udpnat2: Fix timeout

common/udpnat2/service.go

@@ -3,7 +3,6 @@ package udpnat
 import (
 	"context"
 	"net/netip"
-	"sync"
 	"time"
 
 	"github.com/sagernet/sing/common"
@@ -19,10 +18,6 @@ type Service struct {
 	handler N.UDPConnectionHandlerEx
 	prepare PrepareFunc
 	metrics Metrics
-
-	timeout   time.Duration
-	closeOnce sync.Once
-	doneChan  chan struct{}
 }
 
 type PrepareFunc func(source M.Socksaddr, destination M.Socksaddr, userData any) (bool, context.Context, N.PacketWriter, N.CloseHandlerFunc)
@@ -58,37 +53,12 @@ func New(handler N.UDPConnectionHandlerEx, prepare PrepareFunc, timeout time.Dur
 		conn.Close()
 	})
 	return &Service{
-		cache:    cache,
-		handler:  handler,
-		prepare:  prepare,
-		timeout:  timeout,
-		doneChan: make(chan struct{}),
+		cache:   cache,
+		handler: handler,
+		prepare: prepare,
 	}
 }
 
-func (s *Service) Start() error {
-	ticker := time.NewTicker(s.timeout)
-	go func() {
-		defer ticker.Stop()
-		for {
-			select {
-			case <-ticker.C:
-				s.PurgeExpired()
-			case <-s.doneChan:
-				s.Purge()
-				return
-			}
-		}
-	}()
-	return nil
-}
-
-func (s *Service) Close() {
-	s.closeOnce.Do(func() {
-		close(s.doneChan)
-	})
-}
-
 func (s *Service) NewPacket(bufferSlices [][]byte, source M.Socksaddr, destination M.Socksaddr, userData any) {
 	conn, loaded := s.cache.Get(source.AddrPort())
 	if !loaded {
@@ -105,6 +75,7 @@ func (s *Service) NewPacket(bufferSlices [][]byte, source M.Socksaddr, destinati
 			doneChan:     make(chan struct{}),
 			readDeadline: pipe.MakeDeadline(),
 		}
+		s.PurgeExpired()
 		s.cache.Add(source.AddrPort(), conn)
 		go s.handler.NewPacketConnectionEx(ctx, conn, source, destination, onClose)
 		s.metrics.Creates++