Improve host address handling using DnsEndPoint

Signed-off-by: noisyfox <timemanager.rick@gmail.com>

shadowsocks-csharp/Controller/Service/TCPRelay.cs

@@ -302,8 +302,7 @@ namespace Shadowsocks.Controller
                 if (ar.AsyncState != null)
                 {
                     connection.EndSend(ar);
-                    // TODO: need fix
-                    //Logging.Debug(remote.LocalEndPoint, remote.DestEndPoint, RecvSize, "TCP Relay");
+                    Logging.Debug(remote.LocalEndPoint, remote.DestEndPoint, RecvSize, "TCP Relay");
                     connection.BeginReceive(_connetionRecvBuffer, 0, RecvSize, SocketFlags.None, new AsyncCallback(ReadAll), null);
                 }
                 else
@@ -311,8 +310,7 @@ namespace Shadowsocks.Controller
                     int bytesRead = connection.EndReceive(ar);
                     if (bytesRead > 0)
                     {
-                        // TODO: need fix
-                        //Logging.Debug(remote.LocalEndPoint, remote.DestEndPoint, RecvSize, "TCP Relay");
+                        Logging.Debug(remote.LocalEndPoint, remote.DestEndPoint, RecvSize, "TCP Relay");
                         connection.BeginReceive(_connetionRecvBuffer, 0, RecvSize, SocketFlags.None, new AsyncCallback(ReadAll), null);
                     }
                     else
@@ -344,8 +342,7 @@ namespace Shadowsocks.Controller
         private class ProxyTimer : Timer
         {
             public IProxy Proxy;
-            public string DestHost;
-            public int DestPort;
+            public EndPoint DestEndPoint;
             public Server Server;
 
             public ProxyTimer(int p) : base(p)
@@ -373,7 +370,11 @@ namespace Shadowsocks.Controller
                     bool parsed = IPAddress.TryParse(_config.proxyServer, out ipAddress);
                     if (!parsed)
                     {
-                        // TODO really necessary to resolve a proxy's address? Maybe from local hosts?
+                        /*
+                         * TODO really necessary to resolve a proxy's address? Maybe from local hosts?
+                         * also we may simplify it by using dual-mode socket with 
+                         * the approach described in DirectConnect.BeginConnectDest
+                         */
                         IPHostEntry ipHostInfo = Dns.GetHostEntry(_config.proxyServer);
                         ipAddress = ipHostInfo.AddressList[0];
                     }
@@ -394,8 +395,7 @@ namespace Shadowsocks.Controller
                 proxyTimer.Enabled = true;
 
                 proxyTimer.Proxy = remote;
-                proxyTimer.DestHost = server.server;
-                proxyTimer.DestPort = server.server_port;
+                proxyTimer.DestEndPoint = ProxyUtils.GetEndPoint(server.server, server.server_port);
                 proxyTimer.Server = server;
 
                 _proxyConnected = false;
@@ -433,8 +433,7 @@ namespace Shadowsocks.Controller
             try
             {
                 ProxyTimer timer = (ProxyTimer)ar.AsyncState;
-                var destHost = timer.DestHost;
-                var destPort = timer.DestPort;
+                var destEndPoint = timer.DestEndPoint;
                 server = timer.Server;
                 timer.Elapsed -= proxyConnectTimer_Elapsed;
                 timer.Enabled = false;
@@ -462,7 +461,7 @@ namespace Shadowsocks.Controller
                 
                 _destConnected = false;
                 // Connect to the remote endpoint.
-                remote.BeginConnectDest(destHost, destPort, new AsyncCallback(ConnectCallback), connectTimer);
+                remote.BeginConnectDest(destEndPoint, new AsyncCallback(ConnectCallback), connectTimer);
             }
             catch (ArgumentException)
             {

shadowsocks-csharp/Proxy/DirectConnect.cs

@@ -35,9 +35,7 @@ namespace Shadowsocks.Proxy
         public EndPoint LocalEndPoint => _remote.LocalEndPoint;
 
         public EndPoint ProxyEndPoint { get; } = new FakeEndPoint();
-        public string DestHost { get; private set; }
-        public int DestPort { get; private set; }
-
+        public EndPoint DestEndPoint { get; private set; }
 
         public void BeginConnectProxy(EndPoint remoteEP, AsyncCallback callback, object state)
         {
@@ -52,27 +50,41 @@ namespace Shadowsocks.Proxy
             // do nothing
         }
 
-        public void BeginConnectDest(string host, int port, AsyncCallback callback, object state)
+        public void BeginConnectDest(EndPoint destEndPoint, AsyncCallback callback, object state)
         {
-            // TODO async resolving
-            IPAddress ipAddress;
-            bool parsed = IPAddress.TryParse(host, out ipAddress);
-            if (!parsed)
+            EndPoint realEndPoint = DestEndPoint = destEndPoint;
+
+            /*
+             * On windows vista or later, dual-mode socket is supported, so that
+             * we don't need to resolve a DnsEndPoint manually.
+             * We could just create a dual-mode socket and pass the DnsEndPoint
+             * directly to it's BeginConnect and the system will handle it correctlly
+             * so that we won't worry about async resolving any more.
+             * 
+             * see: https://blogs.msdn.microsoft.com/webdev/2013/01/08/dual-mode-sockets-never-create-an-ipv4-socket-again/
+             * 
+             * But it seems that we can't use this feature because DnsEndPoint
+             * doesn't have a specific AddressFamily before it has been
+             * resolved (we don't know whether it's ipv4 or ipv6) and we don't have
+             * a dual-mode socket to use on windows xp :(
+             */
+            var dep = realEndPoint as DnsEndPoint;
+            if (dep != null)
             {
-                IPHostEntry ipHostInfo = Dns.GetHostEntry(host);
-                ipAddress = ipHostInfo.AddressList[0];
-            }
-            IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);
+                // need to resolve manually
+                // TODO async resolving
+                IPHostEntry ipHostInfo = Dns.GetHostEntry(dep.Host);
+                IPAddress ipAddress = ipHostInfo.AddressList[0];
 
-            DestHost = host;
-            DestPort = port;
+                realEndPoint = new IPEndPoint(ipAddress, dep.Port);
+            }
 
             if (_remote == null)
             {
-                _remote = new Socket(remoteEP.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
+                _remote = new Socket(realEndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
                 _remote.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.NoDelay, true);
             }
-            _remote.BeginConnect(remoteEP, callback, state);
+            _remote.BeginConnect(realEndPoint, callback, state);
         }
 
         public void EndConnectDest(IAsyncResult asyncResult)

shadowsocks-csharp/Proxy/IProxy.cs

@@ -11,15 +11,13 @@ namespace Shadowsocks.Proxy
 
         EndPoint ProxyEndPoint { get; }
 
-        string DestHost { get; }
-
-        int DestPort { get; }
+        EndPoint DestEndPoint { get; }
 
         void BeginConnectProxy(EndPoint remoteEP, AsyncCallback callback, object state);
 
         void EndConnectProxy(IAsyncResult asyncResult);
 
-        void BeginConnectDest(string host, int port, AsyncCallback callback, object state);
+        void BeginConnectDest(EndPoint destEndPoint, AsyncCallback callback, object state);
 
         void EndConnectDest(IAsyncResult asyncResult);
 
@@ -37,4 +35,20 @@ namespace Shadowsocks.Proxy
 
         void Close();
     }
+
+    public static class ProxyUtils
+    {
+        public static EndPoint GetEndPoint(string host, int port)
+        {
+            IPAddress ipAddress;
+            bool parsed = IPAddress.TryParse(host, out ipAddress);
+            if (parsed)
+            {
+                return new IPEndPoint(ipAddress, port);
+            }
+
+            // maybe is a domain name
+            return new DnsEndPoint(host, port);
+        }
+    }
 }

shadowsocks-csharp/Proxy/Socks5Proxy.cs

@@ -47,8 +47,7 @@ namespace Shadowsocks.Proxy
 
         public EndPoint LocalEndPoint => _remote.LocalEndPoint;
         public EndPoint ProxyEndPoint { get; private set; }
-        public string DestHost { get; private set; }
-        public int DestPort { get; private set; }
+        public EndPoint DestEndPoint { get; private set; }
 
         public void BeginConnectProxy(EndPoint remoteEP, AsyncCallback callback, object state)
         {
@@ -74,20 +73,32 @@ namespace Shadowsocks.Proxy
             }
         }
 
-        public void BeginConnectDest(string host, int port, AsyncCallback callback, object state)
+        public void BeginConnectDest(EndPoint destEndPoint, AsyncCallback callback, object state)
         {
-            DestHost = host;
-            DestPort = port;
+            DestEndPoint = destEndPoint;
 
             byte[] request = null;
             byte atyp = 0;
-            
-            IPAddress ipAddress;
-            bool parsed = IPAddress.TryParse(host, out ipAddress);
-            if (parsed)
+            int port;
+
+            var dep = destEndPoint as DnsEndPoint;
+            if (dep != null)
+            {
+                // is a domain name, we will leave it to server
+
+                atyp = 3; // DOMAINNAME
+                var enc = Encoding.UTF8;
+                var hostByteCount = enc.GetByteCount(dep.Host);
+
+                request = new byte[4 + 1/*length byte*/ + hostByteCount + 2];
+                request[4] = (byte)hostByteCount;
+                enc.GetBytes(dep.Host, 0, dep.Host.Length, request, 5);
+
+                port = dep.Port;
+            }
+            else
             {
-                IPEndPoint ep = new IPEndPoint(ipAddress, port);
-                switch (ep.AddressFamily)
+                switch (DestEndPoint.AddressFamily)
                 {
                     case AddressFamily.InterNetwork:
                         request = new byte[4 + 4 + 2];
@@ -100,23 +111,10 @@ namespace Shadowsocks.Proxy
                     default:
                         throw new Exception(I18N.GetString("Proxy request failed"));
                 }
-
-                var addr = ep.Address.GetAddressBytes();
+                port = ((IPEndPoint) DestEndPoint).Port;
+                var addr = ((IPEndPoint)DestEndPoint).Address.GetAddressBytes();
                 Array.Copy(addr, 0, request, 4, request.Length - 4 - 2);
             }
-            else
-            {
-                // maybe is a domain name, we will leave it to server
-                // need ValidateTcpPort? porttest > 1 && porttest < 65535?
-
-                atyp = 3; // DOMAINNAME
-                var enc = Encoding.UTF8;
-                var hostByteCount = enc.GetByteCount(host);
-                
-                request = new byte[4 + 1/*length byte*/ + hostByteCount + 2];
-                request[4] = (byte)hostByteCount;
-                enc.GetBytes(host, 0, host.Length, request, 5);
-            }
 
             // 构造request包剩余部分
             request[0] = 5;
@@ -131,7 +129,6 @@ namespace Shadowsocks.Proxy
             st.AsyncState = state;
 
             _remote?.BeginSend(request, 0, request.Length, 0, Socks5RequestSendCallback, st);
-
         }
 
         public void EndConnectDest(IAsyncResult asyncResult)