serde(default)]
+    pub public_host: Option<String>,
+
+    /// Public port for tg:// link generation (overrides server.port).
+    #[serde(default)]
+    pub public_port: Option<u16>,
 }
 
 impl Default for GeneralConfig {
@@ -129,7 +287,15 @@ impl Default for GeneralConfig {
             fast_mode: true,
             use_middle_proxy: false,
             ad_tag: None,
+            proxy_secret_path: None,
+            middle_proxy_nat_ip: None,
+            middle_proxy_nat_probe: false,
+            middle_proxy_nat_stun: None,
+            stun_iface_mismatch_ignore: false,
+            unknown_dc_log_path: default_unknown_dc_log_path(),
             log_level: LogLevel::Normal,
+            disable_colors: false,
+            links: LinksConfig::default(),
         }
     }
 }
@@ -139,18 +305,28 @@ pub struct ServerConfig {
     #[serde(default = "default_port")]
     pub port: u16,
 
-    #[serde(default = "default_listen_addr")]
-    pub listen_addr_ipv4: String,
-    
+    #[serde(default)]
+    pub listen_addr_ipv4: Option<String>,
+
     #[serde(default)]
     pub listen_addr_ipv6: Option<String>,
-    
+
     #[serde(default)]
     pub listen_unix_sock: Option<String>,
-    
+
+    /// Unix socket file permissions (octal, e.g. "0666" or "0777").
+    /// Applied via chmod after bind. Default: no change (inherits umask).
+    #[serde(default)]
+    pub listen_unix_sock_perm: Option<String>,
+
+    /// Enable TCP listening. Default: true when no unix socket, false when
+    /// listen_unix_sock is set. Set explicitly to override auto-detection.
+    #[serde(default)]
+    pub listen_tcp: Option<bool>,
+
     #[serde(default)]
     pub metrics_port: Option<u16>,
-    
+
     #[serde(default = "default_metrics_whitelist")]
     pub metrics_whitelist: Vec<IpAddr>,
 
@@ -162,9 +338,11 @@ impl Default for ServerConfig {
     fn default() -> Self {
         Self {
             port: default_port(),
-            listen_addr_ipv4: default_listen_addr(),
+            listen_addr_ipv4: Some(default_listen_addr()),
             listen_addr_ipv6: Some("::".to_string()),
             listen_unix_sock: None,
+            listen_unix_sock_perm: None,
+            listen_tcp: None,
             metrics_port: None,
             metrics_whitelist: default_metrics_whitelist(),
             listeners: Vec::new(),
@@ -176,13 +354,13 @@ impl Default for ServerConfig {
 pub struct TimeoutsConfig {
     #[serde(default = "default_handshake_timeout")]
     pub client_handshake: u64,
-    
+
     #[serde(default = "default_connect_timeout")]
     pub tg_connect: u64,
-    
+
     #[serde(default = "default_keepalive")]
     pub client_keepalive: u64,
-    
+
     #[serde(default = "default_ack_timeout")]
     pub client_ack: u64,
 }
@@ -202,16 +380,19 @@ impl Default for TimeoutsConfig {
 pub struct AntiCensorshipConfig {
     #[serde(default = "default_tls_domain")]
     pub tls_domain: String,
-    
+
     #[serde(default = "default_true")]
     pub mask: bool,
-    
+
     #[serde(default)]
     pub mask_host: Option<String>,
-    
+
     #[serde(default = "default_mask_port")]
     pub mask_port: u16,
 
+    #[serde(default)]
+    pub mask_unix_sock: Option<String>,
+
     #[serde(default = "default_fake_cert_len")]
     pub fake_cert_len: usize,
 }
@@ -223,6 +404,7 @@ impl Default for AntiCensorshipConfig {
             mask: true,
             mask_host: None,
             mask_port: default_mask_port(),
+            mask_unix_sock: None,
             fake_cert_len: default_fake_cert_len(),
         }
     }
@@ -235,19 +417,22 @@ pub struct AccessConfig {
 
     #[serde(default)]
     pub user_max_tcp_conns: HashMap<String, usize>,
-    
+
     #[serde(default)]
     pub user_expirations: HashMap<String, DateTime<Utc>>,
-    
+
     #[serde(default)]
     pub user_data_quota: HashMap<String, u64>,
 
+    #[serde(default)]
+    pub user_max_unique_ips: HashMap<String, usize>,
+
     #[serde(default = "default_replay_check_len")]
     pub replay_check_len: usize,
-    
+
     #[serde(default = "default_replay_window_secs")]
     pub replay_window_secs: u64,
-    
+
     #[serde(default)]
     pub ignore_time_skew: bool,
 }
@@ -255,12 +440,16 @@ pub struct AccessConfig {
 impl Default for AccessConfig {
     fn default() -> Self {
         let mut users = HashMap::new();
-        users.insert("default".to_string(), "00000000000000000000000000000000".to_string());
+        users.insert(
+            "default".to_string(),
+            "00000000000000000000000000000000".to_string(),
+        );
         Self {
             users,
             user_max_tcp_conns: HashMap::new(),
             user_expirations: HashMap::new(),
             user_data_quota: HashMap::new(),
+            user_max_unique_ips: HashMap::new(),
             replay_check_len: default_replay_check_len(),
             replay_window_secs: default_replay_window_secs(),
             ignore_time_skew: false,
@@ -308,10 +497,111 @@ pub struct UpstreamConfig {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ListenerConfig {
     pub ip: IpAddr,
+    /// IP address or hostname to announce in proxy links.
+    /// Takes precedence over `announce_ip` if both are set.
+    #[serde(default)]
+    pub announce: Option<String>,
+    /// Deprecated: Use `announce` instead. IP address to announce in proxy links.
+    /// Migrated to `announce` automatically if `announce` is not set.
     #[serde(default)]
     pub announce_ip: Option<IpAddr>,
 }
 
+// ============= ShowLink =============
+
+/// Controls which users' proxy links are displayed at startup.
+///
+/// In TOML, this can be:
+/// - `show_link = "*"`          — show links for all users
+/// - `show_link = ["a", "b"]`   — show links for specific users
+/// - omitted                    — show no links (default)
+#[derive(Debug, Clone)]
+pub enum ShowLink {
+    /// Don't show any links (default when omitted)
+    None,
+    /// Show links for all configured users
+    All,
+    /// Show links for specific users
+    Specific(Vec<String>),
+}
+
+impl Default for ShowLink {
+    fn default() -> Self {
+        ShowLink::None
+    }
+}
+
+impl ShowLink {
+    /// Returns true if no links should be shown
+    pub fn is_empty(&self) -> bool {
+        matches!(self, ShowLink::None) || matches!(self, ShowLink::Specific(v) if v.is_empty())
+    }
+
+    /// Resolve the list of user names to display, given all configured users
+    pub fn resolve_users<'a>(&'a self, all_users: &'a HashMap<String, String>) -> Vec<&'a String> {
+        match self {
+            ShowLink::None => vec![],
+            ShowLink::All => {
+                let mut names: Vec<&String> = all_users.keys().collect();
+                names.sort();
+                names
+            }
+            ShowLink::Specific(names) => names.iter().collect(),
+        }
+    }
+}
+
+impl Serialize for ShowLink {
+    fn serialize<S: serde::Serializer>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error> {
+        match self {
+            ShowLink::None => Vec::<String>::new().serialize(serializer),
+            ShowLink::All => serializer.serialize_str("*"),
+            ShowLink::Specific(v) => v.serialize(serializer),
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for ShowLink {
+    fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> std::result::Result<Self, D::Error> {
+        use serde::de;
+
+        struct ShowLinkVisitor;
+
+        impl<'de> de::Visitor<'de> for ShowLinkVisitor {
+            type Value = ShowLink;
+
+            fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+                formatter.write_str(r#""*" or an array of user names"#)
+            }
+
+            fn visit_str<E: de::Error>(self, v: &str) -> std::result::Result<ShowLink, E> {
+                if v == "*" {
+                    Ok(ShowLink::All)
+                } else {
+                    Err(de::Error::invalid_value(
+                        de::Unexpected::Str(v),
+                        &r#""*""#,
+                    ))
+                }
+            }
+
+            fn visit_seq<A: de::SeqAccess<'de>>(self, mut seq: A) -> std::result::Result<ShowLink, A::Error> {
+                let mut names = Vec::new();
+                while let Some(name) = seq.next_element::<String>()? {
+                    names.push(name);
+                }
+                if names.is_empty() {
+                    Ok(ShowLink::None)
+                } else {
+                    Ok(ShowLink::Specific(names))
+                }
+            }
+        }
+
+        deserializer.deserialize_any(ShowLinkVisitor)
+    }
+}
+
 // ============= Main Config =============
 
 #[derive(Debug, Clone, Serialize, Deserialize, Default)]
@@ -335,16 +625,16 @@ pub struct ProxyConfig {
     pub upstreams: Vec<UpstreamConfig>,
 
     #[serde(default)]
-    pub show_link: Vec<String>,
+    pub show_link: ShowLink,
 
     /// DC address overrides for non-standard DCs (CDN, media, test, etc.)
-    /// Keys are DC indices as strings, values are "ip:port" addresses.
+    /// Keys are DC indices as strings, values are one or more \"ip:port\" addresses.
     /// Matches the C implementation's `proxy_for <dc_id> <ip>:<port>` config directive.
     /// Example in config.toml:
     ///   [dc_overrides]
-    ///   "203" = "149.154.175.100:443"
-    #[serde(default)]
-    pub dc_overrides: HashMap<String, String>,
+    ///   \"203\" = [\"149.154.175.100:443\", \"91.105.192.100:443\"]
+    #[serde(default, deserialize_with = "deserialize_dc_overrides")]
+    pub dc_overrides: HashMap<String, Vec<String>>,
 
     /// Default DC index (1-5) for unmapped non-standard DCs.
     /// Matches the C implementation's `default <dc_id>` config directive.
@@ -355,12 +645,12 @@ pub struct ProxyConfig {
 
 impl ProxyConfig {
     pub fn load<P: AsRef<Path>>(path: P) -> Result<Self> {
-        let content = std::fs::read_to_string(path)
-            .map_err(|e| ProxyError::Config(e.to_string()))?;
-        
-        let mut config: ProxyConfig = toml::from_str(&content)
-            .map_err(|e| ProxyError::Config(e.to_string()))?;
-        
+        let content =
+            std::fs::read_to_string(path).map_err(|e| ProxyError::Config(e.to_string()))?;
+
+        let mut config: ProxyConfig =
+            toml::from_str(&content).map_err(|e| ProxyError::Config(e.to_string()))?;
+
         // Validate secrets
         for (user, secret) in &config.access.users {
             if !secret.chars().all(|c| c.is_ascii_hexdigit()) || secret.len() != 32 {
@@ -370,66 +660,139 @@ impl ProxyConfig {
                 });
             }
         }
-        
+
         // Validate tls_domain
         if config.censorship.tls_domain.is_empty() {
             return Err(ProxyError::Config("tls_domain cannot be empty".to_string()));
         }
-        
-        // Default mask_host to tls_domain if not set
-        if config.censorship.mask_host.is_none() {
+
+        // Validate mask_unix_sock
+        if let Some(ref sock_path) = config.censorship.mask_unix_sock {
+            if sock_path.is_empty() {
+                return Err(ProxyError::Config(
+                    "mask_unix_sock cannot be empty".to_string(),
+                ));
+            }
+            #[cfg(unix)]
+            if sock_path.len() > 107 {
+                return Err(ProxyError::Config(format!(
+                    "mask_unix_sock path too long: {} bytes (max 107)",
+                    sock_path.len()
+                )));
+            }
+            #[cfg(not(unix))]
+            return Err(ProxyError::Config(
+                "mask_unix_sock is only supported on Unix platforms".to_string(),
+            ));
+
+            if config.censorship.mask_host.is_some() {
+                return Err(ProxyError::Config(
+                    "mask_unix_sock and mask_host are mutually exclusive".to_string(),
+                ));
+            }
+        }
+
+        // Default mask_host to tls_domain if not set and no unix socket configured
+        if config.censorship.mask_host.is_none() && config.censorship.mask_unix_sock.is_none() {
             config.censorship.mask_host = Some(config.censorship.tls_domain.clone());
         }
-        
+
         // Random fake_cert_len
         use rand::Rng;
         config.censorship.fake_cert_len = rand::rng().gen_range(1024..4096);
-        
-        // Migration: Populate listeners if empty
-        if config.server.listeners.is_empty() {
-            if let Ok(ipv4) = config.server.listen_addr_ipv4.parse::<IpAddr>() {
+
+        // Resolve listen_tcp: explicit value wins, otherwise auto-detect.
+        // If unix socket is set → TCP only when listen_addr_ipv4 or listeners are explicitly provided.
+        // If no unix socket → TCP always (backward compat).
+        let listen_tcp = config.server.listen_tcp.unwrap_or_else(|| {
+            if config.server.listen_unix_sock.is_some() {
+                // Unix socket present: TCP only if user explicitly set addresses or listeners
+                config.server.listen_addr_ipv4.is_some()
+                    || !config.server.listeners.is_empty()
+            } else {
+                true
+            }
+        });
+
+        // Migration: Populate listeners if empty (skip when listen_tcp = false)
+        if config.server.listeners.is_empty() && listen_tcp {
+            let ipv4_str = config.server.listen_addr_ipv4
+                .as_deref()
+                .unwrap_or("0.0.0.0");
+            if let Ok(ipv4) = ipv4_str.parse::<IpAddr>() {
                 config.server.listeners.push(ListenerConfig {
                     ip: ipv4,
+                    announce: None,
                     announce_ip: None,
                 });
             }
             if let Some(ipv6_str) = &config.server.listen_addr_ipv6 {
-                 if let Ok(ipv6) = ipv6_str.parse::<IpAddr>() {
+                if let Ok(ipv6) = ipv6_str.parse::<IpAddr>() {
                     config.server.listeners.push(ListenerConfig {
                         ip: ipv6,
+                        announce: None,
                         announce_ip: None,
                     });
                 }
             }
         }
 
+        // Migration: announce_ip → announce for each listener
+        for listener in &mut config.server.listeners {
+            if listener.announce.is_none() && listener.announce_ip.is_some() {
+                listener.announce = Some(listener.announce_ip.unwrap().to_string());
+            }
+        }
+
+        // Migration: show_link (top-level) → general.links.show
+        if !config.show_link.is_empty() && config.general.links.show.is_empty() {
+            config.general.links.show = config.show_link.clone();
+        }
+
         // Migration: Populate upstreams if empty (Default Direct)
         if config.upstreams.is_empty() {
-             config.upstreams.push(UpstreamConfig {
+            config.upstreams.push(UpstreamConfig {
                 upstream_type: UpstreamType::Direct { interface: None },
                 weight: 1,
                 enabled: true,
             });
         }
-        
+
+        // Ensure default DC203 override is present.
+        config
+            .dc_overrides
+            .entry("203".to_string())
+            .or_insert_with(|| vec!["91.105.192.100:443".to_string()]);
+
         Ok(config)
     }
-    
+
     pub fn validate(&self) -> Result<()> {
         if self.access.users.is_empty() {
             return Err(ProxyError::Config("No users configured".to_string()));
         }
-        
+
         if !self.general.modes.classic && !self.general.modes.secure && !self.general.modes.tls {
             return Err(ProxyError::Config("No modes enabled".to_string()));
         }
-        
+
         if self.censorship.tls_domain.contains(' ') || self.censorship.tls_domain.contains('/') {
-            return Err(ProxyError::Config(
-                format!("Invalid tls_domain: '{}'. Must be a valid domain name", self.censorship.tls_domain)
-            ));
+            return Err(ProxyError::Config(format!(
+                "Invalid tls_domain: '{}'. Must be a valid domain name",
+                self.censorship.tls_domain
+            )));
         }
-        
+
+        if let Some(tag) = &self.general.ad_tag {
+            let zeros = "00000000000000000000000000000000";
+            if tag == zeros {
+                warn!("ad_tag is all zeros; register a valid proxy tag via @MTProxybot to enable sponsored channel");
+            }
+            if tag.len() != 32 || tag.chars().any(|c| !c.is_ascii_hexdigit()) {
+                warn!("ad_tag is not a 32-char hex string; ensure you use value issued by @MTProxybot");
+            }
+        }
+
         Ok(())
     }
-}
+}

src/crypto/hash.rs

@@ -55,6 +55,49 @@ pub fn crc32(data: &[u8]) -> u32 {
     crc32fast::hash(data)
 }
 
+/// Build the exact prekey buffer used by Telegram Middle Proxy KDF.
+///
+/// Returned buffer layout (IPv4):
+/// nonce_srv | nonce_clt | clt_ts | srv_ip | clt_port | purpose | clt_ip | srv_port | secret | nonce_srv | [clt_v6 | srv_v6] | nonce_clt
+pub fn build_middleproxy_prekey(
+    nonce_srv: &[u8; 16],
+    nonce_clt: &[u8; 16],
+    clt_ts: &[u8; 4],
+    srv_ip: Option<&[u8]>,
+    clt_port: &[u8; 2],
+    purpose: &[u8],
+    clt_ip: Option<&[u8]>,
+    srv_port: &[u8; 2],
+    secret: &[u8],
+    clt_ipv6: Option<&[u8; 16]>,
+    srv_ipv6: Option<&[u8; 16]>,
+) -> Vec<u8> {
+    const EMPTY_IP: [u8; 4] = [0, 0, 0, 0];
+
+    let srv_ip = srv_ip.unwrap_or(&EMPTY_IP);
+    let clt_ip = clt_ip.unwrap_or(&EMPTY_IP);
+
+    let mut s = Vec::with_capacity(256);
+    s.extend_from_slice(nonce_srv);
+    s.extend_from_slice(nonce_clt);
+    s.extend_from_slice(clt_ts);
+    s.extend_from_slice(srv_ip);
+    s.extend_from_slice(clt_port);
+    s.extend_from_slice(purpose);
+    s.extend_from_slice(clt_ip);
+    s.extend_from_slice(srv_port);
+    s.extend_from_slice(secret);
+    s.extend_from_slice(nonce_srv);
+
+    if let (Some(clt_v6), Some(srv_v6)) = (clt_ipv6, srv_ipv6) {
+        s.extend_from_slice(clt_v6);
+        s.extend_from_slice(srv_v6);
+    }
+
+    s.extend_from_slice(nonce_clt);
+    s
+}
+
 /// Middle Proxy key derivation
 ///
 /// Uses MD5 + SHA-1 as mandated by the Telegram Middle Proxy protocol.
@@ -73,30 +116,20 @@ pub fn derive_middleproxy_keys(
     clt_ipv6: Option<&[u8; 16]>,
     srv_ipv6: Option<&[u8; 16]>,
 ) -> ([u8; 32], [u8; 16]) {
-    const EMPTY_IP: [u8; 4] = [0, 0, 0, 0];
-    
-    let srv_ip = srv_ip.unwrap_or(&EMPTY_IP);
-    let clt_ip = clt_ip.unwrap_or(&EMPTY_IP);
-    
-    let mut s = Vec::with_capacity(256);
-    s.extend_from_slice(nonce_srv);
-    s.extend_from_slice(nonce_clt);
-    s.extend_from_slice(clt_ts);
-    s.extend_from_slice(srv_ip);
-    s.extend_from_slice(clt_port);
-    s.extend_from_slice(purpose);
-    s.extend_from_slice(clt_ip);
-    s.extend_from_slice(srv_port);
-    s.extend_from_slice(secret);
-    s.extend_from_slice(nonce_srv);
-    
-    if let (Some(clt_v6), Some(srv_v6)) = (clt_ipv6, srv_ipv6) {
-        s.extend_from_slice(clt_v6);
-        s.extend_from_slice(srv_v6);
-    }
-    
-    s.extend_from_slice(nonce_clt);
-    
+    let s = build_middleproxy_prekey(
+        nonce_srv,
+        nonce_clt,
+        clt_ts,
+        srv_ip,
+        clt_port,
+        purpose,
+        clt_ip,
+        srv_port,
+        secret,
+        clt_ipv6,
+        srv_ipv6,
+    );
+
     let md5_1 = md5(&s[1..]);
     let sha1_sum = sha1(&s);
     let md5_2 = md5(&s[2..]);
@@ -106,4 +139,40 @@ pub fn derive_middleproxy_keys(
     key[12..].copy_from_slice(&sha1_sum);
     
     (key, md5_2)
-}
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn middleproxy_prekey_sha_is_stable() {
+        let nonce_srv = [0x11u8; 16];
+        let nonce_clt = [0x22u8; 16];
+        let clt_ts = 0x44332211u32.to_le_bytes();
+        let srv_ip = Some([149u8, 154, 175, 50].as_ref());
+        let clt_ip = Some([10u8, 0, 0, 1].as_ref());
+        let clt_port = 0x1f90u16.to_le_bytes(); // 8080
+        let srv_port = 0x22b8u16.to_le_bytes(); // 8888
+        let secret = vec![0x55u8; 128];
+
+        let prekey = build_middleproxy_prekey(
+            &nonce_srv,
+            &nonce_clt,
+            &clt_ts,
+            srv_ip,
+            &clt_port,
+            b"CLIENT",
+            clt_ip,
+            &srv_port,
+            &secret,
+            None,
+            None,
+        );
+        let digest = sha256(&prekey);
+        assert_eq!(
+            hex::encode(digest),
+            "934f5facdafd65a44d5c2df90d2f35ddc81faaaeb337949dfeef817c8a7c1e00"
+        );
+    }
+}

src/crypto/mod.rs

@@ -5,5 +5,5 @@ pub mod hash;
 pub mod random;
 
 pub use aes::{AesCtr, AesCbc};
-pub use hash::{sha256, sha256_hmac, sha1, md5, crc32};
-pub use random::SecureRandom;
+pub use hash::{sha256, sha256_hmac, sha1, md5, crc32, derive_middleproxy_keys, build_middleproxy_prekey};
+pub use random::SecureRandom;

src/ip_tracker.rs

@@ -0,0 +1,462 @@
+// src/ip_tracker.rs
+// Модуль для отслеживания и ограничения уникальных IP-адресов пользователей
+
+use std::collections::{HashMap, HashSet};
+use std::net::IpAddr;
+use std::sync::Arc;
+use tokio::sync::RwLock;
+
+/// Трекер уникальных IP-адресов для каждого пользователя MTProxy
+/// 
+/// Предоставляет thread-safe механизм для:
+/// - Отслеживания активных IP-адресов каждого пользователя
+/// - Ограничения количества уникальных IP на пользователя
+/// - Автоматической очистки при отключении клиентов
+#[derive(Debug, Clone)]
+pub struct UserIpTracker {
+    /// Маппинг: Имя пользователя -> Множество активных IP-адресов
+    active_ips: Arc<RwLock<HashMap<String, HashSet<IpAddr>>>>,
+    
+    /// Маппинг: Имя пользователя -> Максимально разрешенное количество уникальных IP
+    max_ips: Arc<RwLock<HashMap<String, usize>>>,
+}
+
+impl UserIpTracker {
+    /// Создать новый пустой трекер
+    pub fn new() -> Self {
+        Self {
+            active_ips: Arc::new(RwLock::new(HashMap::new())),
+            max_ips: Arc::new(RwLock::new(HashMap::new())),
+        }
+    }
+
+    /// Установить лимит уникальных IP для конкретного пользователя
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    /// * `max_ips` - Максимальное количество одновременно активных IP-адресов
+    pub async fn set_user_limit(&self, username: &str, max_ips: usize) {
+        let mut limits = self.max_ips.write().await;
+        limits.insert(username.to_string(), max_ips);
+    }
+
+    /// Загрузить лимиты из конфигурации
+    /// 
+    /// # Arguments
+    /// * `limits` - HashMap с лимитами из config.toml
+    pub async fn load_limits(&self, limits: &HashMap<String, usize>) {
+        let mut max_ips = self.max_ips.write().await;
+        for (user, limit) in limits {
+            max_ips.insert(user.clone(), *limit);
+        }
+    }
+
+    /// Проверить, может ли пользователь подключиться с данного IP-адреса
+    /// и добавить IP в список активных, если проверка успешна
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    /// * `ip` - IP-адрес клиента
+    /// 
+    /// # Returns
+    /// * `Ok(())` - Подключение разрешено, IP добавлен в активные
+    /// * `Err(String)` - Подключение отклонено с описанием причины
+    pub async fn check_and_add(&self, username: &str, ip: IpAddr) -> Result<(), String> {
+        // Получаем лимит для пользователя
+        let max_ips = self.max_ips.read().await;
+        let limit = match max_ips.get(username) {
+            Some(limit) => *limit,
+            None => {
+                // Если лимит не задан - разрешаем безлимитный доступ
+                drop(max_ips);
+                let mut active_ips = self.active_ips.write().await;
+                let user_ips = active_ips
+                    .entry(username.to_string())
+                    .or_insert_with(HashSet::new);
+                user_ips.insert(ip);
+                return Ok(());
+            }
+        };
+        drop(max_ips);
+
+        // Проверяем и обновляем активные IP
+        let mut active_ips = self.active_ips.write().await;
+        let user_ips = active_ips
+            .entry(username.to_string())
+            .or_insert_with(HashSet::new);
+
+        // Если IP уже есть в списке - это повторное подключение, разрешаем
+        if user_ips.contains(&ip) {
+            return Ok(());
+        }
+
+        // Проверяем, не превышен ли лимит
+        if user_ips.len() >= limit {
+            return Err(format!(
+                "IP limit reached for user '{}': {}/{} unique IPs already connected",
+                username,
+                user_ips.len(),
+                limit
+            ));
+        }
+
+        // Лимит не превышен - добавляем новый IP
+        user_ips.insert(ip);
+        Ok(())
+    }
+
+    /// Удалить IP-адрес из списка активных при отключении клиента
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    /// * `ip` - IP-адрес отключившегося клиента
+    pub async fn remove_ip(&self, username: &str, ip: IpAddr) {
+        let mut active_ips = self.active_ips.write().await;
+        
+        if let Some(user_ips) = active_ips.get_mut(username) {
+            user_ips.remove(&ip);
+            
+            // Если у пользователя не осталось активных IP - удаляем запись
+            // для экономии памяти
+            if user_ips.is_empty() {
+                active_ips.remove(username);
+            }
+        }
+    }
+
+    /// Получить текущее количество активных IP-адресов для пользователя
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    /// 
+    /// # Returns
+    /// Количество уникальных активных IP-адресов
+    pub async fn get_active_ip_count(&self, username: &str) -> usize {
+        let active_ips = self.active_ips.read().await;
+        active_ips
+            .get(username)
+            .map(|ips| ips.len())
+            .unwrap_or(0)
+    }
+
+    /// Получить список всех активных IP-адресов для пользователя
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    /// 
+    /// # Returns
+    /// Вектор с активными IP-адресами
+    pub async fn get_active_ips(&self, username: &str) -> Vec<IpAddr> {
+        let active_ips = self.active_ips.read().await;
+        active_ips
+            .get(username)
+            .map(|ips| ips.iter().copied().collect())
+            .unwrap_or_else(Vec::new)
+    }
+
+    /// Получить статистику по всем пользователям
+    /// 
+    /// # Returns
+    /// Вектор кортежей: (имя_пользователя, количество_активных_IP, лимит)
+    pub async fn get_stats(&self) -> Vec<(String, usize, usize)> {
+        let active_ips = self.active_ips.read().await;
+        let max_ips = self.max_ips.read().await;
+
+        let mut stats = Vec::new();
+        
+        // Собираем статистику по пользователям с активными подключениями
+        for (username, user_ips) in active_ips.iter() {
+            let limit = max_ips.get(username).copied().unwrap_or(0);
+            stats.push((username.clone(), user_ips.len(), limit));
+        }
+        
+        stats.sort_by(|a, b| a.0.cmp(&b.0)); // Сортируем по имени пользователя
+        stats
+    }
+
+    /// Очистить все активные IP для пользователя (при необходимости)
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    pub async fn clear_user_ips(&self, username: &str) {
+        let mut active_ips = self.active_ips.write().await;
+        active_ips.remove(username);
+    }
+
+    /// Очистить всю статистику (использовать с осторожностью!)
+    pub async fn clear_all(&self) {
+        let mut active_ips = self.active_ips.write().await;
+        active_ips.clear();
+    }
+
+    /// Проверить, подключен ли пользователь с данного IP
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    /// * `ip` - IP-адрес для проверки
+    /// 
+    /// # Returns
+    /// `true` если IP активен, `false` если нет
+    pub async fn is_ip_active(&self, username: &str, ip: IpAddr) -> bool {
+        let active_ips = self.active_ips.read().await;
+        active_ips
+            .get(username)
+            .map(|ips| ips.contains(&ip))
+            .unwrap_or(false)
+    }
+
+    /// Получить лимит для пользователя
+    /// 
+    /// # Arguments
+    /// * `username` - Имя пользователя
+    /// 
+    /// # Returns
+    /// Лимит IP-адресов или None, если лимит не установлен
+    pub async fn get_user_limit(&self, username: &str) -> Option<usize> {
+        let max_ips = self.max_ips.read().await;
+        max_ips.get(username).copied()
+    }
+
+    /// Форматировать статистику в читаемый текст
+    /// 
+    /// # Returns
+    /// Строка со статистикой для логов или мониторинга
+    pub async fn format_stats(&self) -> String {
+        let stats = self.get_stats().await;
+        
+        if stats.is_empty() {
+            return String::from("No active users");
+        }
+        
+        let mut output = String::from("User IP Statistics:\n");
+        output.push_str("==================\n");
+        
+        for (username, active_count, limit) in stats {
+            output.push_str(&format!(
+                "User: {:<20} Active IPs: {}/{}\n",
+                username,
+                active_count,
+                if limit > 0 { limit.to_string() } else { "unlimited".to_string() }
+            ));
+            
+            let ips = self.get_active_ips(&username).await;
+            for ip in ips {
+                output.push_str(&format!("  └─ {}\n", ip));
+            }
+        }
+        
+        output
+    }
+}
+
+impl Default for UserIpTracker {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+// ============================================================================
+// ТЕСТЫ
+// ============================================================================
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
+
+    fn test_ipv4(oct1: u8, oct2: u8, oct3: u8, oct4: u8) -> IpAddr {
+        IpAddr::V4(Ipv4Addr::new(oct1, oct2, oct3, oct4))
+    }
+
+    fn test_ipv6() -> IpAddr {
+        IpAddr::V6(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1))
+    }
+
+    #[tokio::test]
+    async fn test_basic_ip_limit() {
+        let tracker = UserIpTracker::new();
+        tracker.set_user_limit("test_user", 2).await;
+
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        let ip2 = test_ipv4(192, 168, 1, 2);
+        let ip3 = test_ipv4(192, 168, 1, 3);
+
+        // Первые два IP должны быть приняты
+        assert!(tracker.check_and_add("test_user", ip1).await.is_ok());
+        assert!(tracker.check_and_add("test_user", ip2).await.is_ok());
+
+        // Третий IP должен быть отклонен
+        assert!(tracker.check_and_add("test_user", ip3).await.is_err());
+
+        // Проверяем счетчик
+        assert_eq!(tracker.get_active_ip_count("test_user").await, 2);
+    }
+
+    #[tokio::test]
+    async fn test_reconnection_from_same_ip() {
+        let tracker = UserIpTracker::new();
+        tracker.set_user_limit("test_user", 2).await;
+
+        let ip1 = test_ipv4(192, 168, 1, 1);
+
+        // Первое подключение
+        assert!(tracker.check_and_add("test_user", ip1).await.is_ok());
+        
+        // Повторное подключение с того же IP должно пройти
+        assert!(tracker.check_and_add("test_user", ip1).await.is_ok());
+        
+        // Счетчик не должен увеличиться
+        assert_eq!(tracker.get_active_ip_count("test_user").await, 1);
+    }
+
+    #[tokio::test]
+    async fn test_ip_removal() {
+        let tracker = UserIpTracker::new();
+        tracker.set_user_limit("test_user", 2).await;
+
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        let ip2 = test_ipv4(192, 168, 1, 2);
+        let ip3 = test_ipv4(192, 168, 1, 3);
+
+        // Добавляем два IP
+        assert!(tracker.check_and_add("test_user", ip1).await.is_ok());
+        assert!(tracker.check_and_add("test_user", ip2).await.is_ok());
+        
+        // Третий не должен пройти
+        assert!(tracker.check_and_add("test_user", ip3).await.is_err());
+
+        // Удаляем первый IP
+        tracker.remove_ip("test_user", ip1).await;
+        
+        // Теперь третий должен пройти
+        assert!(tracker.check_and_add("test_user", ip3).await.is_ok());
+        
+        assert_eq!(tracker.get_active_ip_count("test_user").await, 2);
+    }
+
+    #[tokio::test]
+    async fn test_no_limit() {
+        let tracker = UserIpTracker::new();
+        // Не устанавливаем лимит для test_user
+
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        let ip2 = test_ipv4(192, 168, 1, 2);
+        let ip3 = test_ipv4(192, 168, 1, 3);
+
+        // Без лимита все IP должны проходить
+        assert!(tracker.check_and_add("test_user", ip1).await.is_ok());
+        assert!(tracker.check_and_add("test_user", ip2).await.is_ok());
+        assert!(tracker.check_and_add("test_user", ip3).await.is_ok());
+        
+        assert_eq!(tracker.get_active_ip_count("test_user").await, 3);
+    }
+
+    #[tokio::test]
+    async fn test_multiple_users() {
+        let tracker = UserIpTracker::new();
+        tracker.set_user_limit("user1", 2).await;
+        tracker.set_user_limit("user2", 1).await;
+
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        let ip2 = test_ipv4(192, 168, 1, 2);
+
+        // user1 может использовать 2 IP
+        assert!(tracker.check_and_add("user1", ip1).await.is_ok());
+        assert!(tracker.check_and_add("user1", ip2).await.is_ok());
+
+        // user2 может использовать только 1 IP
+        assert!(tracker.check_and_add("user2", ip1).await.is_ok());
+        assert!(tracker.check_and_add("user2", ip2).await.is_err());
+    }
+
+    #[tokio::test]
+    async fn test_ipv6_support() {
+        let tracker = UserIpTracker::new();
+        tracker.set_user_limit("test_user", 2).await;
+
+        let ipv4 = test_ipv4(192, 168, 1, 1);
+        let ipv6 = test_ipv6();
+
+        // Должны работать оба типа адресов
+        assert!(tracker.check_and_add("test_user", ipv4).await.is_ok());
+        assert!(tracker.check_and_add("test_user", ipv6).await.is_ok());
+        
+        assert_eq!(tracker.get_active_ip_count("test_user").await, 2);
+    }
+
+    #[tokio::test]
+    async fn test_get_active_ips() {
+        let tracker = UserIpTracker::new();
+        tracker.set_user_limit("test_user", 3).await;
+
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        let ip2 = test_ipv4(192, 168, 1, 2);
+
+        tracker.check_and_add("test_user", ip1).await.unwrap();
+        tracker.check_and_add("test_user", ip2).await.unwrap();
+
+        let active_ips = tracker.get_active_ips("test_user").await;
+        assert_eq!(active_ips.len(), 2);
+        assert!(active_ips.contains(&ip1));
+        assert!(active_ips.contains(&ip2));
+    }
+
+    #[tokio::test]
+    async fn test_stats() {
+        let tracker = UserIpTracker::new();
+        tracker.set_user_limit("user1", 3).await;
+        tracker.set_user_limit("user2", 2).await;
+
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        let ip2 = test_ipv4(192, 168, 1, 2);
+
+        tracker.check_and_add("user1", ip1).await.unwrap();
+        tracker.check_and_add("user2", ip2).await.unwrap();
+
+        let stats = tracker.get_stats().await;
+        assert_eq!(stats.len(), 2);
+        
+        // Проверяем наличие обоих пользователей в статистике
+        assert!(stats.iter().any(|(name, _, _)| name == "user1"));
+        assert!(stats.iter().any(|(name, _, _)| name == "user2"));
+    }
+
+    #[tokio::test]
+    async fn test_clear_user_ips() {
+        let tracker = UserIpTracker::new();
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        
+        tracker.check_and_add("test_user", ip1).await.unwrap();
+        assert_eq!(tracker.get_active_ip_count("test_user").await, 1);
+        
+        tracker.clear_user_ips("test_user").await;
+        assert_eq!(tracker.get_active_ip_count("test_user").await, 0);
+    }
+
+    #[tokio::test]
+    async fn test_is_ip_active() {
+        let tracker = UserIpTracker::new();
+        let ip1 = test_ipv4(192, 168, 1, 1);
+        let ip2 = test_ipv4(192, 168, 1, 2);
+        
+        tracker.check_and_add("test_user", ip1).await.unwrap();
+        
+        assert!(tracker.is_ip_active("test_user", ip1).await);
+        assert!(!tracker.is_ip_active("test_user", ip2).await);
+    }
+
+    #[tokio::test]
+    async fn test_load_limits_from_config() {
+        let tracker = UserIpTracker::new();
+        
+        let mut config_limits = HashMap::new();
+        config_limits.insert("user1".to_string(), 5);
+        config_limits.insert("user2".to_string(), 3);
+        
+        tracker.load_limits(&config_limits).await;
+        
+        assert_eq!(tracker.get_user_limit("user1").await, Some(5));
+        assert_eq!(tracker.get_user_limit("user2").await, Some(3));
+        assert_eq!(tracker.get_user_limit("user3").await, None);
+    }
+}

src/main.rs

@@ -1,4 +1,4 @@
-//! Telemt - MTProxy on Rust
+//! telemt — Telegram MTProto Proxy
 
 use std::net::SocketAddr;
 use std::sync::Arc;
@@ -6,13 +6,17 @@ use std::time::Duration;
 use tokio::net::TcpListener;
 use tokio::signal;
 use tokio::sync::Semaphore;
-use tracing::{info, error, warn, debug};
-use tracing_subscriber::{fmt, EnvFilter, reload, prelude::*};
+use tracing::{debug, error, info, warn};
+use tracing_subscriber::{EnvFilter, fmt, prelude::*, reload};
+#[cfg(unix)]
+use tokio::net::UnixListener;
 
 mod cli;
 mod config;
 mod crypto;
 mod error;
+mod ip_tracker;
+mod metrics;
 mod protocol;
 mod proxy;
 mod stats;
@@ -20,21 +24,27 @@ mod stream;
 mod transport;
 mod util;
 
-use crate::config::{ProxyConfig, LogLevel};
-use crate::proxy::ClientHandler;
-use crate::stats::{Stats, ReplayChecker};
+use crate::config::{LogLevel, ProxyConfig};
 use crate::crypto::SecureRandom;
-use crate::transport::{create_listener, ListenOptions, UpstreamManager};
-use crate::util::ip::detect_ip;
+use crate::ip_tracker::UserIpTracker;
+use crate::proxy::ClientHandler;
+use crate::stats::{ReplayChecker, Stats};
 use crate::stream::BufferPool;
+use crate::transport::middle_proxy::{
+    MePool, fetch_proxy_config, run_me_ping, MePingFamily, MePingSample, format_sample_line,
+    stun_probe,
+};
+use crate::transport::{ListenOptions, UpstreamManager, create_listener};
+use crate::util::ip::detect_ip;
+use crate::protocol::constants::{TG_MIDDLE_PROXIES_V4, TG_MIDDLE_PROXIES_V6};
 
 fn parse_cli() -> (String, bool, Option<String>) {
     let mut config_path = "config.toml".to_string();
     let mut silent = false;
     let mut log_level: Option<String> = None;
-    
+
     let args: Vec<String> = std::env::args().skip(1).collect();
-    
+
     // Check for --init first (handled before tokio)
     if let Some(init_opts) = cli::parse_init_args(&args) {
         if let Err(e) = cli::run_init(init_opts) {
@@ -43,14 +53,18 @@ fn parse_cli() -> (String, bool, Option<String>) {
         }
         std::process::exit(0);
     }
-    
+
     let mut i = 0;
     while i < args.len() {
         match args[i].as_str() {
-            "--silent" | "-s" => { silent = true; }
+            "--silent" | "-s" => {
+                silent = true;
+            }
             "--log-level" => {
                 i += 1;
-                if i < args.len() { log_level = Some(args[i].clone()); }
+                if i < args.len() {
+                    log_level = Some(args[i].clone());
+                }
             }
             s if s.starts_with("--log-level=") => {
                 log_level = Some(s.trim_start_matches("--log-level=").to_string());
@@ -64,26 +78,67 @@ fn parse_cli() -> (String, bool, Option<String>) {
                 eprintln!("  --help, -h              Show this help");
                 eprintln!();
                 eprintln!("Setup (fire-and-forget):");
-                eprintln!("  --init                  Generate config, install systemd service, start");
+                eprintln!(
+                    "  --init                  Generate config, install systemd service, start"
+                );
                 eprintln!("    --port <PORT>          Listen port (default: 443)");
-                eprintln!("    --domain <DOMAIN>      TLS domain for masking (default: www.google.com)");
-                eprintln!("    --secret <HEX>         32-char hex secret (auto-generated if omitted)");
+                eprintln!(
+                    "    --domain <DOMAIN>      TLS domain for masking (default: www.google.com)"
+                );
+                eprintln!(
+                    "    --secret <HEX>         32-char hex secret (auto-generated if omitted)"
+                );
                 eprintln!("    --user <NAME>          Username (default: user)");
                 eprintln!("    --config-dir <DIR>     Config directory (default: /etc/telemt)");
                 eprintln!("    --no-start             Don't start the service after install");
                 std::process::exit(0);
             }
-            s if !s.starts_with('-') => { config_path = s.to_string(); }
-            other => { eprintln!("Unknown option: {}", other); }
+            s if !s.starts_with('-') => {
+                config_path = s.to_string();
+            }
+            other => {
+                eprintln!("Unknown option: {}", other);
+            }
         }
         i += 1;
     }
-    
+
     (config_path, silent, log_level)
 }
 
+fn print_proxy_links(host: &str, port: u16, config: &ProxyConfig) {
+    info!("--- Proxy Links ({}) ---", host);
+    for user_name in config.general.links.show.resolve_users(&config.access.users) {
+        if let Some(secret) = config.access.users.get(user_name) {
+            info!("User: {}", user_name);
+            if config.general.modes.classic {
+                info!(
+                    "  Classic: tg://proxy?server={}&port={}&secret={}",
+                    host, port, secret
+                );
+            }
+            if config.general.modes.secure {
+                info!(
+                    "  DD:      tg://proxy?server={}&port={}&secret=dd{}",
+                    host, port, secret
+                );
+            }
+            if config.general.modes.tls {
+                let domain_hex = hex::encode(&config.censorship.tls_domain);
+                info!(
+                    "  EE-TLS:  tg://proxy?server={}&port={}&secret=ee{}{}",
+                    host, port, secret, domain_hex
+                );
+            }
+        } else {
+            warn!("User '{}' in show_link not found", user_name);
+        }
+    }
+    info!("------------------------");
+}
+
 #[tokio::main]
-async fn main() -> Result<(), Box<dyn std::error::Error>> {
+async fn main() -> std::result::Result<(), Box<dyn std::error::Error>> {
     let (config_path, cli_silent, cli_log_level) = parse_cli();
 
     let config = match ProxyConfig::load(&config_path) {
@@ -100,7 +155,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             }
         }
     };
-    
+
     if let Err(e) = config.validate() {
         eprintln!("[telemt] Invalid config: {}", e);
         std::process::exit(1);
@@ -115,139 +170,554 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         config.general.log_level.clone()
     };
 
-    // Start with INFO so startup messages are always visible,
-    // then switch to user-configured level after startup
     let (filter_layer, filter_handle) = reload::Layer::new(EnvFilter::new("info"));
+    
+    // Configure color output based on config
+    let fmt_layer = if config.general.disable_colors {
+        fmt::Layer::default().with_ansi(false)
+    } else {
+        fmt::Layer::default().with_ansi(true)
+    };
+    
     tracing_subscriber::registry()
         .with(filter_layer)
-        .with(fmt::Layer::default())
+        .with(fmt_layer)
         .init();
 
     info!("Telemt MTProxy v{}", env!("CARGO_PKG_VERSION"));
     info!("Log level: {}", effective_log_level);
-    info!("Modes: classic={} secure={} tls={}",
-        config.general.modes.classic,
-        config.general.modes.secure,
-        config.general.modes.tls);
+    if config.general.disable_colors {
+        info!("Colors: disabled");
+    }
+    info!(
+        "Modes: classic={} secure={} tls={}",
+        config.general.modes.classic, config.general.modes.secure, config.general.modes.tls
+    );
     info!("TLS domain: {}", config.censorship.tls_domain);
-    info!("Mask: {} -> {}:{}",
-        config.censorship.mask,
-        config.censorship.mask_host.as_deref().unwrap_or(&config.censorship.tls_domain),
-        config.censorship.mask_port);
+    if let Some(ref sock) = config.censorship.mask_unix_sock {
+        info!("Mask: {} -> unix:{}", config.censorship.mask, sock);
+        if !std::path::Path::new(sock).exists() {
+            warn!(
+                "Unix socket '{}' does not exist yet. Masking will fail until it appears.",
+                sock
+            );
+        }
+    } else {
+        info!(
+            "Mask: {} -> {}:{}",
+            config.censorship.mask,
+            config
+                .censorship
+                .mask_host
+                .as_deref()
+                .unwrap_or(&config.censorship.tls_domain),
+            config.censorship.mask_port
+        );
+    }
 
     if config.censorship.tls_domain == "www.google.com" {
         warn!("Using default tls_domain. Consider setting a custom domain.");
     }
-    
+
     let prefer_ipv6 = config.general.prefer_ipv6;
+    let mut use_middle_proxy = config.general.use_middle_proxy;
     let config = Arc::new(config);
     let stats = Arc::new(Stats::new());
     let rng = Arc::new(SecureRandom::new());
-    
+
     let replay_checker = Arc::new(ReplayChecker::new(
         config.access.replay_check_len,
         Duration::from_secs(config.access.replay_window_secs),
     ));
-    
+
     let upstream_manager = Arc::new(UpstreamManager::new(config.upstreams.clone()));
     let buffer_pool = Arc::new(BufferPool::with_config(16 * 1024, 4096));
+
+    // IP Tracker initialization
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.load_limits(&config.access.user_max_unique_ips).await;
     
-        // Connection concurrency limit — prevents OOM under SYN flood / connection storm.
-        // 10000 is generous; each connection uses ~64KB (2x 16KB relay buffers + overhead).
-        // 10000 connections ≈ 640MB peak memory.
-        let max_connections = Arc::new(Semaphore::new(10_000));
-    
-    // Startup DC ping
-    info!("=== Telegram DC Connectivity ===");
-    let ping_results = upstream_manager.ping_all_dcs(prefer_ipv6).await;
-    for upstream_result in &ping_results {
-        info!("  via {}", upstream_result.upstream_name);
-        for dc in &upstream_result.results {
-            match (&dc.rtt_ms, &dc.error) {
-                (Some(rtt), _) => {
-                    info!("    DC{} ({:>21}):  {:.0}ms", dc.dc_idx, dc.dc_addr, rtt);
+    if !config.access.user_max_unique_ips.is_empty() {
+        info!("IP limits configured for {} users", config.access.user_max_unique_ips.len());
+    }
+
+    // Connection concurrency limit
+    let _max_connections = Arc::new(Semaphore::new(10_000));
+
+    // STUN check before choosing transport
+    if use_middle_proxy {
+        match stun_probe(config.general.middle_proxy_nat_stun.clone()).await {
+            Ok(Some(probe)) => {
+                info!(
+                    local_ip = %probe.local_addr.ip(),
+                    reflected_ip = %probe.reflected_addr.ip(),
+                    "STUN Autodetect:"
+                );
+                if probe.local_addr.ip() != probe.reflected_addr.ip()
+                    && !config.general.stun_iface_mismatch_ignore
+                {
+                    match crate::transport::middle_proxy::detect_public_ip().await {
+                        Some(ip) => {
+                            info!(
+                                local_ip = %probe.local_addr.ip(),
+                                reflected_ip = %probe.reflected_addr.ip(),
+                                public_ip = %ip,
+                                "STUN mismatch but public IP auto-detected, continuing with middle proxy"
+                            );
+                        }
+                        None => {
+                            warn!(
+                                "STUN/IP-on-Interface mismatch and public IP auto-detect failed -> fallback to direct-DC"
+                            );
+                            use_middle_proxy = false;
+                        }
+                    }
                 }
-                (None, Some(err)) => {
-                    info!("    DC{} ({:>21}):  FAIL ({})", dc.dc_idx, dc.dc_addr, err);
+            }
+            Ok(None) => warn!("STUN probe returned no address; continuing"),
+            Err(e) => warn!(error = %e, "STUN probe failed; continuing"),
+        }
+    }
+
+    // =====================================================================
+    // Middle Proxy initialization (if enabled)
+    // =====================================================================
+    let me_pool: Option<Arc<MePool>> = if use_middle_proxy {
+        info!("=== Middle Proxy Mode ===");
+
+        // ad_tag (proxy_tag) for advertising
+        let proxy_tag = config.general.ad_tag.as_ref().map(|tag| {
+            hex::decode(tag).unwrap_or_else(|_| {
+                warn!("Invalid ad_tag hex, middle proxy ad_tag will be empty");
+                Vec::new()
+            })
+        });
+
+        // =============================================================
+        // CRITICAL: Download Telegram proxy-secret (NOT user secret!)
+        //
+        // C MTProxy uses TWO separate secrets:
+        //   -S flag    = 16-byte user secret for client obfuscation
+        //   --aes-pwd  = 32-512 byte binary file for ME RPC auth
+        //
+        // proxy-secret is from: https://core.telegram.org/getProxySecret
+        // =============================================================
+        let proxy_secret_path = config.general.proxy_secret_path.as_deref();
+match crate::transport::middle_proxy::fetch_proxy_secret(proxy_secret_path).await {
+    Ok(proxy_secret) => {
+        info!(
+            secret_len = proxy_secret.len() as usize,  // ← ЯВНЫЙ ТИП usize
+            key_sig = format_args!(
+                "0x{:08x}",
+                if proxy_secret.len() >= 4 {
+                    u32::from_le_bytes([
+                        proxy_secret[0],
+                        proxy_secret[1],
+                        proxy_secret[2],
+                        proxy_secret[3],
+                    ])
+                } else {
+                    0
                 }
-                _ => {
-                    info!("    DC{} ({:>21}):  FAIL", dc.dc_idx, dc.dc_addr);
+            ),
+            "Proxy-secret loaded"
+        );
+
+                // Load ME config (v4/v6) + default DC
+                let mut cfg_v4 = fetch_proxy_config(
+                    "https://core.telegram.org/getProxyConfig",
+                )
+                .await
+                .unwrap_or_default();
+                let mut cfg_v6 = fetch_proxy_config(
+                    "https://core.telegram.org/getProxyConfigV6",
+                )
+                .await
+                .unwrap_or_default();
+
+                if cfg_v4.map.is_empty() {
+                    cfg_v4.map = crate::protocol::constants::TG_MIDDLE_PROXIES_V4.clone();
+                }
+                if cfg_v6.map.is_empty() {
+                    cfg_v6.map = crate::protocol::constants::TG_MIDDLE_PROXIES_V6.clone();
+                }
+
+                let pool = MePool::new(
+                    proxy_tag,
+                    proxy_secret,
+                    config.general.middle_proxy_nat_ip,
+                    config.general.middle_proxy_nat_probe,
+                    config.general.middle_proxy_nat_stun.clone(),
+                    cfg_v4.map.clone(),
+                    cfg_v6.map.clone(),
+                    cfg_v4.default_dc.or(cfg_v6.default_dc),
+                );
+
+                match pool.init(2, &rng).await {
+                    Ok(()) => {
+                        info!("Middle-End pool initialized successfully");
+
+                        // Phase 4: Start health monitor
+                        let pool_clone = pool.clone();
+                        let rng_clone = rng.clone();
+                        tokio::spawn(async move {
+                            crate::transport::middle_proxy::me_health_monitor(
+                                pool_clone, rng_clone, 2,
+                            )
+                            .await;
+                        });
+
+                        // Periodic ME connection rotation
+                        let pool_clone_rot = pool.clone();
+                        let rng_clone_rot = rng.clone();
+                        tokio::spawn(async move {
+                            crate::transport::middle_proxy::me_rotation_task(
+                                pool_clone_rot,
+                                rng_clone_rot,
+                                std::time::Duration::from_secs(1800),
+                            )
+                            .await;
+                        });
+
+                        // Periodic updater: getProxyConfig + proxy-secret
+                        let pool_clone2 = pool.clone();
+                        let rng_clone2 = rng.clone();
+                        tokio::spawn(async move {
+                            crate::transport::middle_proxy::me_config_updater(
+                                pool_clone2,
+                                rng_clone2,
+                                std::time::Duration::from_secs(12 * 3600),
+                            )
+                            .await;
+                        });
+
+                        Some(pool)
+                    }
+                    Err(e) => {
+                        error!(error = %e, "Failed to initialize ME pool. Falling back to direct mode.");
+                        None
+                    }
+                }
+            }
+            Err(e) => {
+                error!(error = %e, "Failed to fetch proxy-secret. Falling back to direct mode.");
+                None
+            }
+        }
+    } else {
+        None
+    };
+
+    if me_pool.is_some() {
+        info!("Transport: Middle-End Proxy - all DC-over-RPC");
+    } else {
+        info!("Transport: Direct DC - TCP - standard DC-over-TCP");
+    }
+
+    // Middle-End ping before DC connectivity
+    if let Some(ref pool) = me_pool {
+        let me_results = run_me_ping(pool, &rng).await;
+
+        let v4_ok = me_results.iter().any(|r| {
+            matches!(r.family, MePingFamily::V4)
+                && r.samples.iter().any(|s| s.error.is_none() && s.handshake_ms.is_some())
+        });
+        let v6_ok = me_results.iter().any(|r| {
+            matches!(r.family, MePingFamily::V6)
+                && r.samples.iter().any(|s| s.error.is_none() && s.handshake_ms.is_some())
+        });
+
+        info!("================= Telegram ME Connectivity =================");
+        if v4_ok && v6_ok {
+            info!("  IPv4 and IPv6 available");
+        } else if v4_ok {
+            info!("  IPv4 only / IPv6 unavailable");
+        } else if v6_ok {
+            info!("  IPv6 only / IPv4 unavailable");
+        } else {
+            info!("  No ME connectivity");
+        }
+        info!("  via direct");
+        info!("============================================================");
+
+        use std::collections::BTreeMap;
+        let mut grouped: BTreeMap<i32, Vec<MePingSample>> = BTreeMap::new();
+        for report in me_results {
+            for s in report.samples {
+                let key = s.dc.abs();
+                grouped.entry(key).or_default().push(s);
+            }
+        }
+
+        let family_order = if prefer_ipv6 {
+            vec![(MePingFamily::V6, true), (MePingFamily::V6, false), (MePingFamily::V4, true), (MePingFamily::V4, false)]
+        } else {
+            vec![(MePingFamily::V4, true), (MePingFamily::V4, false), (MePingFamily::V6, true), (MePingFamily::V6, false)]
+        };
+
+        for (dc_abs, samples) in grouped {
+            for (family, is_pos) in &family_order {
+                let fam_samples: Vec<&MePingSample> = samples
+                    .iter()
+                    .filter(|s| matches!(s.family, f if &f == family) && (s.dc >= 0) == *is_pos)
+                    .collect();
+                if fam_samples.is_empty() {
+                    continue;
+                }
+
+                let fam_label = match family {
+                    MePingFamily::V4 => "IPv4",
+                    MePingFamily::V6 => "IPv6",
+                };
+                info!("    DC{} [{}]", dc_abs, fam_label);
+                for sample in fam_samples {
+                    let line = format_sample_line(sample);
+                    info!("{}", line);
                 }
             }
         }
+        info!("============================================================");
     }
-    info!("================================");
-    
+
+    info!("================= Telegram DC Connectivity =================");
+
+    let ping_results = upstream_manager
+        .ping_all_dcs(prefer_ipv6, &config.dc_overrides)
+        .await;
+
+	for upstream_result in &ping_results {
+		let v6_works = upstream_result
+			.v6_results
+			.iter()
+			.any(|r| r.rtt_ms.is_some());
+		let v4_works = upstream_result
+			.v4_results
+			.iter()
+			.any(|r| r.rtt_ms.is_some());
+		
+		if upstream_result.both_available {
+			if prefer_ipv6 {
+				info!("  IPv6 in use / IPv4 is fallback");
+			} else {
+				info!("  IPv4 in use / IPv6 is fallback");
+			}
+		} else {
+			if v6_works && !v4_works {
+				info!("  IPv6 only / IPv4 unavailable)");
+			} else if v4_works && !v6_works {
+				info!("  IPv4 only / IPv6 unavailable)");
+			} else if !v6_works && !v4_works {
+				info!("  No DC connectivity");
+			}
+		}
+
+		info!("  via {}", upstream_result.upstream_name);
+		info!("============================================================");
+
+		// Print IPv6 results first (only if IPv6 is available)
+		if v6_works {
+			for dc in &upstream_result.v6_results {
+				let addr_str = format!("{}:{}", dc.dc_addr.ip(), dc.dc_addr.port());
+				match &dc.rtt_ms {
+					Some(rtt) => {
+						info!("    DC{} [IPv6] {} - {:.0} ms", dc.dc_idx, addr_str, rtt);
+					}
+					None => {
+						let err = dc.error.as_deref().unwrap_or("fail");
+						info!("    DC{} [IPv6] {} - FAIL ({})", dc.dc_idx, addr_str, err);
+					}
+				}
+			}
+
+			info!("============================================================");
+		}
+
+		// Print IPv4 results (only if IPv4 is available)
+		if v4_works {
+			for dc in &upstream_result.v4_results {
+				let addr_str = format!("{}:{}", dc.dc_addr.ip(), dc.dc_addr.port());
+				match &dc.rtt_ms {
+					Some(rtt) => {
+						info!(
+							"    DC{} [IPv4] {}\t\t\t\t{:.0} ms",
+							dc.dc_idx, addr_str, rtt
+						);
+					}
+					None => {
+						let err = dc.error.as_deref().unwrap_or("fail");
+						info!(
+							"    DC{} [IPv4] {}:\t\t\t\tFAIL ({})",
+							dc.dc_idx, addr_str, err
+						);
+					}
+				}
+			}
+
+			info!("============================================================");
+		}
+	}
+
     // Background tasks
     let um_clone = upstream_manager.clone();
-    tokio::spawn(async move { um_clone.run_health_checks(prefer_ipv6).await; });
-    
+    tokio::spawn(async move {
+        um_clone.run_health_checks(prefer_ipv6).await;
+    });
+
     let rc_clone = replay_checker.clone();
-    tokio::spawn(async move { rc_clone.run_periodic_cleanup().await; });
+    tokio::spawn(async move {
+        rc_clone.run_periodic_cleanup().await;
+    });
 
     let detected_ip = detect_ip().await;
-    debug!("Detected IPs: v4={:?} v6={:?}", detected_ip.ipv4, detected_ip.ipv6);
+    debug!(
+        "Detected IPs: v4={:?} v6={:?}",
+        detected_ip.ipv4, detected_ip.ipv6
+    );
 
     let mut listeners = Vec::new();
-    
+
     for listener_conf in &config.server.listeners {
         let addr = SocketAddr::new(listener_conf.ip, config.server.port);
         let options = ListenOptions {
             ipv6_only: listener_conf.ip.is_ipv6(),
             ..Default::default()
         };
-        
+
         match create_listener(addr, &options) {
             Ok(socket) => {
                 let listener = TcpListener::from_std(socket.into())?;
                 info!("Listening on {}", addr);
-                
-                let public_ip = if let Some(ip) = listener_conf.announce_ip {
-                    ip
+
+                // Resolve the public host for link generation
+                let public_host = if let Some(ref announce) = listener_conf.announce {
+                    announce.clone()  // Use announce (IP or hostname) if explicitly set
                 } else if listener_conf.ip.is_unspecified() {
+                    // Auto-detect for unspecified addresses
                     if listener_conf.ip.is_ipv4() {
-                        detected_ip.ipv4.unwrap_or(listener_conf.ip)
+                        detected_ip.ipv4
+                            .map(|ip| ip.to_string())
+                            .unwrap_or_else(|| listener_conf.ip.to_string())
                     } else {
-                        detected_ip.ipv6.unwrap_or(listener_conf.ip)
+                        detected_ip.ipv6
+                            .map(|ip| ip.to_string())
+                            .unwrap_or_else(|| listener_conf.ip.to_string())
                     }
                 } else {
-                    listener_conf.ip
+                    listener_conf.ip.to_string()
                 };
 
-                if !config.show_link.is_empty() {
-                    info!("--- Proxy Links ({}) ---", public_ip);
-                    for user_name in &config.show_link {
-                        if let Some(secret) = config.access.users.get(user_name) {
-                            info!("User: {}", user_name);
-                            if config.general.modes.classic {
-                                info!("  Classic: tg://proxy?server={}&port={}&secret={}",
-                                    public_ip, config.server.port, secret);
-                            }
-                            if config.general.modes.secure {
-                                info!("  DD:      tg://proxy?server={}&port={}&secret=dd{}",
-                                    public_ip, config.server.port, secret);
-                            }
-                            if config.general.modes.tls {
-                                let domain_hex = hex::encode(&config.censorship.tls_domain);
-                                info!("  EE-TLS:  tg://proxy?server={}&port={}&secret=ee{}{}",
-                                    public_ip, config.server.port, secret, domain_hex);
-                            }
-                        } else {
-                            warn!("User '{}' in show_link not found", user_name);
-                        }
-                    }
-                    info!("------------------------");
+                // Show per-listener proxy links only when public_host is not set
+                if config.general.links.public_host.is_none() && !config.general.links.show.is_empty() {
+                    let link_port = config.general.links.public_port.unwrap_or(config.server.port);
+                    print_proxy_links(&public_host, link_port, &config);
                 }
-                
+
                 listeners.push(listener);
-            },
+            }
             Err(e) => {
                 error!("Failed to bind to {}: {}", addr, e);
             }
         }
     }
-    
-    if listeners.is_empty() {
+
+    // Show proxy links once when public_host is set, OR when there are no TCP listeners
+    // (unix-only mode) — use detected IP as fallback
+    if !config.general.links.show.is_empty() && (config.general.links.public_host.is_some() || listeners.is_empty()) {
+        let (host, port) = if let Some(ref h) = config.general.links.public_host {
+            (h.clone(), config.general.links.public_port.unwrap_or(config.server.port))
+        } else {
+            let ip = detected_ip
+                .ipv4
+                .or(detected_ip.ipv6)
+                .map(|ip| ip.to_string());
+            if ip.is_none() {
+                warn!("show_link is configured but public IP could not be detected. Set public_host in config.");
+            }
+            (ip.unwrap_or_else(|| "UNKNOWN".to_string()), config.general.links.public_port.unwrap_or(config.server.port))
+        };
+
+        print_proxy_links(&host, port, &config);
+    }
+
+    // Unix socket setup (before listeners check so unix-only config works)
+    let mut has_unix_listener = false;
+    #[cfg(unix)]
+    if let Some(ref unix_path) = config.server.listen_unix_sock {
+        // Remove stale socket file if present (standard practice)
+        let _ = tokio::fs::remove_file(unix_path).await;
+
+        let unix_listener = UnixListener::bind(unix_path)?;
+
+        // Apply socket permissions if configured
+        if let Some(ref perm_str) = config.server.listen_unix_sock_perm {
+            match u32::from_str_radix(perm_str.trim_start_matches('0'), 8) {
+                Ok(mode) => {
+                    use std::os::unix::fs::PermissionsExt;
+                    let perms = std::fs::Permissions::from_mode(mode);
+                    if let Err(e) = std::fs::set_permissions(unix_path, perms) {
+                        error!("Failed to set unix socket permissions to {}: {}", perm_str, e);
+                    } else {
+                        info!("Listening on unix:{} (mode {})", unix_path, perm_str);
+                    }
+                }
+                Err(e) => {
+                    warn!("Invalid listen_unix_sock_perm '{}': {}. Ignoring.", perm_str, e);
+                    info!("Listening on unix:{}", unix_path);
+                }
+            }
+        } else {
+            info!("Listening on unix:{}", unix_path);
+        }
+
+        has_unix_listener = true;
+
+        let config = config.clone();
+        let stats = stats.clone();
+        let upstream_manager = upstream_manager.clone();
+        let replay_checker = replay_checker.clone();
+        let buffer_pool = buffer_pool.clone();
+        let rng = rng.clone();
+        let me_pool = me_pool.clone();
+        let ip_tracker = ip_tracker.clone();
+
+        tokio::spawn(async move {
+            let unix_conn_counter = std::sync::Arc::new(std::sync::atomic::AtomicU64::new(1));
+
+            loop {
+                match unix_listener.accept().await {
+                    Ok((stream, _)) => {
+                        let conn_id = unix_conn_counter.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
+                        let fake_peer = SocketAddr::from(([127, 0, 0, 1], (conn_id % 65535) as u16));
+
+                        let config = config.clone();
+                        let stats = stats.clone();
+                        let upstream_manager = upstream_manager.clone();
+                        let replay_checker = replay_checker.clone();
+                        let buffer_pool = buffer_pool.clone();
+                        let rng = rng.clone();
+                        let me_pool = me_pool.clone();
+                        let ip_tracker = ip_tracker.clone();
+
+                        tokio::spawn(async move {
+                            if let Err(e) = crate::proxy::client::handle_client_stream(
+                                stream, fake_peer, config, stats,
+                                upstream_manager, replay_checker, buffer_pool, rng,
+                                me_pool, ip_tracker,
+                            ).await {
+                                debug!(error = %e, "Unix socket connection error");
+                            }
+                        });
+                    }
+                    Err(e) => {
+                        error!("Unix socket accept error: {}", e);
+                        tokio::time::sleep(Duration::from_millis(100)).await;
+                    }
+                }
+            }
+        });
+    }
+
+    if listeners.is_empty() && !has_unix_listener {
         error!("No listeners. Exiting.");
         std::process::exit(1);
     }
@@ -258,7 +728,17 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     } else {
         EnvFilter::new(effective_log_level.to_filter_str())
     };
-    filter_handle.reload(runtime_filter).expect("Failed to switch log filter");
+    filter_handle
+        .reload(runtime_filter)
+        .expect("Failed to switch log filter");
+
+    if let Some(port) = config.server.metrics_port {
+        let stats = stats.clone();
+        let whitelist = config.server.metrics_whitelist.clone();
+        tokio::spawn(async move {
+            metrics::serve(port, stats, whitelist).await;
+        });
+    }
 
     for listener in listeners {
         let config = config.clone();
@@ -267,7 +747,9 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         let replay_checker = replay_checker.clone();
         let buffer_pool = buffer_pool.clone();
         let rng = rng.clone();
-        
+        let me_pool = me_pool.clone();
+        let ip_tracker = ip_tracker.clone();
+
         tokio::spawn(async move {
             loop {
                 match listener.accept().await {
@@ -278,12 +760,25 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                         let replay_checker = replay_checker.clone();
                         let buffer_pool = buffer_pool.clone();
                         let rng = rng.clone();
-                        
+                        let me_pool = me_pool.clone();
+                        let ip_tracker = ip_tracker.clone();
+
                         tokio::spawn(async move {
                             if let Err(e) = ClientHandler::new(
-                                stream, peer_addr, config, stats,
-                                upstream_manager, replay_checker, buffer_pool, rng
-                            ).run().await {
+                                stream,
+                                peer_addr,
+                                config,
+                                stats,
+                                upstream_manager,
+                                replay_checker,
+                                buffer_pool,
+                                rng,
+                                me_pool,
+                                ip_tracker,
+                            )
+                            .run()
+                            .await
+                            {
                                 debug!(peer = %peer_addr, error = %e, "Connection error");
                             }
                         });
@@ -303,4 +798,4 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     }
 
     Ok(())
-}
+}

src/metrics.rs

@@ -0,0 +1,197 @@
+use std::convert::Infallible;
+use std::net::{IpAddr, SocketAddr};
+use std::sync::Arc;
+
+use http_body_util::Full;
+use hyper::body::Bytes;
+use hyper::server::conn::http1;
+use hyper::service::service_fn;
+use hyper::{Request, Response, StatusCode};
+use tokio::net::TcpListener;
+use tracing::{info, warn, debug};
+
+use crate::stats::Stats;
+
+pub async fn serve(port: u16, stats: Arc<Stats>, whitelist: Vec<IpAddr>) {
+    let addr = SocketAddr::from(([0, 0, 0, 0], port));
+    let listener = match TcpListener::bind(addr).await {
+        Ok(l) => l,
+        Err(e) => {
+            warn!(error = %e, "Failed to bind metrics on {}", addr);
+            return;
+        }
+    };
+    info!("Metrics endpoint: http://{}/metrics", addr);
+
+    loop {
+        let (stream, peer) = match listener.accept().await {
+            Ok(v) => v,
+            Err(e) => {
+                warn!(error = %e, "Metrics accept error");
+                continue;
+            }
+        };
+
+        if !whitelist.is_empty() && !whitelist.contains(&peer.ip()) {
+            debug!(peer = %peer, "Metrics request denied by whitelist");
+            continue;
+        }
+
+        let stats = stats.clone();
+        tokio::spawn(async move {
+            let svc = service_fn(move |req| {
+                let stats = stats.clone();
+                async move { handle(req, &stats) }
+            });
+            if let Err(e) = http1::Builder::new()
+                .serve_connection(hyper_util::rt::TokioIo::new(stream), svc)
+                .await
+            {
+                debug!(error = %e, "Metrics connection error");
+            }
+        });
+    }
+}
+
+fn handle(req: Request<hyper::body::Incoming>, stats: &Stats) -> Result<Response<Full<Bytes>>, Infallible> {
+    if req.uri().path() != "/metrics" {
+        let resp = Response::builder()
+            .status(StatusCode::NOT_FOUND)
+            .body(Full::new(Bytes::from("Not Found\n")))
+            .unwrap();
+        return Ok(resp);
+    }
+
+    let body = render_metrics(stats);
+    let resp = Response::builder()
+        .status(StatusCode::OK)
+        .header("content-type", "text/plain; version=0.0.4; charset=utf-8")
+        .body(Full::new(Bytes::from(body)))
+        .unwrap();
+    Ok(resp)
+}
+
+fn render_metrics(stats: &Stats) -> String {
+    use std::fmt::Write;
+    let mut out = String::with_capacity(4096);
+
+    let _ = writeln!(out, "# HELP telemt_uptime_seconds Proxy uptime");
+    let _ = writeln!(out, "# TYPE telemt_uptime_seconds gauge");
+    let _ = writeln!(out, "telemt_uptime_seconds {:.1}", stats.uptime_secs());
+
+    let _ = writeln!(out, "# HELP telemt_connections_total Total accepted connections");
+    let _ = writeln!(out, "# TYPE telemt_connections_total counter");
+    let _ = writeln!(out, "telemt_connections_total {}", stats.get_connects_all());
+
+    let _ = writeln!(out, "# HELP telemt_connections_bad_total Bad/rejected connections");
+    let _ = writeln!(out, "# TYPE telemt_connections_bad_total counter");
+    let _ = writeln!(out, "telemt_connections_bad_total {}", stats.get_connects_bad());
+
+    let _ = writeln!(out, "# HELP telemt_handshake_timeouts_total Handshake timeouts");
+    let _ = writeln!(out, "# TYPE telemt_handshake_timeouts_total counter");
+    let _ = writeln!(out, "telemt_handshake_timeouts_total {}", stats.get_handshake_timeouts());
+
+    let _ = writeln!(out, "# HELP telemt_user_connections_total Per-user total connections");
+    let _ = writeln!(out, "# TYPE telemt_user_connections_total counter");
+    let _ = writeln!(out, "# HELP telemt_user_connections_current Per-user active connections");
+    let _ = writeln!(out, "# TYPE telemt_user_connections_current gauge");
+    let _ = writeln!(out, "# HELP telemt_user_octets_from_client Per-user bytes received");
+    let _ = writeln!(out, "# TYPE telemt_user_octets_from_client counter");
+    let _ = writeln!(out, "# HELP telemt_user_octets_to_client Per-user bytes sent");
+    let _ = writeln!(out, "# TYPE telemt_user_octets_to_client counter");
+    let _ = writeln!(out, "# HELP telemt_user_msgs_from_client Per-user messages received");
+    let _ = writeln!(out, "# TYPE telemt_user_msgs_from_client counter");
+    let _ = writeln!(out, "# HELP telemt_user_msgs_to_client Per-user messages sent");
+    let _ = writeln!(out, "# TYPE telemt_user_msgs_to_client counter");
+
+    for entry in stats.iter_user_stats() {
+        let user = entry.key();
+        let s = entry.value();
+        let _ = writeln!(out, "telemt_user_connections_total{{user=\"{}\"}} {}", user, s.connects.load(std::sync::atomic::Ordering::Relaxed));
+        let _ = writeln!(out, "telemt_user_connections_current{{user=\"{}\"}} {}", user, s.curr_connects.load(std::sync::atomic::Ordering::Relaxed));
+        let _ = writeln!(out, "telemt_user_octets_from_client{{user=\"{}\"}} {}", user, s.octets_from_client.load(std::sync::atomic::Ordering::Relaxed));
+        let _ = writeln!(out, "telemt_user_octets_to_client{{user=\"{}\"}} {}", user, s.octets_to_client.load(std::sync::atomic::Ordering::Relaxed));
+        let _ = writeln!(out, "telemt_user_msgs_from_client{{user=\"{}\"}} {}", user, s.msgs_from_client.load(std::sync::atomic::Ordering::Relaxed));
+        let _ = writeln!(out, "telemt_user_msgs_to_client{{user=\"{}\"}} {}", user, s.msgs_to_client.load(std::sync::atomic::Ordering::Relaxed));
+    }
+
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_render_metrics_format() {
+        let stats = Arc::new(Stats::new());
+        stats.increment_connects_all();
+        stats.increment_connects_all();
+        stats.increment_connects_bad();
+        stats.increment_handshake_timeouts();
+        stats.increment_user_connects("alice");
+        stats.increment_user_curr_connects("alice");
+        stats.add_user_octets_from("alice", 1024);
+        stats.add_user_octets_to("alice", 2048);
+        stats.increment_user_msgs_from("alice");
+        stats.increment_user_msgs_to("alice");
+        stats.increment_user_msgs_to("alice");
+
+        let output = render_metrics(&stats);
+
+        assert!(output.contains("telemt_connections_total 2"));
+        assert!(output.contains("telemt_connections_bad_total 1"));
+        assert!(output.contains("telemt_handshake_timeouts_total 1"));
+        assert!(output.contains("telemt_user_connections_total{user=\"alice\"} 1"));
+        assert!(output.contains("telemt_user_connections_current{user=\"alice\"} 1"));
+        assert!(output.contains("telemt_user_octets_from_client{user=\"alice\"} 1024"));
+        assert!(output.contains("telemt_user_octets_to_client{user=\"alice\"} 2048"));
+        assert!(output.contains("telemt_user_msgs_from_client{user=\"alice\"} 1"));
+        assert!(output.contains("telemt_user_msgs_to_client{user=\"alice\"} 2"));
+    }
+
+    #[test]
+    fn test_render_empty_stats() {
+        let stats = Stats::new();
+        let output = render_metrics(&stats);
+        assert!(output.contains("telemt_connections_total 0"));
+        assert!(output.contains("telemt_connections_bad_total 0"));
+        assert!(output.contains("telemt_handshake_timeouts_total 0"));
+        assert!(!output.contains("user="));
+    }
+
+    #[test]
+    fn test_render_has_type_annotations() {
+        let stats = Stats::new();
+        let output = render_metrics(&stats);
+        assert!(output.contains("# TYPE telemt_uptime_seconds gauge"));
+        assert!(output.contains("# TYPE telemt_connections_total counter"));
+        assert!(output.contains("# TYPE telemt_connections_bad_total counter"));
+        assert!(output.contains("# TYPE telemt_handshake_timeouts_total counter"));
+    }
+
+    #[tokio::test]
+    async fn test_endpoint_integration() {
+        let stats = Arc::new(Stats::new());
+        stats.increment_connects_all();
+        stats.increment_connects_all();
+        stats.increment_connects_all();
+
+        let port = 19091u16;
+        let s = stats.clone();
+        tokio::spawn(async move {
+            serve(port, s, vec![]).await;
+        });
+        tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+
+        let resp = reqwest::get(format!("http://127.0.0.1:{}/metrics", port))
+            .await.unwrap();
+        assert_eq!(resp.status(), 200);
+        let body = resp.text().await.unwrap();
+        assert!(body.contains("telemt_connections_total 3"));
+
+        let resp404 = reqwest::get(format!("http://127.0.0.1:{}/other", port))
+            .await.unwrap();
+        assert_eq!(resp404.status(), 404);
+    }
+}

src/protocol/constants.rs

@@ -202,6 +202,17 @@ pub static RESERVED_NONCE_CONTINUES: &[[u8; 4]] = &[
 // ============= RPC Constants (for Middle Proxy) =============
 
 /// RPC Proxy Request
+
+/// RPC Flags (from Erlang mtp_rpc.erl)
+pub const RPC_FLAG_NOT_ENCRYPTED: u32 = 0x2;
+pub const RPC_FLAG_HAS_AD_TAG: u32    = 0x8;
+pub const RPC_FLAG_MAGIC: u32          = 0x1000;
+pub const RPC_FLAG_EXTMODE2: u32       = 0x20000;
+pub const RPC_FLAG_PAD: u32            = 0x8000000;
+pub const RPC_FLAG_INTERMEDIATE: u32   = 0x20000000;
+pub const RPC_FLAG_ABRIDGED: u32       = 0x40000000;
+pub const RPC_FLAG_QUICKACK: u32       = 0x80000000;
+
 pub const RPC_PROXY_REQ: [u8; 4] = [0xee, 0xf1, 0xce, 0x36];
 /// RPC Proxy Answer
 pub const RPC_PROXY_ANS: [u8; 4] = [0x0d, 0xda, 0x03, 0x44];
@@ -228,7 +239,56 @@ pub mod rpc_flags {
     pub const FLAG_QUICKACK: u32 = 0x80000000;
 }
 
-#[cfg(test)]
+
+    // ============= Middle-End Proxy Servers =============
+    pub const ME_PROXY_PORT: u16 = 8888;
+    
+    pub static TG_MIDDLE_PROXIES_FLAT_V4: LazyLock<Vec<(IpAddr, u16)>> = LazyLock::new(|| {
+        vec![
+            (IpAddr::V4(Ipv4Addr::new(149, 154, 175, 50)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(149, 154, 161, 144)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(149, 154, 175, 100)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(91, 108, 4, 136)), 8888),
+            (IpAddr::V4(Ipv4Addr::new(91, 108, 56, 183)), 8888),
+        ]
+    });
+    
+    // ============= RPC Constants (u32 native endian) =============
+    // From mtproto-common.h + net-tcp-rpc-common.h + mtproto-proxy.c
+    
+    pub const RPC_NONCE_U32: u32           = 0x7acb87aa;
+    pub const RPC_HANDSHAKE_U32: u32       = 0x7682eef5;
+    pub const RPC_HANDSHAKE_ERROR_U32: u32 = 0x6a27beda;
+    pub const TL_PROXY_TAG_U32: u32        = 0xdb1e26ae;  // mtproto-proxy.c:121
+    
+    // mtproto-common.h
+    pub const RPC_PROXY_REQ_U32: u32       = 0x36cef1ee;
+    pub const RPC_PROXY_ANS_U32: u32       = 0x4403da0d;
+    pub const RPC_CLOSE_CONN_U32: u32      = 0x1fcf425d;
+    pub const RPC_CLOSE_EXT_U32: u32       = 0x5eb634a2;
+    pub const RPC_SIMPLE_ACK_U32: u32      = 0x3bac409b;
+    pub const RPC_PING_U32: u32            = 0x5730a2df;
+    pub const RPC_PONG_U32: u32            = 0x8430eaa7;
+    
+    pub const RPC_CRYPTO_NONE_U32: u32 = 0;
+    pub const RPC_CRYPTO_AES_U32: u32  = 1;
+    
+    pub mod proxy_flags {
+        pub const FLAG_HAS_AD_TAG: u32    = 1;
+        pub const FLAG_NOT_ENCRYPTED: u32 = 0x2;
+        pub const FLAG_HAS_AD_TAG2: u32   = 0x8;
+        pub const FLAG_MAGIC: u32         = 0x1000;
+        pub const FLAG_EXTMODE2: u32      = 0x20000;
+        pub const FLAG_PAD: u32           = 0x8000000;
+        pub const FLAG_INTERMEDIATE: u32  = 0x20000000;
+        pub const FLAG_ABRIDGED: u32      = 0x40000000;
+        pub const FLAG_QUICKACK: u32      = 0x80000000;
+    }
+    
+    pub const ME_CONNECT_TIMEOUT_SECS: u64 = 5;
+    pub const ME_HANDSHAKE_TIMEOUT_SECS: u64 = 10;
+    
+    #[cfg(test)]
 mod tests {
     use super::*;
     

src/protocol/obfuscation.rs

@@ -160,6 +160,12 @@ pub fn prepare_tg_nonce(
 }
 
 /// Encrypt the outgoing nonce for Telegram
+/// Legacy helper — **do not use**.
+/// WARNING: logic diverges from Python/C reference (SHA256 of 48 bytes, IV from head).
+/// Kept only to avoid breaking external callers; prefer `encrypt_tg_nonce_with_ciphers`.
+#[deprecated(
+    note = "Incorrect MTProto obfuscation KDF; use proxy::handshake::encrypt_tg_nonce_with_ciphers"
+)]
 pub fn encrypt_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> Vec<u8> {
     let key_iv = &nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN];
     let enc_key = sha256(key_iv);
@@ -208,4 +214,4 @@ mod tests {
         assert!(is_valid_nonce(&nonce));
         assert_eq!(nonce.len(), HANDSHAKE_LEN);
     }
-}
+}

src/protocol/tls.rs

@@ -8,6 +8,8 @@ use crate::crypto::{sha256_hmac, SecureRandom};
 use crate::error::{ProxyError, Result};
 use super::constants::*;
 use std::time::{SystemTime, UNIX_EPOCH};
+use num_bigint::BigUint;
+use num_traits::One;
 
 // ============= Public Constants =============
 
@@ -311,13 +313,27 @@ pub fn validate_tls_handshake(
     None
 }
 
+fn curve25519_prime() -> BigUint {
+    (BigUint::one() << 255) - BigUint::from(19u32)
+}
+
 /// Generate a fake X25519 public key for TLS
 ///
-/// This generates random bytes that look like a valid X25519 public key.
-/// Since we're not doing real TLS, the actual cryptographic properties don't matter.
+/// Produces a quadratic residue mod p = 2^255 - 19 by computing n² mod p,
+/// which matches Python/C behavior and avoids DPI fingerprinting.
 pub fn gen_fake_x25519_key(rng: &SecureRandom) -> [u8; 32] {
-    let bytes = rng.bytes(32);
-    bytes.try_into().unwrap()
+    let mut n_bytes = [0u8; 32];
+    n_bytes.copy_from_slice(&rng.bytes(32));
+
+    let n = BigUint::from_bytes_le(&n_bytes);
+    let p = curve25519_prime();
+    let pk = (&n * &n) % &p;
+
+    let mut out = pk.to_bytes_le();
+    out.resize(32, 0);
+    let mut result = [0u8; 32];
+    result.copy_from_slice(&out[..32]);
+    result
 }
 
 /// Build TLS ServerHello response
@@ -498,6 +514,17 @@ mod tests {
         assert_eq!(key2.len(), 32);
         assert_ne!(key1, key2); // Should be random
     }
+
+    #[test]
+    fn test_fake_x25519_key_is_quadratic_residue() {
+        let rng = SecureRandom::new();
+        let key = gen_fake_x25519_key(&rng);
+        let p = curve25519_prime();
+        let k_num = BigUint::from_bytes_le(&key);
+        let exponent = (&p - BigUint::one()) >> 1;
+        let legendre = k_num.modpow(&exponent, &p);
+        assert_eq!(legendre, BigUint::one());
+    }
     
     #[test]
     fn test_tls_extension_builder() {
@@ -641,4 +668,4 @@ mod tests {
         // Should return None (no match) but not panic
         assert!(result.is_none());
     }
-}
+}

src/proxy/client.rs

@@ -1,28 +1,195 @@
 //! Client Handler
 
+use std::future::Future;
 use std::net::SocketAddr;
+use std::pin::Pin;
 use std::sync::Arc;
 use std::time::Duration;
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite};
 use tokio::net::TcpStream;
-use tokio::io::{AsyncRead, AsyncWrite, AsyncReadExt, AsyncWriteExt};
 use tokio::time::timeout;
-use tracing::{debug, info, warn, error, trace};
+use tracing::{debug, warn};
+
+/// Post-handshake future (relay phase, runs outside handshake timeout)
+type PostHandshakeFuture = Pin<Box<dyn Future<Output = Result<()>> + Send>>;
+
+/// Result of the handshake phase
+enum HandshakeOutcome {
+    /// Handshake succeeded, relay work to do (outside timeout)
+    NeedsRelay(PostHandshakeFuture),
+    /// Already fully handled (bad client masking, etc.)
+    Handled,
+}
 
 use crate::config::ProxyConfig;
-use crate::error::{ProxyError, Result, HandshakeResult};
+use crate::crypto::SecureRandom;
+use crate::error::{HandshakeResult, ProxyError, Result};
+use crate::ip_tracker::UserIpTracker;
 use crate::protocol::constants::*;
 use crate::protocol::tls;
-use crate::stats::{Stats, ReplayChecker};
-use crate::transport::{configure_client_socket, UpstreamManager};
-use crate::stream::{CryptoReader, CryptoWriter, FakeTlsReader, FakeTlsWriter, BufferPool};
-use crate::crypto::{AesCtr, SecureRandom};
+use crate::stats::{ReplayChecker, Stats};
+use crate::stream::{BufferPool, CryptoReader, CryptoWriter};
+use crate::transport::middle_proxy::MePool;
+use crate::transport::{UpstreamManager, configure_client_socket};
 
-use crate::proxy::handshake::{
-    handle_tls_handshake, handle_mtproto_handshake, 
-    HandshakeSuccess, generate_tg_nonce, encrypt_tg_nonce,
-};
-use crate::proxy::relay::relay_bidirectional;
+use crate::proxy::direct_relay::handle_via_direct;
+use crate::proxy::handshake::{HandshakeSuccess, handle_mtproto_handshake, handle_tls_handshake};
 use crate::proxy::masking::handle_bad_client;
+use crate::proxy::middle_relay::handle_via_middle_proxy;
+
+pub async fn handle_client_stream<S>(
+    mut stream: S,
+    peer: SocketAddr,
+    config: Arc<ProxyConfig>,
+    stats: Arc<Stats>,
+    upstream_manager: Arc<UpstreamManager>,
+    replay_checker: Arc<ReplayChecker>,
+    buffer_pool: Arc<BufferPool>,
+    rng: Arc<SecureRandom>,
+    me_pool: Option<Arc<MePool>>,
+    ip_tracker: Arc<UserIpTracker>,
+) -> Result<()>
+where
+    S: AsyncRead + AsyncWrite + Unpin + Send + 'static,
+{
+    stats.increment_connects_all();
+    debug!(peer = %peer, "New connection (generic stream)");
+
+    let handshake_timeout = Duration::from_secs(config.timeouts.client_handshake);
+    let stats_for_timeout = stats.clone();
+
+    // For non-TCP streams, use a synthetic local address
+    let local_addr: SocketAddr = format!("0.0.0.0:{}", config.server.port)
+        .parse()
+        .unwrap_or_else(|_| "0.0.0.0:443".parse().unwrap());
+
+    // Phase 1: handshake (with timeout)
+    let outcome = match timeout(handshake_timeout, async {
+        let mut first_bytes = [0u8; 5];
+        stream.read_exact(&mut first_bytes).await?;
+
+        let is_tls = tls::is_tls_handshake(&first_bytes[..3]);
+        debug!(peer = %peer, is_tls = is_tls, "Handshake type detected");
+
+        if is_tls {
+            let tls_len = u16::from_be_bytes([first_bytes[3], first_bytes[4]]) as usize;
+
+            if tls_len < 512 {
+                debug!(peer = %peer, tls_len = tls_len, "TLS handshake too short");
+                stats.increment_connects_bad();
+                let (reader, writer) = tokio::io::split(stream);
+                handle_bad_client(reader, writer, &first_bytes, &config).await;
+                return Ok(HandshakeOutcome::Handled);
+            }
+
+            let mut handshake = vec![0u8; 5 + tls_len];
+            handshake[..5].copy_from_slice(&first_bytes);
+            stream.read_exact(&mut handshake[5..]).await?;
+
+            let (read_half, write_half) = tokio::io::split(stream);
+
+            let (mut tls_reader, tls_writer, _tls_user) = match handle_tls_handshake(
+                &handshake, read_half, write_half, peer,
+                &config, &replay_checker, &rng,
+            ).await {
+                HandshakeResult::Success(result) => result,
+                HandshakeResult::BadClient { reader, writer } => {
+                    stats.increment_connects_bad();
+                    handle_bad_client(reader, writer, &handshake, &config).await;
+                    return Ok(HandshakeOutcome::Handled);
+                }
+                HandshakeResult::Error(e) => return Err(e),
+            };
+
+            debug!(peer = %peer, "Reading MTProto handshake through TLS");
+            let mtproto_data = tls_reader.read_exact(HANDSHAKE_LEN).await?;
+            let mtproto_handshake: [u8; HANDSHAKE_LEN] = mtproto_data[..].try_into()
+                .map_err(|_| ProxyError::InvalidHandshake("Short MTProto handshake".into()))?;
+
+            let (crypto_reader, crypto_writer, success) = match handle_mtproto_handshake(
+                &mtproto_handshake, tls_reader, tls_writer, peer,
+                &config, &replay_checker, true,
+            ).await {
+                HandshakeResult::Success(result) => result,
+                HandshakeResult::BadClient { reader: _, writer: _ } => {
+                    stats.increment_connects_bad();
+                    debug!(peer = %peer, "Valid TLS but invalid MTProto handshake");
+                    return Ok(HandshakeOutcome::Handled);
+                }
+                HandshakeResult::Error(e) => return Err(e),
+            };
+
+            Ok(HandshakeOutcome::NeedsRelay(Box::pin(
+                RunningClientHandler::handle_authenticated_static(
+                    crypto_reader, crypto_writer, success,
+                    upstream_manager, stats, config, buffer_pool, rng, me_pool,
+                    local_addr, peer, ip_tracker.clone(),
+                ),
+            )))
+        } else {
+            if !config.general.modes.classic && !config.general.modes.secure {
+                debug!(peer = %peer, "Non-TLS modes disabled");
+                stats.increment_connects_bad();
+                let (reader, writer) = tokio::io::split(stream);
+                handle_bad_client(reader, writer, &first_bytes, &config).await;
+                return Ok(HandshakeOutcome::Handled);
+            }
+
+            let mut handshake = [0u8; HANDSHAKE_LEN];
+            handshake[..5].copy_from_slice(&first_bytes);
+            stream.read_exact(&mut handshake[5..]).await?;
+
+            let (read_half, write_half) = tokio::io::split(stream);
+
+            let (crypto_reader, crypto_writer, success) = match handle_mtproto_handshake(
+                &handshake, read_half, write_half, peer,
+                &config, &replay_checker, false,
+            ).await {
+                HandshakeResult::Success(result) => result,
+                HandshakeResult::BadClient { reader, writer } => {
+                    stats.increment_connects_bad();
+                    handle_bad_client(reader, writer, &handshake, &config).await;
+                    return Ok(HandshakeOutcome::Handled);
+                }
+                HandshakeResult::Error(e) => return Err(e),
+            };
+
+            Ok(HandshakeOutcome::NeedsRelay(Box::pin(
+                RunningClientHandler::handle_authenticated_static(
+                    crypto_reader,
+                    crypto_writer,
+                    success,
+                    upstream_manager,
+                    stats,
+                    config,
+                    buffer_pool,
+                    rng,
+                    me_pool,
+                    local_addr,
+                    peer,
+                    ip_tracker.clone(),
+                )
+            )))
+        }
+    }).await {
+        Ok(Ok(outcome)) => outcome,
+        Ok(Err(e)) => {
+            debug!(peer = %peer, error = %e, "Handshake failed");
+            return Err(e);
+        }
+        Err(_) => {
+            stats_for_timeout.increment_handshake_timeouts();
+            debug!(peer = %peer, "Handshake timeout");
+            return Err(ProxyError::TgHandshakeTimeout);
+        }
+    };
+
+    // Phase 2: relay (WITHOUT handshake timeout — relay has its own activity timeouts)
+    match outcome {
+        HandshakeOutcome::NeedsRelay(fut) => fut.await,
+        HandshakeOutcome::Handled => Ok(()),
+    }
+}
 
 pub struct ClientHandler;
 
@@ -35,6 +202,8 @@ pub struct RunningClientHandler {
     upstream_manager: Arc<UpstreamManager>,
     buffer_pool: Arc<BufferPool>,
     rng: Arc<SecureRandom>,
+    me_pool: Option<Arc<MePool>>,
+    ip_tracker: Arc<UserIpTracker>,
 }
 
 impl ClientHandler {
@@ -47,10 +216,20 @@ impl ClientHandler {
         replay_checker: Arc<ReplayChecker>,
         buffer_pool: Arc<BufferPool>,
         rng: Arc<SecureRandom>,
+        me_pool: Option<Arc<MePool>>,
+        ip_tracker: Arc<UserIpTracker>,
     ) -> RunningClientHandler {
         RunningClientHandler {
-            stream, peer, config, stats, replay_checker,
-            upstream_manager, buffer_pool, rng,
+            stream,
+            peer,
+            config,
+            stats,
+            replay_checker,
+            upstream_manager,
+            buffer_pool,
+            rng,
+            me_pool,
+            ip_tracker,
         }
     }
 }
@@ -58,10 +237,11 @@ impl ClientHandler {
 impl RunningClientHandler {
     pub async fn run(mut self) -> Result<()> {
         self.stats.increment_connects_all();
-        
+
         let peer = self.peer;
+        let ip_tracker = self.ip_tracker.clone();
         debug!(peer = %peer, "New connection");
-        
+
         if let Err(e) = configure_client_socket(
             &self.stream,
             self.config.timeouts.client_keepalive,
@@ -69,151 +249,209 @@ impl RunningClientHandler {
         ) {
             debug!(peer = %peer, error = %e, "Failed to configure client socket");
         }
-        
+
         let handshake_timeout = Duration::from_secs(self.config.timeouts.client_handshake);
         let stats = self.stats.clone();
-        
-        let result = timeout(handshake_timeout, self.do_handshake()).await;
-        
-        match result {
-            Ok(Ok(())) => {
-                debug!(peer = %peer, "Connection handled successfully");
-                Ok(())
-            }
+
+        // Phase 1: handshake (with timeout)
+        let outcome = match timeout(handshake_timeout, self.do_handshake()).await {
+            Ok(Ok(outcome)) => outcome,
             Ok(Err(e)) => {
                 debug!(peer = %peer, error = %e, "Handshake failed");
-                Err(e)
+                return Err(e);
             }
             Err(_) => {
                 stats.increment_handshake_timeouts();
                 debug!(peer = %peer, "Handshake timeout");
-                Err(ProxyError::TgHandshakeTimeout)
+                return Err(ProxyError::TgHandshakeTimeout);
             }
+        };
+
+        // Phase 2: relay (WITHOUT handshake timeout — relay has its own activity timeouts)
+        match outcome {
+            HandshakeOutcome::NeedsRelay(fut) => fut.await,
+            HandshakeOutcome::Handled => Ok(()),
         }
     }
-    
-    async fn do_handshake(mut self) -> Result<()> {
+
+    async fn do_handshake(mut self) -> Result<HandshakeOutcome> {
         let mut first_bytes = [0u8; 5];
         self.stream.read_exact(&mut first_bytes).await?;
-        
+
         let is_tls = tls::is_tls_handshake(&first_bytes[..3]);
         let peer = self.peer;
-        
+        let ip_tracker = self.ip_tracker.clone();
+
         debug!(peer = %peer, is_tls = is_tls, "Handshake type detected");
-        
+
         if is_tls {
             self.handle_tls_client(first_bytes).await
         } else {
             self.handle_direct_client(first_bytes).await
         }
     }
-    
-    async fn handle_tls_client(mut self, first_bytes: [u8; 5]) -> Result<()> {
+
+    async fn handle_tls_client(mut self, first_bytes: [u8; 5]) -> Result<HandshakeOutcome> {
         let peer = self.peer;
-        
+        let ip_tracker = self.ip_tracker.clone();
+
         let tls_len = u16::from_be_bytes([first_bytes[3], first_bytes[4]]) as usize;
-        
+
         debug!(peer = %peer, tls_len = tls_len, "Reading TLS handshake");
-        
+
         if tls_len < 512 {
             debug!(peer = %peer, tls_len = tls_len, "TLS handshake too short");
             self.stats.increment_connects_bad();
             let (reader, writer) = self.stream.into_split();
             handle_bad_client(reader, writer, &first_bytes, &self.config).await;
-            return Ok(());
+            return Ok(HandshakeOutcome::Handled);
         }
-        
+
         let mut handshake = vec![0u8; 5 + tls_len];
         handshake[..5].copy_from_slice(&first_bytes);
         self.stream.read_exact(&mut handshake[5..]).await?;
-        
+
         let config = self.config.clone();
         let replay_checker = self.replay_checker.clone();
         let stats = self.stats.clone();
         let buffer_pool = self.buffer_pool.clone();
-        
+
+        let local_addr = self.stream.local_addr().map_err(ProxyError::Io)?;
         let (read_half, write_half) = self.stream.into_split();
-        
+
         let (mut tls_reader, tls_writer, _tls_user) = match handle_tls_handshake(
-            &handshake, read_half, write_half, peer,
-            &config, &replay_checker, &self.rng,
-        ).await {
+            &handshake,
+            read_half,
+            write_half,
+            peer,
+            &config,
+            &replay_checker,
+            &self.rng,
+        )
+        .await
+        {
             HandshakeResult::Success(result) => result,
             HandshakeResult::BadClient { reader, writer } => {
                 stats.increment_connects_bad();
                 handle_bad_client(reader, writer, &handshake, &config).await;
-                return Ok(());
+                return Ok(HandshakeOutcome::Handled);
             }
             HandshakeResult::Error(e) => return Err(e),
         };
-        
+
         debug!(peer = %peer, "Reading MTProto handshake through TLS");
         let mtproto_data = tls_reader.read_exact(HANDSHAKE_LEN).await?;
-        let mtproto_handshake: [u8; HANDSHAKE_LEN] = mtproto_data[..].try_into()
+        let mtproto_handshake: [u8; HANDSHAKE_LEN] = mtproto_data[..]
+            .try_into()
             .map_err(|_| ProxyError::InvalidHandshake("Short MTProto handshake".into()))?;
-        
+
         let (crypto_reader, crypto_writer, success) = match handle_mtproto_handshake(
-            &mtproto_handshake, tls_reader, tls_writer, peer,
-            &config, &replay_checker, true,
-        ).await {
+            &mtproto_handshake,
+            tls_reader,
+            tls_writer,
+            peer,
+            &config,
+            &replay_checker,
+            true,
+        )
+        .await
+        {
             HandshakeResult::Success(result) => result,
-            HandshakeResult::BadClient { reader: _, writer: _ } => {
+            HandshakeResult::BadClient {
+                reader: _,
+                writer: _,
+            } => {
                 stats.increment_connects_bad();
                 debug!(peer = %peer, "Valid TLS but invalid MTProto handshake");
-                return Ok(());
+                return Ok(HandshakeOutcome::Handled);
             }
             HandshakeResult::Error(e) => return Err(e),
         };
-        
-        Self::handle_authenticated_static(
-            crypto_reader, crypto_writer, success,
-            self.upstream_manager, self.stats, self.config,
-            buffer_pool, self.rng,
-        ).await
+
+        Ok(HandshakeOutcome::NeedsRelay(Box::pin(
+            Self::handle_authenticated_static(
+                crypto_reader,
+                crypto_writer,
+                success,
+                self.upstream_manager,
+                self.stats,
+                self.config,
+                buffer_pool,
+                self.rng,
+                self.me_pool,
+                local_addr,
+                peer,
+                self.ip_tracker,
+            ),
+        )))
     }
-    
-    async fn handle_direct_client(mut self, first_bytes: [u8; 5]) -> Result<()> {
+
+    async fn handle_direct_client(mut self, first_bytes: [u8; 5]) -> Result<HandshakeOutcome> {
         let peer = self.peer;
-        
+        let ip_tracker = self.ip_tracker.clone();
+
         if !self.config.general.modes.classic && !self.config.general.modes.secure {
             debug!(peer = %peer, "Non-TLS modes disabled");
             self.stats.increment_connects_bad();
             let (reader, writer) = self.stream.into_split();
             handle_bad_client(reader, writer, &first_bytes, &self.config).await;
-            return Ok(());
+            return Ok(HandshakeOutcome::Handled);
         }
-        
+
         let mut handshake = [0u8; HANDSHAKE_LEN];
         handshake[..5].copy_from_slice(&first_bytes);
         self.stream.read_exact(&mut handshake[5..]).await?;
-        
+
         let config = self.config.clone();
         let replay_checker = self.replay_checker.clone();
         let stats = self.stats.clone();
         let buffer_pool = self.buffer_pool.clone();
-        
+
+        let local_addr = self.stream.local_addr().map_err(ProxyError::Io)?;
         let (read_half, write_half) = self.stream.into_split();
-        
+
         let (crypto_reader, crypto_writer, success) = match handle_mtproto_handshake(
-            &handshake, read_half, write_half, peer,
-            &config, &replay_checker, false,
-        ).await {
+            &handshake,
+            read_half,
+            write_half,
+            peer,
+            &config,
+            &replay_checker,
+            false,
+        )
+        .await
+        {
             HandshakeResult::Success(result) => result,
             HandshakeResult::BadClient { reader, writer } => {
                 stats.increment_connects_bad();
                 handle_bad_client(reader, writer, &handshake, &config).await;
-                return Ok(());
+                return Ok(HandshakeOutcome::Handled);
             }
             HandshakeResult::Error(e) => return Err(e),
         };
-        
-        Self::handle_authenticated_static(
-            crypto_reader, crypto_writer, success,
-            self.upstream_manager, self.stats, self.config,
-            buffer_pool, self.rng,
-        ).await
+
+        Ok(HandshakeOutcome::NeedsRelay(Box::pin(
+            Self::handle_authenticated_static(
+                crypto_reader,
+                crypto_writer,
+                success,
+                self.upstream_manager,
+                self.stats,
+                self.config,
+                buffer_pool,
+                self.rng,
+                self.me_pool,
+                local_addr,
+                peer,
+                self.ip_tracker,
+            ),
+        )))
     }
-    
+
+    /// Main dispatch after successful handshake.
+    /// Two modes:
+    ///   - Direct: TCP relay to TG DC (existing behavior)  
+    ///   - Middle Proxy: RPC multiplex through ME pool (new — supports CDN DCs)
     async fn handle_authenticated_static<R, W>(
         client_reader: CryptoReader<R>,
         client_writer: CryptoWriter<W>,
@@ -223,180 +461,124 @@ impl RunningClientHandler {
         config: Arc<ProxyConfig>,
         buffer_pool: Arc<BufferPool>,
         rng: Arc<SecureRandom>,
+        me_pool: Option<Arc<MePool>>,
+        local_addr: SocketAddr,
+        peer_addr: SocketAddr,
+        ip_tracker: Arc<UserIpTracker>,
     ) -> Result<()>
     where
         R: AsyncRead + Unpin + Send + 'static,
         W: AsyncWrite + Unpin + Send + 'static,
     {
         let user = &success.user;
-        
-        if let Err(e) = Self::check_user_limits_static(user, &config, &stats) {
+
+        if let Err(e) = Self::check_user_limits_static(user, &config, &stats, peer_addr, &ip_tracker).await {
             warn!(user = %user, error = %e, "User limit exceeded");
             return Err(e);
         }
-        
-        let dc_addr = Self::get_dc_addr_static(success.dc_idx, &config)?;
-        
-        info!(
-            user = %user,
-            peer = %success.peer,
-            dc = success.dc_idx,
-            dc_addr = %dc_addr,
-            proto = ?success.proto_tag,
-            "Connecting to Telegram"
-        );
-        
-        // Pass dc_idx for latency-based upstream selection
-        let tg_stream = upstream_manager.connect(dc_addr, Some(success.dc_idx)).await?;
-        
-        debug!(peer = %success.peer, dc_addr = %dc_addr, "Connected, performing TG handshake");
-        
-        let (tg_reader, tg_writer) = Self::do_tg_handshake_static(
-            tg_stream, &success, &config, rng.as_ref(),
-        ).await?;
-        
-        debug!(peer = %success.peer, "TG handshake complete, starting relay");
-        
-        stats.increment_user_connects(user);
-        stats.increment_user_curr_connects(user);
-        
-        let relay_result = relay_bidirectional(
-            client_reader, client_writer,
-            tg_reader, tg_writer,
-            user, Arc::clone(&stats), buffer_pool,
-        ).await;
-        
-        stats.decrement_user_curr_connects(user);
-        
-        match &relay_result {
-            Ok(()) => debug!(user = %user, "Relay completed"),
-            Err(e) => debug!(user = %user, error = %e, "Relay ended with error"),
+
+        // IP Cleanup Guard: автоматически удаляет IP при выходе из scope
+        struct IpCleanupGuard {
+            tracker: Arc<UserIpTracker>,
+            user: String,
+            ip: std::net::IpAddr,
         }
         
-        relay_result
+        impl Drop for IpCleanupGuard {
+            fn drop(&mut self) {
+                let tracker = self.tracker.clone();
+                let user = self.user.clone();
+                let ip = self.ip;
+                tokio::spawn(async move {
+                    tracker.remove_ip(&user, ip).await;
+                    debug!(user = %user, ip = %ip, "IP cleaned up on disconnect");
+                });
+            }
+        }
+        
+        let _cleanup = IpCleanupGuard {
+            tracker: ip_tracker,
+            user: user.clone(),
+            ip: peer_addr.ip(),
+        };
+
+        // Decide: middle proxy or direct
+        if config.general.use_middle_proxy {
+            if let Some(ref pool) = me_pool {
+                return handle_via_middle_proxy(
+                    client_reader,
+                    client_writer,
+                    success,
+                    pool.clone(),
+                    stats,
+                    config,
+                    buffer_pool,
+                    local_addr,
+                    rng,
+                )
+                .await;
+            }
+            warn!("use_middle_proxy=true but MePool not initialized, falling back to direct");
+        }
+
+        // Direct mode (original behavior)
+        handle_via_direct(
+            client_reader,
+            client_writer,
+            success,
+            upstream_manager,
+            stats,
+            config,
+            buffer_pool,
+            rng,
+        )
+        .await
     }
-    
-    fn check_user_limits_static(user: &str, config: &ProxyConfig, stats: &Stats) -> Result<()> {
+
+    async fn check_user_limits_static(
+        user: &str, 
+        config: &ProxyConfig, 
+        stats: &Stats,
+        peer_addr: SocketAddr,
+        ip_tracker: &UserIpTracker,
+    ) -> Result<()> {
         if let Some(expiration) = config.access.user_expirations.get(user) {
             if chrono::Utc::now() > *expiration {
-                return Err(ProxyError::UserExpired { user: user.to_string() });
+                return Err(ProxyError::UserExpired {
+                    user: user.to_string(),
+                });
             }
         }
-        
+
+        // IP limit check
+        if let Err(reason) = ip_tracker.check_and_add(user, peer_addr.ip()).await {
+            warn!(
+                user = %user, 
+                ip = %peer_addr.ip(),
+                reason = %reason,
+                "IP limit exceeded"
+            );
+            return Err(ProxyError::ConnectionLimitExceeded {
+                user: user.to_string(),
+            });
+        }
+
         if let Some(limit) = config.access.user_max_tcp_conns.get(user) {
             if stats.get_user_curr_connects(user) >= *limit as u64 {
-                return Err(ProxyError::ConnectionLimitExceeded { user: user.to_string() });
+                return Err(ProxyError::ConnectionLimitExceeded {
+                    user: user.to_string(),
+                });
             }
         }
-        
+
         if let Some(quota) = config.access.user_data_quota.get(user) {
             if stats.get_user_total_octets(user) >= *quota {
-                return Err(ProxyError::DataQuotaExceeded { user: user.to_string() });
+                return Err(ProxyError::DataQuotaExceeded {
+                    user: user.to_string(),
+                });
             }
         }
-        
+
         Ok(())
     }
-    
-    /// Resolve DC index to a target address.
-    ///
-    /// Matches the C implementation's behavior exactly:
-    ///
-    /// 1. Look up DC in known clusters (standard DCs ±1..±5)
-    /// 2. If not found and `force=1` → fall back to `default_cluster`
-    ///
-    /// In the C code:
-    /// - `proxy-multi.conf` is downloaded from Telegram, contains only DC ±1..±5
-    /// - `default 2;` directive sets the default cluster
-    /// - `mf_cluster_lookup(CurConf, target_dc, 1)` returns default_cluster
-    ///   for any unknown DC (like CDN DC 203)
-    ///
-    /// So DC 203, DC 101, DC -300, etc. all route to the default DC (2).
-    /// There is NO modular arithmetic in the C implementation.
-    fn get_dc_addr_static(dc_idx: i16, config: &ProxyConfig) -> Result<SocketAddr> {
-        let datacenters = if config.general.prefer_ipv6 {
-            &*TG_DATACENTERS_V6
-        } else {
-            &*TG_DATACENTERS_V4
-        };
-    
-        let num_dcs = datacenters.len(); // 5
-    
-        // === Step 1: Check dc_overrides (like C's `proxy_for <dc> <ip>:<port>`) ===
-        let dc_key = dc_idx.to_string();
-        if let Some(addr_str) = config.dc_overrides.get(&dc_key) {
-            match addr_str.parse::<SocketAddr>() {
-                Ok(addr) => {
-                    debug!(dc_idx = dc_idx, addr = %addr, "Using DC override from config");
-                    return Ok(addr);
-                }
-                Err(_) => {
-                    warn!(dc_idx = dc_idx, addr_str = %addr_str,
-                        "Invalid DC override address in config, ignoring");
-                }
-            }
-        }
-    
-        // === Step 2: Standard DCs ±1..±5 — direct lookup ===
-        let abs_dc = dc_idx.unsigned_abs() as usize;
-        if abs_dc >= 1 && abs_dc <= num_dcs {
-            return Ok(SocketAddr::new(datacenters[abs_dc - 1], TG_DATACENTER_PORT));
-        }
-    
-        // === Step 3: Unknown DC — fall back to default_cluster ===
-        // Exactly like C's `mf_cluster_lookup(CurConf, target_dc, force=1)`
-        // which returns `MC->default_cluster` when the DC is not found.
-        // Telegram's proxy-multi.conf uses `default 2;`
-        let default_dc = config.default_dc.unwrap_or(2) as usize;
-        let fallback_idx = if default_dc >= 1 && default_dc <= num_dcs {
-            default_dc - 1
-        } else {
-            1 // DC 2 (index 1) — matches Telegram's `default 2;`
-        };
-    
-        info!(
-            original_dc = dc_idx,
-            fallback_dc = (fallback_idx + 1) as u16,
-            fallback_addr = %datacenters[fallback_idx],
-            "Special DC ---> default_cluster"
-        );
-    
-        Ok(SocketAddr::new(datacenters[fallback_idx], TG_DATACENTER_PORT))
-    }
-    
-    async fn do_tg_handshake_static(
-        mut stream: TcpStream,
-        success: &HandshakeSuccess,
-        config: &ProxyConfig,
-        rng: &SecureRandom,
-    ) -> Result<(CryptoReader<tokio::net::tcp::OwnedReadHalf>, CryptoWriter<tokio::net::tcp::OwnedWriteHalf>)> {
-        let (nonce, tg_enc_key, tg_enc_iv, tg_dec_key, tg_dec_iv) = generate_tg_nonce(
-            success.proto_tag,
-            &success.dec_key,
-            success.dec_iv,
-            rng,
-            config.general.fast_mode,
-        );
-        
-        let encrypted_nonce = encrypt_tg_nonce(&nonce);
-        
-        debug!(
-            peer = %success.peer,
-            nonce_head = %hex::encode(&nonce[..16]),
-            "Sending nonce to Telegram"
-        );
-        
-        stream.write_all(&encrypted_nonce).await?;
-        stream.flush().await?;
-        
-        let (read_half, write_half) = stream.into_split();
-        
-        let decryptor = AesCtr::new(&tg_dec_key, tg_dec_iv);
-        let encryptor = AesCtr::new(&tg_enc_key, tg_enc_iv);
-        
-        Ok((
-            CryptoReader::new(read_half, decryptor),
-            CryptoWriter::new(write_half, encryptor),
-        ))
-    }
-}
+}

src/proxy/direct_relay.rs

@@ -0,0 +1,185 @@
+use std::fs::OpenOptions;
+use std::io::Write;
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt};
+use tokio::net::TcpStream;
+use tracing::{debug, info, warn};
+
+use crate::config::ProxyConfig;
+use crate::crypto::SecureRandom;
+use crate::error::Result;
+use crate::protocol::constants::*;
+use crate::proxy::handshake::{HandshakeSuccess, encrypt_tg_nonce_with_ciphers, generate_tg_nonce};
+use crate::proxy::relay::relay_bidirectional;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader, CryptoWriter};
+use crate::transport::UpstreamManager;
+
+pub(crate) async fn handle_via_direct<R, W>(
+    client_reader: CryptoReader<R>,
+    client_writer: CryptoWriter<W>,
+    success: HandshakeSuccess,
+    upstream_manager: Arc<UpstreamManager>,
+    stats: Arc<Stats>,
+    config: Arc<ProxyConfig>,
+    buffer_pool: Arc<BufferPool>,
+    rng: Arc<SecureRandom>,
+) -> Result<()>
+where
+    R: AsyncRead + Unpin + Send + 'static,
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let user = &success.user;
+    let dc_addr = get_dc_addr_static(success.dc_idx, &config)?;
+
+    info!(
+        user = %user,
+        peer = %success.peer,
+        dc = success.dc_idx,
+        dc_addr = %dc_addr,
+        proto = ?success.proto_tag,
+        mode = "direct",
+        "Connecting to Telegram DC"
+    );
+
+    let tg_stream = upstream_manager
+        .connect(dc_addr, Some(success.dc_idx))
+        .await?;
+
+    debug!(peer = %success.peer, dc_addr = %dc_addr, "Connected, performing TG handshake");
+
+    let (tg_reader, tg_writer) =
+        do_tg_handshake_static(tg_stream, &success, &config, rng.as_ref()).await?;
+
+    debug!(peer = %success.peer, "TG handshake complete, starting relay");
+
+    stats.increment_user_connects(user);
+    stats.increment_user_curr_connects(user);
+
+    let relay_result = relay_bidirectional(
+        client_reader,
+        client_writer,
+        tg_reader,
+        tg_writer,
+        user,
+        Arc::clone(&stats),
+        buffer_pool,
+    )
+    .await;
+
+    stats.decrement_user_curr_connects(user);
+
+    match &relay_result {
+        Ok(()) => debug!(user = %user, "Direct relay completed"),
+        Err(e) => debug!(user = %user, error = %e, "Direct relay ended with error"),
+    }
+
+    relay_result
+}
+
+fn get_dc_addr_static(dc_idx: i16, config: &ProxyConfig) -> Result<SocketAddr> {
+    let datacenters = if config.general.prefer_ipv6 {
+        &*TG_DATACENTERS_V6
+    } else {
+        &*TG_DATACENTERS_V4
+    };
+
+    let num_dcs = datacenters.len();
+
+    let dc_key = dc_idx.to_string();
+    if let Some(addrs) = config.dc_overrides.get(&dc_key) {
+        let prefer_v6 = config.general.prefer_ipv6;
+        let mut parsed = Vec::new();
+        for addr_str in addrs {
+            match addr_str.parse::<SocketAddr>() {
+                Ok(addr) => parsed.push(addr),
+                Err(_) => warn!(dc_idx = dc_idx, addr_str = %addr_str, "Invalid DC override address in config, ignoring"),
+            }
+        }
+
+        if let Some(addr) = parsed
+            .iter()
+            .find(|a| a.is_ipv6() == prefer_v6)
+            .or_else(|| parsed.first())
+            .copied()
+        {
+            debug!(dc_idx = dc_idx, addr = %addr, count = parsed.len(), "Using DC override from config");
+            return Ok(addr);
+        }
+    }
+
+    let abs_dc = dc_idx.unsigned_abs() as usize;
+    if abs_dc >= 1 && abs_dc <= num_dcs {
+        return Ok(SocketAddr::new(datacenters[abs_dc - 1], TG_DATACENTER_PORT));
+    }
+
+    // Unknown DC requested by client without override: log and fall back.
+    if !config.dc_overrides.contains_key(&dc_key) {
+        warn!(dc_idx = dc_idx, "Requested non-standard DC with no override; falling back to default cluster");
+        if let Some(path) = &config.general.unknown_dc_log_path {
+            if let Ok(mut file) = OpenOptions::new().create(true).append(true).open(path) {
+                let _ = writeln!(file, "dc_idx={dc_idx}");
+            }
+        }
+    }
+
+    let default_dc = config.default_dc.unwrap_or(2) as usize;
+    let fallback_idx = if default_dc >= 1 && default_dc <= num_dcs {
+        default_dc - 1
+    } else {
+        1
+    };
+
+    info!(
+        original_dc = dc_idx,
+        fallback_dc = (fallback_idx + 1) as u16,
+        fallback_addr = %datacenters[fallback_idx],
+        "Special DC ---> default_cluster"
+    );
+
+    Ok(SocketAddr::new(
+        datacenters[fallback_idx],
+        TG_DATACENTER_PORT,
+    ))
+}
+
+async fn do_tg_handshake_static(
+    mut stream: TcpStream,
+    success: &HandshakeSuccess,
+    config: &ProxyConfig,
+    rng: &SecureRandom,
+) -> Result<(
+    CryptoReader<tokio::net::tcp::OwnedReadHalf>,
+    CryptoWriter<tokio::net::tcp::OwnedWriteHalf>,
+)> {
+    let (nonce, _tg_enc_key, _tg_enc_iv, _tg_dec_key, _tg_dec_iv) = generate_tg_nonce(
+        success.proto_tag,
+        success.dc_idx,
+        &success.dec_key,
+        success.dec_iv,
+        &success.enc_key,
+        success.enc_iv,
+        rng,
+        config.general.fast_mode,
+    );
+
+    let (encrypted_nonce, tg_encryptor, tg_decryptor) = encrypt_tg_nonce_with_ciphers(&nonce);
+
+    debug!(
+        peer = %success.peer,
+        nonce_head = %hex::encode(&nonce[..16]),
+        "Sending nonce to Telegram"
+    );
+
+    stream.write_all(&encrypted_nonce).await?;
+    stream.flush().await?;
+
+    let (read_half, write_half) = stream.into_split();
+
+    Ok((
+        CryptoReader::new(read_half, tg_decryptor),
+        CryptoWriter::new(write_half, tg_encryptor),
+    ))
+}

src/proxy/handshake.rs

@@ -61,26 +61,26 @@ where
     W: AsyncWrite + Unpin,
 {
     debug!(peer = %peer, handshake_len = handshake.len(), "Processing TLS handshake");
-    
+
     if handshake.len() < tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1 {
         debug!(peer = %peer, "TLS handshake too short");
         return HandshakeResult::BadClient { reader, writer };
     }
-    
+
     let digest = &handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN];
     let digest_half = &digest[..tls::TLS_DIGEST_HALF_LEN];
-    
-    if replay_checker.check_tls_digest(digest_half) {
+
+    if replay_checker.check_and_add_tls_digest(digest_half) {
         warn!(peer = %peer, "TLS replay attack detected (duplicate digest)");
         return HandshakeResult::BadClient { reader, writer };
     }
-    
+
     let secrets: Vec<(String, Vec<u8>)> = config.access.users.iter()
         .filter_map(|(name, hex)| {
             hex::decode(hex).ok().map(|bytes| (name.clone(), bytes))
         })
         .collect();
-    
+
     let validation = match tls::validate_tls_handshake(
         handshake,
         &secrets,
@@ -96,12 +96,12 @@ where
             return HandshakeResult::BadClient { reader, writer };
         }
     };
-    
+
     let secret = match secrets.iter().find(|(name, _)| *name == validation.user) {
         Some((_, s)) => s,
         None => return HandshakeResult::BadClient { reader, writer },
     };
-    
+
     let response = tls::build_server_hello(
         secret,
         &validation.digest,
@@ -109,27 +109,25 @@ where
         config.censorship.fake_cert_len,
         rng,
     );
-    
+
     debug!(peer = %peer, response_len = response.len(), "Sending TLS ServerHello");
-    
+
     if let Err(e) = writer.write_all(&response).await {
         warn!(peer = %peer, error = %e, "Failed to write TLS ServerHello");
         return HandshakeResult::Error(ProxyError::Io(e));
     }
-    
+
     if let Err(e) = writer.flush().await {
         warn!(peer = %peer, error = %e, "Failed to flush TLS ServerHello");
         return HandshakeResult::Error(ProxyError::Io(e));
     }
-    
-    replay_checker.add_tls_digest(digest_half);
-    
+
     info!(
         peer = %peer,
         user = %validation.user,
         "TLS handshake successful"
     );
-    
+
     HandshakeResult::Success((
         FakeTlsReader::new(reader),
         FakeTlsWriter::new(writer),
@@ -152,75 +150,72 @@ where
     W: AsyncWrite + Unpin + Send,
 {
     trace!(peer = %peer, handshake = ?hex::encode(handshake), "MTProto handshake bytes");
-    
+
     let dec_prekey_iv = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
-    
-    if replay_checker.check_handshake(dec_prekey_iv) {
+
+    if replay_checker.check_and_add_handshake(dec_prekey_iv) {
         warn!(peer = %peer, "MTProto replay attack detected");
         return HandshakeResult::BadClient { reader, writer };
     }
-    
+
     let enc_prekey_iv: Vec<u8> = dec_prekey_iv.iter().rev().copied().collect();
-    
+
     for (user, secret_hex) in &config.access.users {
         let secret = match hex::decode(secret_hex) {
             Ok(s) => s,
             Err(_) => continue,
         };
-        
+
         let dec_prekey = &dec_prekey_iv[..PREKEY_LEN];
         let dec_iv_bytes = &dec_prekey_iv[PREKEY_LEN..];
-        
+
         let mut dec_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
         dec_key_input.extend_from_slice(dec_prekey);
         dec_key_input.extend_from_slice(&secret);
         let dec_key = sha256(&dec_key_input);
-        
+
         let dec_iv = u128::from_be_bytes(dec_iv_bytes.try_into().unwrap());
-        
+
         let mut decryptor = AesCtr::new(&dec_key, dec_iv);
         let decrypted = decryptor.decrypt(handshake);
-        
+
         let tag_bytes: [u8; 4] = decrypted[PROTO_TAG_POS..PROTO_TAG_POS + 4]
             .try_into()
             .unwrap();
-        
+
         let proto_tag = match ProtoTag::from_bytes(tag_bytes) {
             Some(tag) => tag,
             None => continue,
         };
-        
+
         let mode_ok = match proto_tag {
             ProtoTag::Secure => {
                 if is_tls { config.general.modes.tls } else { config.general.modes.secure }
             }
             ProtoTag::Intermediate | ProtoTag::Abridged => config.general.modes.classic,
         };
-        
+
         if !mode_ok {
             debug!(peer = %peer, user = %user, proto = ?proto_tag, "Mode not enabled");
             continue;
         }
-        
+
         let dc_idx = i16::from_le_bytes(
             decrypted[DC_IDX_POS..DC_IDX_POS + 2].try_into().unwrap()
         );
-        
+
         let enc_prekey = &enc_prekey_iv[..PREKEY_LEN];
         let enc_iv_bytes = &enc_prekey_iv[PREKEY_LEN..];
-        
+
         let mut enc_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
         enc_key_input.extend_from_slice(enc_prekey);
         enc_key_input.extend_from_slice(&secret);
         let enc_key = sha256(&enc_key_input);
-        
+
         let enc_iv = u128::from_be_bytes(enc_iv_bytes.try_into().unwrap());
-        
-        replay_checker.add_handshake(dec_prekey_iv);
-        
-        let decryptor = AesCtr::new(&dec_key, dec_iv);
+
         let encryptor = AesCtr::new(&enc_key, enc_iv);
-        
+
         let success = HandshakeSuccess {
             user: user.clone(),
             dc_idx,
@@ -232,7 +227,7 @@ where
             peer,
             is_tls,
         };
-        
+
         info!(
             peer = %peer,
             user = %user,
@@ -241,14 +236,14 @@ where
             tls = is_tls,
             "MTProto handshake successful"
         );
-        
+
         return HandshakeResult::Success((
             CryptoReader::new(reader, decryptor),
             CryptoWriter::new(writer, encryptor),
             success,
         ));
     }
-    
+
     debug!(peer = %peer, "MTProto handshake: no matching user found");
     HandshakeResult::BadClient { reader, writer }
 }
@@ -256,94 +251,136 @@ where
 /// Generate nonce for Telegram connection
 pub fn generate_tg_nonce(
     proto_tag: ProtoTag, 
-    client_dec_key: &[u8; 32],
-    client_dec_iv: u128,
+    dc_idx: i16,
+    _client_dec_key: &[u8; 32],
+    _client_dec_iv: u128,
+    client_enc_key: &[u8; 32],
+    client_enc_iv: u128,
     rng: &SecureRandom,
     fast_mode: bool,
 ) -> ([u8; HANDSHAKE_LEN], [u8; 32], u128, [u8; 32], u128) {
     loop {
         let bytes = rng.bytes(HANDSHAKE_LEN);
         let mut nonce: [u8; HANDSHAKE_LEN] = bytes.try_into().unwrap();
-        
+
         if RESERVED_NONCE_FIRST_BYTES.contains(&nonce[0]) { continue; }
-        
+
         let first_four: [u8; 4] = nonce[..4].try_into().unwrap();
         if RESERVED_NONCE_BEGINNINGS.contains(&first_four) { continue; }
-        
+
         let continue_four: [u8; 4] = nonce[4..8].try_into().unwrap();
         if RESERVED_NONCE_CONTINUES.contains(&continue_four) { continue; }
-        
+
         nonce[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
-        
+        // CRITICAL: write dc_idx so upstream DC knows where to route
+        nonce[DC_IDX_POS..DC_IDX_POS + 2].copy_from_slice(&dc_idx.to_le_bytes());
+
         if fast_mode {
-            nonce[SKIP_LEN..SKIP_LEN + KEY_LEN].copy_from_slice(client_dec_key);
-            nonce[SKIP_LEN + KEY_LEN..SKIP_LEN + KEY_LEN + IV_LEN]
-                .copy_from_slice(&client_dec_iv.to_be_bytes());
+            let mut key_iv = Vec::with_capacity(KEY_LEN + IV_LEN);
+            key_iv.extend_from_slice(client_enc_key);
+            key_iv.extend_from_slice(&client_enc_iv.to_be_bytes());
+            key_iv.reverse(); // Python/C behavior: reversed enc_key+enc_iv in nonce
+            nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN].copy_from_slice(&key_iv);
         }
-        
+
         let enc_key_iv = &nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN];
         let dec_key_iv: Vec<u8> = enc_key_iv.iter().rev().copied().collect();
-        
+
         let tg_enc_key: [u8; 32] = enc_key_iv[..KEY_LEN].try_into().unwrap();
         let tg_enc_iv = u128::from_be_bytes(enc_key_iv[KEY_LEN..].try_into().unwrap());
-        
+
         let tg_dec_key: [u8; 32] = dec_key_iv[..KEY_LEN].try_into().unwrap();
         let tg_dec_iv = u128::from_be_bytes(dec_key_iv[KEY_LEN..].try_into().unwrap());
-        
+
         return (nonce, tg_enc_key, tg_enc_iv, tg_dec_key, tg_dec_iv);
     }
 }
 
-/// Encrypt nonce for sending to Telegram
-pub fn encrypt_tg_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> Vec<u8> {
+/// Encrypt nonce for sending to Telegram and return cipher objects with correct counter state
+pub fn encrypt_tg_nonce_with_ciphers(nonce: &[u8; HANDSHAKE_LEN]) -> (Vec<u8>, AesCtr, AesCtr) {
     let enc_key_iv = &nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN];
-    let key: [u8; 32] = enc_key_iv[..KEY_LEN].try_into().unwrap();
-    let iv = u128::from_be_bytes(enc_key_iv[KEY_LEN..].try_into().unwrap());
-    
-    let mut encryptor = AesCtr::new(&key, iv);
-    let encrypted_full = encryptor.encrypt(nonce);
-    
+    let dec_key_iv: Vec<u8> = enc_key_iv.iter().rev().copied().collect();
+
+    let enc_key: [u8; 32] = enc_key_iv[..KEY_LEN].try_into().unwrap();
+    let enc_iv = u128::from_be_bytes(enc_key_iv[KEY_LEN..].try_into().unwrap());
+
+    let dec_key: [u8; 32] = dec_key_iv[..KEY_LEN].try_into().unwrap();
+    let dec_iv = u128::from_be_bytes(dec_key_iv[KEY_LEN..].try_into().unwrap());
+
+    let mut encryptor = AesCtr::new(&enc_key, enc_iv);
+    let encrypted_full = encryptor.encrypt(nonce);  // counter: 0 → 4
+
     let mut result = nonce[..PROTO_TAG_POS].to_vec();
     result.extend_from_slice(&encrypted_full[PROTO_TAG_POS..]);
-    
-    result
+
+    let decryptor = AesCtr::new(&dec_key, dec_iv);
+
+    (result, encryptor, decryptor)
+}
+
+/// Encrypt nonce for sending to Telegram (legacy function for compatibility)
+pub fn encrypt_tg_nonce(nonce: &[u8; HANDSHAKE_LEN]) -> Vec<u8> {
+    let (encrypted, _, _) = encrypt_tg_nonce_with_ciphers(nonce);
+    encrypted
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    
+
     #[test]
     fn test_generate_tg_nonce() {
         let client_dec_key = [0x42u8; 32];
         let client_dec_iv = 12345u128;
-        
+        let client_enc_key = [0x24u8; 32];
+        let client_enc_iv = 54321u128;
+
         let rng = SecureRandom::new();
         let (nonce, _tg_enc_key, _tg_enc_iv, _tg_dec_key, _tg_dec_iv) = 
-            generate_tg_nonce(ProtoTag::Secure, &client_dec_key, client_dec_iv, &rng, false);
-        
+            generate_tg_nonce(
+                ProtoTag::Secure,
+                2,
+                &client_dec_key,
+                client_dec_iv,
+                &client_enc_key,
+                client_enc_iv,
+                &rng,
+                false,
+            );
+
         assert_eq!(nonce.len(), HANDSHAKE_LEN);
-        
+
         let tag_bytes: [u8; 4] = nonce[PROTO_TAG_POS..PROTO_TAG_POS + 4].try_into().unwrap();
         assert_eq!(ProtoTag::from_bytes(tag_bytes), Some(ProtoTag::Secure));
     }
-    
+
     #[test]
     fn test_encrypt_tg_nonce() {
         let client_dec_key = [0x42u8; 32];
         let client_dec_iv = 12345u128;
-        
+        let client_enc_key = [0x24u8; 32];
+        let client_enc_iv = 54321u128;
+
         let rng = SecureRandom::new();
         let (nonce, _, _, _, _) = 
-            generate_tg_nonce(ProtoTag::Secure, &client_dec_key, client_dec_iv, &rng, false);
-        
+            generate_tg_nonce(
+                ProtoTag::Secure,
+                2,
+                &client_dec_key,
+                client_dec_iv,
+                &client_enc_key,
+                client_enc_iv,
+                &rng,
+                false,
+            );
+
         let encrypted = encrypt_tg_nonce(&nonce);
-        
+
         assert_eq!(encrypted.len(), HANDSHAKE_LEN);
         assert_eq!(&encrypted[..PROTO_TAG_POS], &nonce[..PROTO_TAG_POS]);
         assert_ne!(&encrypted[PROTO_TAG_POS..], &nonce[PROTO_TAG_POS..]);
     }
-    
+
     #[test]
     fn test_handshake_success_zeroize_on_drop() {
         let success = HandshakeSuccess {
@@ -357,11 +394,11 @@ mod tests {
             peer: "127.0.0.1:1234".parse().unwrap(),
             is_tls: true,
         };
-        
+
         assert_eq!(success.dec_key, [0xAA; 32]);
         assert_eq!(success.enc_key, [0xCC; 32]);
-        
+
         drop(success);
         // Drop impl zeroizes key material without panic
     }
-}
+}

src/proxy/masking.rs

@@ -3,6 +3,8 @@
 use std::time::Duration;
 use std::str;
 use tokio::net::TcpStream;
+#[cfg(unix)]
+use tokio::net::UnixStream;
 use tokio::io::{AsyncRead, AsyncWrite, AsyncReadExt, AsyncWriteExt};
 use tokio::time::timeout;
 use tracing::debug;
@@ -24,33 +26,33 @@ fn detect_client_type(data: &[u8]) -> &'static str {
             return "HTTP";
         }
     }
-    
+
     // Check for TLS ClientHello (0x16 = handshake, 0x03 0x01-0x03 = TLS version)
     if data.len() > 3 && data[0] == 0x16 && data[1] == 0x03 {
         return "TLS-scanner";
     }
-    
+
     // Check for SSH
     if data.starts_with(b"SSH-") {
         return "SSH";
     }
-    
+
     // Port scanner (very short data)
     if data.len() < 10 {
         return "port-scanner";
     }
-    
+
     "unknown"
 }
 
 /// Handle a bad client by forwarding to mask host
 pub async fn handle_bad_client<R, W>(
-    mut reader: R,
-    mut writer: W,
+    reader: R,
+    writer: W,
     initial_data: &[u8],
     config: &ProxyConfig,
-) 
-where 
+)
+where
     R: AsyncRead + Unpin + Send + 'static,
     W: AsyncWrite + Unpin + Send + 'static,
 {
@@ -59,13 +61,41 @@ where
         consume_client_data(reader).await;
         return;
     }
-    
+
     let client_type = detect_client_type(initial_data);
-    
+
+    // Connect via Unix socket or TCP
+    #[cfg(unix)]
+    if let Some(ref sock_path) = config.censorship.mask_unix_sock {
+        debug!(
+            client_type = client_type,
+            sock = %sock_path,
+            data_len = initial_data.len(),
+            "Forwarding bad client to mask unix socket"
+        );
+
+        let connect_result = timeout(MASK_TIMEOUT, UnixStream::connect(sock_path)).await;
+        match connect_result {
+            Ok(Ok(stream)) => {
+                let (mask_read, mask_write) = stream.into_split();
+                relay_to_mask(reader, writer, mask_read, mask_write, initial_data).await;
+            }
+            Ok(Err(e)) => {
+                debug!(error = %e, "Failed to connect to mask unix socket");
+                consume_client_data(reader).await;
+            }
+            Err(_) => {
+                debug!("Timeout connecting to mask unix socket");
+                consume_client_data(reader).await;
+            }
+        }
+        return;
+    }
+
     let mask_host = config.censorship.mask_host.as_deref()
         .unwrap_or(&config.censorship.tls_domain);
     let mask_port = config.censorship.mask_port;
-    
+
     debug!(
         client_type = client_type,
         host = %mask_host,
@@ -73,35 +103,45 @@ where
         data_len = initial_data.len(),
         "Forwarding bad client to mask host"
     );
-    
+
     // Connect to mask host
     let mask_addr = format!("{}:{}", mask_host, mask_port);
-    let connect_result = timeout(
-        MASK_TIMEOUT,
-        TcpStream::connect(&mask_addr)
-    ).await;
-    
-    let mask_stream = match connect_result {
-        Ok(Ok(s)) => s,
+    let connect_result = timeout(MASK_TIMEOUT, TcpStream::connect(&mask_addr)).await;
+    match connect_result {
+        Ok(Ok(stream)) => {
+            let (mask_read, mask_write) = stream.into_split();
+            relay_to_mask(reader, writer, mask_read, mask_write, initial_data).await;
+        }
         Ok(Err(e)) => {
             debug!(error = %e, "Failed to connect to mask host");
             consume_client_data(reader).await;
-            return;
         }
         Err(_) => {
             debug!("Timeout connecting to mask host");
             consume_client_data(reader).await;
-            return;
         }
-    };
-    
-    let (mut mask_read, mut mask_write) = mask_stream.into_split();
-    
+    }
+}
+
+/// Relay traffic between client and mask backend
+async fn relay_to_mask<R, W, MR, MW>(
+    mut reader: R,
+    mut writer: W,
+    mut mask_read: MR,
+    mut mask_write: MW,
+    initial_data: &[u8],
+)
+where
+    R: AsyncRead + Unpin + Send + 'static,
+    W: AsyncWrite + Unpin + Send + 'static,
+    MR: AsyncRead + Unpin + Send + 'static,
+    MW: AsyncWrite + Unpin + Send + 'static,
+{
     // Send initial data to mask host
     if mask_write.write_all(initial_data).await.is_err() {
         return;
     }
-    
+
     // Relay traffic
     let c2m = tokio::spawn(async move {
         let mut buf = vec![0u8; MASK_BUFFER_SIZE];
@@ -119,7 +159,7 @@ where
             }
         }
     });
-    
+
     let m2c = tokio::spawn(async move {
         let mut buf = vec![0u8; MASK_BUFFER_SIZE];
         loop {
@@ -136,7 +176,7 @@ where
             }
         }
     });
-    
+
     // Wait for either to complete
     tokio::select! {
         _ = c2m => {}
@@ -152,4 +192,4 @@ async fn consume_client_data<R: AsyncRead + Unpin>(mut reader: R) {
             break;
         }
     }
-}
+}

src/proxy/middle_relay.rs

@@ -0,0 +1,295 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+use tracing::{debug, info, trace};
+
+use crate::config::ProxyConfig;
+use crate::crypto::SecureRandom;
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+use crate::proxy::handshake::HandshakeSuccess;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader, CryptoWriter};
+use crate::transport::middle_proxy::{MePool, MeResponse, proto_flags_for_tag};
+
+pub(crate) async fn handle_via_middle_proxy<R, W>(
+    mut crypto_reader: CryptoReader<R>,
+    mut crypto_writer: CryptoWriter<W>,
+    success: HandshakeSuccess,
+    me_pool: Arc<MePool>,
+    stats: Arc<Stats>,
+    _config: Arc<ProxyConfig>,
+    _buffer_pool: Arc<BufferPool>,
+    local_addr: SocketAddr,
+    rng: Arc<SecureRandom>,
+) -> Result<()>
+where
+    R: AsyncRead + Unpin + Send + 'static,
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let user = success.user.clone();
+    let peer = success.peer;
+    let proto_tag = success.proto_tag;
+
+    info!(
+        user = %user,
+        peer = %peer,
+        dc = success.dc_idx,
+        proto = ?proto_tag,
+        mode = "middle_proxy",
+        "Routing via Middle-End"
+    );
+
+    let (conn_id, mut me_rx) = me_pool.registry().register().await;
+
+    stats.increment_user_connects(&user);
+    stats.increment_user_curr_connects(&user);
+
+    let proto_flags = proto_flags_for_tag(proto_tag, me_pool.has_proxy_tag());
+    debug!(
+        user = %user,
+        conn_id,
+        proto_flags = format_args!("0x{:08x}", proto_flags),
+        "ME relay started"
+    );
+
+    let translated_local_addr = me_pool.translate_our_addr(local_addr);
+
+    let result: Result<()> = loop {
+        tokio::select! {
+            client_frame = read_client_payload(&mut crypto_reader, proto_tag) => {
+                match client_frame {
+                    Ok(Some((payload, quickack))) => {
+                        trace!(conn_id, bytes = payload.len(), "C->ME frame");
+                        stats.add_user_octets_from(&user, payload.len() as u64);
+                        let mut flags = proto_flags;
+                        if quickack {
+                            flags |= RPC_FLAG_QUICKACK;
+                        }
+                        if payload.len() >= 8 && payload[..8].iter().all(|b| *b == 0) {
+                            flags |= RPC_FLAG_NOT_ENCRYPTED;
+                        }
+                        me_pool.send_proxy_req(
+                            conn_id,
+                            success.dc_idx,
+                            peer,
+                            translated_local_addr,
+                            &payload,
+                            flags,
+                        ).await?;
+                    }
+                    Ok(None) => {
+                        debug!(conn_id, "Client EOF");
+                        let _ = me_pool.send_close(conn_id).await;
+                        break Ok(());
+                    }
+                    Err(e) => break Err(e),
+                }
+            }
+            me_msg = me_rx.recv() => {
+                match me_msg {
+                    Some(MeResponse::Data { flags, data }) => {
+                        trace!(conn_id, bytes = data.len(), flags, "ME->C data");
+                        stats.add_user_octets_to(&user, data.len() as u64);
+                        write_client_payload(&mut crypto_writer, proto_tag, flags, &data, rng.as_ref()).await?;
+                    }
+                    Some(MeResponse::Ack(confirm)) => {
+                        trace!(conn_id, confirm, "ME->C quickack");
+                        write_client_ack(&mut crypto_writer, proto_tag, confirm).await?;
+                    }
+                    Some(MeResponse::Close) => {
+                        debug!(conn_id, "ME sent close");
+                        break Ok(());
+                    }
+                    None => {
+                        debug!(conn_id, "ME channel closed");
+                        break Err(ProxyError::Proxy("ME connection lost".into()));
+                    }
+                }
+            }
+        }
+    };
+
+    debug!(user = %user, conn_id, "ME relay cleanup");
+    me_pool.registry().unregister(conn_id).await;
+    stats.decrement_user_curr_connects(&user);
+    result
+}
+
+async fn read_client_payload<R>(
+    client_reader: &mut CryptoReader<R>,
+    proto_tag: ProtoTag,
+) -> Result<Option<(Vec<u8>, bool)>>
+where
+    R: AsyncRead + Unpin + Send + 'static,
+{
+    let (len, quickack) = match proto_tag {
+        ProtoTag::Abridged => {
+            let mut first = [0u8; 1];
+            match client_reader.read_exact(&mut first).await {
+                Ok(_) => {}
+                Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => return Ok(None),
+                Err(e) => return Err(ProxyError::Io(e)),
+            }
+
+            let quickack = (first[0] & 0x80) != 0;
+            let len_words = if (first[0] & 0x7f) == 0x7f {
+                let mut ext = [0u8; 3];
+                client_reader
+                    .read_exact(&mut ext)
+                    .await
+                    .map_err(ProxyError::Io)?;
+                u32::from_le_bytes([ext[0], ext[1], ext[2], 0]) as usize
+            } else {
+                (first[0] & 0x7f) as usize
+            };
+
+            let len = len_words
+                .checked_mul(4)
+                .ok_or_else(|| ProxyError::Proxy("Abridged frame length overflow".into()))?;
+            (len, quickack)
+        }
+        ProtoTag::Intermediate | ProtoTag::Secure => {
+            let mut len_buf = [0u8; 4];
+            match client_reader.read_exact(&mut len_buf).await {
+                Ok(_) => {}
+                Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => return Ok(None),
+                Err(e) => return Err(ProxyError::Io(e)),
+            }
+            let quickack = (len_buf[3] & 0x80) != 0;
+            ((u32::from_le_bytes(len_buf) & 0x7fff_ffff) as usize, quickack)
+        }
+    };
+
+    if len > 16 * 1024 * 1024 {
+        return Err(ProxyError::Proxy(format!("Frame too large: {len}")));
+    }
+
+    let mut payload = vec![0u8; len];
+    client_reader
+        .read_exact(&mut payload)
+        .await
+        .map_err(ProxyError::Io)?;
+
+    // Secure Intermediate: remove random padding (last len%4 bytes)
+    if proto_tag == ProtoTag::Secure {
+        let rem = len % 4;
+        if rem != 0 && payload.len() >= rem {
+            payload.truncate(len - rem);
+        }
+    }
+    Ok(Some((payload, quickack)))
+}
+
+async fn write_client_payload<W>(
+    client_writer: &mut CryptoWriter<W>,
+    proto_tag: ProtoTag,
+    flags: u32,
+    data: &[u8],
+    rng: &SecureRandom,
+) -> Result<()>
+where
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let quickack = (flags & RPC_FLAG_QUICKACK) != 0;
+
+    match proto_tag {
+        ProtoTag::Abridged => {
+            if data.len() % 4 != 0 {
+                return Err(ProxyError::Proxy(format!(
+                    "Abridged payload must be 4-byte aligned, got {}",
+                    data.len()
+                )));
+            }
+
+            let len_words = data.len() / 4;
+            if len_words < 0x7f {
+                let mut first = len_words as u8;
+                if quickack {
+                    first |= 0x80;
+                }
+                client_writer
+                    .write_all(&[first])
+                    .await
+                    .map_err(ProxyError::Io)?;
+            } else if len_words < (1 << 24) {
+                let mut first = 0x7fu8;
+                if quickack {
+                    first |= 0x80;
+                }
+                let lw = (len_words as u32).to_le_bytes();
+                client_writer
+                    .write_all(&[first, lw[0], lw[1], lw[2]])
+                    .await
+                    .map_err(ProxyError::Io)?;
+            } else {
+                return Err(ProxyError::Proxy(format!(
+                    "Abridged frame too large: {}",
+                    data.len()
+                )));
+            }
+
+            client_writer
+                .write_all(data)
+                .await
+                .map_err(ProxyError::Io)?;
+        }
+        ProtoTag::Intermediate | ProtoTag::Secure => {
+            let padding_len = if proto_tag == ProtoTag::Secure {
+                (rng.bytes(1)[0] % 4) as usize
+            } else {
+                0
+            };
+            let mut len = (data.len() + padding_len) as u32;
+            if quickack {
+                len |= 0x8000_0000;
+            }
+            client_writer
+                .write_all(&len.to_le_bytes())
+                .await
+                .map_err(ProxyError::Io)?;
+            client_writer
+                .write_all(data)
+                .await
+                .map_err(ProxyError::Io)?;
+            if padding_len > 0 {
+                let pad = rng.bytes(padding_len);
+                client_writer
+                    .write_all(&pad)
+                    .await
+                    .map_err(ProxyError::Io)?;
+            }
+        }
+    }
+
+    // Avoid unconditional per-frame flush (throughput killer on large downloads).
+    // Flush only when low-latency ack semantics are requested or when
+    // CryptoWriter has buffered pending ciphertext that must be drained.
+    if quickack || client_writer.has_pending() {
+        client_writer.flush().await.map_err(ProxyError::Io)?;
+    }
+
+    Ok(())
+}
+
+async fn write_client_ack<W>(
+    client_writer: &mut CryptoWriter<W>,
+    proto_tag: ProtoTag,
+    confirm: u32,
+) -> Result<()>
+where
+    W: AsyncWrite + Unpin + Send + 'static,
+{
+    let bytes = if proto_tag == ProtoTag::Abridged {
+        confirm.to_be_bytes()
+    } else {
+        confirm.to_le_bytes()
+    };
+    client_writer
+        .write_all(&bytes)
+        .await
+        .map_err(ProxyError::Io)?;
+    // ACK should remain low-latency.
+    client_writer.flush().await.map_err(ProxyError::Io)
+}

src/proxy/mod.rs

@@ -1,11 +1,13 @@
 //! Proxy Defs
 
-pub mod handshake;
 pub mod client;
-pub mod relay;
+pub mod direct_relay;
+pub mod handshake;
 pub mod masking;
+pub mod middle_relay;
+pub mod relay;
 
-pub use handshake::*;
 pub use client::ClientHandler;
+pub use handshake::*;
+pub use masking::*;
 pub use relay::*;
-pub use masking::*;

src/proxy/relay.rs

@@ -1,195 +1,466 @@
-//! Bidirectional Relay
-    
-    use std::sync::Arc;
-    use std::time::Duration;
-    use tokio::io::{AsyncRead, AsyncWrite, AsyncReadExt, AsyncWriteExt};
-    use tokio::time::Instant;
-    use tracing::{debug, trace, warn};
-    use crate::error::Result;
-    use crate::stats::Stats;
-    use crate::stream::BufferPool;
-    
-    // Activity timeout for iOS compatibility (30 minutes)
-    const ACTIVITY_TIMEOUT_SECS: u64 = 1800;
-    
-    /// Relay data bidirectionally between client and server.
-    ///
-    /// Uses a single-task select!-based loop instead of spawning two tasks.
-    /// This eliminates:
-    /// - 2× task spawn overhead per connection
-    /// - Zombie task problem (old code used select! on JoinHandles but
-    ///   never aborted the losing task — it would run for up to 30 min)
-    /// - Extra Arc<AtomicU64> allocations for cross-task byte counters
-    ///
-    /// The flush()-per-write was also removed: TCP_NODELAY is set on all
-    /// sockets (socket.rs), so data is pushed immediately without Nagle
-    /// buffering. Explicit flush() on every small read was causing a
-    /// syscall storm and defeating CryptoWriter's internal coalescing.
-    pub async fn relay_bidirectional<CR, CW, SR, SW>(
-        mut client_reader: CR,
-        mut client_writer: CW,
-        mut server_reader: SR,
-        mut server_writer: SW,
-        user: &str,
+//! Bidirectional Relay — poll-based, no head-of-line blocking
+//!
+//! ## What changed and why
+//!
+//! Previous implementation used a single-task `select! { biased; ... }` loop
+//! where each branch called `write_all()`. This caused head-of-line blocking:
+//! while `write_all()` waited for a slow writer (e.g. client on 3G downloading
+//! media), the entire loop was blocked — the other direction couldn't make progress.
+//!
+//! Symptoms observed in production:
+//! - Media loading at ~8 KB/s despite fast server connection
+//! - Stop-and-go pattern with 50–500ms gaps between chunks
+//! - `biased` select starving S→C direction
+//! - Some users unable to load media at all
+//!
+//! ## New architecture
+//!
+//! Uses `tokio::io::copy_bidirectional` which polls both directions concurrently
+//! in a single task via non-blocking `poll_read` / `poll_write` calls:
+//!
+//! Old (select! + write_all — BLOCKING):
+//!
+//!   loop {
+//!       select! {
+//!           biased;
+//!           data = client.read()  => { server.write_all(data).await; }  ← BLOCKS here
+//!           data = server.read()  => { client.write_all(data).await; }  ← can't run
+//!       }
+//!   }
+//!
+//! New (copy_bidirectional — CONCURRENT):
+//!
+//!   poll(cx) {
+//!       // Both directions polled in the same poll cycle
+//!       C→S: poll_read(client) → poll_write(server)   // non-blocking
+//!       S→C: poll_read(server) → poll_write(client)   // non-blocking
+//!       // If one writer is Pending, the other direction still progresses
+//!   }
+//!
+//! Benefits:
+//! - No head-of-line blocking: slow client download doesn't block uploads
+//! - No biased starvation: fair polling of both directions
+//! - Proper flush: `copy_bidirectional` calls `poll_flush` when reader stalls,
+//!   so CryptoWriter's pending ciphertext is always drained (fixes "stuck at 95%")
+//! - No deadlock risk: old write_all could deadlock when both TCP buffers filled;
+//!   poll-based approach lets TCP flow control work correctly
+//!
+//! Stats tracking:
+//! - `StatsIo` wraps client side, intercepts `poll_read` / `poll_write`
+//! - `poll_read` on client = C→S (client sending) → `octets_from`, `msgs_from`
+//! - `poll_write` on client = S→C (to client)     → `octets_to`, `msgs_to`
+//! - `SharedCounters` (atomics) let the watchdog read stats without locking
+
+use std::io;
+use std::pin::Pin;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::task::{Context, Poll};
+use std::time::Duration;
+use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt, ReadBuf, copy_bidirectional};
+use tokio::time::Instant;
+use tracing::{debug, trace, warn};
+use crate::error::Result;
+use crate::stats::Stats;
+use crate::stream::BufferPool;
+
+// ============= Constants =============
+
+/// Activity timeout for iOS compatibility.
+///
+/// iOS keeps Telegram connections alive in background for up to 30 minutes.
+/// Closing earlier causes unnecessary reconnects and handshake overhead.
+const ACTIVITY_TIMEOUT: Duration = Duration::from_secs(1800);
+
+/// Watchdog check interval — also used for periodic rate logging.
+///
+/// 10 seconds gives responsive timeout detection (±10s accuracy)
+/// without measurable overhead from atomic reads.
+const WATCHDOG_INTERVAL: Duration = Duration::from_secs(10);
+
+// ============= CombinedStream =============
+
+/// Combines separate read and write halves into a single bidirectional stream.
+///
+/// `copy_bidirectional` requires `AsyncRead + AsyncWrite` on each side,
+/// but the handshake layer produces split reader/writer pairs
+/// (e.g. `CryptoReader<FakeTlsReader<OwnedReadHalf>>` + `CryptoWriter<...>`).
+///
+/// This wrapper reunifies them with zero overhead — each trait method
+/// delegates directly to the corresponding half. No buffering, no copies.
+///
+/// Safety: `poll_read` only touches `reader`, `poll_write` only touches `writer`,
+/// so there's no aliasing even though both are called on the same `&mut self`.
+struct CombinedStream<R, W> {
+    reader: R,
+    writer: W,
+}
+
+impl<R, W> CombinedStream<R, W> {
+    fn new(reader: R, writer: W) -> Self {
+        Self { reader, writer }
+    }
+}
+
+impl<R: AsyncRead + Unpin, W: Unpin> AsyncRead for CombinedStream<R, W> {
+    #[inline]
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().reader).poll_read(cx, buf)
+    }
+}
+
+impl<R: Unpin, W: AsyncWrite + Unpin> AsyncWrite for CombinedStream<R, W> {
+    #[inline]
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        Pin::new(&mut self.get_mut().writer).poll_write(cx, buf)
+    }
+
+    #[inline]
+    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().writer).poll_flush(cx)
+    }
+
+    #[inline]
+    fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().writer).poll_shutdown(cx)
+    }
+}
+
+// ============= SharedCounters =============
+
+/// Atomic counters shared between the relay (via StatsIo) and the watchdog task.
+///
+/// Using `Relaxed` ordering is sufficient because:
+/// - Counters are monotonically increasing (no ABA problem)
+/// - Slight staleness in watchdog reads is harmless (±10s check interval anyway)
+/// - No ordering dependencies between different counters
+struct SharedCounters {
+    /// Bytes read from client (C→S direction)
+    c2s_bytes: AtomicU64,
+    /// Bytes written to client (S→C direction)
+    s2c_bytes: AtomicU64,
+    /// Number of poll_read completions (≈ C→S chunks)
+    c2s_ops: AtomicU64,
+    /// Number of poll_write completions (≈ S→C chunks)
+    s2c_ops: AtomicU64,
+    /// Milliseconds since relay epoch of last I/O activity
+    last_activity_ms: AtomicU64,
+}
+
+impl SharedCounters {
+    fn new() -> Self {
+        Self {
+            c2s_bytes: AtomicU64::new(0),
+            s2c_bytes: AtomicU64::new(0),
+            c2s_ops: AtomicU64::new(0),
+            s2c_ops: AtomicU64::new(0),
+            last_activity_ms: AtomicU64::new(0),
+        }
+    }
+
+    /// Record activity at this instant.
+    #[inline]
+    fn touch(&self, now: Instant, epoch: Instant) {
+        let ms = now.duration_since(epoch).as_millis() as u64;
+        self.last_activity_ms.store(ms, Ordering::Relaxed);
+    }
+
+    /// How long since last recorded activity.
+    fn idle_duration(&self, now: Instant, epoch: Instant) -> Duration {
+        let last_ms = self.last_activity_ms.load(Ordering::Relaxed);
+        let now_ms = now.duration_since(epoch).as_millis() as u64;
+        Duration::from_millis(now_ms.saturating_sub(last_ms))
+    }
+}
+
+// ============= StatsIo =============
+
+/// Transparent I/O wrapper that tracks per-user statistics and activity.
+///
+/// Wraps the **client** side of the relay. Direction mapping:
+///
+/// | poll method  | direction | stats updated                        |
+/// |-------------|-----------|--------------------------------------|
+/// | `poll_read`  | C→S       | `octets_from`, `msgs_from`, counters |
+/// | `poll_write` | S→C       | `octets_to`, `msgs_to`, counters     |
+///
+/// Both update the shared activity timestamp for the watchdog.
+///
+/// Note on message counts: the original code counted one `read()`/`write_all()`
+/// as one "message". Here we count `poll_read`/`poll_write` completions instead.
+/// Byte counts are identical; op counts may differ slightly due to different
+/// internal buffering in `copy_bidirectional`. This is fine for monitoring.
+struct StatsIo<S> {
+    inner: S,
+    counters: Arc<SharedCounters>,
+    stats: Arc<Stats>,
+    user: String,
+    epoch: Instant,
+}
+
+impl<S> StatsIo<S> {
+    fn new(
+        inner: S,
+        counters: Arc<SharedCounters>,
         stats: Arc<Stats>,
-        buffer_pool: Arc<BufferPool>,
-    ) -> Result<()>
-    where
-        CR: AsyncRead + Unpin + Send + 'static,
-        CW: AsyncWrite + Unpin + Send + 'static,
-        SR: AsyncRead + Unpin + Send + 'static,
-        SW: AsyncWrite + Unpin + Send + 'static,
-    {
-        // Get buffers from pool — one per direction
-        let mut c2s_buf = buffer_pool.get();
-        let cap = c2s_buf.capacity();
-        c2s_buf.resize(cap, 0);
-    
-        let mut s2c_buf = buffer_pool.get();
-        let cap = s2c_buf.capacity();
-        s2c_buf.resize(cap, 0);
-    
-        let activity_timeout = Duration::from_secs(ACTIVITY_TIMEOUT_SECS);
-    
-        let mut c2s_total: u64 = 0;
-        let mut s2c_total: u64 = 0;
-        let mut c2s_msgs: u64 = 0;
-        let mut s2c_msgs: u64 = 0;
-    
-        // For periodic rate logging
-        let mut c2s_prev: u64 = 0;
-        let mut s2c_prev: u64 = 0;
-        let mut last_log = Instant::now();
-    
-        let user_owned = user.to_string();
-    
-        loop {
-            tokio::select! {
-                biased;
-    
-                // Client -> Server direction
-                result = tokio::time::timeout(activity_timeout, client_reader.read(&mut c2s_buf)) => {
-                    match result {
-                        Err(_) => {
-                            // Activity timeout
-                            warn!(
-                                user = %user_owned,
-                                c2s_bytes = c2s_total,
-                                s2c_bytes = s2c_total,
-                                "Activity timeout (C->S)"
-                            );
-                            break;
-                        }
-                        Ok(Ok(0)) => {
-                            // Client closed
-                            debug!(
-                                user = %user_owned,
-                                c2s_bytes = c2s_total,
-                                s2c_bytes = s2c_total,
-                                "Client closed connection"
-                            );
-                            break;
-                        }
-                        Ok(Ok(n)) => {
-                            c2s_total += n as u64;
-                            c2s_msgs += 1;
-    
-                            stats.add_user_octets_from(&user_owned, n as u64);
-                            stats.increment_user_msgs_from(&user_owned);
-    
-                            trace!(user = %user_owned, bytes = n, "C->S");
-    
-                            // Write without flush — TCP_NODELAY handles push
-                            if let Err(e) = server_writer.write_all(&c2s_buf[..n]).await {
-                                debug!(user = %user_owned, error = %e, "Write to server failed");
-                                break;
-                            }
-                        }
-                        Ok(Err(e)) => {
-                            debug!(user = %user_owned, error = %e, "Client read error");
-                            break;
-                        }
-                    }
-                }
-    
-                // Server -> Client direction
-                result = tokio::time::timeout(activity_timeout, server_reader.read(&mut s2c_buf)) => {
-                    match result {
-                        Err(_) => {
-                            warn!(
-                                user = %user_owned,
-                                c2s_bytes = c2s_total,
-                                s2c_bytes = s2c_total,
-                                "Activity timeout (S->C)"
-                            );
-                            break;
-                        }
-                        Ok(Ok(0)) => {
-                            debug!(
-                                user = %user_owned,
-                                c2s_bytes = c2s_total,
-                                s2c_bytes = s2c_total,
-                                "Server closed connection"
-                            );
-                            break;
-                        }
-                        Ok(Ok(n)) => {
-                            s2c_total += n as u64;
-                            s2c_msgs += 1;
-    
-                            stats.add_user_octets_to(&user_owned, n as u64);
-                            stats.increment_user_msgs_to(&user_owned);
-    
-                            trace!(user = %user_owned, bytes = n, "S->C");
-    
-                            if let Err(e) = client_writer.write_all(&s2c_buf[..n]).await {
-                                debug!(user = %user_owned, error = %e, "Write to client failed");
-                                break;
-                            }
-                        }
-                        Ok(Err(e)) => {
-                            debug!(user = %user_owned, error = %e, "Server read error");
-                            break;
-                        }
-                    }
+        user: String,
+        epoch: Instant,
+    ) -> Self {
+        // Mark initial activity so the watchdog doesn't fire before data flows
+        counters.touch(Instant::now(), epoch);
+        Self { inner, counters, stats, user, epoch }
+    }
+}
+
+impl<S: AsyncRead + Unpin> AsyncRead for StatsIo<S> {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        let this = self.get_mut();
+        let before = buf.filled().len();
+
+        match Pin::new(&mut this.inner).poll_read(cx, buf) {
+            Poll::Ready(Ok(())) => {
+                let n = buf.filled().len() - before;
+                if n > 0 {
+                    // C→S: client sent data
+                    this.counters.c2s_bytes.fetch_add(n as u64, Ordering::Relaxed);
+                    this.counters.c2s_ops.fetch_add(1, Ordering::Relaxed);
+                    this.counters.touch(Instant::now(), this.epoch);
+
+                    this.stats.add_user_octets_from(&this.user, n as u64);
+                    this.stats.increment_user_msgs_from(&this.user);
+
+                    trace!(user = %this.user, bytes = n, "C->S");
                 }
+                Poll::Ready(Ok(()))
             }
-    
-            // Periodic rate logging (every 10s)
-            let elapsed = last_log.elapsed();
-            if elapsed > Duration::from_secs(10) {
-                let secs = elapsed.as_secs_f64();
-                let c2s_delta = c2s_total - c2s_prev;
-                let s2c_delta = s2c_total - s2c_prev;
-    
+            other => other,
+        }
+    }
+}
+
+impl<S: AsyncWrite + Unpin> AsyncWrite for StatsIo<S> {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        let this = self.get_mut();
+
+        match Pin::new(&mut this.inner).poll_write(cx, buf) {
+            Poll::Ready(Ok(n)) => {
+                if n > 0 {
+                    // S→C: data written to client
+                    this.counters.s2c_bytes.fetch_add(n as u64, Ordering::Relaxed);
+                    this.counters.s2c_ops.fetch_add(1, Ordering::Relaxed);
+                    this.counters.touch(Instant::now(), this.epoch);
+
+                    this.stats.add_user_octets_to(&this.user, n as u64);
+                    this.stats.increment_user_msgs_to(&this.user);
+
+                    trace!(user = %this.user, bytes = n, "S->C");
+                }
+                Poll::Ready(Ok(n))
+            }
+            other => other,
+        }
+    }
+
+    #[inline]
+    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().inner).poll_flush(cx)
+    }
+
+    #[inline]
+    fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Pin::new(&mut self.get_mut().inner).poll_shutdown(cx)
+    }
+}
+
+// ============= Relay =============
+
+/// Relay data bidirectionally between client and server.
+///
+/// Uses `tokio::io::copy_bidirectional` for concurrent, non-blocking data transfer.
+///
+/// ## API compatibility
+///
+/// Signature is identical to the previous implementation. The `_buffer_pool`
+/// parameter is retained for call-site compatibility — `copy_bidirectional`
+/// manages its own internal buffers (8 KB per direction).
+///
+/// ## Guarantees preserved
+///
+/// - Activity timeout: 30 minutes of inactivity → clean shutdown
+/// - Per-user stats: bytes and ops counted per direction
+/// - Periodic rate logging: every 10 seconds when active
+/// - Clean shutdown: both write sides are shut down on exit
+/// - Error propagation: I/O errors are returned as `ProxyError::Io`
+pub async fn relay_bidirectional<CR, CW, SR, SW>(
+    client_reader: CR,
+    client_writer: CW,
+    server_reader: SR,
+    server_writer: SW,
+    user: &str,
+    stats: Arc<Stats>,
+    _buffer_pool: Arc<BufferPool>,
+) -> Result<()>
+where
+    CR: AsyncRead + Unpin + Send + 'static,
+    CW: AsyncWrite + Unpin + Send + 'static,
+    SR: AsyncRead + Unpin + Send + 'static,
+    SW: AsyncWrite + Unpin + Send + 'static,
+{
+    let epoch = Instant::now();
+    let counters = Arc::new(SharedCounters::new());
+    let user_owned = user.to_string();
+
+    // ── Combine split halves into bidirectional streams ──────────────
+    let client_combined = CombinedStream::new(client_reader, client_writer);
+    let mut server = CombinedStream::new(server_reader, server_writer);
+
+    // Wrap client with stats/activity tracking
+    let mut client = StatsIo::new(
+        client_combined,
+        Arc::clone(&counters),
+        Arc::clone(&stats),
+        user_owned.clone(),
+        epoch,
+    );
+
+    // ── Watchdog: activity timeout + periodic rate logging ──────────
+    let wd_counters = Arc::clone(&counters);
+    let wd_user = user_owned.clone();
+
+    let watchdog = async {
+        let mut prev_c2s: u64 = 0;
+        let mut prev_s2c: u64 = 0;
+
+        loop {
+            tokio::time::sleep(WATCHDOG_INTERVAL).await;
+
+            let now = Instant::now();
+            let idle = wd_counters.idle_duration(now, epoch);
+
+            // ── Activity timeout ────────────────────────────────────
+            if idle >= ACTIVITY_TIMEOUT {
+                let c2s = wd_counters.c2s_bytes.load(Ordering::Relaxed);
+                let s2c = wd_counters.s2c_bytes.load(Ordering::Relaxed);
+                warn!(
+                    user = %wd_user,
+                    c2s_bytes = c2s,
+                    s2c_bytes = s2c,
+                    idle_secs = idle.as_secs(),
+                    "Activity timeout"
+                );
+                return; // Causes select! to cancel copy_bidirectional
+            }
+
+            // ── Periodic rate logging ───────────────────────────────
+            let c2s = wd_counters.c2s_bytes.load(Ordering::Relaxed);
+            let s2c = wd_counters.s2c_bytes.load(Ordering::Relaxed);
+            let c2s_delta = c2s - prev_c2s;
+            let s2c_delta = s2c - prev_s2c;
+
+            if c2s_delta > 0 || s2c_delta > 0 {
+                let secs = WATCHDOG_INTERVAL.as_secs_f64();
                 debug!(
-                    user = %user_owned,
+                    user = %wd_user,
                     c2s_kbps = (c2s_delta as f64 / secs / 1024.0) as u64,
                     s2c_kbps = (s2c_delta as f64 / secs / 1024.0) as u64,
-                    c2s_total = c2s_total,
-                    s2c_total = s2c_total,
+                    c2s_total = c2s,
+                    s2c_total = s2c,
                     "Relay active"
                 );
-    
-                c2s_prev = c2s_total;
-                s2c_prev = s2c_total;
-                last_log = Instant::now();
             }
+
+            prev_c2s = c2s;
+            prev_s2c = s2c;
+        }
+    };
+
+    // ── Run bidirectional copy + watchdog concurrently ───────────────
+    //
+    // copy_bidirectional polls both directions in the same poll() call:
+    //   C→S: poll_read(client/StatsIo) → poll_write(server)
+    //   S→C: poll_read(server)         → poll_write(client/StatsIo)
+    //
+    // When one direction's writer returns Pending, the other direction
+    // continues — no head-of-line blocking.
+    //
+    // When the watchdog fires, select! drops the copy future,
+    // releasing the &mut borrows on client and server.
+    let copy_result = tokio::select! {
+        result = copy_bidirectional(&mut client, &mut server) => Some(result),
+        _ = watchdog => None, // Activity timeout — cancel relay
+    };
+
+    // ── Clean shutdown ──────────────────────────────────────────────
+    // After select!, the losing future is dropped, borrows released.
+    // Shut down both write sides for clean TCP FIN.
+    let _ = client.shutdown().await;
+    let _ = server.shutdown().await;
+
+    // ── Final logging ───────────────────────────────────────────────
+    let c2s_ops = counters.c2s_ops.load(Ordering::Relaxed);
+    let s2c_ops = counters.s2c_ops.load(Ordering::Relaxed);
+    let duration = epoch.elapsed();
+
+    match copy_result {
+        Some(Ok((c2s, s2c))) => {
+            // Normal completion — one side closed the connection
+            debug!(
+                user = %user_owned,
+                c2s_bytes = c2s,
+                s2c_bytes = s2c,
+                c2s_msgs = c2s_ops,
+                s2c_msgs = s2c_ops,
+                duration_secs = duration.as_secs(),
+                "Relay finished"
+            );
+            Ok(())
+        }
+        Some(Err(e)) => {
+            // I/O error in one of the directions
+            let c2s = counters.c2s_bytes.load(Ordering::Relaxed);
+            let s2c = counters.s2c_bytes.load(Ordering::Relaxed);
+            debug!(
+                user = %user_owned,
+                c2s_bytes = c2s,
+                s2c_bytes = s2c,
+                c2s_msgs = c2s_ops,
+                s2c_msgs = s2c_ops,
+                duration_secs = duration.as_secs(),
+                error = %e,
+                "Relay error"
+            );
+            Err(e.into())
+        }
+        None => {
+            // Activity timeout (watchdog fired)
+            let c2s = counters.c2s_bytes.load(Ordering::Relaxed);
+            let s2c = counters.s2c_bytes.load(Ordering::Relaxed);
+            debug!(
+                user = %user_owned,
+                c2s_bytes = c2s,
+                s2c_bytes = s2c,
+                c2s_msgs = c2s_ops,
+                s2c_msgs = s2c_ops,
+                duration_secs = duration.as_secs(),
+                "Relay finished (activity timeout)"
+            );
+            Ok(())
         }
-    
-        // Clean shutdown of both directions
-        let _ = server_writer.shutdown().await;
-        let _ = client_writer.shutdown().await;
-    
-        debug!(
-            user = %user_owned,
-            c2s_bytes = c2s_total,
-            s2c_bytes = s2c_total,
-            c2s_msgs = c2s_msgs,
-            s2c_msgs = s2c_msgs,
-            "Relay finished"
-        );
-    
-        Ok(())
     }
-    
+}

src/stats/mod.rs

@@ -97,6 +97,12 @@ impl Stats {
             .unwrap_or(0)
     }
     
+    pub fn get_handshake_timeouts(&self) -> u64 { self.handshake_timeouts.load(Ordering::Relaxed) }
+
+    pub fn iter_user_stats(&self) -> dashmap::iter::Iter<'_, String, UserStats> {
+        self.user_stats.iter()
+    }
+
     pub fn uptime_secs(&self) -> f64 {
         self.start_time.read()
             .map(|t| t.elapsed().as_secs_f64())
@@ -212,28 +218,41 @@ impl ReplayChecker {
         (hasher.finish() as usize) & self.shard_mask
     }
 
-    fn check(&self, data: &[u8]) -> bool {
+    fn check_and_add_internal(&self, data: &[u8]) -> bool {
         self.checks.fetch_add(1, Ordering::Relaxed);
         let idx = self.get_shard_idx(data);
         let mut shard = self.shards[idx].lock();
-        let found = shard.check(data, Instant::now(), self.window);
+        let now = Instant::now();
+        let found = shard.check(data, now, self.window);
         if found {
             self.hits.fetch_add(1, Ordering::Relaxed);
+        } else {
+            shard.add(data, now, self.window);
+            self.additions.fetch_add(1, Ordering::Relaxed);
         }
         found
     }
 
-    fn add(&self, data: &[u8]) {
+    fn add_only(&self, data: &[u8]) {
         self.additions.fetch_add(1, Ordering::Relaxed);
         let idx = self.get_shard_idx(data);
         let mut shard = self.shards[idx].lock();
         shard.add(data, Instant::now(), self.window);
     }
 
-    pub fn check_handshake(&self, data: &[u8]) -> bool { self.check(data) }
-    pub fn add_handshake(&self, data: &[u8]) { self.add(data) }
-    pub fn check_tls_digest(&self, data: &[u8]) -> bool { self.check(data) }
-    pub fn add_tls_digest(&self, data: &[u8]) { self.add(data) }
+    pub fn check_and_add_handshake(&self, data: &[u8]) -> bool {
+        self.check_and_add_internal(data)
+    }
+
+    pub fn check_and_add_tls_digest(&self, data: &[u8]) -> bool {
+        self.check_and_add_internal(data)
+    }
+
+    // Compatibility helpers (non-atomic split operations) — prefer check_and_add_*.
+    pub fn check_handshake(&self, data: &[u8]) -> bool { self.check_and_add_handshake(data) }
+    pub fn add_handshake(&self, data: &[u8]) { self.add_only(data) }
+    pub fn check_tls_digest(&self, data: &[u8]) -> bool { self.check_and_add_tls_digest(data) }
+    pub fn add_tls_digest(&self, data: &[u8]) { self.add_only(data) }
     
     pub fn stats(&self) -> ReplayStats {
         let mut total_entries = 0;
@@ -326,10 +345,9 @@ mod tests {
     #[test]
     fn test_replay_checker_basic() {
         let checker = ReplayChecker::new(100, Duration::from_secs(60));
-        assert!(!checker.check_handshake(b"test1"));
-        checker.add_handshake(b"test1");
-        assert!(checker.check_handshake(b"test1"));
-        assert!(!checker.check_handshake(b"test2"));
+        assert!(!checker.check_handshake(b"test1")); // first time, inserts
+        assert!(checker.check_handshake(b"test1"));  // duplicate
+        assert!(!checker.check_handshake(b"test2")); // new key inserts
     }
     
     #[test]
@@ -343,7 +361,7 @@ mod tests {
     #[test]
     fn test_replay_checker_expiration() {
         let checker = ReplayChecker::new(100, Duration::from_millis(50));
-        checker.add_handshake(b"expire");
+        assert!(!checker.check_handshake(b"expire"));
         assert!(checker.check_handshake(b"expire"));
         std::thread::sleep(Duration::from_millis(100));
         assert!(!checker.check_handshake(b"expire"));
@@ -352,25 +370,25 @@ mod tests {
     #[test]
     fn test_replay_checker_stats() {
         let checker = ReplayChecker::new(100, Duration::from_secs(60));
-        checker.add_handshake(b"k1");
-        checker.add_handshake(b"k2");
-        checker.check_handshake(b"k1");
-        checker.check_handshake(b"k3");
+        assert!(!checker.check_handshake(b"k1"));
+        assert!(!checker.check_handshake(b"k2"));
+        assert!(checker.check_handshake(b"k1"));
+        assert!(!checker.check_handshake(b"k3"));
         let stats = checker.stats();
-        assert_eq!(stats.total_additions, 2);
-        assert_eq!(stats.total_checks, 2);
+        assert_eq!(stats.total_additions, 3);
+        assert_eq!(stats.total_checks, 4);
         assert_eq!(stats.total_hits, 1);
     }
     
     #[test]
     fn test_replay_checker_many_keys() {
-        let checker = ReplayChecker::new(1000, Duration::from_secs(60));
+        let checker = ReplayChecker::new(10_000, Duration::from_secs(60));
         for i in 0..500u32 {
-            checker.add(&i.to_le_bytes());
+            checker.add_only(&i.to_le_bytes());
         }
         for i in 0..500u32 {
-            assert!(checker.check(&i.to_le_bytes()));
+            assert!(checker.check_handshake(&i.to_le_bytes()));
         }
         assert_eq!(checker.stats().total_entries, 500);
     }
-}
+}

src/stream/buffer_pool.rs

@@ -381,9 +381,14 @@ mod tests {
         // Add a buffer to pool
         pool.preallocate(1);
         
-        // Now try_get should succeed
-        assert!(pool.try_get().is_some());
+        // Now try_get should succeed once while the buffer is held
+        let buf = pool.try_get();
+        assert!(buf.is_some());
+        // While buffer is held, pool is empty
         assert!(pool.try_get().is_none());
+        // Drop buffer -> returns to pool, should be obtainable again
+        drop(buf);
+        assert!(pool.try_get().is_some());
     }
     
     #[test]
@@ -448,4 +453,4 @@ mod tests {
         // All buffers should be returned
         assert!(stats.pooled > 0);
     }
-}
+}

src/stream/tls_stream.rs

@@ -32,7 +32,7 @@
 //! and uploads from iOS will break (media/file sending), while small traffic
 //! may still work.
 
-use bytes::{Bytes, BytesMut, BufMut};
+use bytes::{Bytes, BytesMut};
 use std::io::{self, Error, ErrorKind, Result};
 use std::pin::Pin;
 use std::task::{Context, Poll};
@@ -51,9 +51,10 @@ use super::state::{StreamState, HeaderBuffer, YieldBuffer, WriteBuffer};
 /// TLS record header size (type + version + length)
 const TLS_HEADER_SIZE: usize = 5;
 
-/// Maximum TLS fragment size per spec (plaintext fragment).
-/// We use this for *outgoing* chunking, because we build plain ApplicationData records.
-const MAX_TLS_PAYLOAD: usize = 16384;
+/// Maximum TLS fragment size we emit for Application Data.
+/// Real TLS 1.3 ciphertexts often add ~16-24 bytes AEAD overhead, so to mimic
+/// on-the-wire record sizes we allow up to 16384 + 24 bytes of plaintext.
+const MAX_TLS_PAYLOAD: usize = 16384 + 24;
 
 /// Maximum pending write buffer for one record remainder.
 /// Note: we never queue unlimited amount of data here; state holds at most one record.
@@ -918,10 +919,8 @@ mod tests {
         let reader = ChunkedReader::new(&record, 100);
         let mut tls_reader = FakeTlsReader::new(reader);
         
-        let mut buf = vec![0u8; payload.len()];
-        tls_reader.read_exact(&mut buf).await.unwrap();
-        
-        assert_eq!(&buf, payload);
+        let buf = tls_reader.read_exact(payload.len()).await.unwrap();
+        assert_eq!(&buf[..], payload);
     }
     
     #[tokio::test]
@@ -935,13 +934,11 @@ mod tests {
         let reader = ChunkedReader::new(&data, 100);
         let mut tls_reader = FakeTlsReader::new(reader);
         
-        let mut buf1 = vec![0u8; payload1.len()];
-        tls_reader.read_exact(&mut buf1).await.unwrap();
-        assert_eq!(&buf1, payload1);
+        let buf1 = tls_reader.read_exact(payload1.len()).await.unwrap();
+        assert_eq!(&buf1[..], payload1);
         
-        let mut buf2 = vec![0u8; payload2.len()];
-        tls_reader.read_exact(&mut buf2).await.unwrap();
-        assert_eq!(&buf2, payload2);
+        let buf2 = tls_reader.read_exact(payload2.len()).await.unwrap();
+        assert_eq!(&buf2[..], payload2);
     }
     
     #[tokio::test]
@@ -953,10 +950,9 @@ mod tests {
         let reader = ChunkedReader::new(&record, 1); // 1 byte at a time!
         let mut tls_reader = FakeTlsReader::new(reader);
         
-        let mut buf = vec![0u8; payload.len()];
-        tls_reader.read_exact(&mut buf).await.unwrap();
+        let buf = tls_reader.read_exact(payload.len()).await.unwrap();
         
-        assert_eq!(&buf, payload);
+        assert_eq!(&buf[..], payload);
     }
     
     #[tokio::test]
@@ -967,10 +963,9 @@ mod tests {
         let reader = ChunkedReader::new(&record, 7); // Awkward chunk size
         let mut tls_reader = FakeTlsReader::new(reader);
         
-        let mut buf = vec![0u8; payload.len()];
-        tls_reader.read_exact(&mut buf).await.unwrap();
+        let buf = tls_reader.read_exact(payload.len()).await.unwrap();
         
-        assert_eq!(&buf, payload);
+        assert_eq!(&buf[..], payload);
     }
     
     #[tokio::test]
@@ -983,10 +978,9 @@ mod tests {
         let reader = ChunkedReader::new(&data, 100);
         let mut tls_reader = FakeTlsReader::new(reader);
         
-        let mut buf = vec![0u8; payload.len()];
-        tls_reader.read_exact(&mut buf).await.unwrap();
+        let buf = tls_reader.read_exact(payload.len()).await.unwrap();
         
-        assert_eq!(&buf, payload);
+        assert_eq!(&buf[..], payload);
     }
     
     #[tokio::test]
@@ -1000,10 +994,9 @@ mod tests {
         let reader = ChunkedReader::new(&data, 3); // Small chunks
         let mut tls_reader = FakeTlsReader::new(reader);
         
-        let mut buf = vec![0u8; payload.len()];
-        tls_reader.read_exact(&mut buf).await.unwrap();
+        let buf = tls_reader.read_exact(payload.len()).await.unwrap();
         
-        assert_eq!(&buf, payload);
+        assert_eq!(&buf[..], payload);
     }
     
     #[tokio::test]
@@ -1244,4 +1237,4 @@ mod tests {
         let bytes = header.to_bytes();
         assert_eq!(bytes, [0x17, 0x03, 0x03, 0x12, 0x34]);
     }
-}
+}

src/transport/middle_proxy/codec.rs

@@ -0,0 +1,180 @@
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+use crate::crypto::{AesCbc, crc32};
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+
+pub(crate) fn build_rpc_frame(seq_no: i32, payload: &[u8]) -> Vec<u8> {
+    let total_len = (4 + 4 + payload.len() + 4) as u32;
+    let mut frame = Vec::with_capacity(total_len as usize);
+    frame.extend_from_slice(&total_len.to_le_bytes());
+    frame.extend_from_slice(&seq_no.to_le_bytes());
+    frame.extend_from_slice(payload);
+    let c = crc32(&frame);
+    frame.extend_from_slice(&c.to_le_bytes());
+    frame
+}
+
+pub(crate) async fn read_rpc_frame_plaintext(
+    rd: &mut (impl AsyncReadExt + Unpin),
+) -> Result<(i32, Vec<u8>)> {
+    let mut len_buf = [0u8; 4];
+    rd.read_exact(&mut len_buf).await.map_err(ProxyError::Io)?;
+    let total_len = u32::from_le_bytes(len_buf) as usize;
+
+    if !(12..=(1 << 24)).contains(&total_len) {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "Bad RPC frame length: {total_len}"
+        )));
+    }
+
+    let mut rest = vec![0u8; total_len - 4];
+    rd.read_exact(&mut rest).await.map_err(ProxyError::Io)?;
+
+    let mut full = Vec::with_capacity(total_len);
+    full.extend_from_slice(&len_buf);
+    full.extend_from_slice(&rest);
+
+    let crc_offset = total_len - 4;
+    let expected_crc = u32::from_le_bytes(full[crc_offset..crc_offset + 4].try_into().unwrap());
+    let actual_crc = crc32(&full[..crc_offset]);
+    if expected_crc != actual_crc {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "CRC mismatch: 0x{expected_crc:08x} vs 0x{actual_crc:08x}"
+        )));
+    }
+
+    let seq_no = i32::from_le_bytes(full[4..8].try_into().unwrap());
+    let payload = full[8..crc_offset].to_vec();
+    Ok((seq_no, payload))
+}
+
+pub(crate) fn build_nonce_payload(key_selector: u32, crypto_ts: u32, nonce: &[u8; 16]) -> [u8; 32] {
+    let mut p = [0u8; 32];
+    p[0..4].copy_from_slice(&RPC_NONCE_U32.to_le_bytes());
+    p[4..8].copy_from_slice(&key_selector.to_le_bytes());
+    p[8..12].copy_from_slice(&RPC_CRYPTO_AES_U32.to_le_bytes());
+    p[12..16].copy_from_slice(&crypto_ts.to_le_bytes());
+    p[16..32].copy_from_slice(nonce);
+    p
+}
+
+pub(crate) fn parse_nonce_payload(d: &[u8]) -> Result<(u32, u32, u32, [u8; 16])> {
+    if d.len() < 32 {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "Nonce payload too short: {} bytes",
+            d.len()
+        )));
+    }
+
+    let t = u32::from_le_bytes(d[0..4].try_into().unwrap());
+    if t != RPC_NONCE_U32 {
+        return Err(ProxyError::InvalidHandshake(format!(
+            "Expected RPC_NONCE 0x{RPC_NONCE_U32:08x}, got 0x{t:08x}"
+        )));
+    }
+
+    let key_select = u32::from_le_bytes(d[4..8].try_into().unwrap());
+    let schema = u32::from_le_bytes(d[8..12].try_into().unwrap());
+    let ts = u32::from_le_bytes(d[12..16].try_into().unwrap());
+    let mut nonce = [0u8; 16];
+    nonce.copy_from_slice(&d[16..32]);
+    Ok((key_select, schema, ts, nonce))
+}
+
+pub(crate) fn build_handshake_payload(
+    our_ip: [u8; 4],
+    our_port: u16,
+    peer_ip: [u8; 4],
+    peer_port: u16,
+) -> [u8; 32] {
+    let mut p = [0u8; 32];
+    p[0..4].copy_from_slice(&RPC_HANDSHAKE_U32.to_le_bytes());
+
+    // Keep C memory layout compatibility for PID IPv4 bytes.
+    p[8..12].copy_from_slice(&our_ip);
+    p[12..14].copy_from_slice(&our_port.to_le_bytes());
+    let pid = (std::process::id() & 0xffff) as u16;
+    p[14..16].copy_from_slice(&pid.to_le_bytes());
+    let utime = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs() as u32;
+    p[16..20].copy_from_slice(&utime.to_le_bytes());
+
+    p[20..24].copy_from_slice(&peer_ip);
+    p[24..26].copy_from_slice(&peer_port.to_le_bytes());
+    p
+}
+
+pub(crate) fn cbc_encrypt_padded(
+    key: &[u8; 32],
+    iv: &[u8; 16],
+    plaintext: &[u8],
+) -> Result<(Vec<u8>, [u8; 16])> {
+    let pad = (16 - (plaintext.len() % 16)) % 16;
+    let mut buf = plaintext.to_vec();
+    let pad_pattern: [u8; 4] = [0x04, 0x00, 0x00, 0x00];
+    for i in 0..pad {
+        buf.push(pad_pattern[i % 4]);
+    }
+
+    let cipher = AesCbc::new(*key, *iv);
+    cipher
+        .encrypt_in_place(&mut buf)
+        .map_err(|e| ProxyError::Crypto(format!("CBC encrypt: {e}")))?;
+
+    let mut new_iv = [0u8; 16];
+    if buf.len() >= 16 {
+        new_iv.copy_from_slice(&buf[buf.len() - 16..]);
+    }
+    Ok((buf, new_iv))
+}
+
+pub(crate) fn cbc_decrypt_inplace(
+    key: &[u8; 32],
+    iv: &[u8; 16],
+    data: &mut [u8],
+) -> Result<[u8; 16]> {
+    let mut new_iv = [0u8; 16];
+    if data.len() >= 16 {
+        new_iv.copy_from_slice(&data[data.len() - 16..]);
+    }
+
+    AesCbc::new(*key, *iv)
+        .decrypt_in_place(data)
+        .map_err(|e| ProxyError::Crypto(format!("CBC decrypt: {e}")))?;
+    Ok(new_iv)
+}
+
+pub(crate) struct RpcWriter {
+    pub(crate) writer: tokio::io::WriteHalf<tokio::net::TcpStream>,
+    pub(crate) key: [u8; 32],
+    pub(crate) iv: [u8; 16],
+    pub(crate) seq_no: i32,
+}
+
+impl RpcWriter {
+    pub(crate) async fn send(&mut self, payload: &[u8]) -> Result<()> {
+        let frame = build_rpc_frame(self.seq_no, payload);
+        self.seq_no += 1;
+
+        let pad = (16 - (frame.len() % 16)) % 16;
+        let mut buf = frame;
+        let pad_pattern: [u8; 4] = [0x04, 0x00, 0x00, 0x00];
+        for i in 0..pad {
+            buf.push(pad_pattern[i % 4]);
+        }
+
+        let cipher = AesCbc::new(self.key, self.iv);
+        cipher
+            .encrypt_in_place(&mut buf)
+            .map_err(|e| ProxyError::Crypto(format!("{e}")))?;
+
+        if buf.len() >= 16 {
+            self.iv.copy_from_slice(&buf[buf.len() - 16..]);
+        }
+        self.writer.write_all(&buf).await.map_err(ProxyError::Io)?;
+        self.writer.flush().await.map_err(ProxyError::Io)
+    }
+}

src/transport/middle_proxy/config_updater.rs

@@ -0,0 +1,113 @@
+use std::collections::HashMap;
+use std::net::IpAddr;
+use std::sync::Arc;
+use std::time::Duration;
+
+use regex::Regex;
+use httpdate;
+use tracing::{debug, info, warn};
+
+use crate::error::Result;
+
+use super::MePool;
+use super::secret::download_proxy_secret;
+use crate::crypto::SecureRandom;
+use std::time::SystemTime;
+
+#[derive(Debug, Clone, Default)]
+pub struct ProxyConfigData {
+    pub map: HashMap<i32, Vec<(IpAddr, u16)>>,
+    pub default_dc: Option<i32>,
+}
+
+pub async fn fetch_proxy_config(url: &str) -> Result<ProxyConfigData> {
+    let resp = reqwest::get(url)
+        .await
+        .map_err(|e| crate::error::ProxyError::Proxy(format!("fetch_proxy_config GET failed: {e}")))?
+        ;
+
+    if let Some(date) = resp.headers().get(reqwest::header::DATE) {
+        if let Ok(date_str) = date.to_str() {
+            if let Ok(server_time) = httpdate::parse_http_date(date_str) {
+                if let Ok(skew) = SystemTime::now().duration_since(server_time).or_else(|e| {
+                    server_time.duration_since(SystemTime::now()).map_err(|_| e)
+                }) {
+                    let skew_secs = skew.as_secs();
+                    if skew_secs > 60 {
+                        warn!(skew_secs, "Time skew >60s detected from fetch_proxy_config Date header");
+                    } else if skew_secs > 30 {
+                        warn!(skew_secs, "Time skew >30s detected from fetch_proxy_config Date header");
+                    }
+                }
+            }
+        }
+    }
+
+    let text = resp
+        .text()
+        .await
+        .map_err(|e| crate::error::ProxyError::Proxy(format!("fetch_proxy_config read failed: {e}")))?;
+
+    let re_proxy = Regex::new(r"proxy_for\s+(-?\d+)\s+([^\s:]+):(\d+)\s*;").unwrap();
+    let re_default = Regex::new(r"default\s+(-?\d+)\s*;").unwrap();
+
+    let mut map: HashMap<i32, Vec<(IpAddr, u16)>> = HashMap::new();
+    for cap in re_proxy.captures_iter(&text) {
+        if let (Some(dc), Some(host), Some(port)) = (cap.get(1), cap.get(2), cap.get(3)) {
+            if let Ok(dc_idx) = dc.as_str().parse::<i32>() {
+                if let Ok(ip) = host.as_str().parse::<IpAddr>() {
+                    if let Ok(port_num) = port.as_str().parse::<u16>() {
+                        map.entry(dc_idx).or_default().push((ip, port_num));
+                    }
+                }
+            }
+        }
+    }
+
+    let default_dc = re_default
+        .captures(&text)
+        .and_then(|c| c.get(1))
+        .and_then(|m| m.as_str().parse::<i32>().ok());
+
+    Ok(ProxyConfigData { map, default_dc })
+}
+
+pub async fn me_config_updater(pool: Arc<MePool>, rng: Arc<SecureRandom>, interval: Duration) {
+    let mut tick = tokio::time::interval(interval);
+    // skip immediate tick to avoid double-fetch right after startup
+    tick.tick().await;
+    loop {
+        tick.tick().await;
+
+        // Update proxy config v4
+        if let Ok(cfg) = fetch_proxy_config("https://core.telegram.org/getProxyConfig").await {
+            let changed = pool.update_proxy_maps(cfg.map.clone(), None).await;
+            if let Some(dc) = cfg.default_dc {
+                pool.default_dc.store(dc, std::sync::atomic::Ordering::Relaxed);
+            }
+            if changed {
+                info!("ME config updated (v4), reconciling connections");
+                pool.reconcile_connections(&rng).await;
+            } else {
+                debug!("ME config v4 unchanged");
+            }
+        } else {
+            warn!("getProxyConfig update failed");
+        }
+
+        // Update proxy config v6 (optional)
+        if let Ok(cfg_v6) = fetch_proxy_config("https://core.telegram.org/getProxyConfigV6").await {
+            let _ = pool.update_proxy_maps(HashMap::new(), Some(cfg_v6.map)).await;
+        }
+
+        // Update proxy-secret
+        match download_proxy_secret().await {
+            Ok(secret) => {
+                if pool.update_secret(secret).await {
+                    info!("proxy-secret updated and pool reconnect scheduled");
+                }
+            }
+            Err(e) => warn!(error = %e, "proxy-secret update failed"),
+        }
+    }
+}

src/transport/middle_proxy/handshake.rs

@@ -0,0 +1,412 @@
+use std::net::{IpAddr, SocketAddr};
+use std::time::{Duration, Instant};
+use socket2::{SockRef, TcpKeepalive};
+#[cfg(target_os = "linux")]
+use libc;
+#[cfg(target_os = "linux")]
+use std::os::fd::{AsRawFd, RawFd};
+#[cfg(target_os = "linux")]
+use std::os::raw::c_int;
+
+use bytes::BytesMut;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, ReadHalf, WriteHalf};
+use tokio::net::TcpStream;
+use tokio::time::timeout;
+use tracing::{debug, info, warn};
+
+use crate::crypto::{SecureRandom, build_middleproxy_prekey, derive_middleproxy_keys, sha256};
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::{
+    ME_CONNECT_TIMEOUT_SECS, ME_HANDSHAKE_TIMEOUT_SECS, RPC_CRYPTO_AES_U32, RPC_HANDSHAKE_ERROR_U32,
+    RPC_HANDSHAKE_U32, RPC_PING_U32, RPC_PONG_U32, RPC_NONCE_U32,
+};
+
+use super::codec::{
+    build_handshake_payload, build_nonce_payload, build_rpc_frame, cbc_decrypt_inplace,
+    cbc_encrypt_padded, parse_nonce_payload, read_rpc_frame_plaintext,
+};
+use super::wire::{extract_ip_material, IpMaterial};
+use super::MePool;
+
+/// Result of a successful ME handshake with timings.
+pub(crate) struct HandshakeOutput {
+    pub rd: ReadHalf<TcpStream>,
+    pub wr: WriteHalf<TcpStream>,
+    pub read_key: [u8; 32],
+    pub read_iv: [u8; 16],
+    pub write_key: [u8; 32],
+    pub write_iv: [u8; 16],
+    pub handshake_ms: f64,
+}
+
+impl MePool {
+    /// TCP connect with timeout + return RTT in milliseconds.
+    pub(crate) async fn connect_tcp(&self, addr: SocketAddr) -> Result<(TcpStream, f64)> {
+        let start = Instant::now();
+        let stream = timeout(Duration::from_secs(ME_CONNECT_TIMEOUT_SECS), TcpStream::connect(addr))
+            .await
+            .map_err(|_| ProxyError::ConnectionTimeout { addr: addr.to_string() })??;
+        let connect_ms = start.elapsed().as_secs_f64() * 1000.0;
+        stream.set_nodelay(true).ok();
+        if let Err(e) = Self::configure_keepalive(&stream) {
+            warn!(error = %e, "ME keepalive setup failed");
+        }
+        #[cfg(target_os = "linux")]
+        if let Err(e) = Self::configure_user_timeout(stream.as_raw_fd()) {
+            warn!(error = %e, "ME TCP_USER_TIMEOUT setup failed");
+        }
+        Ok((stream, connect_ms))
+    }
+
+    fn configure_keepalive(stream: &TcpStream) -> std::io::Result<()> {
+        let sock = SockRef::from(stream);
+        let ka = TcpKeepalive::new()
+            .with_time(Duration::from_secs(30))
+            .with_interval(Duration::from_secs(10))
+            .with_retries(3);
+        sock.set_tcp_keepalive(&ka)?;
+        sock.set_keepalive(true)?;
+        Ok(())
+    }
+
+    #[cfg(target_os = "linux")]
+    fn configure_user_timeout(fd: RawFd) -> std::io::Result<()> {
+        let timeout_ms: c_int = 30_000;
+        let rc = unsafe {
+            libc::setsockopt(
+                fd,
+                libc::IPPROTO_TCP,
+                libc::TCP_USER_TIMEOUT,
+                &timeout_ms as *const _ as *const libc::c_void,
+                std::mem::size_of_val(&timeout_ms) as libc::socklen_t,
+            )
+        };
+        if rc != 0 {
+            return Err(std::io::Error::last_os_error());
+        }
+        Ok(())
+    }
+
+    /// Perform full ME RPC handshake on an established TCP stream.
+    /// Returns cipher keys/ivs and split halves; does not register writer.
+    pub(crate) async fn handshake_only(
+        &self,
+        stream: TcpStream,
+        addr: SocketAddr,
+        rng: &SecureRandom,
+    ) -> Result<HandshakeOutput> {
+        let hs_start = Instant::now();
+
+        let local_addr = stream.local_addr().map_err(ProxyError::Io)?;
+        let peer_addr = stream.peer_addr().map_err(ProxyError::Io)?;
+
+        let _ = self.maybe_detect_nat_ip(local_addr.ip()).await;
+        let reflected = if self.nat_probe {
+            self.maybe_reflect_public_addr().await
+        } else {
+            None
+        };
+
+        let local_addr_nat = self.translate_our_addr_with_reflection(local_addr, reflected);
+        let peer_addr_nat = SocketAddr::new(self.translate_ip_for_nat(peer_addr.ip()), peer_addr.port());
+        let (mut rd, mut wr) = tokio::io::split(stream);
+
+        let my_nonce: [u8; 16] = rng.bytes(16).try_into().unwrap();
+        let crypto_ts = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as u32;
+
+        let ks = self.key_selector().await;
+        let nonce_payload = build_nonce_payload(ks, crypto_ts, &my_nonce);
+        let nonce_frame = build_rpc_frame(-2, &nonce_payload);
+        let dump = hex_dump(&nonce_frame[..nonce_frame.len().min(44)]);
+        info!(
+            key_selector = format_args!("0x{ks:08x}"),
+            crypto_ts,
+            frame_len = nonce_frame.len(),
+            nonce_frame_hex = %dump,
+            "Sending ME nonce frame"
+        );
+        wr.write_all(&nonce_frame).await.map_err(ProxyError::Io)?;
+        wr.flush().await.map_err(ProxyError::Io)?;
+
+        let (srv_seq, srv_nonce_payload) = timeout(
+            Duration::from_secs(ME_HANDSHAKE_TIMEOUT_SECS),
+            read_rpc_frame_plaintext(&mut rd),
+        )
+        .await
+        .map_err(|_| ProxyError::TgHandshakeTimeout)??;
+
+        if srv_seq != -2 {
+            return Err(ProxyError::InvalidHandshake(format!("Expected seq=-2, got {srv_seq}")));
+        }
+
+        let (srv_key_select, schema, srv_ts, srv_nonce) = parse_nonce_payload(&srv_nonce_payload)?;
+        if schema != RPC_CRYPTO_AES_U32 {
+            warn!(schema = format_args!("0x{schema:08x}"), "Unsupported ME crypto schema");
+            return Err(ProxyError::InvalidHandshake(format!(
+                "Unsupported crypto schema: 0x{schema:x}"
+            )));
+        }
+
+        if srv_key_select != ks {
+            return Err(ProxyError::InvalidHandshake(format!(
+                "Server key_select 0x{srv_key_select:08x} != client 0x{ks:08x}"
+            )));
+        }
+
+        let skew = crypto_ts.abs_diff(srv_ts);
+        if skew > 30 {
+            return Err(ProxyError::InvalidHandshake(format!(
+                "nonce crypto_ts skew too large: client={crypto_ts}, server={srv_ts}, skew={skew}s"
+            )));
+        }
+
+        info!(
+            %local_addr,
+            %local_addr_nat,
+            reflected_ip = reflected.map(|r| r.ip()).as_ref().map(ToString::to_string),
+            %peer_addr,
+            %peer_addr_nat,
+            key_selector = format_args!("0x{ks:08x}"),
+            crypto_schema = format_args!("0x{schema:08x}"),
+            skew_secs = skew,
+            "ME key derivation parameters"
+        );
+
+        let ts_bytes = crypto_ts.to_le_bytes();
+        let server_port_bytes = peer_addr_nat.port().to_le_bytes();
+        let client_port_bytes = local_addr_nat.port().to_le_bytes();
+
+        let server_ip = extract_ip_material(peer_addr_nat);
+        let client_ip = extract_ip_material(local_addr_nat);
+
+        let (srv_ip_opt, clt_ip_opt, clt_v6_opt, srv_v6_opt, hs_our_ip, hs_peer_ip) = match (server_ip, client_ip) {
+            (IpMaterial::V4(mut srv), IpMaterial::V4(mut clt)) => {
+                srv.reverse();
+                clt.reverse();
+                (Some(srv), Some(clt), None, None, clt, srv)
+            }
+            (IpMaterial::V6(srv), IpMaterial::V6(clt)) => {
+                let zero = [0u8; 4];
+                (None, None, Some(clt), Some(srv), zero, zero)
+            }
+            _ => {
+                return Err(ProxyError::InvalidHandshake(
+                    "mixed IPv4/IPv6 endpoints are not supported for ME key derivation".to_string(),
+                ));
+            }
+        };
+
+        let diag_level: u8 = std::env::var("ME_DIAG").ok().and_then(|v| v.parse().ok()).unwrap_or(0);
+
+        let secret: Vec<u8> = self.proxy_secret.read().await.clone();
+
+        let prekey_client = build_middleproxy_prekey(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"CLIENT",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            &secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+        let prekey_server = build_middleproxy_prekey(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"SERVER",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            &secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+
+        let (wk, wi) = derive_middleproxy_keys(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"CLIENT",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            &secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+        let (rk, ri) = derive_middleproxy_keys(
+            &srv_nonce,
+            &my_nonce,
+            &ts_bytes,
+            srv_ip_opt.as_ref().map(|x| &x[..]),
+            &client_port_bytes,
+            b"SERVER",
+            clt_ip_opt.as_ref().map(|x| &x[..]),
+            &server_port_bytes,
+            &secret,
+            clt_v6_opt.as_ref(),
+            srv_v6_opt.as_ref(),
+        );
+
+        let hs_payload = build_handshake_payload(hs_our_ip, local_addr.port(), hs_peer_ip, peer_addr.port());
+        let hs_frame = build_rpc_frame(-1, &hs_payload);
+        if diag_level >= 1 {
+            info!(
+                write_key = %hex_dump(&wk),
+                write_iv = %hex_dump(&wi),
+                read_key = %hex_dump(&rk),
+                read_iv = %hex_dump(&ri),
+                srv_ip = %srv_ip_opt.map(|ip| hex_dump(&ip)).unwrap_or_default(),
+                clt_ip = %clt_ip_opt.map(|ip| hex_dump(&ip)).unwrap_or_default(),
+                srv_port = %hex_dump(&server_port_bytes),
+                clt_port = %hex_dump(&client_port_bytes),
+                crypto_ts = %hex_dump(&ts_bytes),
+                nonce_srv = %hex_dump(&srv_nonce),
+                nonce_clt = %hex_dump(&my_nonce),
+                prekey_sha256_client = %hex_dump(&sha256(&prekey_client)),
+                prekey_sha256_server = %hex_dump(&sha256(&prekey_server)),
+                hs_plain = %hex_dump(&hs_frame),
+                proxy_secret_sha256 = %hex_dump(&sha256(&secret)),
+                "ME diag: derived keys and handshake plaintext"
+            );
+        }
+        if diag_level >= 2 {
+            info!(
+                prekey_client = %hex_dump(&prekey_client),
+                prekey_server = %hex_dump(&prekey_server),
+                "ME diag: full prekey buffers"
+            );
+        }
+
+        let (encrypted_hs, mut write_iv) = cbc_encrypt_padded(&wk, &wi, &hs_frame)?;
+        if diag_level >= 1 {
+            info!(
+                hs_cipher = %hex_dump(&encrypted_hs),
+                "ME diag: handshake ciphertext"
+            );
+        }
+        wr.write_all(&encrypted_hs).await.map_err(ProxyError::Io)?;
+        wr.flush().await.map_err(ProxyError::Io)?;
+
+        let deadline = Instant::now() + Duration::from_secs(ME_HANDSHAKE_TIMEOUT_SECS);
+        let mut enc_buf = BytesMut::with_capacity(256);
+        let mut dec_buf = BytesMut::with_capacity(256);
+        let mut read_iv = ri;
+        let mut handshake_ok = false;
+
+        while Instant::now() < deadline && !handshake_ok {
+            let remaining = deadline - Instant::now();
+            let mut tmp = [0u8; 256];
+            let n = match timeout(remaining, rd.read(&mut tmp)).await {
+                Ok(Ok(0)) => {
+                    return Err(ProxyError::Io(std::io::Error::new(
+                        std::io::ErrorKind::UnexpectedEof,
+                        "ME closed during handshake",
+                    )));
+                }
+                Ok(Ok(n)) => n,
+                Ok(Err(e)) => return Err(ProxyError::Io(e)),
+                Err(_) => return Err(ProxyError::TgHandshakeTimeout),
+            };
+
+            enc_buf.extend_from_slice(&tmp[..n]);
+
+            let blocks = enc_buf.len() / 16 * 16;
+            if blocks > 0 {
+                let mut chunk = vec![0u8; blocks];
+                chunk.copy_from_slice(&enc_buf[..blocks]);
+                read_iv = cbc_decrypt_inplace(&rk, &read_iv, &mut chunk)?;
+                dec_buf.extend_from_slice(&chunk);
+                let _ = enc_buf.split_to(blocks);
+            }
+
+            while dec_buf.len() >= 4 {
+                let fl = u32::from_le_bytes(dec_buf[0..4].try_into().unwrap()) as usize;
+
+                if fl == 4 {
+                    let _ = dec_buf.split_to(4);
+                    continue;
+                }
+                if !(12..=(1 << 24)).contains(&fl) {
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "Bad HS response frame len: {fl}"
+                    )));
+                }
+                if dec_buf.len() < fl {
+                    break;
+                }
+
+                let frame = dec_buf.split_to(fl);
+                let pe = fl - 4;
+                let ec = u32::from_le_bytes(frame[pe..pe + 4].try_into().unwrap());
+                let ac = crate::crypto::crc32(&frame[..pe]);
+                if ec != ac {
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "HS CRC mismatch: 0x{ec:08x} vs 0x{ac:08x}"
+                    )));
+                }
+
+                let hs_type = u32::from_le_bytes(frame[8..12].try_into().unwrap());
+                if hs_type == RPC_HANDSHAKE_ERROR_U32 {
+                    let err_code = if frame.len() >= 16 {
+                        i32::from_le_bytes(frame[12..16].try_into().unwrap())
+                    } else {
+                        -1
+                    };
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "ME rejected handshake (error={err_code})"
+                    )));
+                }
+                if hs_type != RPC_HANDSHAKE_U32 {
+                    return Err(ProxyError::InvalidHandshake(format!(
+                        "Expected HANDSHAKE 0x{RPC_HANDSHAKE_U32:08x}, got 0x{hs_type:08x}"
+                    )));
+                }
+
+                handshake_ok = true;
+                break;
+            }
+        }
+
+        if !handshake_ok {
+            return Err(ProxyError::TgHandshakeTimeout);
+        }
+
+        let handshake_ms = hs_start.elapsed().as_secs_f64() * 1000.0;
+        info!(%addr, "RPC handshake OK");
+
+        Ok(HandshakeOutput {
+            rd,
+            wr,
+            read_key: rk,
+            read_iv,
+            write_key: wk,
+            write_iv,
+            handshake_ms,
+        })
+    }
+}
+
+fn hex_dump(data: &[u8]) -> String {
+    const MAX: usize = 64;
+    let mut out = String::with_capacity(data.len() * 2 + 3);
+    for (i, b) in data.iter().take(MAX).enumerate() {
+        if i > 0 {
+            out.push(' ');
+        }
+        out.push_str(&format!("{b:02x}"));
+    }
+    if data.len() > MAX {
+        out.push_str(" …");
+    }
+    out
+}

src/transport/middle_proxy/health.rs

@@ -0,0 +1,113 @@
+use std::collections::HashMap;
+use std::net::SocketAddr;
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+
+use tracing::{debug, info, warn};
+use rand::seq::SliceRandom;
+
+use crate::crypto::SecureRandom;
+
+use super::MePool;
+
+pub async fn me_health_monitor(pool: Arc<MePool>, rng: Arc<SecureRandom>, _min_connections: usize) {
+    let mut backoff: HashMap<i32, u64> = HashMap::new();
+    let mut last_attempt: HashMap<i32, Instant> = HashMap::new();
+    loop {
+        tokio::time::sleep(Duration::from_secs(30)).await;
+        // Per-DC coverage check
+        let map = pool.proxy_map_v4.read().await.clone();
+        let writer_addrs: std::collections::HashSet<SocketAddr> = pool
+            .writers
+            .read()
+            .await
+            .iter()
+            .map(|w| w.addr)
+            .collect();
+
+        for (dc, addrs) in map.iter() {
+            let dc_addrs: Vec<SocketAddr> = addrs
+                .iter()
+                .map(|(ip, port)| SocketAddr::new(*ip, *port))
+                .collect();
+            let has_coverage = dc_addrs.iter().any(|a| writer_addrs.contains(a));
+            if !has_coverage {
+                let delay = *backoff.get(dc).unwrap_or(&30);
+                let now = Instant::now();
+                if let Some(last) = last_attempt.get(dc) {
+                    if now.duration_since(*last).as_secs() < delay {
+                        continue;
+                    }
+                }
+                warn!(dc = %dc, delay, "DC has no ME coverage, reconnecting...");
+                let mut shuffled = dc_addrs.clone();
+                shuffled.shuffle(&mut rand::rng());
+                let mut reconnected = false;
+                for addr in shuffled {
+                    match pool.connect_one(addr, &rng).await {
+                        Ok(()) => {
+                            info!(%addr, dc = %dc, "ME reconnected for DC coverage");
+                            backoff.insert(*dc, 30);
+                            last_attempt.insert(*dc, now);
+                            reconnected = true;
+                            break;
+                        }
+                        Err(e) => debug!(%addr, dc = %dc, error = %e, "ME reconnect failed"),
+                    }
+                }
+                if !reconnected {
+                    let next = (*backoff.get(dc).unwrap_or(&30)).saturating_mul(2).min(300);
+                    backoff.insert(*dc, next);
+                    last_attempt.insert(*dc, now);
+                }
+            }
+        }
+
+        // IPv6 coverage check (if available)
+        let map_v6 = pool.proxy_map_v6.read().await.clone();
+        let writer_addrs_v6: std::collections::HashSet<SocketAddr> = pool
+            .writers
+            .read()
+            .await
+            .iter()
+            .map(|w| w.addr)
+            .collect();
+        for (dc, addrs) in map_v6.iter() {
+            let dc_addrs: Vec<SocketAddr> = addrs
+                .iter()
+                .map(|(ip, port)| SocketAddr::new(*ip, *port))
+                .collect();
+            let has_coverage = dc_addrs.iter().any(|a| writer_addrs_v6.contains(a));
+            if !has_coverage {
+                let delay = *backoff.get(dc).unwrap_or(&30);
+                let now = Instant::now();
+                if let Some(last) = last_attempt.get(dc) {
+                    if now.duration_since(*last).as_secs() < delay {
+                        continue;
+                    }
+                }
+                warn!(dc = %dc, delay, "IPv6 DC has no ME coverage, reconnecting...");
+                let mut shuffled = dc_addrs.clone();
+                shuffled.shuffle(&mut rand::rng());
+                let mut reconnected = false;
+                for addr in shuffled {
+                    match pool.connect_one(addr, &rng).await {
+                        Ok(()) => {
+                            info!(%addr, dc = %dc, "ME reconnected for IPv6 DC coverage");
+                            backoff.insert(*dc, 30);
+                            last_attempt.insert(*dc, now);
+                            reconnected = true;
+                            break;
+                        }
+                        Err(e) => debug!(%addr, dc = %dc, error = %e, "ME reconnect failed (IPv6)"),
+                    }
+                }
+                if !reconnected {
+                    let next = (*backoff.get(dc).unwrap_or(&30)).saturating_mul(2).min(300);
+                    backoff.insert(*dc, next);
+                    last_attempt.insert(*dc, now);
+                }
+            }
+        }
+    }
+}

src/transport/middle_proxy/mod.rs

@@ -0,0 +1,34 @@
+//! Middle Proxy RPC transport.
+
+mod codec;
+mod handshake;
+mod health;
+mod pool;
+mod pool_nat;
+mod ping;
+mod reader;
+mod registry;
+mod send;
+mod secret;
+mod rotation;
+mod config_updater;
+mod wire;
+
+use bytes::Bytes;
+
+pub use health::me_health_monitor;
+pub use ping::{run_me_ping, format_sample_line, MePingReport, MePingSample, MePingFamily};
+pub use pool::MePool;
+pub use pool_nat::{stun_probe, detect_public_ip, StunProbeResult};
+pub use registry::ConnRegistry;
+pub use secret::fetch_proxy_secret;
+pub use config_updater::{fetch_proxy_config, me_config_updater};
+pub use rotation::me_rotation_task;
+pub use wire::proto_flags_for_tag;
+
+#[derive(Debug)]
+pub enum MeResponse {
+    Data { flags: u32, data: Bytes },
+    Ack(u32),
+    Close,
+}

src/transport/middle_proxy/ping.rs

@@ -0,0 +1,164 @@
+use std::net::{IpAddr, SocketAddr};
+use std::sync::Arc;
+
+use crate::crypto::SecureRandom;
+use crate::error::ProxyError;
+
+use super::MePool;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum MePingFamily {
+    V4,
+    V6,
+}
+
+#[derive(Debug, Clone)]
+pub struct MePingSample {
+    pub dc: i32,
+    pub addr: SocketAddr,
+    pub connect_ms: Option<f64>,
+    pub handshake_ms: Option<f64>,
+    pub error: Option<String>,
+    pub family: MePingFamily,
+}
+
+#[derive(Debug, Clone)]
+pub struct MePingReport {
+    pub dc: i32,
+    pub family: MePingFamily,
+    pub samples: Vec<MePingSample>,
+}
+
+pub fn format_sample_line(sample: &MePingSample) -> String {
+    let sign = if sample.dc >= 0 { "+" } else { "-" };
+    let addr = format!("{}:{}", sample.addr.ip(), sample.addr.port());
+
+    match (sample.connect_ms, sample.handshake_ms.as_ref(), sample.error.as_ref()) {
+        (Some(conn), Some(hs), None) => format!(
+            "     {sign} {addr}\tPing: {:.0} ms / RPC: {:.0} ms / OK",
+            conn, hs
+        ),
+        (Some(conn), None, Some(err)) => format!(
+            "     {sign} {addr}\tPing: {:.0} ms / RPC: FAIL ({err})",
+            conn
+        ),
+        (None, _, Some(err)) => format!("     {sign} {addr}\tPing: FAIL ({err})"),
+        (Some(conn), None, None) => format!("     {sign} {addr}\tPing: {:.0} ms / RPC: FAIL", conn),
+        _ => format!("     {sign} {addr}\tPing: FAIL"),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::net::{IpAddr, Ipv4Addr, SocketAddr};
+
+    fn sample(base: MePingSample) -> MePingSample {
+        base
+    }
+
+    #[test]
+    fn ok_line_contains_both_timings() {
+        let s = sample(MePingSample {
+            dc: 4,
+            addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(1, 2, 3, 4)), 8888),
+            connect_ms: Some(12.3),
+            handshake_ms: Some(34.7),
+            error: None,
+            family: MePingFamily::V4,
+        });
+        let line = format_sample_line(&s);
+        assert!(line.contains("Ping: 12 ms"));
+        assert!(line.contains("RPC: 35 ms"));
+        assert!(line.contains("OK"));
+    }
+
+    #[test]
+    fn error_line_mentions_reason() {
+        let s = sample(MePingSample {
+            dc: -5,
+            addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(5, 6, 7, 8)), 80),
+            connect_ms: Some(10.0),
+            handshake_ms: None,
+            error: Some("handshake timeout".to_string()),
+            family: MePingFamily::V4,
+        });
+        let line = format_sample_line(&s);
+        assert!(line.contains("- 5.6.7.8:80"));
+        assert!(line.contains("handshake timeout"));
+    }
+}
+
+pub async fn run_me_ping(pool: &Arc<MePool>, rng: &SecureRandom) -> Vec<MePingReport> {
+    let mut reports = Vec::new();
+
+    let v4_map = pool.proxy_map_v4.read().await.clone();
+    let v6_map = pool.proxy_map_v6.read().await.clone();
+
+    let mut grouped: Vec<(MePingFamily, i32, Vec<(IpAddr, u16)>)> = Vec::new();
+    for (dc, addrs) in v4_map {
+        grouped.push((MePingFamily::V4, dc, addrs));
+    }
+    for (dc, addrs) in v6_map {
+        grouped.push((MePingFamily::V6, dc, addrs));
+    }
+
+    for (family, dc, addrs) in grouped {
+        let mut samples = Vec::new();
+        for (ip, port) in addrs {
+            let addr = SocketAddr::new(ip, port);
+            let mut connect_ms = None;
+            let mut handshake_ms = None;
+            let mut error = None;
+
+            match pool.connect_tcp(addr).await {
+                Ok((stream, conn_rtt)) => {
+                    connect_ms = Some(conn_rtt);
+                    match pool.handshake_only(stream, addr, rng).await {
+                        Ok(hs) => {
+                            handshake_ms = Some(hs.handshake_ms);
+                            // drop halves to close
+                            drop(hs.rd);
+                            drop(hs.wr);
+                        }
+                        Err(e) => {
+                            error = Some(short_err(&e));
+                        }
+                    }
+                }
+                Err(e) => {
+                    error = Some(short_err(&e));
+                }
+            }
+
+            samples.push(MePingSample {
+                dc,
+                addr,
+                connect_ms,
+                handshake_ms,
+                error,
+                family,
+            });
+        }
+
+        reports.push(MePingReport {
+            dc,
+            family,
+            samples,
+        });
+    }
+
+    reports
+}
+
+fn short_err(err: &ProxyError) -> String {
+    match err {
+        ProxyError::ConnectionTimeout { .. } => "connect timeout".to_string(),
+        ProxyError::TgHandshakeTimeout => "handshake timeout".to_string(),
+        ProxyError::InvalidHandshake(e) => format!("bad handshake: {e}"),
+        ProxyError::Crypto(e) => format!("crypto: {e}"),
+        ProxyError::Proxy(e) => format!("proxy: {e}"),
+        ProxyError::Io(e) => format!("io: {e}"),
+        _ => format!("{err}"),
+    }
+}

src/transport/middle_proxy/pool.rs

@@ -0,0 +1,467 @@
+use std::collections::HashMap;
+use std::net::{IpAddr, SocketAddr};
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, AtomicI32, AtomicU64, Ordering};
+use bytes::BytesMut;
+use rand::Rng;
+use rand::seq::SliceRandom;
+use tokio::sync::{Mutex, RwLock};
+use tokio_util::sync::CancellationToken;
+use tracing::{debug, info, warn};
+use std::time::Duration;
+
+use crate::crypto::SecureRandom;
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+
+use super::ConnRegistry;
+use super::registry::{BoundConn, ConnMeta};
+use super::codec::RpcWriter;
+use super::reader::reader_loop;
+use super::MeResponse;
+
+const ME_ACTIVE_PING_SECS: u64 = 25;
+const ME_ACTIVE_PING_JITTER_SECS: i64 = 5;
+
+#[derive(Clone)]
+pub struct MeWriter {
+    pub id: u64,
+    pub addr: SocketAddr,
+    pub writer: Arc<Mutex<RpcWriter>>,
+    pub cancel: CancellationToken,
+    pub degraded: Arc<AtomicBool>,
+}
+
+pub struct MePool {
+    pub(super) registry: Arc<ConnRegistry>,
+    pub(super) writers: Arc<RwLock<Vec<MeWriter>>>,
+    pub(super) rr: AtomicU64,
+    pub(super) proxy_tag: Option<Vec<u8>>,
+    pub(super) proxy_secret: Arc<RwLock<Vec<u8>>>,
+    pub(super) nat_ip_cfg: Option<IpAddr>,
+    pub(super) nat_ip_detected: Arc<RwLock<Option<IpAddr>>>,
+    pub(super) nat_probe: bool,
+    pub(super) nat_stun: Option<String>,
+    pub(super) proxy_map_v4: Arc<RwLock<HashMap<i32, Vec<(IpAddr, u16)>>>>,
+    pub(super) proxy_map_v6: Arc<RwLock<HashMap<i32, Vec<(IpAddr, u16)>>>>,
+    pub(super) default_dc: AtomicI32,
+    pub(super) next_writer_id: AtomicU64,
+    pub(super) ping_tracker: Arc<Mutex<HashMap<i64, (std::time::Instant, u64)>>>,
+    pub(super) rtt_stats: Arc<Mutex<HashMap<u64, (f64, f64)>>>,
+    pub(super) nat_reflection_cache: Arc<Mutex<Option<(std::time::Instant, std::net::SocketAddr)>>>,
+    pool_size: usize,
+}
+
+impl MePool {
+    pub fn new(
+        proxy_tag: Option<Vec<u8>>,
+        proxy_secret: Vec<u8>,
+        nat_ip: Option<IpAddr>,
+        nat_probe: bool,
+        nat_stun: Option<String>,
+        proxy_map_v4: HashMap<i32, Vec<(IpAddr, u16)>>,
+        proxy_map_v6: HashMap<i32, Vec<(IpAddr, u16)>>,
+        default_dc: Option<i32>,
+    ) -> Arc<Self> {
+        Arc::new(Self {
+            registry: Arc::new(ConnRegistry::new()),
+            writers: Arc::new(RwLock::new(Vec::new())),
+            rr: AtomicU64::new(0),
+            proxy_tag,
+            proxy_secret: Arc::new(RwLock::new(proxy_secret)),
+            nat_ip_cfg: nat_ip,
+            nat_ip_detected: Arc::new(RwLock::new(None)),
+            nat_probe,
+            nat_stun,
+            pool_size: 2,
+            proxy_map_v4: Arc::new(RwLock::new(proxy_map_v4)),
+            proxy_map_v6: Arc::new(RwLock::new(proxy_map_v6)),
+            default_dc: AtomicI32::new(default_dc.unwrap_or(0)),
+            next_writer_id: AtomicU64::new(1),
+            ping_tracker: Arc::new(Mutex::new(HashMap::new())),
+            rtt_stats: Arc::new(Mutex::new(HashMap::new())),
+            nat_reflection_cache: Arc::new(Mutex::new(None)),
+        })
+    }
+
+    pub fn has_proxy_tag(&self) -> bool {
+        self.proxy_tag.is_some()
+    }
+
+    pub fn translate_our_addr(&self, addr: SocketAddr) -> SocketAddr {
+        let ip = self.translate_ip_for_nat(addr.ip());
+        SocketAddr::new(ip, addr.port())
+    }
+
+    pub fn registry(&self) -> &Arc<ConnRegistry> {
+        &self.registry
+    }
+
+    fn writers_arc(&self) -> Arc<RwLock<Vec<MeWriter>>> {
+        self.writers.clone()
+    }
+
+    pub async fn reconcile_connections(self: &Arc<Self>, rng: &SecureRandom) {
+        use std::collections::HashSet;
+        let map = self.proxy_map_v4.read().await.clone();
+        let dc_addrs: Vec<(i32, Vec<(IpAddr, u16)>)> = map
+            .iter()
+            .map(|(dc, addrs)| (*dc, addrs.clone()))
+            .collect();
+        let writers = self.writers.read().await;
+        let current: HashSet<SocketAddr> = writers.iter().map(|w| w.addr).collect();
+        drop(writers);
+
+        for (_dc, addrs) in map.iter() {
+            let dc_addrs: Vec<SocketAddr> = addrs
+                .iter()
+                .map(|(ip, port)| SocketAddr::new(*ip, *port))
+                .collect();
+            if !dc_addrs.iter().any(|a| current.contains(a)) {
+                let mut shuffled = dc_addrs.clone();
+                shuffled.shuffle(&mut rand::rng());
+                for addr in shuffled {
+                    if self.connect_one(addr, rng).await.is_ok() {
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    pub async fn update_proxy_maps(
+        &self,
+        new_v4: HashMap<i32, Vec<(IpAddr, u16)>>,
+        new_v6: Option<HashMap<i32, Vec<(IpAddr, u16)>>>,
+    ) -> bool {
+        let mut changed = false;
+        {
+            let mut guard = self.proxy_map_v4.write().await;
+            if !new_v4.is_empty() && *guard != new_v4 {
+                *guard = new_v4;
+                changed = true;
+            }
+        }
+        if let Some(v6) = new_v6 {
+            let mut guard = self.proxy_map_v6.write().await;
+            if !v6.is_empty() && *guard != v6 {
+                *guard = v6;
+            }
+        }
+        changed
+    }
+
+    pub async fn update_secret(&self, new_secret: Vec<u8>) -> bool {
+        if new_secret.len() < 32 {
+            warn!(len = new_secret.len(), "proxy-secret update ignored (too short)");
+            return false;
+        }
+        let mut guard = self.proxy_secret.write().await;
+        if *guard != new_secret {
+            *guard = new_secret;
+            drop(guard);
+            self.reconnect_all().await;
+            return true;
+        }
+        false
+    }
+
+    pub async fn reconnect_all(&self) {
+        // Graceful: do not drop all at once. New connections will use updated secret.
+        // Existing writers remain until health monitor replaces them.
+        // No-op here to avoid total outage.
+    }
+
+    pub(super) async fn key_selector(&self) -> u32 {
+        let secret = self.proxy_secret.read().await;
+        if secret.len() >= 4 {
+            u32::from_le_bytes([secret[0], secret[1], secret[2], secret[3]])
+        } else {
+            0
+        }
+    }
+
+    pub async fn init(self: &Arc<Self>, pool_size: usize, rng: &Arc<SecureRandom>) -> Result<()> {
+        let map = self.proxy_map_v4.read().await.clone();
+        let dc_addrs: Vec<(i32, Vec<(IpAddr, u16)>)> = map
+            .iter()
+            .map(|(dc, addrs)| (*dc, addrs.clone()))
+            .collect();
+        let ks = self.key_selector().await;
+        info!(
+            me_servers = map.len(),
+            pool_size,
+            key_selector = format_args!("0x{ks:08x}"),
+            secret_len = self.proxy_secret.read().await.len(),
+            "Initializing ME pool"
+        );
+
+        // Ensure at least one connection per DC; run DCs in parallel.
+        let mut join = tokio::task::JoinSet::new();
+        for (dc, addrs) in dc_addrs.iter().cloned() {
+            if addrs.is_empty() {
+                continue;
+            }
+            let pool = Arc::clone(self);
+            let rng_clone = Arc::clone(rng);
+            join.spawn(async move {
+                pool.connect_primary_for_dc(dc, addrs, rng_clone).await;
+            });
+        }
+        while let Some(_res) = join.join_next().await {}
+
+        // Additional connections up to pool_size total (round-robin across DCs)
+        for (dc, addrs) in dc_addrs.iter() {
+            for (ip, port) in addrs {
+                if self.connection_count() >= pool_size {
+                    break;
+                }
+                let addr = SocketAddr::new(*ip, *port);
+                if let Err(e) = self.connect_one(addr, rng.as_ref()).await {
+                    debug!(%addr, dc = %dc, error = %e, "Extra ME connect failed");
+                }
+            }
+            if self.connection_count() >= pool_size {
+                break;
+            }
+        }
+
+        if self.writers.read().await.is_empty() {
+            return Err(ProxyError::Proxy("No ME connections".into()));
+        }
+        Ok(())
+    }
+
+    pub(crate) async fn connect_one(self: &Arc<Self>, addr: SocketAddr, rng: &SecureRandom) -> Result<()> {
+        let secret_len = self.proxy_secret.read().await.len();
+        if secret_len < 32 {
+            return Err(ProxyError::Proxy("proxy-secret too short for ME auth".into()));
+        }
+
+        let (stream, _connect_ms) = self.connect_tcp(addr).await?;
+        let hs = self.handshake_only(stream, addr, rng).await?;
+
+        let writer_id = self.next_writer_id.fetch_add(1, Ordering::Relaxed);
+        let cancel = CancellationToken::new();
+        let degraded = Arc::new(AtomicBool::new(false));
+        let rpc_w = Arc::new(Mutex::new(RpcWriter {
+            writer: hs.wr,
+            key: hs.write_key,
+            iv: hs.write_iv,
+            seq_no: 0,
+        }));
+        let writer = MeWriter {
+            id: writer_id,
+            addr,
+            writer: rpc_w.clone(),
+            cancel: cancel.clone(),
+            degraded: degraded.clone(),
+        };
+        self.writers.write().await.push(writer.clone());
+
+        let reg = self.registry.clone();
+        let writers_arc = self.writers_arc();
+        let ping_tracker = self.ping_tracker.clone();
+        let rtt_stats = self.rtt_stats.clone();
+        let pool = Arc::downgrade(self);
+        let cancel_ping = cancel.clone();
+        let rpc_w_ping = rpc_w.clone();
+        let ping_tracker_ping = ping_tracker.clone();
+
+        tokio::spawn(async move {
+            let cancel_reader = cancel.clone();
+            let res = reader_loop(
+                hs.rd,
+                hs.read_key,
+                hs.read_iv,
+                reg.clone(),
+                BytesMut::new(),
+                BytesMut::new(),
+                rpc_w.clone(),
+                ping_tracker.clone(),
+                rtt_stats.clone(),
+                writer_id,
+                degraded.clone(),
+                cancel_reader.clone(),
+            )
+            .await;
+            if let Some(pool) = pool.upgrade() {
+                pool.remove_writer_and_reroute(writer_id).await;
+            }
+            if let Err(e) = res {
+                warn!(error = %e, "ME reader ended");
+            }
+            let mut ws = writers_arc.write().await;
+            ws.retain(|w| w.id != writer_id);
+            info!(remaining = ws.len(), "Dead ME writer removed from pool");
+        });
+
+        let pool_ping = Arc::downgrade(self);
+        tokio::spawn(async move {
+            let mut ping_id: i64 = rand::random::<i64>();
+            loop {
+                let jitter = rand::rng()
+                    .random_range(-ME_ACTIVE_PING_JITTER_SECS..=ME_ACTIVE_PING_JITTER_SECS);
+                let wait = (ME_ACTIVE_PING_SECS as i64 + jitter).max(5) as u64;
+                tokio::select! {
+                    _ = cancel_ping.cancelled() => {
+                        break;
+                    }
+                    _ = tokio::time::sleep(Duration::from_secs(wait)) => {}
+                }
+                let mut p = Vec::with_capacity(12);
+                p.extend_from_slice(&RPC_PING_U32.to_le_bytes());
+                p.extend_from_slice(&ping_id.to_le_bytes());
+                ping_id = ping_id.wrapping_add(1);
+                {
+                    let mut tracker = ping_tracker_ping.lock().await;
+                    tracker.insert(ping_id, (std::time::Instant::now(), writer_id));
+                }
+                if let Err(e) = rpc_w_ping.lock().await.send(&p).await {
+                    debug!(error = %e, "Active ME ping failed, removing dead writer");
+                    cancel_ping.cancel();
+                    if let Some(pool) = pool_ping.upgrade() {
+                        pool.remove_writer_and_reroute(writer_id).await;
+                    }
+                    break;
+                }
+            }
+        });
+
+        Ok(())
+    }
+
+    async fn connect_primary_for_dc(
+        self: Arc<Self>,
+        dc: i32,
+        mut addrs: Vec<(IpAddr, u16)>,
+        rng: Arc<SecureRandom>,
+    ) {
+        if addrs.is_empty() {
+            return;
+        }
+        addrs.shuffle(&mut rand::rng());
+        for (ip, port) in addrs {
+            let addr = SocketAddr::new(ip, port);
+            match self.connect_one(addr, rng.as_ref()).await {
+                Ok(()) => {
+                    info!(%addr, dc = %dc, "ME connected");
+                    return;
+                }
+                Err(e) => warn!(%addr, dc = %dc, error = %e, "ME connect failed, trying next"),
+            }
+        }
+        warn!(dc = %dc, "All ME servers for DC failed at init");
+    }
+
+    pub(crate) async fn remove_writer_and_reroute(&self, writer_id: u64) {
+        let mut queue = self.remove_writer_only(writer_id).await;
+        while let Some(bound) = queue.pop() {
+            if !self.reroute_conn(&bound, &mut queue).await {
+                let _ = self.registry.route(bound.conn_id, super::MeResponse::Close).await;
+            }
+        }
+    }
+
+    async fn remove_writer_only(&self, writer_id: u64) -> Vec<BoundConn> {
+        {
+            let mut ws = self.writers.write().await;
+            if let Some(pos) = ws.iter().position(|w| w.id == writer_id) {
+                let w = ws.remove(pos);
+                w.cancel.cancel();
+            }
+        }
+        self.registry.writer_lost(writer_id).await
+    }
+
+    async fn reroute_conn(&self, bound: &BoundConn, backlog: &mut Vec<BoundConn>) -> bool {
+        let payload = super::wire::build_proxy_req_payload(
+            bound.conn_id,
+            bound.meta.client_addr,
+            bound.meta.our_addr,
+            &[],
+            self.proxy_tag.as_deref(),
+            bound.meta.proto_flags,
+        );
+
+        let mut attempts = 0;
+        loop {
+            let writers_snapshot = {
+                let ws = self.writers.read().await;
+                if ws.is_empty() {
+                    return false;
+                }
+                ws.clone()
+            };
+            let mut candidates = self.candidate_indices_for_dc(&writers_snapshot, bound.meta.target_dc).await;
+            if candidates.is_empty() {
+                return false;
+            }
+            candidates.sort_by_key(|idx| {
+                writers_snapshot[*idx]
+                    .degraded
+                    .load(Ordering::Relaxed)
+                    .then_some(1usize)
+                    .unwrap_or(0)
+            });
+            let start = self.rr.fetch_add(1, Ordering::Relaxed) as usize % candidates.len();
+
+            for offset in 0..candidates.len() {
+                let idx = candidates[(start + offset) % candidates.len()];
+                let w = &writers_snapshot[idx];
+                if let Ok(mut guard) = w.writer.try_lock() {
+                    let send_res = guard.send(&payload).await;
+                    drop(guard);
+                    match send_res {
+                        Ok(()) => {
+                            self.registry
+                                .bind_writer(bound.conn_id, w.id, w.writer.clone(), bound.meta.clone())
+                                .await;
+                            return true;
+                        }
+                        Err(e) => {
+                            warn!(error = %e, writer_id = w.id, "ME reroute send failed");
+                            backlog.extend(self.remove_writer_only(w.id).await);
+                        }
+                    }
+                    continue;
+                }
+            }
+
+            let w = writers_snapshot[candidates[start]].clone();
+            match w.writer.lock().await.send(&payload).await {
+                Ok(()) => {
+                    self.registry
+                        .bind_writer(bound.conn_id, w.id, w.writer.clone(), bound.meta.clone())
+                        .await;
+                    return true;
+                }
+                Err(e) => {
+                    warn!(error = %e, writer_id = w.id, "ME reroute send failed (blocking)");
+                    backlog.extend(self.remove_writer_only(w.id).await);
+                }
+            }
+
+            attempts += 1;
+            if attempts > 3 {
+                return false;
+            }
+        }
+    }
+
+}
+
+fn hex_dump(data: &[u8]) -> String {
+    const MAX: usize = 64;
+    let mut out = String::with_capacity(data.len() * 2 + 3);
+    for (i, b) in data.iter().take(MAX).enumerate() {
+        if i > 0 {
+            out.push(' ');
+        }
+        out.push_str(&format!("{b:02x}"));
+    }
+    if data.len() > MAX {
+        out.push_str(" …");
+    }
+    out
+}

src/transport/middle_proxy/pool_nat.rs

@@ -0,0 +1,255 @@
+use std::net::{IpAddr, Ipv4Addr};
+use std::time::Duration;
+
+use tracing::{info, warn};
+
+use crate::error::{ProxyError, Result};
+
+use super::MePool;
+use std::time::Instant;
+
+#[derive(Debug, Clone, Copy)]
+pub struct StunProbeResult {
+    pub local_addr: std::net::SocketAddr,
+    pub reflected_addr: std::net::SocketAddr,
+}
+
+pub async fn stun_probe(stun_addr: Option<String>) -> Result<Option<StunProbeResult>> {
+    let stun_addr = stun_addr.unwrap_or_else(|| "stun.l.google.com:19302".to_string());
+    fetch_stun_binding(&stun_addr).await
+}
+
+pub async fn detect_public_ip() -> Option<IpAddr> {
+    fetch_public_ipv4_with_retry().await.ok().flatten().map(IpAddr::V4)
+}
+
+impl MePool {
+    pub(super) fn translate_ip_for_nat(&self, ip: IpAddr) -> IpAddr {
+        let nat_ip = self
+            .nat_ip_cfg
+            .or_else(|| self.nat_ip_detected.try_read().ok().and_then(|g| (*g).clone()));
+
+        let Some(nat_ip) = nat_ip else {
+            return ip;
+        };
+
+        match (ip, nat_ip) {
+            (IpAddr::V4(src), IpAddr::V4(dst))
+                if is_privateish(IpAddr::V4(src))
+                    || src.is_loopback()
+                    || src.is_unspecified() =>
+            {
+                IpAddr::V4(dst)
+            }
+            (IpAddr::V6(src), IpAddr::V6(dst)) if src.is_loopback() || src.is_unspecified() => {
+                IpAddr::V6(dst)
+            }
+            (orig, _) => orig,
+        }
+    }
+
+    pub(super) fn translate_our_addr_with_reflection(
+        &self,
+        addr: std::net::SocketAddr,
+        reflected: Option<std::net::SocketAddr>,
+    ) -> std::net::SocketAddr {
+        let ip = if let Some(r) = reflected {
+            // Use reflected IP (not port) only when local address is non-public.
+            if is_privateish(addr.ip()) || addr.ip().is_loopback() || addr.ip().is_unspecified() {
+                r.ip()
+            } else {
+                self.translate_ip_for_nat(addr.ip())
+            }
+        } else {
+            self.translate_ip_for_nat(addr.ip())
+        };
+
+        // Keep the kernel-assigned TCP source port; STUN port can differ.
+        std::net::SocketAddr::new(ip, addr.port())
+    }
+
+    pub(super) async fn maybe_detect_nat_ip(&self, local_ip: IpAddr) -> Option<IpAddr> {
+        if self.nat_ip_cfg.is_some() {
+            return self.nat_ip_cfg;
+        }
+
+        if !(is_privateish(local_ip) || local_ip.is_loopback() || local_ip.is_unspecified()) {
+            return None;
+        }
+
+        if let Some(ip) = self.nat_ip_detected.read().await.clone() {
+            return Some(ip);
+        }
+
+        match fetch_public_ipv4_with_retry().await {
+            Ok(Some(ip)) => {
+                {
+                    let mut guard = self.nat_ip_detected.write().await;
+                    *guard = Some(IpAddr::V4(ip));
+                }
+                info!(public_ip = %ip, "Auto-detected public IP for NAT translation");
+                Some(IpAddr::V4(ip))
+            }
+            Ok(None) => None,
+            Err(e) => {
+                warn!(error = %e, "Failed to auto-detect public IP");
+                None
+            }
+        }
+    }
+
+    pub(super) async fn maybe_reflect_public_addr(&self) -> Option<std::net::SocketAddr> {
+        const STUN_CACHE_TTL: Duration = Duration::from_secs(600);
+        if let Ok(mut cache) = self.nat_reflection_cache.try_lock() {
+            if let Some((ts, addr)) = *cache {
+                if ts.elapsed() < STUN_CACHE_TTL {
+                    return Some(addr);
+                }
+            }
+        }
+
+        let stun_addr = self
+            .nat_stun
+            .clone()
+            .unwrap_or_else(|| "stun.l.google.com:19302".to_string());
+        match fetch_stun_binding(&stun_addr).await {
+            Ok(sa) => {
+                if let Some(result) = sa {
+                    info!(local = %result.local_addr, reflected = %result.reflected_addr, "NAT probe: reflected address");
+                    if let Ok(mut cache) = self.nat_reflection_cache.try_lock() {
+                        *cache = Some((Instant::now(), result.reflected_addr));
+                    }
+                    Some(result.reflected_addr)
+                } else {
+                    None
+                }
+            }
+            Err(e) => {
+                warn!(error = %e, "NAT probe failed");
+                None
+            }
+        }
+    }
+}
+
+async fn fetch_public_ipv4_with_retry() -> Result<Option<Ipv4Addr>> {
+    let providers = [
+        "https://checkip.amazonaws.com",
+        "http://v4.ident.me",
+        "http://ipv4.icanhazip.com",
+    ];
+    for url in providers {
+        if let Ok(Some(ip)) = fetch_public_ipv4_once(url).await {
+            return Ok(Some(ip));
+        }
+    }
+    Ok(None)
+}
+
+async fn fetch_public_ipv4_once(url: &str) -> Result<Option<Ipv4Addr>> {
+    let res = reqwest::get(url).await.map_err(|e| {
+        ProxyError::Proxy(format!("public IP detection request failed: {e}"))
+    })?;
+
+    let text = res.text().await.map_err(|e| {
+        ProxyError::Proxy(format!("public IP detection read failed: {e}"))
+    })?;
+
+    let ip = text.trim().parse().ok();
+    Ok(ip)
+}
+
+async fn fetch_stun_binding(stun_addr: &str) -> Result<Option<StunProbeResult>> {
+    use rand::RngCore;
+    use tokio::net::UdpSocket;
+
+    let socket = UdpSocket::bind("0.0.0.0:0")
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN bind failed: {e}")))?;
+    socket
+        .connect(stun_addr)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN connect failed: {e}")))?;
+
+    // Build minimal Binding Request.
+    let mut req = vec![0u8; 20];
+    req[0..2].copy_from_slice(&0x0001u16.to_be_bytes()); // Binding Request
+    req[2..4].copy_from_slice(&0u16.to_be_bytes()); // length
+    req[4..8].copy_from_slice(&0x2112A442u32.to_be_bytes()); // magic cookie
+    rand::rng().fill_bytes(&mut req[8..20]);
+
+    socket
+        .send(&req)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN send failed: {e}")))?;
+
+    let mut buf = [0u8; 128];
+    let n = socket
+        .recv(&mut buf)
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("STUN recv failed: {e}")))?;
+    if n < 20 {
+        return Ok(None);
+    }
+
+    // Parse attributes.
+    let mut idx = 20;
+    while idx + 4 <= n {
+        let atype = u16::from_be_bytes(buf[idx..idx + 2].try_into().unwrap());
+        let alen = u16::from_be_bytes(buf[idx + 2..idx + 4].try_into().unwrap()) as usize;
+        idx += 4;
+        if idx + alen > n {
+            break;
+        }
+        match atype {
+            0x0020 /* XOR-MAPPED-ADDRESS */ | 0x0001 /* MAPPED-ADDRESS */ => {
+                if alen < 8 {
+                    break;
+                }
+                let family = buf[idx + 1];
+                if family != 0x01 {
+                    // only IPv4 supported here
+                    break;
+                }
+                let port_bytes = [buf[idx + 2], buf[idx + 3]];
+                let ip_bytes = [buf[idx + 4], buf[idx + 5], buf[idx + 6], buf[idx + 7]];
+
+                let (port, ip) = if atype == 0x0020 {
+                    let magic = 0x2112A442u32.to_be_bytes();
+                    let port = u16::from_be_bytes(port_bytes) ^ ((magic[0] as u16) << 8 | magic[1] as u16);
+                    let ip = [
+                        ip_bytes[0] ^ magic[0],
+                        ip_bytes[1] ^ magic[1],
+                        ip_bytes[2] ^ magic[2],
+                        ip_bytes[3] ^ magic[3],
+                    ];
+                    (port, ip)
+                } else {
+                    (u16::from_be_bytes(port_bytes), ip_bytes)
+                };
+                let reflected = std::net::SocketAddr::new(
+                    IpAddr::V4(Ipv4Addr::new(ip[0], ip[1], ip[2], ip[3])),
+                    port,
+                );
+                let local_addr = socket.local_addr().map_err(|e| {
+                    ProxyError::Proxy(format!("STUN local_addr failed: {e}"))
+                })?;
+                return Ok(Some(StunProbeResult {
+                    local_addr,
+                    reflected_addr: reflected,
+                }));
+            }
+            _ => {}
+        }
+        idx += (alen + 3) & !3; // 4-byte alignment
+    }
+
+    Ok(None)
+}
+
+fn is_privateish(ip: IpAddr) -> bool {
+    match ip {
+        IpAddr::V4(v4) => v4.is_private() || v4.is_link_local(),
+        IpAddr::V6(v6) => v6.is_unique_local(),
+    }
+}

src/transport/middle_proxy/reader.rs

@@ -0,0 +1,179 @@
+use std::collections::HashMap;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::time::Instant;
+
+use bytes::{Bytes, BytesMut};
+use tokio::io::AsyncReadExt;
+use tokio::net::TcpStream;
+use tokio::sync::Mutex;
+use tokio_util::sync::CancellationToken;
+use tracing::{debug, trace, warn};
+
+use crate::crypto::{AesCbc, crc32};
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::*;
+
+use super::codec::RpcWriter;
+use super::{ConnRegistry, MeResponse};
+
+pub(crate) async fn reader_loop(
+    mut rd: tokio::io::ReadHalf<TcpStream>,
+    dk: [u8; 32],
+    mut div: [u8; 16],
+    reg: Arc<ConnRegistry>,
+    enc_leftover: BytesMut,
+    mut dec: BytesMut,
+    writer: Arc<Mutex<RpcWriter>>,
+    ping_tracker: Arc<Mutex<HashMap<i64, (Instant, u64)>>>,
+    rtt_stats: Arc<Mutex<HashMap<u64, (f64, f64)>>>,
+    _writer_id: u64,
+    degraded: Arc<AtomicBool>,
+    cancel: CancellationToken,
+) -> Result<()> {
+    let mut raw = enc_leftover;
+    let mut expected_seq: i32 = 0;
+
+    loop {
+        let mut tmp = [0u8; 16_384];
+        let n = tokio::select! {
+            res = rd.read(&mut tmp) => res.map_err(ProxyError::Io)?,
+            _ = cancel.cancelled() => return Ok(()),
+        };
+        if n == 0 {
+            return Ok(());
+        }
+        raw.extend_from_slice(&tmp[..n]);
+
+        let blocks = raw.len() / 16 * 16;
+        if blocks > 0 {
+            let mut new_iv = [0u8; 16];
+            new_iv.copy_from_slice(&raw[blocks - 16..blocks]);
+
+            let mut chunk = vec![0u8; blocks];
+            chunk.copy_from_slice(&raw[..blocks]);
+            AesCbc::new(dk, div)
+                .decrypt_in_place(&mut chunk)
+                .map_err(|e| ProxyError::Crypto(format!("{e}")))?;
+            div = new_iv;
+            dec.extend_from_slice(&chunk);
+            let _ = raw.split_to(blocks);
+        }
+
+        while dec.len() >= 12 {
+            let fl = u32::from_le_bytes(dec[0..4].try_into().unwrap()) as usize;
+            if fl == 4 {
+                let _ = dec.split_to(4);
+                continue;
+            }
+            if !(12..=(1 << 24)).contains(&fl) {
+                warn!(frame_len = fl, "Invalid RPC frame len");
+                dec.clear();
+                break;
+            }
+            if dec.len() < fl {
+                break;
+            }
+
+            let frame = dec.split_to(fl);
+            let pe = fl - 4;
+            let ec = u32::from_le_bytes(frame[pe..pe + 4].try_into().unwrap());
+            if crc32(&frame[..pe]) != ec {
+                warn!("CRC mismatch in data frame");
+                continue;
+            }
+
+            let seq_no = i32::from_le_bytes(frame[4..8].try_into().unwrap());
+            if seq_no != expected_seq {
+                warn!(seq_no, expected = expected_seq, "ME RPC seq mismatch");
+                expected_seq = seq_no.wrapping_add(1);
+            } else {
+                expected_seq = expected_seq.wrapping_add(1);
+            }
+
+            let payload = &frame[8..pe];
+            if payload.len() < 4 {
+                continue;
+            }
+
+            let pt = u32::from_le_bytes(payload[0..4].try_into().unwrap());
+            let body = &payload[4..];
+
+            if pt == RPC_PROXY_ANS_U32 && body.len() >= 12 {
+                let flags = u32::from_le_bytes(body[0..4].try_into().unwrap());
+                let cid = u64::from_le_bytes(body[4..12].try_into().unwrap());
+                let data = Bytes::copy_from_slice(&body[12..]);
+                trace!(cid, flags, len = data.len(), "RPC_PROXY_ANS");
+
+                let routed = reg.route(cid, MeResponse::Data { flags, data }).await;
+                if !routed {
+                    reg.unregister(cid).await;
+                    send_close_conn(&writer, cid).await;
+                }
+            } else if pt == RPC_SIMPLE_ACK_U32 && body.len() >= 12 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                let cfm = u32::from_le_bytes(body[8..12].try_into().unwrap());
+                trace!(cid, cfm, "RPC_SIMPLE_ACK");
+
+                let routed = reg.route(cid, MeResponse::Ack(cfm)).await;
+                if !routed {
+                    reg.unregister(cid).await;
+                    send_close_conn(&writer, cid).await;
+                }
+            } else if pt == RPC_CLOSE_EXT_U32 && body.len() >= 8 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                debug!(cid, "RPC_CLOSE_EXT from ME");
+                reg.route(cid, MeResponse::Close).await;
+                reg.unregister(cid).await;
+            } else if pt == RPC_CLOSE_CONN_U32 && body.len() >= 8 {
+                let cid = u64::from_le_bytes(body[0..8].try_into().unwrap());
+                debug!(cid, "RPC_CLOSE_CONN from ME");
+                reg.route(cid, MeResponse::Close).await;
+                reg.unregister(cid).await;
+            } else if pt == RPC_PING_U32 && body.len() >= 8 {
+                let ping_id = i64::from_le_bytes(body[0..8].try_into().unwrap());
+                trace!(ping_id, "RPC_PING -> RPC_PONG");
+                let mut pong = Vec::with_capacity(12);
+                pong.extend_from_slice(&RPC_PONG_U32.to_le_bytes());
+                pong.extend_from_slice(&ping_id.to_le_bytes());
+                if let Err(e) = writer.lock().await.send(&pong).await {
+                    warn!(error = %e, "PONG send failed");
+                    break;
+                }
+            } else if pt == RPC_PONG_U32 && body.len() >= 8 {
+                let ping_id = i64::from_le_bytes(body[0..8].try_into().unwrap());
+                if let Some((sent, wid)) = {
+                    let mut guard = ping_tracker.lock().await;
+                    guard.remove(&ping_id)
+                } {
+                    let rtt = sent.elapsed().as_secs_f64() * 1000.0;
+                    let mut stats = rtt_stats.lock().await;
+                    let entry = stats.entry(wid).or_insert((rtt, rtt));
+                    entry.1 = entry.1 * 0.8 + rtt * 0.2;
+                    if rtt < entry.0 {
+                        entry.0 = rtt;
+                    }
+                    let degraded_now = entry.1 > entry.0 * 2.0;
+                    degraded.store(degraded_now, Ordering::Relaxed);
+                    trace!(writer_id = wid, rtt_ms = rtt, ema_ms = entry.1, base_ms = entry.0, degraded = degraded_now, "ME RTT sample");
+                }
+            } else {
+                debug!(
+                    rpc_type = format_args!("0x{pt:08x}"),
+                    len = body.len(),
+                    "Unknown RPC"
+                );
+            }
+        }
+    }
+}
+
+async fn send_close_conn(writer: &Arc<Mutex<RpcWriter>>, conn_id: u64) {
+    let mut p = Vec::with_capacity(12);
+    p.extend_from_slice(&RPC_CLOSE_CONN_U32.to_le_bytes());
+    p.extend_from_slice(&conn_id.to_le_bytes());
+
+    if let Err(e) = writer.lock().await.send(&p).await {
+        debug!(conn_id, error = %e, "Failed to send RPC_CLOSE_CONN");
+    }
+}

src/transport/middle_proxy/registry.rs

@@ -0,0 +1,133 @@
+use std::collections::HashMap;
+use std::net::SocketAddr;
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::Arc;
+
+use tokio::sync::{mpsc, Mutex, RwLock};
+
+use super::codec::RpcWriter;
+use super::MeResponse;
+
+#[derive(Clone)]
+pub struct ConnMeta {
+    pub target_dc: i16,
+    pub client_addr: SocketAddr,
+    pub our_addr: SocketAddr,
+    pub proto_flags: u32,
+}
+
+#[derive(Clone)]
+pub struct BoundConn {
+    pub conn_id: u64,
+    pub meta: ConnMeta,
+}
+
+#[derive(Clone)]
+pub struct ConnWriter {
+    pub writer_id: u64,
+    pub writer: Arc<Mutex<RpcWriter>>,
+}
+
+pub struct ConnRegistry {
+    map: RwLock<HashMap<u64, mpsc::Sender<MeResponse>>>,
+    writers: RwLock<HashMap<u64, Arc<Mutex<RpcWriter>>>>,
+    writer_for_conn: RwLock<HashMap<u64, u64>>,
+    conns_for_writer: RwLock<HashMap<u64, Vec<u64>>>,
+    meta: RwLock<HashMap<u64, ConnMeta>>,
+    next_id: AtomicU64,
+}
+
+impl ConnRegistry {
+    pub fn new() -> Self {
+        let start = rand::random::<u64>() | 1;
+        Self {
+            map: RwLock::new(HashMap::new()),
+            writers: RwLock::new(HashMap::new()),
+            writer_for_conn: RwLock::new(HashMap::new()),
+            conns_for_writer: RwLock::new(HashMap::new()),
+            meta: RwLock::new(HashMap::new()),
+            next_id: AtomicU64::new(start),
+        }
+    }
+
+    pub async fn register(&self) -> (u64, mpsc::Receiver<MeResponse>) {
+        let id = self.next_id.fetch_add(1, Ordering::Relaxed);
+        let (tx, rx) = mpsc::channel(1024);
+        self.map.write().await.insert(id, tx);
+        (id, rx)
+    }
+
+    pub async fn unregister(&self, id: u64) {
+        self.map.write().await.remove(&id);
+        self.meta.write().await.remove(&id);
+        if let Some(writer_id) = self.writer_for_conn.write().await.remove(&id) {
+            if let Some(list) = self.conns_for_writer.write().await.get_mut(&writer_id) {
+                list.retain(|c| *c != id);
+            }
+        }
+    }
+
+    pub async fn route(&self, id: u64, resp: MeResponse) -> bool {
+        let m = self.map.read().await;
+        if let Some(tx) = m.get(&id) {
+            tx.try_send(resp).is_ok()
+        } else {
+            false
+        }
+    }
+
+    pub async fn bind_writer(
+        &self,
+        conn_id: u64,
+        writer_id: u64,
+        writer: Arc<Mutex<RpcWriter>>,
+        meta: ConnMeta,
+    ) {
+        self.meta.write().await.entry(conn_id).or_insert(meta);
+        self.writer_for_conn.write().await.insert(conn_id, writer_id);
+        self.writers.write().await.entry(writer_id).or_insert_with(|| writer.clone());
+        self.conns_for_writer
+            .write()
+            .await
+            .entry(writer_id)
+            .or_insert_with(Vec::new)
+            .push(conn_id);
+    }
+
+    pub async fn get_writer(&self, conn_id: u64) -> Option<ConnWriter> {
+        let writer_id = {
+            let guard = self.writer_for_conn.read().await;
+            guard.get(&conn_id).cloned()
+        }?;
+        let writer = {
+            let guard = self.writers.read().await;
+            guard.get(&writer_id).cloned()
+        }?;
+        Some(ConnWriter { writer_id, writer })
+    }
+
+    pub async fn writer_lost(&self, writer_id: u64) -> Vec<BoundConn> {
+        self.writers.write().await.remove(&writer_id);
+        let conns = self.conns_for_writer.write().await.remove(&writer_id).unwrap_or_default();
+
+        let mut out = Vec::new();
+        let mut writer_for_conn = self.writer_for_conn.write().await;
+        let meta = self.meta.read().await;
+
+        for conn_id in conns {
+            writer_for_conn.remove(&conn_id);
+            if let Some(m) = meta.get(&conn_id) {
+                out.push(BoundConn {
+                    conn_id,
+                    meta: m.clone(),
+                });
+            }
+        }
+        out
+    }
+
+    pub async fn get_meta(&self, conn_id: u64) -> Option<ConnMeta> {
+        let guard = self.meta.read().await;
+        guard.get(&conn_id).cloned()
+    }
+}

src/transport/middle_proxy/rotation.rs

@@ -0,0 +1,37 @@
+use std::sync::Arc;
+use std::time::Duration;
+
+use tracing::{info, warn};
+
+use crate::crypto::SecureRandom;
+
+use super::MePool;
+
+/// Periodically refresh ME connections to avoid long-lived degradation.
+pub async fn me_rotation_task(pool: Arc<MePool>, rng: Arc<SecureRandom>, interval: Duration) {
+    let interval = interval.max(Duration::from_secs(600));
+    loop {
+        tokio::time::sleep(interval).await;
+
+        let candidate = {
+            let ws = pool.writers.read().await;
+            ws.get(0).cloned()
+        };
+
+        let Some(w) = candidate else {
+            continue;
+        };
+
+        info!(addr = %w.addr, writer_id = w.id, "Rotating ME connection");
+        match pool.connect_one(w.addr, rng.as_ref()).await {
+            Ok(()) => {
+                // Remove old writer after new one is up.
+                pool.remove_writer_and_reroute(w.id).await;
+            }
+            Err(e) => {
+                warn!(addr = %w.addr, writer_id = w.id, error = %e, "ME rotation connect failed");
+            }
+        }
+    }
+}
+

src/transport/middle_proxy/secret.rs

@@ -0,0 +1,100 @@
+use std::time::Duration;
+
+use tracing::{debug, info, warn};
+use std::time::SystemTime;
+use httpdate;
+
+use crate::error::{ProxyError, Result};
+
+/// Fetch Telegram proxy-secret binary.
+pub async fn fetch_proxy_secret(cache_path: Option<&str>) -> Result<Vec<u8>> {
+    let cache = cache_path.unwrap_or("proxy-secret");
+
+    // 1) Try fresh download first.
+    match download_proxy_secret().await {
+        Ok(data) => {
+            if let Err(e) = tokio::fs::write(cache, &data).await {
+                warn!(error = %e, "Failed to cache proxy-secret (non-fatal)");
+            } else {
+                debug!(path = cache, len = data.len(), "Cached proxy-secret");
+            }
+            return Ok(data);
+        }
+        Err(download_err) => {
+            warn!(error = %download_err, "Proxy-secret download failed, trying cache/file fallback");
+            // Fall through to cache/file.
+        }
+    }
+
+    // 2) Fallback to cache/file regardless of age; require len>=32.
+    match tokio::fs::read(cache).await {
+        Ok(data) if data.len() >= 32 => {
+            let age_hours = tokio::fs::metadata(cache)
+                .await
+                .ok()
+                .and_then(|m| m.modified().ok())
+                .and_then(|m| std::time::SystemTime::now().duration_since(m).ok())
+                .map(|d| d.as_secs() / 3600);
+            info!(
+                path = cache,
+                len = data.len(),
+                age_hours,
+                "Loaded proxy-secret from cache/file after download failure"
+            );
+            Ok(data)
+        }
+        Ok(data) => Err(ProxyError::Proxy(format!(
+            "Cached proxy-secret too short: {} bytes (need >= 32)",
+            data.len()
+        ))),
+        Err(e) => Err(ProxyError::Proxy(format!(
+            "Failed to read proxy-secret cache after download failure: {e}"
+        ))),
+    }
+}
+
+pub async fn download_proxy_secret() -> Result<Vec<u8>> {
+    let resp = reqwest::get("https://core.telegram.org/getProxySecret")
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("Failed to download proxy-secret: {e}")))?;
+
+    if !resp.status().is_success() {
+        return Err(ProxyError::Proxy(format!(
+            "proxy-secret download HTTP {}",
+            resp.status()
+        )));
+    }
+
+    if let Some(date) = resp.headers().get(reqwest::header::DATE) {
+        if let Ok(date_str) = date.to_str() {
+            if let Ok(server_time) = httpdate::parse_http_date(date_str) {
+                if let Ok(skew) = SystemTime::now().duration_since(server_time).or_else(|e| {
+                    server_time.duration_since(SystemTime::now()).map_err(|_| e)
+                }) {
+                    let skew_secs = skew.as_secs();
+                    if skew_secs > 60 {
+                        warn!(skew_secs, "Time skew >60s detected from proxy-secret Date header");
+                    } else if skew_secs > 30 {
+                        warn!(skew_secs, "Time skew >30s detected from proxy-secret Date header");
+                    }
+                }
+            }
+        }
+    }
+
+    let data = resp
+        .bytes()
+        .await
+        .map_err(|e| ProxyError::Proxy(format!("Read proxy-secret body: {e}")))?
+        .to_vec();
+
+    if data.len() < 32 {
+        return Err(ProxyError::Proxy(format!(
+            "proxy-secret too short: {} bytes (need >= 32)",
+            data.len()
+        )));
+    }
+
+    info!(len = data.len(), "Downloaded proxy-secret OK");
+    Ok(data)
+}

src/transport/middle_proxy/send.rs

@@ -0,0 +1,220 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+use std::sync::atomic::Ordering;
+use std::time::Duration;
+
+use tokio::sync::Mutex;
+use tracing::{debug, warn};
+
+use crate::error::{ProxyError, Result};
+use crate::protocol::constants::RPC_CLOSE_EXT_U32;
+
+use super::MePool;
+use super::wire::build_proxy_req_payload;
+use crate::crypto::SecureRandom;
+use rand::seq::SliceRandom;
+use super::registry::ConnMeta;
+
+impl MePool {
+    pub async fn send_proxy_req(
+        self: &Arc<Self>,
+        conn_id: u64,
+        target_dc: i16,
+        client_addr: SocketAddr,
+        our_addr: SocketAddr,
+        data: &[u8],
+        proto_flags: u32,
+    ) -> Result<()> {
+        let payload = build_proxy_req_payload(
+            conn_id,
+            client_addr,
+            our_addr,
+            data,
+            self.proxy_tag.as_deref(),
+            proto_flags,
+        );
+        let meta = ConnMeta {
+            target_dc,
+            client_addr,
+            our_addr,
+            proto_flags,
+        };
+        let mut emergency_attempts = 0;
+
+        loop {
+            if let Some(current) = self.registry.get_writer(conn_id).await {
+                let send_res = {
+                    if let Ok(mut guard) = current.writer.try_lock() {
+                        let r = guard.send(&payload).await;
+                        drop(guard);
+                        r
+                    } else {
+                        current.writer.lock().await.send(&payload).await
+                    }
+                };
+                match send_res {
+                    Ok(()) => return Ok(()),
+                    Err(e) => {
+                        warn!(error = %e, writer_id = current.writer_id, "ME write failed");
+                        self.remove_writer_and_reroute(current.writer_id).await;
+                        continue;
+                    }
+                }
+            }
+
+            let mut writers_snapshot = {
+                let ws = self.writers.read().await;
+                if ws.is_empty() {
+                    return Err(ProxyError::Proxy("All ME connections dead".into()));
+                }
+                ws.clone()
+            };
+
+            let mut candidate_indices = self.candidate_indices_for_dc(&writers_snapshot, target_dc).await;
+            if candidate_indices.is_empty() {
+                // Emergency connect-on-demand
+                if emergency_attempts >= 3 {
+                    return Err(ProxyError::Proxy("No ME writers available for target DC".into()));
+                }
+                emergency_attempts += 1;
+                let map = self.proxy_map_v4.read().await;
+                if let Some(addrs) = map.get(&(target_dc as i32)) {
+                    let mut shuffled = addrs.clone();
+                    shuffled.shuffle(&mut rand::rng());
+                    drop(map);
+                    for (ip, port) in shuffled {
+                        let addr = SocketAddr::new(ip, port);
+                        if self.connect_one(addr, &SecureRandom::new()).await.is_ok() {
+                            break;
+                        }
+                    }
+                    tokio::time::sleep(Duration::from_millis(100 * emergency_attempts)).await;
+                    let ws2 = self.writers.read().await;
+                    writers_snapshot = ws2.clone();
+                    drop(ws2);
+                    candidate_indices = self.candidate_indices_for_dc(&writers_snapshot, target_dc).await;
+                }
+                if candidate_indices.is_empty() {
+                    return Err(ProxyError::Proxy("No ME writers available for target DC".into()));
+                }
+            }
+
+            candidate_indices.sort_by_key(|idx| {
+                writers_snapshot[*idx]
+                    .degraded
+                    .load(Ordering::Relaxed)
+                    .then_some(1usize)
+                    .unwrap_or(0)
+            });
+
+            let start = self.rr.fetch_add(1, Ordering::Relaxed) as usize % candidate_indices.len();
+
+            for offset in 0..candidate_indices.len() {
+                let idx = candidate_indices[(start + offset) % candidate_indices.len()];
+                let w = &writers_snapshot[idx];
+                if let Ok(mut guard) = w.writer.try_lock() {
+                    let send_res = guard.send(&payload).await;
+                    drop(guard);
+                    match send_res {
+                        Ok(()) => {
+                            self.registry
+                                .bind_writer(conn_id, w.id, w.writer.clone(), meta.clone())
+                                .await;
+                            return Ok(());
+                        }
+                        Err(e) => {
+                            warn!(error = %e, writer_id = w.id, "ME write failed");
+                            self.remove_writer_and_reroute(w.id).await;
+                            continue;
+                        }
+                    }
+                }
+            }
+
+            let w = writers_snapshot[candidate_indices[start]].clone();
+            match w.writer.lock().await.send(&payload).await {
+                Ok(()) => {
+                    self.registry
+                        .bind_writer(conn_id, w.id, w.writer.clone(), meta.clone())
+                        .await;
+                    return Ok(());
+                }
+                Err(e) => {
+                    warn!(error = %e, writer_id = w.id, "ME write failed (blocking)");
+                    self.remove_writer_and_reroute(w.id).await;
+                }
+            }
+        }
+    }
+
+    pub async fn send_close(self: &Arc<Self>, conn_id: u64) -> Result<()> {
+        if let Some(w) = self.registry.get_writer(conn_id).await {
+            let mut p = Vec::with_capacity(12);
+            p.extend_from_slice(&RPC_CLOSE_EXT_U32.to_le_bytes());
+            p.extend_from_slice(&conn_id.to_le_bytes());
+            if let Err(e) = w.writer.lock().await.send(&p).await {
+                debug!(error = %e, "ME close write failed");
+                self.remove_writer_and_reroute(w.writer_id).await;
+            }
+        } else {
+            debug!(conn_id, "ME close skipped (writer missing)");
+        }
+
+        self.registry.unregister(conn_id).await;
+        Ok(())
+    }
+
+    pub fn connection_count(&self) -> usize {
+        self.writers.try_read().map(|w| w.len()).unwrap_or(0)
+    }
+    
+    pub(super) async fn candidate_indices_for_dc(
+        &self,
+        writers: &[super::pool::MeWriter],
+        target_dc: i16,
+    ) -> Vec<usize> {
+        let mut preferred = Vec::<SocketAddr>::new();
+        let key = target_dc as i32;
+        let map = self.proxy_map_v4.read().await;
+
+        if let Some(v) = map.get(&key) {
+            preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
+        }
+        if preferred.is_empty() {
+            let abs = key.abs();
+            if let Some(v) = map.get(&abs) {
+                preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
+            }
+        }
+        if preferred.is_empty() {
+            let abs = key.abs();
+            if let Some(v) = map.get(&-abs) {
+                preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
+            }
+        }
+        if preferred.is_empty() {
+            let def = self.default_dc.load(Ordering::Relaxed);
+            if def != 0 {
+                if let Some(v) = map.get(&def) {
+                    preferred.extend(v.iter().map(|(ip, port)| SocketAddr::new(*ip, *port)));
+                }
+            }
+        }
+
+        if preferred.is_empty() {
+            return (0..writers.len()).collect();
+        }
+
+        let mut out = Vec::new();
+        for (idx, w) in writers.iter().enumerate() {
+            if preferred.iter().any(|p| *p == w.addr) {
+                out.push(idx);
+            }
+        }
+        if out.is_empty() {
+            return (0..writers.len()).collect();
+        }
+        out
+    }
+
+}

src/transport/middle_proxy/wire.rs

@@ -0,0 +1,118 @@
+use std::net::{IpAddr, Ipv4Addr, SocketAddr};
+
+use crate::protocol::constants::*;
+
+#[derive(Clone, Copy)]
+pub(crate) enum IpMaterial {
+    V4([u8; 4]),
+    V6([u8; 16]),
+}
+
+pub(crate) fn extract_ip_material(addr: SocketAddr) -> IpMaterial {
+    match addr.ip() {
+        IpAddr::V4(v4) => IpMaterial::V4(v4.octets()),
+        IpAddr::V6(v6) => {
+            if let Some(v4) = v6.to_ipv4_mapped() {
+                IpMaterial::V4(v4.octets())
+            } else {
+                IpMaterial::V6(v6.octets())
+            }
+        }
+    }
+}
+
+fn ipv4_to_mapped_v6_c_compat(ip: Ipv4Addr) -> [u8; 16] {
+    let mut buf = [0u8; 16];
+
+    // Matches tl_store_long(0) + tl_store_int(-0x10000).
+    buf[8..12].copy_from_slice(&(-0x10000i32).to_le_bytes());
+
+    // Matches tl_store_int(htonl(remote_ip_host_order)).
+    buf[12..16].copy_from_slice(&ip.octets());
+
+    buf
+}
+
+fn append_mapped_addr_and_port(buf: &mut Vec<u8>, addr: SocketAddr) {
+    match addr.ip() {
+        IpAddr::V4(v4) => buf.extend_from_slice(&ipv4_to_mapped_v6_c_compat(v4)),
+        IpAddr::V6(v6) => buf.extend_from_slice(&v6.octets()),
+    }
+    buf.extend_from_slice(&(addr.port() as u32).to_le_bytes());
+}
+
+pub(crate) fn build_proxy_req_payload(
+    conn_id: u64,
+    client_addr: SocketAddr,
+    our_addr: SocketAddr,
+    data: &[u8],
+    proxy_tag: Option<&[u8]>,
+    proto_flags: u32,
+) -> Vec<u8> {
+    let mut b = Vec::with_capacity(128 + data.len());
+
+    b.extend_from_slice(&RPC_PROXY_REQ_U32.to_le_bytes());
+    b.extend_from_slice(&proto_flags.to_le_bytes());
+    b.extend_from_slice(&conn_id.to_le_bytes());
+
+    append_mapped_addr_and_port(&mut b, client_addr);
+    append_mapped_addr_and_port(&mut b, our_addr);
+
+    if proto_flags & RPC_FLAG_HAS_AD_TAG != 0 {
+        let extra_start = b.len();
+        b.extend_from_slice(&0u32.to_le_bytes());
+
+        if let Some(tag) = proxy_tag {
+            b.extend_from_slice(&TL_PROXY_TAG_U32.to_le_bytes());
+
+            if tag.len() < 254 {
+                b.push(tag.len() as u8);
+                b.extend_from_slice(tag);
+                let pad = (4 - ((1 + tag.len()) % 4)) % 4;
+                b.extend(std::iter::repeat_n(0u8, pad));
+            } else {
+                b.push(0xfe);
+                let len_bytes = (tag.len() as u32).to_le_bytes();
+                b.extend_from_slice(&len_bytes[..3]);
+                b.extend_from_slice(tag);
+                let pad = (4 - (tag.len() % 4)) % 4;
+                b.extend(std::iter::repeat_n(0u8, pad));
+            }
+        }
+
+        let extra_bytes = (b.len() - extra_start - 4) as u32;
+        b[extra_start..extra_start + 4].copy_from_slice(&extra_bytes.to_le_bytes());
+    }
+
+    b.extend_from_slice(data);
+    b
+}
+
+pub fn proto_flags_for_tag(tag: crate::protocol::constants::ProtoTag, has_proxy_tag: bool) -> u32 {
+    use crate::protocol::constants::ProtoTag;
+
+    let mut flags = RPC_FLAG_MAGIC | RPC_FLAG_EXTMODE2;
+    if has_proxy_tag {
+        flags |= RPC_FLAG_HAS_AD_TAG;
+    }
+
+    match tag {
+        ProtoTag::Abridged => flags | RPC_FLAG_ABRIDGED,
+        ProtoTag::Intermediate => flags | RPC_FLAG_INTERMEDIATE,
+        ProtoTag::Secure => flags | RPC_FLAG_PAD | RPC_FLAG_INTERMEDIATE,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_ipv4_mapped_encoding() {
+        let ip = Ipv4Addr::new(149, 154, 175, 50);
+        let buf = ipv4_to_mapped_v6_c_compat(ip);
+        assert_eq!(&buf[0..10], &[0u8; 10]);
+        assert_eq!(&buf[10..12], &[0xff, 0xff]);
+        assert_eq!(&buf[12..16], &[149, 154, 175, 50]);
+    }
+}

src/transport/mod.rs

@@ -10,4 +10,5 @@ pub use pool::ConnectionPool;
 pub use proxy_protocol::{ProxyProtocolInfo, parse_proxy_protocol};
 pub use socket::*;
 pub use socks::*;
-pub use upstream::{UpstreamManager, StartupPingResult, DcPingResult};
+pub use upstream::{DcPingResult, StartupPingResult, UpstreamManager};
+pub mod middle_proxy;

src/transport/pool.rs

@@ -285,12 +285,17 @@ where
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::io::ErrorKind;
     use tokio::net::TcpListener;
     
     #[tokio::test]
     async fn test_pool_basic() {
         // Start a test server
-        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let listener = match TcpListener::bind("127.0.0.1:0").await {
+            Ok(l) => l,
+            Err(e) if e.kind() == ErrorKind::PermissionDenied => return,
+            Err(e) => panic!("bind failed: {e}"),
+        };
         let addr = listener.local_addr().unwrap();
         
         // Accept connections in background
@@ -303,7 +308,11 @@ mod tests {
         let pool = ConnectionPool::new();
         
         // Get a connection
-        let conn1 = pool.get(addr).await.unwrap();
+        let conn1 = match pool.get(addr).await {
+            Ok(c) => c,
+            Err(ProxyError::Io(e)) if e.kind() == ErrorKind::PermissionDenied => return,
+            Err(e) => panic!("connect failed: {e}"),
+        };
         
         // Return it to pool
         pool.put(addr, conn1).await;
@@ -335,4 +344,4 @@ mod tests {
         assert_eq!(stats.endpoints, 0);
         assert_eq!(stats.total_connections, 0);
     }
-}
+}

src/transport/socket.rs

@@ -205,15 +205,29 @@ pub fn create_listener(addr: SocketAddr, options: &ListenOptions) -> Result<Sock
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::io::ErrorKind;
     use tokio::net::TcpListener;
     
     #[tokio::test]
     async fn test_configure_socket() {
-        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let listener = match TcpListener::bind("127.0.0.1:0").await {
+            Ok(l) => l,
+            Err(e) if e.kind() == ErrorKind::PermissionDenied => return,
+            Err(e) => panic!("bind failed: {e}"),
+        };
         let addr = listener.local_addr().unwrap();
         
-        let stream = TcpStream::connect(addr).await.unwrap();
-        configure_tcp_socket(&stream, true, Duration::from_secs(30)).unwrap();
+        let stream = match TcpStream::connect(addr).await {
+            Ok(s) => s,
+            Err(e) if e.kind() == ErrorKind::PermissionDenied => return,
+            Err(e) => panic!("connect failed: {e}"),
+        };
+        if let Err(e) = configure_tcp_socket(&stream, true, Duration::from_secs(30)) {
+            if e.kind() == ErrorKind::PermissionDenied {
+                return;
+            }
+            panic!("configure_tcp_socket failed: {e}");
+        }
     }
     
     #[test]
@@ -234,4 +248,4 @@ mod tests {
         assert!(opts.reuse_port);
         assert_eq!(opts.backlog, 1024);
     }
-}
+}

src/transport/upstream.rs

@@ -1,5 +1,8 @@
 //! Upstream Management with per-DC latency-weighted selection
+//! 
+//! IPv6/IPv4 connectivity checks with configurable preference.
 
+use std::collections::HashMap;
 use std::net::{SocketAddr, IpAddr};
 use std::sync::Arc;
 use std::time::Duration;
@@ -18,6 +21,9 @@ use crate::transport::socks::{connect_socks4, connect_socks5};
 /// Number of Telegram datacenters
 const NUM_DCS: usize = 5;
 
+/// Timeout for individual DC ping attempt
+const DC_PING_TIMEOUT_SECS: u64 = 5;
+
 // ============= RTT Tracking =============
 
 #[derive(Debug, Clone, Copy)]
@@ -30,19 +36,42 @@ impl LatencyEma {
     const fn new(alpha: f64) -> Self {
         Self { value_ms: None, alpha }
     }
-    
+
     fn update(&mut self, sample_ms: f64) {
         self.value_ms = Some(match self.value_ms {
             None => sample_ms,
             Some(prev) => prev * (1.0 - self.alpha) + sample_ms * self.alpha,
         });
     }
-    
+
     fn get(&self) -> Option<f64> {
         self.value_ms
     }
 }
 
+// ============= Per-DC IP Preference Tracking =============
+
+/// Tracks which IP version works for each DC
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum IpPreference {
+    /// Not yet tested
+    Unknown,
+    /// IPv6 works
+    PreferV6,
+    /// Only IPv4 works (IPv6 failed)
+    PreferV4,
+    /// Both work
+    BothWork,
+    /// Both failed
+    Unavailable,
+}
+
+impl Default for IpPreference {
+    fn default() -> Self {
+        Self::Unknown
+    }
+}
+
 // ============= Upstream State =============
 
 #[derive(Debug)]
@@ -53,6 +82,8 @@ struct UpstreamState {
     last_check: std::time::Instant,
     /// Per-DC latency EMA (index 0 = DC1, index 4 = DC5)
     dc_latency: [LatencyEma; NUM_DCS],
+    /// Per-DC IP version preference (learned from connectivity tests)
+    dc_ip_pref: [IpPreference; NUM_DCS],
 }
 
 impl UpstreamState {
@@ -63,16 +94,11 @@ impl UpstreamState {
             fails: 0,
             last_check: std::time::Instant::now(),
             dc_latency: [LatencyEma::new(0.3); NUM_DCS],
+            dc_ip_pref: [IpPreference::Unknown; NUM_DCS],
         }
     }
-    
+
     /// Map DC index to latency array slot (0..NUM_DCS).
-    ///
-    /// Matches the C implementation's `mf_cluster_lookup` behavior:
-    /// - Standard DCs ±1..±5 → direct mapping to array index 0..4
-    /// - Unknown DCs (CDN, media, etc.) → default DC slot (index 1 = DC 2)
-    ///   This matches Telegram's `default 2;` in proxy-multi.conf.
-    /// - There is NO modular arithmetic in the C implementation.
     fn dc_array_idx(dc_idx: i16) -> Option<usize> {
         let abs_dc = dc_idx.unsigned_abs() as usize;
         if abs_dc == 0 {
@@ -82,25 +108,22 @@ impl UpstreamState {
             Some(abs_dc - 1)
         } else {
             // Unknown DC → default cluster (DC 2, index 1)
-            // Same as C: mf_cluster_lookup returns default_cluster
             Some(1)
         }
     }
-    
+
     /// Get latency for a specific DC, falling back to average across all known DCs
     fn effective_latency(&self, dc_idx: Option<i16>) -> Option<f64> {
-        // Try DC-specific latency first
         if let Some(di) = dc_idx.and_then(Self::dc_array_idx) {
             if let Some(ms) = self.dc_latency[di].get() {
                 return Some(ms);
             }
         }
-        
-        // Fallback: average of all known DC latencies
+
         let (sum, count) = self.dc_latency.iter()
             .filter_map(|l| l.get())
             .fold((0.0, 0u32), |(s, c), v| (s + v, c + 1));
-        
+
         if count > 0 { Some(sum / count as f64) } else { None }
     }
 }
@@ -114,11 +137,14 @@ pub struct DcPingResult {
     pub error: Option<String>,
 }
 
-/// Result of startup ping for one upstream
+/// Result of startup ping for one upstream (separate v6/v4 results)
 #[derive(Debug, Clone)]
 pub struct StartupPingResult {
-    pub results: Vec<DcPingResult>,
+    pub v6_results: Vec<DcPingResult>,
+    pub v4_results: Vec<DcPingResult>,
     pub upstream_name: String,
+    /// True if both IPv6 and IPv4 have at least one working DC
+    pub both_available: bool,
 }
 
 // ============= Upstream Manager =============
@@ -134,22 +160,13 @@ impl UpstreamManager {
             .filter(|c| c.enabled)
             .map(UpstreamState::new)
             .collect();
-            
+
         Self {
             upstreams: Arc::new(RwLock::new(states)),
         }
     }
-    
+
     /// Select upstream using latency-weighted random selection.
-    ///
-    /// `effective_weight = config_weight × latency_factor`
-    ///
-    /// where `latency_factor = 1000 / latency_ms` if latency is known,
-    /// or `1.0` if no latency data is available.
-    ///
-    /// This means a 50ms upstream gets factor 20, a 200ms upstream gets
-    /// factor 5 — the faster route is 4× more likely to be chosen
-    /// (all else being equal).
     async fn select_upstream(&self, dc_idx: Option<i16>) -> Option<usize> {
         let upstreams = self.upstreams.read().await;
         if upstreams.is_empty() {
@@ -161,34 +178,32 @@ impl UpstreamManager {
             .filter(|(_, u)| u.healthy)
             .map(|(i, _)| i)
             .collect();
-            
+
         if healthy.is_empty() {
-            // All unhealthy — pick any
             return Some(rand::rng().gen_range(0..upstreams.len()));
         }
-        
+
         if healthy.len() == 1 {
             return Some(healthy[0]);
         }
-        
-        // Calculate latency-weighted scores
+
         let weights: Vec<(usize, f64)> = healthy.iter().map(|&i| {
             let base = upstreams[i].config.weight as f64;
             let latency_factor = upstreams[i].effective_latency(dc_idx)
                 .map(|ms| if ms > 1.0 { 1000.0 / ms } else { 1000.0 })
                 .unwrap_or(1.0);
-            
+
             (i, base * latency_factor)
         }).collect();
-        
+
         let total: f64 = weights.iter().map(|(_, w)| w).sum();
-        
+
         if total <= 0.0 {
             return Some(healthy[rand::rng().gen_range(0..healthy.len())]);
         }
-        
+
         let mut choice: f64 = rand::rng().gen_range(0.0..total);
-        
+
         for &(idx, weight) in &weights {
             if choice < weight {
                 trace!(
@@ -202,25 +217,22 @@ impl UpstreamManager {
             }
             choice -= weight;
         }
-        
+
         Some(healthy[0])
     }
-    
+
     /// Connect to target through a selected upstream.
-    ///
-    /// `dc_idx` is used for latency-based upstream selection and RTT tracking.
-    /// Pass `None` if DC index is unknown.
     pub async fn connect(&self, target: SocketAddr, dc_idx: Option<i16>) -> Result<TcpStream> {
         let idx = self.select_upstream(dc_idx).await
             .ok_or_else(|| ProxyError::Config("No upstreams available".to_string()))?;
-            
+
         let upstream = {
             let guard = self.upstreams.read().await;
             guard[idx].config.clone()
         };
-        
+
         let start = Instant::now();
-        
+
         match self.connect_via_upstream(&upstream, target).await {
             Ok(stream) => {
                 let rtt_ms = start.elapsed().as_secs_f64() * 1000.0;
@@ -231,8 +243,7 @@ impl UpstreamManager {
                     }
                     u.healthy = true;
                     u.fails = 0;
-                    
-                    // Store per-DC latency
+
                     if let Some(di) = dc_idx.and_then(UpstreamState::dc_array_idx) {
                         u.dc_latency[di].update(rtt_ms);
                     }
@@ -253,104 +264,107 @@ impl UpstreamManager {
             }
         }
     }
-    
+
     async fn connect_via_upstream(&self, config: &UpstreamConfig, target: SocketAddr) -> Result<TcpStream> {
         match &config.upstream_type {
             UpstreamType::Direct { interface } => {
                 let bind_ip = interface.as_ref()
                     .and_then(|s| s.parse::<IpAddr>().ok());
-                
+
                 let socket = create_outgoing_socket_bound(target, bind_ip)?;
-                
+
                 socket.set_nonblocking(true)?;
                 match socket.connect(&target.into()) {
                     Ok(()) => {},
                     Err(err) if err.raw_os_error() == Some(libc::EINPROGRESS) || err.kind() == std::io::ErrorKind::WouldBlock => {},
                     Err(err) => return Err(ProxyError::Io(err)),
                 }
-                
+
                 let std_stream: std::net::TcpStream = socket.into();
                 let stream = TcpStream::from_std(std_stream)?;
-                
+
                 stream.writable().await?;
                 if let Some(e) = stream.take_error()? {
                     return Err(ProxyError::Io(e));
                 }
-                
+
                 Ok(stream)
             },
             UpstreamType::Socks4 { address, interface, user_id } => {
                 let proxy_addr: SocketAddr = address.parse()
                     .map_err(|_| ProxyError::Config("Invalid SOCKS4 address".to_string()))?;
-                    
+
                 let bind_ip = interface.as_ref()
                     .and_then(|s| s.parse::<IpAddr>().ok());
-                
+
                 let socket = create_outgoing_socket_bound(proxy_addr, bind_ip)?;
-                
+
                 socket.set_nonblocking(true)?;
                 match socket.connect(&proxy_addr.into()) {
                     Ok(()) => {},
                     Err(err) if err.raw_os_error() == Some(libc::EINPROGRESS) || err.kind() == std::io::ErrorKind::WouldBlock => {},
                     Err(err) => return Err(ProxyError::Io(err)),
                 }
-                
+
                 let std_stream: std::net::TcpStream = socket.into();
                 let mut stream = TcpStream::from_std(std_stream)?;
-                
+
                 stream.writable().await?;
                 if let Some(e) = stream.take_error()? {
                     return Err(ProxyError::Io(e));
                 }
-                
+
                 connect_socks4(&mut stream, target, user_id.as_deref()).await?;
                 Ok(stream)
             },
             UpstreamType::Socks5 { address, interface, username, password } => {
                 let proxy_addr: SocketAddr = address.parse()
                     .map_err(|_| ProxyError::Config("Invalid SOCKS5 address".to_string()))?;
-                    
+
                 let bind_ip = interface.as_ref()
                     .and_then(|s| s.parse::<IpAddr>().ok());
-                
+
                 let socket = create_outgoing_socket_bound(proxy_addr, bind_ip)?;
-                
+
                 socket.set_nonblocking(true)?;
                 match socket.connect(&proxy_addr.into()) {
                     Ok(()) => {},
                     Err(err) if err.raw_os_error() == Some(libc::EINPROGRESS) || err.kind() == std::io::ErrorKind::WouldBlock => {},
                     Err(err) => return Err(ProxyError::Io(err)),
                 }
-                
+
                 let std_stream: std::net::TcpStream = socket.into();
                 let mut stream = TcpStream::from_std(std_stream)?;
-                
+
                 stream.writable().await?;
                 if let Some(e) = stream.take_error()? {
                     return Err(ProxyError::Io(e));
                 }
-                
+
                 connect_socks5(&mut stream, target, username.as_deref(), password.as_deref()).await?;
                 Ok(stream)
             },
         }
     }
-    
-    // ============= Startup Ping =============
-    
+
+    // ============= Startup Ping (test both IPv6 and IPv4) =============
+
     /// Ping all Telegram DCs through all upstreams.
-    pub async fn ping_all_dcs(&self, prefer_ipv6: bool) -> Vec<StartupPingResult> {
+    /// Tests BOTH IPv6 and IPv4, returns separate results for each.
+    pub async fn ping_all_dcs(
+        &self,
+        prefer_ipv6: bool,
+        dc_overrides: &HashMap<String, Vec<String>>,
+    ) -> Vec<StartupPingResult> {
         let upstreams: Vec<(usize, UpstreamConfig)> = {
             let guard = self.upstreams.read().await;
             guard.iter().enumerate()
                 .map(|(i, u)| (i, u.config.clone()))
                 .collect()
         };
-        
-        let datacenters = if prefer_ipv6 { &*TG_DATACENTERS_V6 } else { &*TG_DATACENTERS_V4 };
-        
+
         let mut all_results = Vec::new();
-        
+
         for (upstream_idx, upstream_config) in &upstreams {
             let upstream_name = match &upstream_config.upstream_type {
                 UpstreamType::Direct { interface } => {
@@ -359,130 +373,312 @@ impl UpstreamManager {
                 UpstreamType::Socks4 { address, .. } => format!("socks4://{}", address),
                 UpstreamType::Socks5 { address, .. } => format!("socks5://{}", address),
             };
-            
-            let mut dc_results = Vec::new();
-            
-            for (dc_zero_idx, dc_ip) in datacenters.iter().enumerate() {
-                let dc_addr = SocketAddr::new(*dc_ip, TG_DATACENTER_PORT);
-                
-                let ping_result = tokio::time::timeout(
-                    Duration::from_secs(5),
-                    self.ping_single_dc(upstream_config, dc_addr)
+
+            let mut v6_results = Vec::new();
+            let mut v4_results = Vec::new();
+
+            // === Ping IPv6 first ===
+            for dc_zero_idx in 0..NUM_DCS {
+                let dc_v6 = TG_DATACENTERS_V6[dc_zero_idx];
+                let addr_v6 = SocketAddr::new(dc_v6, TG_DATACENTER_PORT);
+
+                let result = tokio::time::timeout(
+                    Duration::from_secs(DC_PING_TIMEOUT_SECS),
+                    self.ping_single_dc(&upstream_config, addr_v6)
                 ).await;
-                
-                let result = match ping_result {
+
+                let ping_result = match result {
                     Ok(Ok(rtt_ms)) => {
-                        // Store per-DC latency
                         let mut guard = self.upstreams.write().await;
                         if let Some(u) = guard.get_mut(*upstream_idx) {
                             u.dc_latency[dc_zero_idx].update(rtt_ms);
                         }
                         DcPingResult {
                             dc_idx: dc_zero_idx + 1,
-                            dc_addr,
+                            dc_addr: addr_v6,
                             rtt_ms: Some(rtt_ms),
                             error: None,
                         }
                     }
                     Ok(Err(e)) => DcPingResult {
                         dc_idx: dc_zero_idx + 1,
-                        dc_addr,
+                        dc_addr: addr_v6,
                         rtt_ms: None,
                         error: Some(e.to_string()),
                     },
                     Err(_) => DcPingResult {
                         dc_idx: dc_zero_idx + 1,
-                        dc_addr,
+                        dc_addr: addr_v6,
                         rtt_ms: None,
-                        error: Some("timeout (5s)".to_string()),
+                        error: Some("timeout".to_string()),
                     },
                 };
-                
-                dc_results.push(result);
+                v6_results.push(ping_result);
             }
-            
+
+            // === Then ping IPv4 ===
+            for dc_zero_idx in 0..NUM_DCS {
+                let dc_v4 = TG_DATACENTERS_V4[dc_zero_idx];
+                let addr_v4 = SocketAddr::new(dc_v4, TG_DATACENTER_PORT);
+
+                let result = tokio::time::timeout(
+                    Duration::from_secs(DC_PING_TIMEOUT_SECS),
+                    self.ping_single_dc(&upstream_config, addr_v4)
+                ).await;
+
+                let ping_result = match result {
+                    Ok(Ok(rtt_ms)) => {
+                        let mut guard = self.upstreams.write().await;
+                        if let Some(u) = guard.get_mut(*upstream_idx) {
+                            u.dc_latency[dc_zero_idx].update(rtt_ms);
+                        }
+                        DcPingResult {
+                            dc_idx: dc_zero_idx + 1,
+                            dc_addr: addr_v4,
+                            rtt_ms: Some(rtt_ms),
+                            error: None,
+                        }
+                    }
+                    Ok(Err(e)) => DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: addr_v4,
+                        rtt_ms: None,
+                        error: Some(e.to_string()),
+                    },
+                    Err(_) => DcPingResult {
+                        dc_idx: dc_zero_idx + 1,
+                        dc_addr: addr_v4,
+                        rtt_ms: None,
+                        error: Some("timeout".to_string()),
+                    },
+                };
+                v4_results.push(ping_result);
+            }
+
+            // === Ping DC overrides (v4/v6) ===
+            for (dc_key, addrs) in dc_overrides {
+                let dc_num: i16 = match dc_key.parse::<i16>() {
+                    Ok(v) if v > 0 => v,
+                    Err(_) => {
+                        warn!(dc = %dc_key, "Invalid dc_overrides key, skipping");
+                        continue;
+                    },
+                    _ => continue,
+                };
+                let dc_idx = dc_num as usize;
+                for addr_str in addrs {
+                    match addr_str.parse::<SocketAddr>() {
+                        Ok(addr) => {
+                            let is_v6 = addr.is_ipv6();
+                            let result = tokio::time::timeout(
+                                Duration::from_secs(DC_PING_TIMEOUT_SECS),
+                                self.ping_single_dc(&upstream_config, addr)
+                            ).await;
+
+                            let ping_result = match result {
+                                Ok(Ok(rtt_ms)) => DcPingResult {
+                                    dc_idx,
+                                    dc_addr: addr,
+                                    rtt_ms: Some(rtt_ms),
+                                    error: None,
+                                },
+                                Ok(Err(e)) => DcPingResult {
+                                    dc_idx,
+                                    dc_addr: addr,
+                                    rtt_ms: None,
+                                    error: Some(e.to_string()),
+                                },
+                                Err(_) => DcPingResult {
+                                    dc_idx,
+                                    dc_addr: addr,
+                                    rtt_ms: None,
+                                    error: Some("timeout".to_string()),
+                                },
+                            };
+
+                            if is_v6 {
+                                v6_results.push(ping_result);
+                            } else {
+                                v4_results.push(ping_result);
+                            }
+                        }
+                        Err(_) => warn!(dc = %dc_idx, addr = %addr_str, "Invalid dc_overrides address, skipping"),
+                    }
+                }
+            }
+
+            // Check if both IP versions have at least one working DC
+            let v6_has_working = v6_results.iter().any(|r| r.rtt_ms.is_some());
+            let v4_has_working = v4_results.iter().any(|r| r.rtt_ms.is_some());
+            let both_available = v6_has_working && v4_has_working;
+
+            // Update IP preference for each DC
+            {
+                let mut guard = self.upstreams.write().await;
+                if let Some(u) = guard.get_mut(*upstream_idx) {
+                    for dc_zero_idx in 0..NUM_DCS {
+                        let v6_ok = v6_results[dc_zero_idx].rtt_ms.is_some();
+                        let v4_ok = v4_results[dc_zero_idx].rtt_ms.is_some();
+
+                        u.dc_ip_pref[dc_zero_idx] = match (v6_ok, v4_ok) {
+                            (true, true) => IpPreference::BothWork,
+                            (true, false) => IpPreference::PreferV6,
+                            (false, true) => IpPreference::PreferV4,
+                            (false, false) => IpPreference::Unavailable,
+                        };
+                    }
+                }
+            }
+
             all_results.push(StartupPingResult {
-                results: dc_results,
+                v6_results,
+                v4_results,
                 upstream_name,
+                both_available,
             });
         }
-        
+
         all_results
     }
-    
+
     async fn ping_single_dc(&self, config: &UpstreamConfig, target: SocketAddr) -> Result<f64> {
         let start = Instant::now();
         let _stream = self.connect_via_upstream(config, target).await?;
         Ok(start.elapsed().as_secs_f64() * 1000.0)
     }
-    
+
     // ============= Health Checks =============
-    
+
     /// Background health check: rotates through DCs, 30s interval.
+    /// Uses preferred IP version based on config.
     pub async fn run_health_checks(&self, prefer_ipv6: bool) {
-        let datacenters = if prefer_ipv6 { &*TG_DATACENTERS_V6 } else { &*TG_DATACENTERS_V4 };
         let mut dc_rotation = 0usize;
-        
+
         loop {
             tokio::time::sleep(Duration::from_secs(30)).await;
-            
-            let dc_zero_idx = dc_rotation % datacenters.len();
+
+            let dc_zero_idx = dc_rotation % NUM_DCS;
             dc_rotation += 1;
-            
-            let check_target = SocketAddr::new(datacenters[dc_zero_idx], TG_DATACENTER_PORT);
-            
+
+            let dc_addr = if prefer_ipv6 {
+                SocketAddr::new(TG_DATACENTERS_V6[dc_zero_idx], TG_DATACENTER_PORT)
+            } else {
+                SocketAddr::new(TG_DATACENTERS_V4[dc_zero_idx], TG_DATACENTER_PORT)
+            };
+
+            let fallback_addr = if prefer_ipv6 {
+                SocketAddr::new(TG_DATACENTERS_V4[dc_zero_idx], TG_DATACENTER_PORT)
+            } else {
+                SocketAddr::new(TG_DATACENTERS_V6[dc_zero_idx], TG_DATACENTER_PORT)
+            };
+
             let count = self.upstreams.read().await.len();
+
             for i in 0..count {
                 let config = {
                     let guard = self.upstreams.read().await;
                     guard[i].config.clone()
                 };
-                
+
                 let start = Instant::now();
                 let result = tokio::time::timeout(
                     Duration::from_secs(10),
-                    self.connect_via_upstream(&config, check_target)
+                    self.connect_via_upstream(&config, dc_addr)
                 ).await;
-                
-                let mut guard = self.upstreams.write().await;
-                let u = &mut guard[i];
-                
+
                 match result {
                     Ok(Ok(_stream)) => {
                         let rtt_ms = start.elapsed().as_secs_f64() * 1000.0;
+                        let mut guard = self.upstreams.write().await;
+                        let u = &mut guard[i];
                         u.dc_latency[dc_zero_idx].update(rtt_ms);
-                        
+
                         if !u.healthy {
                             info!(
-                                rtt = format!("{:.0}ms", rtt_ms),
+                                rtt = format!("{:.0} ms", rtt_ms),
                                 dc = dc_zero_idx + 1,
                                 "Upstream recovered"
                             );
                         }
                         u.healthy = true;
                         u.fails = 0;
+                        u.last_check = std::time::Instant::now();
                     }
-                    Ok(Err(e)) => {
-                        u.fails += 1;
-                        debug!(dc = dc_zero_idx + 1, fails = u.fails,
-                            "Health check failed: {}", e);
-                        if u.fails > 3 {
-                            u.healthy = false;
-                            warn!("Upstream unhealthy (fails)");
-                        }
-                    }
-                    Err(_) => {
-                        u.fails += 1;
-                        debug!(dc = dc_zero_idx + 1, fails = u.fails,
-                            "Health check timeout");
-                        if u.fails > 3 {
-                            u.healthy = false;
-                            warn!("Upstream unhealthy (timeout)");
+                    Ok(Err(_)) | Err(_) => {
+                        // Try fallback
+                        debug!(dc = dc_zero_idx + 1, "Health check failed, trying fallback");
+
+                        let start2 = Instant::now();
+                        let result2 = tokio::time::timeout(
+                            Duration::from_secs(10),
+                            self.connect_via_upstream(&config, fallback_addr)
+                        ).await;
+
+                        let mut guard = self.upstreams.write().await;
+                        let u = &mut guard[i];
+
+                        match result2 {
+                            Ok(Ok(_stream)) => {
+                                let rtt_ms = start2.elapsed().as_secs_f64() * 1000.0;
+                                u.dc_latency[dc_zero_idx].update(rtt_ms);
+
+                                if !u.healthy {
+                                    info!(
+                                        rtt = format!("{:.0} ms", rtt_ms),
+                                        dc = dc_zero_idx + 1,
+                                        "Upstream recovered (fallback)"
+                                    );
+                                }
+                                u.healthy = true;
+                                u.fails = 0;
+                            }
+                            Ok(Err(e)) => {
+                                u.fails += 1;
+                                debug!(dc = dc_zero_idx + 1, fails = u.fails,
+                                    "Health check failed (both): {}", e);
+                                if u.fails > 3 {
+                                    u.healthy = false;
+                                    warn!("Upstream unhealthy (fails)");
+                                }
+                            }
+                            Err(_) => {
+                                u.fails += 1;
+                                debug!(dc = dc_zero_idx + 1, fails = u.fails,
+                                    "Health check timeout (both)");
+                                if u.fails > 3 {
+                                    u.healthy = false;
+                                    warn!("Upstream unhealthy (timeout)");
+                                }
+                            }
                         }
+                        u.last_check = std::time::Instant::now();
                     }
                 }
-                u.last_check = std::time::Instant::now();
             }
         }
     }
-}
+
+    /// Get the preferred IP for a DC (for use by other components)
+    pub async fn get_dc_ip_preference(&self, dc_idx: i16) -> Option<IpPreference> {
+        let guard = self.upstreams.read().await;
+        if guard.is_empty() {
+            return None;
+        }
+
+        UpstreamState::dc_array_idx(dc_idx)
+            .map(|idx| guard[0].dc_ip_pref[idx])
+    }
+
+    /// Get preferred DC address based on config preference
+    pub async fn get_dc_addr(&self, dc_idx: i16, prefer_ipv6: bool) -> Option<SocketAddr> {
+        let arr_idx = UpstreamState::dc_array_idx(dc_idx)?;
+
+        let ip = if prefer_ipv6 {
+            TG_DATACENTERS_V6[arr_idx]
+        } else {
+            TG_DATACENTERS_V4[arr_idx]
+        };
+
+        Some(SocketAddr::new(ip, TG_DATACENTER_PORT))
+    }
+}

tools/dc.py

@@ -0,0 +1,204 @@
+"""Telegram datacenter server checker."""
+
+from __future__ import annotations
+
+import asyncio
+from dataclasses import dataclass, field
+from itertools import groupby
+from operator import attrgetter
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+from telethon import TelegramClient
+from telethon.tl.functions.help import GetConfigRequest
+
+if TYPE_CHECKING:
+    from telethon.tl.types import DcOption
+
+API_ID: int = 123456
+API_HASH: str = ""
+SESSION_NAME: str = "session"
+OUTPUT_FILE: Path = Path("telegram_servers.txt")
+
+_CONSOLE_FLAG_MAP: dict[str, str] = {
+    "IPv6": "IPv6",
+    "MEDIA-ONLY": "🎬 MEDIA-ONLY",
+    "CDN": "📦 CDN",
+    "TCPO": "🔒 TCPO",
+    "STATIC": "📌 STATIC",
+}
+
+
+@dataclass(frozen=True, slots=True)
+class DCServer:
+    """Typed representation of a Telegram DC server.
+
+    Attributes:
+        dc_id: Datacenter identifier.
+        ip: Server IP address.
+        port: Server port.
+        flags: Active flag labels (plain, without emoji).
+    """
+
+    dc_id: int
+    ip: str
+    port: int
+    flags: frozenset[str] = field(default_factory=frozenset)
+
+    @classmethod
+    def from_option(cls, dc: DcOption) -> DCServer:
+        """Create from a Telethon DcOption.
+
+        Args:
+            dc: Raw DcOption object.
+
+        Returns:
+            Parsed DCServer instance.
+        """
+        checks: dict[str, bool] = {
+            "IPv6": dc.ipv6,
+            "MEDIA-ONLY": dc.media_only,
+            "CDN": dc.cdn,
+            "TCPO": dc.tcpo_only,
+            "STATIC": dc.static,
+        }
+        return cls(
+            dc_id=dc.id,
+            ip=dc.ip_address,
+            port=dc.port,
+            flags=frozenset(k for k, v in checks.items() if v),
+        )
+
+    def flags_display(self, *, emoji: bool = False) -> str:
+        """Formatted flags string.
+
+        Args:
+            emoji: Whether to include emoji prefixes.
+
+        Returns:
+            Bracketed flags or '[STANDARD]'.
+        """
+        if not self.flags:
+            return "[STANDARD]"
+        labels = sorted(
+            _CONSOLE_FLAG_MAP[f] if emoji else f for f in self.flags
+        )
+        return f"[{', '.join(labels)}]"
+
+
+class TelegramDCChecker:
+    """Fetches and displays Telegram DC configuration.
+
+    Attributes:
+        _client: Telethon client instance.
+        _servers: Parsed server list.
+    """
+
+    def __init__(self) -> None:
+        """Initialize the checker."""
+        self._client = TelegramClient(SESSION_NAME, API_ID, API_HASH)
+        self._servers: list[DCServer] = []
+
+    async def run(self) -> None:
+        """Connect, fetch config, display and save results."""
+        print("🔄 Подключаемся к Telegram...")  # noqa: T201
+        try:
+            await self._client.start()
+            print("✅ Подключение установлено!\n")  # noqa: T201
+
+            print("📡 Запрашиваем конфигурацию серверов...")  # noqa: T201
+            config = await self._client(GetConfigRequest())
+            self._servers = [DCServer.from_option(dc) for dc in config.dc_options]
+
+            self._print(config)
+            self._save(config)
+        finally:
+            await self._client.disconnect()
+            print("\n👋 Отключились от Telegram")  # noqa: T201
+
+    def _grouped(self) -> dict[int, list[DCServer]]:
+        """Group servers by DC ID.
+
+        Returns:
+            Ordered mapping of DC ID to servers.
+        """
+        ordered = sorted(self._servers, key=attrgetter("dc_id"))
+        return {k: list(g) for k, g in groupby(ordered, key=attrgetter("dc_id"))}
+
+    def _print(self, config: object) -> None:
+        """Print results to stdout in original format.
+
+        Args:
+            config: Raw Telegram config.
+        """
+        sep = "=" * 80
+        dash = "-" * 80
+        total = len(self._servers)
+
+        print(f"📊 Получено серверов: {total}\n")  # noqa: T201
+        print(sep)  # noqa: T201
+
+        for dc_id, servers in self._grouped().items():
+            print(f"\n🌐 DATACENTER {dc_id} ({len(servers)} серверов)")  # noqa: T201
+            print(dash)  # noqa: T201
+            for s in servers:
+                print(f"  {s.ip:45}:{s.port:5} {s.flags_display(emoji=True)}")  # noqa: T201
+
+        ipv4 = total - self._flag_count("IPv6")
+        print(f"\n{sep}")  # noqa: T201
+        print("📈 СТАТИСТИКА:")  # noqa: T201
+        print(sep)  # noqa: T201
+        print(f"  Всего серверов:      {total}")  # noqa: T201
+        print(f"  IPv4 серверы:        {ipv4}")  # noqa: T201
+        print(f"  IPv6 серверы:        {self._flag_count('IPv6')}")  # noqa: T201
+        print(f"  Media-only:          {self._flag_count('MEDIA-ONLY')}")  # noqa: T201
+        print(f"  CDN серверы:         {self._flag_count('CDN')}")  # noqa: T201
+        print(f"  TCPO-only:           {self._flag_count('TCPO')}")  # noqa: T201
+        print(f"  Static:              {self._flag_count('STATIC')}")  # noqa: T201
+
+        print(f"\n{sep}")  # noqa: T201
+        print("ℹ️  ДОПОЛНИТЕЛЬНАЯ ИНФОРМАЦИЯ:")  # noqa: T201
+        print(sep)  # noqa: T201
+        print(f"  Дата конфигурации:   {config.date}")  # noqa: T201  # type: ignore[attr-defined]
+        print(f"  Expires:             {config.expires}")  # noqa: T201  # type: ignore[attr-defined]
+        print(f"  Test mode:           {config.test_mode}")  # noqa: T201  # type: ignore[attr-defined]
+        print(f"  This DC:             {config.this_dc}")  # noqa: T201  # type: ignore[attr-defined]
+
+    def _flag_count(self, flag: str) -> int:
+        """Count servers with a given flag.
+
+        Args:
+            flag: Flag name.
+
+        Returns:
+            Count of matching servers.
+        """
+        return sum(1 for s in self._servers if flag in s.flags)
+
+    def _save(self, config: object) -> None:
+        """Save results to file in original format.
+
+        Args:
+            config: Raw Telegram config.
+        """
+        parts: list[str] = []
+        parts.append("TELEGRAM DATACENTER SERVERS\n")
+        parts.append("=" * 80 + "\n\n")
+
+        for dc_id, servers in self._grouped().items():
+            parts.append(f"\nDATACENTER {dc_id} ({len(servers)} servers)\n")
+            parts.append("-" * 80 + "\n")
+            for s in servers:
+                parts.append(f"  {s.ip}:{s.port} {s.flags_display(emoji=False)}\n")
+
+        parts.append(f"\n\nTotal servers: {len(self._servers)}\n")
+        parts.append(f"Generated: {config.date}\n")  # type: ignore[attr-defined]
+
+        OUTPUT_FILE.write_text("".join(parts), encoding="utf-8")
+
+        print(f"\n💾 Сохраняем результаты в файл {OUTPUT_FILE}...")  # noqa: T201
+        print(f"✅ Результаты сохранены в {OUTPUT_FILE}")  # noqa: T201
+
+
+if __name__ == "__main__":
+    asyncio.run(TelegramDCChecker().run())