Socks inbound: Initialize TempUDPConn's Timer at the beginning (#7203)

Fixes https://github.com/XTLS/Xray-core/pull/7200

---------

Co-authored-by: Eliot the Cougar <1861169+eliotcougar@users.noreply.github.com>

proxy/socks/temp_udp_listen.go

@@ -2,10 +2,10 @@ package socks
 
 import (
 	"context"
-	"net"
 	"sync/atomic"
 	"time"
 
+	"github.com/xtls/xray-core/common/net"
 	"github.com/xtls/xray-core/common/signal"
 )
 
@@ -14,6 +14,9 @@ func NewTempUDPConn(udpConn net.PacketConn, tcpConn net.Conn, expectedRemote *ne
 		PacketConn:        udpConn,
 		AssociatedTCPConn: tcpConn,
 	}
+	t.Timer = signal.CancelAfterInactivity(context.Background(), func() {
+		t.Close()
+	}, net.ConnIdleTimeout)
 	t.ExpectedRemote.Store(expectedRemote)
 	return t
 }
@@ -60,9 +63,7 @@ func (c *TempUDPConn) RemoteAddr() net.Addr {
 }
 
 func (c *TempUDPConn) SetTimeout(d time.Duration) {
-	c.Timer = signal.CancelAfterInactivity(context.Background(), func() {
-		c.Close()
-	}, d)
+	c.Timer.SetTimeout(d)
 }
 
 func (c *TempUDPConn) Close() error {