fix: sing-based listener panic

adapter/outbound/shadowsocks.go

@@ -193,7 +193,7 @@ func (ss *ShadowSocks) ListenPacketWithDialer(ctx context.Context, dialer C.Dial
 	if err != nil {
 		return nil, err
 	}
-	pc = ss.method.DialPacketConn(N.NewBindPacketConn(N.NewEnhancePacketConn(pc), addr))
+	pc = ss.method.DialPacketConn(N.NewBindPacketConn(pc, addr))
 	return newPacketConn(pc, ss), nil
 }
 

common/net/bind.go

@@ -37,9 +37,9 @@ func (c *bindPacketConn) Upstream() any {
 	return c.EnhancePacketConn
 }
 
-func NewBindPacketConn(pc EnhancePacketConn, rAddr net.Addr) net.Conn {
+func NewBindPacketConn(pc net.PacketConn, rAddr net.Addr) net.Conn {
 	return &bindPacketConn{
-		EnhancePacketConn: pc,
+		EnhancePacketConn: NewEnhancePacketConn(pc),
 		rAddr:             rAddr,
 	}
 }

common/net/packet.go

@@ -15,20 +15,24 @@ var NewDeadlinePacketConn = deadline.NewPacketConn
 var NewDeadlineEnhancePacketConn = deadline.NewEnhancePacketConn
 
 type threadSafePacketConn struct {
-	net.PacketConn
+	EnhancePacketConn
 	access sync.Mutex
 }
 
 func (c *threadSafePacketConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 	c.access.Lock()
 	defer c.access.Unlock()
-	return c.PacketConn.WriteTo(b, addr)
+	return c.EnhancePacketConn.WriteTo(b, addr)
 }
 
 func (c *threadSafePacketConn) Upstream() any {
-	return c.PacketConn
+	return c.EnhancePacketConn
+}
+
+func (c *threadSafePacketConn) ReaderReplaceable() bool {
+	return true
 }
 
 func NewThreadSafePacketConn(pc net.PacketConn) net.PacketConn {
-	return &threadSafePacketConn{PacketConn: pc}
+	return &threadSafePacketConn{EnhancePacketConn: NewEnhancePacketConn(pc)}
 }

common/net/refconn.go

@@ -82,10 +82,15 @@ func NewRefConn(conn net.Conn, ref any) net.Conn {
 }
 
 type refPacketConn struct {
-	pc  net.PacketConn
+	pc  EnhancePacketConn
 	ref any
 }
 
+func (pc *refPacketConn) WaitReadFrom() (data []byte, put func(), addr net.Addr, err error) {
+	defer runtime.KeepAlive(pc.ref)
+	return pc.pc.WaitReadFrom()
+}
+
 func (pc *refPacketConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
 	defer runtime.KeepAlive(pc.ref)
 	return pc.pc.ReadFrom(p)
@@ -121,6 +126,18 @@ func (pc *refPacketConn) SetWriteDeadline(t time.Time) error {
 	return pc.pc.SetWriteDeadline(t)
 }
 
-func NewRefPacketConn(pc net.PacketConn, ref any) net.PacketConn {
-	return &refPacketConn{pc: pc, ref: ref}
+func (pc *refPacketConn) Upstream() any {
+	return pc.pc
+}
+
+func (pc *refPacketConn) ReaderReplaceable() bool { // Relay() will handle reference
+	return true
+}
+
+func (pc *refPacketConn) WriterReplaceable() bool { // Relay() will handle reference
+	return true
+}
+
+func NewRefPacketConn(pc net.PacketConn, ref any) net.PacketConn {
+	return &refPacketConn{pc: NewEnhancePacketConn(pc), ref: ref}
 }

listener/sing/sing.go

@@ -58,6 +58,14 @@ func (c *waitCloseConn) Upstream() any {
 	return c.ExtendedConn
 }
 
+func (c *waitCloseConn) ReaderReplaceable() bool {
+	return true
+}
+
+func (c *waitCloseConn) WriterReplaceable() bool {
+	return true
+}
+
 func UpstreamMetadata(metadata M.Metadata) M.Metadata {
 	return M.Metadata{
 		Source:      metadata.Source,
@@ -116,7 +124,7 @@ func (h *ListenerHandler) NewPacketConnection(ctx context.Context, conn network.
 		defer mutex.Unlock()
 		conn2 = nil
 	}()
-	readWaiter, isReadWaiter := bufio.CreatePacketReadWaiter(conn)
+	connReader := network.UnwrapPacketReader(conn) // decrease runtime cost for bufio.CreatePacketReadWaiter
 	for {
 		var (
 			buff *buf.Buffer
@@ -127,7 +135,9 @@ func (h *ListenerHandler) NewPacketConnection(ctx context.Context, conn network.
 			buff = buf.NewPacket() // do not use stack buffer
 			return buff
 		}
-		if isReadWaiter {
+		// syscallPacketReadWaiter.WaitReadPacket will cache newBuffer function
+		// so create new PacketReadWaiter in each loop
+		if readWaiter, isReadWaiter := bufio.CreatePacketReadWaiter(connReader); isReadWaiter {
 			dest, err = readWaiter.WaitReadPacket(newBuffer)
 		} else {
 			dest, err = conn.ReadPacket(newBuffer())

listener/sing_shadowsocks/server.go

@@ -22,6 +22,7 @@ import (
 	"github.com/sagernet/sing/common/buf"
 	"github.com/sagernet/sing/common/bufio"
 	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/common/network"
 )
 
 type Listener struct {
@@ -92,7 +93,7 @@ func New(config LC.ShadowsocksServer, tcpIn chan<- C.ConnContext, udpIn chan<- C
 
 			go func() {
 				conn := bufio.NewPacketConn(ul)
-				readWaiter, isReadWaiter := bufio.CreatePacketReadWaiter(conn)
+				connReader := network.UnwrapPacketReader(conn) // decrease runtime cost for bufio.CreatePacketReadWaiter
 				for {
 					var (
 						buff *buf.Buffer
@@ -103,7 +104,9 @@ func New(config LC.ShadowsocksServer, tcpIn chan<- C.ConnContext, udpIn chan<- C
 						buff = buf.NewPacket() // do not use stack buffer
 						return buff
 					}
-					if isReadWaiter {
+					// syscallPacketReadWaiter.WaitReadPacket will cache newBuffer function
+					// so create new PacketReadWaiter in each loop
+					if readWaiter, isReadWaiter := bufio.CreatePacketReadWaiter(connReader); isReadWaiter {
 						dest, err = readWaiter.WaitReadPacket(newBuffer)
 					} else {
 						dest, err = conn.ReadPacket(newBuffer())

listener/sing_tun/dns.go

@@ -109,7 +109,8 @@ func (h *ListenerHandler) NewPacketConnection(ctx context.Context, conn network.
 			defer mutex.Unlock()
 			conn2 = nil
 		}()
-		readWaiter, isReadWaiter := bufio.CreatePacketReadWaiter(conn)
+
+		connReader := network.UnwrapPacketReader(conn) // decrease runtime cost for bufio.CreatePacketReadWaiter
 		for {
 			var (
 				buff *buf.Buffer
@@ -123,7 +124,9 @@ func (h *ListenerHandler) NewPacketConnection(ctx context.Context, conn network.
 				return buff
 			}
 			_ = conn.SetReadDeadline(time.Now().Add(DefaultDnsReadTimeout))
-			if isReadWaiter {
+			// syscallPacketReadWaiter.WaitReadPacket will cache newBuffer function
+			// so create new PacketReadWaiter in each loop
+			if readWaiter, isReadWaiter := bufio.CreatePacketReadWaiter(connReader); isReadWaiter {
 				dest, err = readWaiter.WaitReadPacket(newBuffer)
 			} else {
 				dest, err = conn.ReadPacket(newBuffer())

tunnel/statistic/tracker.go

@@ -211,6 +211,10 @@ func (ut *udpTracker) Close() error {
 	return ut.PacketConn.Close()
 }
 
+func (ut *udpTracker) Upstream() any {
+	return ut.PacketConn
+}
+
 func NewUDPTracker(conn C.PacketConn, manager *Manager, metadata *C.Metadata, rule C.Rule, uploadTotal int64, downloadTotal int64, pushToManager bool) *udpTracker {
 	metadata.RemoteDst = parseRemoteDestination(nil, conn)