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

server/proxy/xtcp.go

@@ -16,6 +16,7 @@ package proxy
 
 import (
 	"fmt"
+	"net"
 	"reflect"
 	"sync"
 
@@ -73,10 +74,7 @@ func (pxy *XTCPProxy) Run() (remoteAddr string, err error) {
 				if errRet != nil {
 					continue
 				}
-				m := &msg.NatHoleSid{
-					Sid: sid,
-				}
-				errRet = msg.WriteMsg(workConn, m)
+				errRet = writeNatHoleSid(workConn, pxy.wireProtocol, sid)
 				if errRet != nil {
 					xl.Warnf("write nat hole sid package error, %v", errRet)
 				}
@@ -87,6 +85,13 @@ func (pxy *XTCPProxy) Run() (remoteAddr string, err error) {
 	return
 }
 
+func writeNatHoleSid(workConn net.Conn, wireProtocol string, sid string) error {
+	workMsgConn := msg.NewConn(workConn, msg.NewReadWriter(workConn, wireProtocol))
+	return workMsgConn.WriteMsg(&msg.NatHoleSid{
+		Sid: sid,
+	})
+}
+
 func (pxy *XTCPProxy) Close() {
 	pxy.closeOnce.Do(func() {
 		pxy.BaseProxy.Close()

server/proxy/xtcp_test.go

@@ -0,0 +1,93 @@
+// 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.
+
+package proxy
+
+import (
+	"bufio"
+	"encoding/binary"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/fatedier/frp/pkg/msg"
+	"github.com/fatedier/frp/pkg/proto/wire"
+)
+
+func TestWriteNatHoleSidUsesWireV2MessageFrame(t *testing.T) {
+	client, server := net.Pipe()
+	defer client.Close()
+	defer server.Close()
+	setPipeDeadline(t, client, server)
+
+	errCh := make(chan error, 1)
+	go func() {
+		errCh <- writeNatHoleSid(server, wire.ProtocolV2, "sid-v2")
+	}()
+
+	frame, err := wire.NewConn(client).ReadFrame()
+	require.NoError(t, err)
+	require.Equal(t, wire.FrameTypeMessage, frame.Type)
+	require.GreaterOrEqual(t, len(frame.Payload), 2)
+	require.Equal(t, msg.V2TypeNatHoleSid, binary.BigEndian.Uint16(frame.Payload[:2]))
+
+	var out msg.NatHoleSid
+	require.NoError(t, msg.DecodeV2MessageFrameInto(frame, &out))
+	require.Equal(t, "sid-v2", out.Sid)
+	require.NoError(t, <-errCh)
+}
+
+func TestWriteNatHoleSidUsesLegacyCodecForWireV1AndDefault(t *testing.T) {
+	for _, tc := range []struct {
+		name         string
+		wireProtocol string
+	}{
+		{name: "default", wireProtocol: ""},
+		{name: "v1", wireProtocol: wire.ProtocolV1},
+	} {
+		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() {
+				errCh <- writeNatHoleSid(server, tc.wireProtocol, "sid-legacy")
+			}()
+
+			reader := bufio.NewReader(client)
+			typeByte, err := reader.ReadByte()
+			require.NoError(t, err)
+			require.Equal(t, msg.TypeNatHoleSid, typeByte)
+			require.NoError(t, reader.UnreadByte())
+
+			var out msg.NatHoleSid
+			require.NoError(t, msg.ReadMsgInto(reader, &out))
+			require.Equal(t, "sid-legacy", 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))
+	}
+}