race condition fix

common/control/bind_finder_default.go

@@ -3,6 +3,7 @@ package control
 import (
 	"net"
 	"net/netip"
+	"sync"
 
 	E "github.com/sagernet/sing/common/exceptions"
 )
@@ -11,6 +12,7 @@ var _ InterfaceFinder = (*DefaultInterfaceFinder)(nil)
 
 type DefaultInterfaceFinder struct {
 	interfaces []Interface
+	access     sync.RWMutex
 }
 
 func NewDefaultInterfaceFinder() *DefaultInterfaceFinder {
@@ -31,7 +33,9 @@ func (f *DefaultInterfaceFinder) Update() error {
 		}
 		interfaces = append(interfaces, iif)
 	}
+	f.access.Lock()
 	f.interfaces = interfaces
+	f.access.Unlock()
 	return nil
 }
 
@@ -61,11 +65,14 @@ func (f *DefaultInterfaceFinder) ByName(name string) (*Interface, error) {
 }
 
 func (f *DefaultInterfaceFinder) ByIndex(index int) (*Interface, error) {
+	f.access.RLock()
 	for _, netInterface := range f.interfaces {
 		if netInterface.Index == index {
 			return &netInterface, nil
 		}
 	}
+	f.access.RUnlock()
+
 	_, err := net.InterfaceByIndex(index)
 	if err == nil {
 		err = f.Update()

common/udpnat2/conn.go

@@ -58,6 +58,9 @@ func (c *natConn) WritePacket(buffer *buf.Buffer, destination M.Socksaddr) error
 }
 
 func (c *natConn) InitializeReadWaiter(options N.ReadWaitOptions) (needCopy bool) {
+	c.handlerAccess.Lock()
+	defer c.handlerAccess.Unlock()
+
 	c.readWaitOptions = options
 	return false
 }

common/udpnat2/service.go

@@ -70,11 +70,11 @@ func (s *Service) NewPacket(bufferSlices [][]byte, source M.Socksaddr, destinati
 	if !ok {
 		return
 	}
+	conn.handlerAccess.RLock()
 	buffer := conn.readWaitOptions.NewPacketBuffer()
 	for _, bufferSlice := range bufferSlices {
 		buffer.Write(bufferSlice)
 	}
-	conn.handlerAccess.RLock()
 	handler := conn.handler
 	conn.handlerAccess.RUnlock()
 	if handler != nil {