improve yamux logging (#4952)

client/connector.go

@@ -17,7 +17,6 @@ package client
 import (
 	"context"
 	"crypto/tls"
-	"io"
 	"net"
 	"strconv"
 	"strings"
@@ -115,7 +114,8 @@ func (c *defaultConnectorImpl) Open() error {
 
 	fmuxCfg := fmux.DefaultConfig()
 	fmuxCfg.KeepAliveInterval = time.Duration(c.cfg.Transport.TCPMuxKeepaliveInterval) * time.Second
-	fmuxCfg.LogOutput = io.Discard
+	// Use trace level for yamux logs
+	fmuxCfg.LogOutput = xlog.NewTraceWriter(xl)
 	fmuxCfg.MaxStreamWindowSize = 6 * 1024 * 1024
 	session, err := fmux.Client(conn, fmuxCfg)
 	if err != nil {

client/control.go

@@ -276,10 +276,12 @@ func (ctl *Control) heartbeatWorker() {
 }
 
 func (ctl *Control) worker() {
+	xl := ctl.xl
 	go ctl.heartbeatWorker()
 	go ctl.msgDispatcher.Run()
 
 	<-ctl.msgDispatcher.Done()
+	xl.Debugf("control message dispatcher exited")
 	ctl.closeSession()
 
 	ctl.pm.Close()

go.mod

@@ -82,4 +82,4 @@ require (
 )
 
 // TODO(fatedier): Temporary use the modified version, update to the official version after merging into the official repository.
-replace github.com/hashicorp/yamux => github.com/fatedier/yamux v0.0.0-20230628132301-7aca4898904d
+replace github.com/hashicorp/yamux => github.com/fatedier/yamux v0.0.0-20250825093530-d0154be01cd6

go.sum

@@ -22,8 +22,8 @@ github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1m
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
 github.com/fatedier/golib v0.5.1 h1:hcKAnaw5mdI/1KWRGejxR+i1Hn/NvbY5UsMKDr7o13M=
 github.com/fatedier/golib v0.5.1/go.mod h1:W6kIYkIFxHsTzbgqg5piCxIiDo4LzwgTY6R5W8l9NFQ=
-github.com/fatedier/yamux v0.0.0-20230628132301-7aca4898904d h1:ynk1ra0RUqDWQfvFi5KtMiSobkVQ3cNc0ODb8CfIETo=
+github.com/fatedier/yamux v0.0.0-20250825093530-d0154be01cd6 h1:u92UUy6FURPmNsMBUuongRWC0rBqN6gd01Dzu+D21NE=
-github.com/fatedier/yamux v0.0.0-20230628132301-7aca4898904d/go.mod h1:CtWFDAQgb7dxtzFs4tWbplKIe2jSi3+5vKbgIO0SLnQ=
+github.com/fatedier/yamux v0.0.0-20250825093530-d0154be01cd6/go.mod h1:c5/tk6G0dSpXGzJN7Wk1OEie8grdSJAmeawId9Zvd34=
 github.com/go-jose/go-jose/v4 v4.0.5 h1:M6T8+mKZl/+fNNuFHvGIzDz7BTLQPIounk/b9dw3AaE=
 github.com/go-jose/go-jose/v4 v4.0.5/go.mod h1:s3P1lRrkT8igV8D9OjyL4WRyHvjB6a4JSllnOrmmBOA=
 github.com/go-logr/logr v1.4.2 h1:6pFjapn8bFcIbiKo3XT4j/BhANplGihG6tvd+8rYgrY=

pkg/util/xlog/log_writer.go

@@ -0,0 +1,65 @@
+// Copyright 2025 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package xlog
+
+import "strings"
+
+// LogWriter forwards writes to frp's logger at configurable level.
+// It is safe for concurrent use as long as the underlying Logger is thread-safe.
+type LogWriter struct {
+	xl      *Logger
+	logFunc func(string)
+}
+
+func (w LogWriter) Write(p []byte) (n int, err error) {
+	msg := strings.TrimSpace(string(p))
+	w.logFunc(msg)
+	return len(p), nil
+}
+
+func NewTraceWriter(xl *Logger) LogWriter {
+	return LogWriter{
+		xl:      xl,
+		logFunc: func(msg string) { xl.Tracef("%s", msg) },
+	}
+}
+
+func NewDebugWriter(xl *Logger) LogWriter {
+	return LogWriter{
+		xl:      xl,
+		logFunc: func(msg string) { xl.Debugf("%s", msg) },
+	}
+}
+
+func NewInfoWriter(xl *Logger) LogWriter {
+	return LogWriter{
+		xl:      xl,
+		logFunc: func(msg string) { xl.Infof("%s", msg) },
+	}
+}
+
+func NewWarnWriter(xl *Logger) LogWriter {
+	return LogWriter{
+		xl:      xl,
+		logFunc: func(msg string) { xl.Warnf("%s", msg) },
+	}
+}
+
+func NewErrorWriter(xl *Logger) LogWriter {
+	return LogWriter{
+		xl:      xl,
+		logFunc: func(msg string) { xl.Errorf("%s", msg) },
+	}
+}

server/service.go

@@ -19,7 +19,6 @@ import (
 	"context"
 	"crypto/tls"
 	"fmt"
-	"io"
 	"net"
 	"net/http"
 	"os"
@@ -516,7 +515,8 @@ func (svr *Service) HandleListener(l net.Listener, internal bool) {
 			if lo.FromPtr(svr.cfg.Transport.TCPMux) && !internal {
 				fmuxCfg := fmux.DefaultConfig()
 				fmuxCfg.KeepAliveInterval = time.Duration(svr.cfg.Transport.TCPMuxKeepaliveInterval) * time.Second
-				fmuxCfg.LogOutput = io.Discard
+				// Use trace level for yamux logs
+				fmuxCfg.LogOutput = xlog.NewTraceWriter(xlog.FromContextSafe(ctx))
 				fmuxCfg.MaxStreamWindowSize = 6 * 1024 * 1024
 				session, err := fmux.Server(frpConn, fmuxCfg)
 				if err != nil {