Improve configuration detector (cone or symmetric)

proxy/socks/server.go

@@ -26,6 +26,7 @@ import (
 type Server struct {
 	config        *ServerConfig
 	policyManager policy.Manager
+	cone          bool
 }
 
 // NewServer creates a new Server object.
@@ -34,6 +35,7 @@ func NewServer(ctx context.Context, config *ServerConfig) (*Server, error) {
 	s := &Server{
 		config:        config,
 		policyManager: v.GetFeature(policy.ManagerType()).(policy.Manager),
+		cone:          ctx.Value("cone").(bool),
 	}
 	return s, nil
 }
@@ -261,7 +263,7 @@ func (s *Server) handleUDPPayload(ctx context.Context, conn internet.Connection,
 
 			payload.UDP = &destination
 
-			if !buf.Cone || dest == nil {
+			if !s.cone || dest == nil {
 				dest = &destination
 			}