fix dns

Tun/Punchnet/DNS/DNSLocalClient.swift

@@ -1,89 +1,58 @@
-//
-//  SDLLocalDNSClient.swift
-//  punchnet
-//
-//  Created by 安礼成 on 2026/4/10.
-//
 import Foundation
 import Network
 
-/// 纯粹的本地 DNS 解析器：负责将 DNS 载荷绕过 TUN 发送到公网 DNS
-final class DNSLocalClient {
-    private var connection: NWConnection?
+final class SDLLocalDNSClient {
+    private var connections: [NWConnection] = []
     private let logger: SDLLogger
-    private let remoteEndpoint: NWEndpoint
     
-    // 用于对外输出收到的原始 DNS 载荷 (注意：这里只输出 UDP 载荷，不带 IP 头)
+    // 准备多个公共 DNS
+    private let dnsServers = ["114.114.114.114", "223.5.5.5", "8.8.8.8"]
+    
     public let payloadFlow: AsyncStream<Data>
     private let payloadContinuation: AsyncStream<Data>.Continuation
-    
-    private let (closeStream, closeContinuation) = AsyncStream.makeStream(of: Void.self)
-    
-    /// - Parameter dnsServer: 物理 DNS 地址，例如 "114.114.114.114"
-    init(dnsServer: String, logger: SDLLogger) {
+
+    init(logger: SDLLogger) {
         self.logger = logger
-        self.remoteEndpoint = .hostPort(host: NWEndpoint.Host(dnsServer), port: 53)
-        
         let (stream, continuation) = AsyncStream.makeStream(of: Data.self, bufferingPolicy: .unbounded)
         self.payloadFlow = stream
         self.payloadContinuation = continuation
     }
-    
+
     func start() {
-        let parameters = NWParameters.udp
-        // 关键：强制绕过 TUN 网卡
-        parameters.prohibitedInterfaceTypes = [.other]
-        parameters.multipathServiceType = .handover
-        
-        let connection = NWConnection(to: self.remoteEndpoint, using: parameters)
-        self.connection = connection
-        
-        connection.stateUpdateHandler = { [weak self] state in
-            switch state {
-            case .ready:
-                self?.logger.log("[LocalDNS] Path ready", level: .debug)
-                self?.receiveLoop()
-            case .failed(let error):
-                self?.logger.log("[LocalDNS] Failed: \(error)", level: .error)
-                self?.closeContinuation.finish()
-            case .cancelled:
-                self?.payloadContinuation.finish()
-                self?.closeContinuation.finish()
-            default: break
+        for server in dnsServers {
+            let endpoint = NWEndpoint.hostPort(host: NWEndpoint.Host(server), port: 53)
+            let parameters = NWParameters.udp
+            parameters.prohibitedInterfaceTypes = [.other]
+            
+            let conn = NWConnection(to: endpoint, using: parameters)
+            
+            conn.stateUpdateHandler = { [weak self] state in
+                if case .ready = state { self?.receiveLoop(for: conn) }
             }
+            conn.start(queue: .global())
+            connections.append(conn)
         }
-        connection.start(queue: .global())
     }
-    
-    /// 发送 DNS 载荷（由上层剥离 IP/UDP 头后的 Data）
+
+    /// 并发查询：对所有服务器广播
     func query(dnsPayload: Data) {
-        guard let connection = self.connection, connection.state == .ready else { return }
-        
-        connection.send(content: dnsPayload, completion: .contentProcessed { [weak self] error in
-            if let error = error {
-                self?.logger.log("[LocalDNS] Send error: \(error)", level: .error)
-            }
-        })
+        for conn in connections where conn.state == .ready {
+            conn.send(content: dnsPayload, completion: .contentProcessed({ _ in }))
+        }
     }
-    
-    private func receiveLoop() {
-        connection?.receiveMessage { [weak self] content, _, _, error in
-            if let data = content, !data.isEmpty {
-                // 直接输出收到的 DNS 响应载荷
+
+    private func receiveLoop(for conn: NWConnection) {
+        conn.receiveMessage { [weak self] content, _, _, error in
+            if let data = content {
+                // ！！！核心：由于 AsyncStream 是流式的
+                // 谁先 yield，上层就先收到谁。
+                // 只要上层收到了第一个有效响应并回填给系统，
+                // 后面迟到的重复响应会被系统协议栈自动忽略（因为 Transaction ID 已失效）
                 self?.payloadContinuation.yield(data)
             }
-            if error == nil && self?.connection?.state == .ready {
-                self?.receiveLoop()
+            if error == nil && conn.state == .ready {
+                self?.receiveLoop(for: conn)
             }
         }
     }
-    
-    func stop() {
-        connection?.cancel()
-    }
-    
-    public func waitClose() async {
-        for await _ in closeStream { }
-    }
-    
 }