amnezia-client/client/platforms/ios/HevSocksTunnel.swift

import HevSocks5Tunnel
import NetworkExtension

public enum Socks5Tunnel {

    private static var tunnelFileDescriptor: Int32? {
        var ctlInfo = ctl_info()
        withUnsafeMutablePointer(to: &ctlInfo.ctl_name) {
            $0.withMemoryRebound(to: CChar.self, capacity: MemoryLayout.size(ofValue: $0.pointee)) {
                _ = strcpy($0, "com.apple.net.utun_control")
            }
        }

        func scanForUtun() -> Int32? {
            for fd: Int32 in 0...1024 {
                var addr = sockaddr_ctl()
                var ret: Int32 = -1
                var len = socklen_t(MemoryLayout.size(ofValue: addr))
                withUnsafeMutablePointer(to: &addr) {
                    $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                        ret = getpeername(fd, $0, &len)
                    }
                }
                if ret != 0 || addr.sc_family != AF_SYSTEM { continue }
                if ctlInfo.ctl_id == 0 {
                    ret = ioctl(fd, CTLIOCGINFO, &ctlInfo)
                    if ret != 0 { continue }
                }
                if addr.sc_id == ctlInfo.ctl_id { return fd }
            }
            return nil
        }

        // On newer iOS versions, utun can appear slightly after settings
        // application. Poll briefly rather than aborting.
        let deadline = Date().addingTimeInterval(3.0)
        repeat {
            if let fd = scanForUtun() { return fd }
            // Sleep a bit to avoid busy-waiting
            usleep(50_000) // 50ms
        } while Date() < deadline

        return nil
    }

    private static var interfaceName: String? {
        guard let tunnelFileDescriptor = self.tunnelFileDescriptor else {
            return nil
        }
        var buffer = [UInt8](repeating: 0, count: Int(IFNAMSIZ))
        return buffer.withUnsafeMutableBufferPointer { mutableBufferPointer in
            guard let baseAddress = mutableBufferPointer.baseAddress else {
                return nil
            }
            var ifnameSize = socklen_t(IFNAMSIZ)
            let result = getsockopt(
                tunnelFileDescriptor,
                2 /* SYSPROTO_CONTROL */,
                2 /* UTUN_OPT_IFNAME */,
                baseAddress,
                &ifnameSize
            )
            if result == 0 {
                return String(cString: baseAddress)
            } else {
                return nil
            }
        }
    }

    @discardableResult
    public static func run(withConfig filePath: String) -> Int32 {
        guard let fileDescriptor = self.tunnelFileDescriptor else {
            // Tunnel FD not ready; do not crash the extension
            return -1
        }
        return hev_socks5_tunnel_main(filePath.cString(using: .utf8), fileDescriptor)
    }

    public static func quit() {
        hev_socks5_tunnel_quit()
    }
}