Fix concurrent write

inbound/default.go

@@ -3,7 +3,6 @@ package inbound
 import (
 	"context"
 	"net"
-	"sync"
 
 	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/common/settings"
@@ -42,7 +41,6 @@ type myInboundAdapter struct {
 	tcpListener          net.Listener
 	udpConn              *net.UDPConn
 	udpAddr              M.Socksaddr
-	packetAccess         sync.RWMutex
 	packetOutboundClosed chan struct{}
 	packetOutbound       chan *myInboundPacket
 }

inbound/default_udp.go

@@ -208,17 +208,12 @@ func (s *myInboundPacketAdapter) Upstream() any {
 }
 
 func (s *myInboundPacketAdapter) WritePacket(buffer *buf.Buffer, destination M.Socksaddr) error {
-	s.packetAccess.RLock()
-	defer s.packetAccess.RUnlock()
-
 	select {
+	case s.packetOutbound <- &myInboundPacket{buffer, destination}:
+		return nil
 	case <-s.packetOutboundClosed:
 		return os.ErrClosed
-	default:
 	}
-
-	s.packetOutbound <- &myInboundPacket{buffer, destination}
-	return nil
 }
 
 func (s *myInboundPacketAdapter) Close() error {