client/visitor: deduplicate visitor connection handshake and wrapping (#5219)

Extract two shared helpers to eliminate duplicated code across STCP,
SUDP, and XTCP visitors:

- dialRawVisitorConn: handles ConnectServer + NewVisitorConn handshake
  (auth, sign key, 10s read deadline, error check)
- wrapVisitorConn: handles encryption + pooled compression wrapping,
  returning a recycleFn for pool resource cleanup

SUDP is upgraded from WithCompression to WithCompressionFromPool,
aligning with the pooled compression used by STCP and XTCP.

client/visitor/sudp.go

@@ -16,21 +16,17 @@ package visitor
 
 import (
 	"fmt"
-	"io"
 	"net"
 	"strconv"
 	"sync"
 	"time"
 
 	"github.com/fatedier/golib/errors"
-	libio "github.com/fatedier/golib/io"
 
 	v1 "github.com/fatedier/frp/pkg/config/v1"
 	"github.com/fatedier/frp/pkg/msg"
-	"github.com/fatedier/frp/pkg/naming"
 	"github.com/fatedier/frp/pkg/proto/udp"
 	netpkg "github.com/fatedier/frp/pkg/util/net"
-	"github.com/fatedier/frp/pkg/util/util"
 	"github.com/fatedier/frp/pkg/util/xlog"
 )
 
@@ -76,6 +72,7 @@ func (sv *SUDPVisitor) dispatcher() {
 
 	var (
 		visitorConn net.Conn
+		recycleFn   func()
 		err         error
 
 		firstPacket *msg.UDPPacket
@@ -93,14 +90,17 @@ func (sv *SUDPVisitor) dispatcher() {
 			return
 		}
 
-		visitorConn, err = sv.getNewVisitorConn()
+		visitorConn, recycleFn, err = sv.getNewVisitorConn()
 		if err != nil {
 			xl.Warnf("newVisitorConn to frps error: %v, try to reconnect", err)
 			continue
 		}
 
 		// visitorConn always be closed when worker done.
-		sv.worker(visitorConn, firstPacket)
+		func() {
+			defer recycleFn()
+			sv.worker(visitorConn, firstPacket)
+		}()
 
 		select {
 		case <-sv.checkCloseCh:
@@ -198,57 +198,17 @@ func (sv *SUDPVisitor) worker(workConn net.Conn, firstPacket *msg.UDPPacket) {
 	xl.Infof("sudp worker is closed")
 }
 
-func (sv *SUDPVisitor) getNewVisitorConn() (net.Conn, error) {
-	xl := xlog.FromContextSafe(sv.ctx)
-	visitorConn, err := sv.helper.ConnectServer()
+func (sv *SUDPVisitor) getNewVisitorConn() (net.Conn, func(), error) {
+	rawConn, err := sv.dialRawVisitorConn(sv.cfg.GetBaseConfig())
 	if err != nil {
-		return nil, fmt.Errorf("frpc connect frps error: %v", err)
+		return nil, func() {}, err
 	}
-
-	now := time.Now().Unix()
-	targetProxyName := naming.BuildTargetServerProxyName(sv.clientCfg.User, sv.cfg.ServerUser, sv.cfg.ServerName)
-	newVisitorConnMsg := &msg.NewVisitorConn{
-		RunID:          sv.helper.RunID(),
-		ProxyName:      targetProxyName,
-		SignKey:        util.GetAuthKey(sv.cfg.SecretKey, now),
-		Timestamp:      now,
-		UseEncryption:  sv.cfg.Transport.UseEncryption,
-		UseCompression: sv.cfg.Transport.UseCompression,
-	}
-	err = msg.WriteMsg(visitorConn, newVisitorConnMsg)
+	rwc, recycleFn, err := wrapVisitorConn(rawConn, sv.cfg.GetBaseConfig())
 	if err != nil {
-		visitorConn.Close()
-		return nil, fmt.Errorf("frpc send newVisitorConnMsg to frps error: %v", err)
+		rawConn.Close()
+		return nil, func() {}, err
 	}
-
-	var newVisitorConnRespMsg msg.NewVisitorConnResp
-	_ = visitorConn.SetReadDeadline(time.Now().Add(10 * time.Second))
-	err = msg.ReadMsgInto(visitorConn, &newVisitorConnRespMsg)
-	if err != nil {
-		visitorConn.Close()
-		return nil, fmt.Errorf("frpc read newVisitorConnRespMsg error: %v", err)
-	}
-	_ = visitorConn.SetReadDeadline(time.Time{})
-
-	if newVisitorConnRespMsg.Error != "" {
-		visitorConn.Close()
-		return nil, fmt.Errorf("start new visitor connection error: %s", newVisitorConnRespMsg.Error)
-	}
-
-	var remote io.ReadWriteCloser
-	remote = visitorConn
-	if sv.cfg.Transport.UseEncryption {
-		remote, err = libio.WithEncryption(remote, []byte(sv.cfg.SecretKey))
-		if err != nil {
-			xl.Errorf("create encryption stream error: %v", err)
-			visitorConn.Close()
-			return nil, err
-		}
-	}
-	if sv.cfg.Transport.UseCompression {
-		remote = libio.WithCompression(remote)
-	}
-	return netpkg.WrapReadWriteCloserToConn(remote, visitorConn), nil
+	return netpkg.WrapReadWriteCloserToConn(rwc, rawConn), recycleFn, nil
 }
 
 func (sv *SUDPVisitor) Close() {