feat: use wire v2 framing for XTCP NatHoleSid (#5343)

client/proxy/xtcp.go

@@ -57,8 +57,7 @@ func NewXTCPProxy(baseProxy *BaseProxy, cfg v1.ProxyConfigurer) Proxy {
 func (pxy *XTCPProxy) InWorkConn(conn net.Conn, startWorkConnMsg *msg.StartWorkConn) {
 	xl := pxy.xl
 	defer conn.Close()
-	var natHoleSidMsg msg.NatHoleSid
-	err := msg.ReadMsgInto(conn, &natHoleSidMsg)
+	natHoleSidMsg, err := readNatHoleSid(conn, pxy.clientCfg.Transport.WireProtocol)
 	if err != nil {
 		xl.Errorf("xtcp read from workConn error: %v", err)
 		return
@@ -131,6 +130,15 @@ func (pxy *XTCPProxy) InWorkConn(conn net.Conn, startWorkConnMsg *msg.StartWorkC
 	pxy.listenByQUIC(listenConn, raddr, startWorkConnMsg)
 }
 
+func readNatHoleSid(conn net.Conn, wireProtocol string) (*msg.NatHoleSid, error) {
+	workMsgConn := msg.NewConn(conn, msg.NewReadWriter(conn, wireProtocol))
+	var natHoleSidMsg msg.NatHoleSid
+	if err := workMsgConn.ReadMsgInto(&natHoleSidMsg); err != nil {
+		return nil, err
+	}
+	return &natHoleSidMsg, nil
+}
+
 func (pxy *XTCPProxy) listenByKCP(listenConn *net.UDPConn, raddr *net.UDPAddr, startWorkConnMsg *msg.StartWorkConn) {
 	xl := pxy.xl
 	listenConn.Close()

client/proxy/xtcp_test.go

@@ -0,0 +1,66 @@
+// Copyright 2026 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !frps
+
+package proxy
+
+import (
+	"net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/fatedier/frp/pkg/msg"
+	"github.com/fatedier/frp/pkg/proto/wire"
+)
+
+func TestReadNatHoleSidUsesSelectedWireProtocol(t *testing.T) {
+	for _, tc := range []struct {
+		name         string
+		wireProtocol string
+	}{
+		{name: "v2", wireProtocol: wire.ProtocolV2},
+		{name: "v1", wireProtocol: wire.ProtocolV1},
+		{name: "default", wireProtocol: ""},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			client, server := net.Pipe()
+			defer client.Close()
+			defer server.Close()
+			setPipeDeadline(t, client, server)
+
+			errCh := make(chan error, 1)
+			go func() {
+				writer := msg.NewConn(server, msg.NewReadWriter(server, tc.wireProtocol))
+				errCh <- writer.WriteMsg(&msg.NatHoleSid{Sid: "sid"})
+			}()
+
+			out, err := readNatHoleSid(client, tc.wireProtocol)
+			require.NoError(t, err)
+			require.Equal(t, "sid", out.Sid)
+			require.NoError(t, <-errCh)
+		})
+	}
+}
+
+func setPipeDeadline(t *testing.T, conns ...net.Conn) {
+	t.Helper()
+
+	deadline := time.Now().Add(time.Second)
+	for _, conn := range conns {
+		require.NoError(t, conn.SetDeadline(deadline))
+	}
+}