VLESS Multiplex (mux.cool): Replace MutexWriter with buf.BufferedWriter (#7359)

Fixes https://github.com/XTLS/Xray-core/pull/7355#issuecomment-6738888441

---------

Co-authored-by: Medium1992 <Medium1992@users.noreply.github.com>

common/buf/writer.go

@@ -236,6 +236,10 @@ func (w *BufferedWriter) Close() error {
 	return common.Close(w.writer)
 }
 
+func (w *BufferedWriter) Interrupt() {
+	common.Interrupt(w.writer)
+}
+
 // SequentialWriter is a Writer that writes MultiBuffer sequentially into the underlying io.Writer.
 type SequentialWriter struct {
 	io.Writer

common/mux/client.go

@@ -188,7 +188,9 @@ var (
 
 // NewClientWorker creates a new mux.Client.
 func NewClientWorker(stream transport.Link, s ClientStrategy) (*ClientWorker, error) {
-	stream.Writer = &MutexWriter{Writer: stream.Writer}
+	writer := buf.NewBufferedWriter(stream.Writer)
+	writer.SetBuffered(false)
+	stream.Writer = writer
 	c := &ClientWorker{
 		sessionManager: NewSessionManager(),
 		link:           stream,

common/mux/server.go

@@ -93,9 +93,11 @@ type ServerWorker struct {
 }
 
 func NewServerWorker(ctx context.Context, d routing.Dispatcher, link *transport.Link) (*ServerWorker, error) {
+	writer := buf.NewBufferedWriter(link.Writer)
+	writer.SetBuffered(false)
 	worker := &ServerWorker{
 		dispatcher:     d,
-		link:           &transport.Link{Reader: link.Reader, Writer: &MutexWriter{Writer: link.Writer}},
+		link:           &transport.Link{Reader: link.Reader, Writer: writer},
 		sessionManager: NewSessionManager(),
 		done:           done.New(),
 		timer:          time.NewTicker(60 * time.Second),

common/mux/writer.go

@@ -1,8 +1,6 @@
 package mux
 
 import (
-	"sync"
-
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/net"
@@ -11,17 +9,6 @@ import (
 	"github.com/xtls/xray-core/common/session"
 )
 
-type MutexWriter struct {
-	sync.Mutex
-	buf.Writer
-}
-
-func (w *MutexWriter) WriteMultiBuffer(mb buf.MultiBuffer) error {
-	w.Lock()
-	defer w.Unlock()
-	return w.Writer.WriteMultiBuffer(mb)
-}
-
 type Writer struct {
 	dest         net.Destination
 	writer       buf.Writer