smux@v1.4.8 & smux/v2@v2.0.18

README.md

@@ -23,6 +23,15 @@
 
 > *Disclaimer: kcptun maintains a single website — [github.com/xtaci/kcptun](https://github.com/xtaci/kcptun). Any websites other than [github.com/xtaci/kcptun](https://github.com/xtaci/kcptun) are not endorsed by xtaci.*
 
+### Requirements
+
+| Target | Minimum | Recommended |
+| --- | --- | --- |
+| System | aix darwin dragonfly freebsd linux netbsd openbsd solaris windows | linux |
+| Memory | >20MB | >32MB |
+| CPU | ANY | amd64 with AES-NI & AVX2 |
+
+
 ### QuickStart
 
 Increase the number of open files on your server, as:

build-release.sh

@@ -6,11 +6,8 @@ cd $BUILD_DIR
 
 sum="sha1sum"
 
-if [ "$GO111MODULE" != "on" ]; then
-	echo "GO111MODULE is off"
-else
-	echo "GO111MODULE is on"
-fi 
+export GO111MODULE=on
+echo "Setting GO111MODULE to" $GO111MODULE
 
 if ! hash sha1sum 2>/dev/null; then
 	if ! hash shasum 2>/dev/null; then

client/main.go

@@ -8,7 +8,6 @@ import (
 	"math/rand"
 	"net"
 	"os"
-	"sync"
 	"time"
 
 	"golang.org/x/crypto/pbkdf2"
@@ -21,19 +20,20 @@ import (
 	smuxv2 "github.com/xtaci/smux/v2"
 )
 
-// SALT is use for pbkdf2 key expansion
-const SALT = "kcp-go"
-
-// maximum supported smux version
-const maxSmuxVer = 2
+const (
+	// SALT is use for pbkdf2 key expansion
+	SALT = "kcp-go"
+	// maximum supported smux version
+	maxSmuxVer = 2
+	// stream copy buffer size
+	bufSize = 4096
+)
 
 // VERSION is injected by buildflags
 var VERSION = "SELFBUILD"
 
-// A pool for stream copying
-var xmitBuf sync.Pool
-
-func handleClient(mux generic.Mux, p1 net.Conn, quiet bool) {
+// handleClient aggregates connection p1 on mux with 'writeLock'
+func handleClient(mux generic.Mux, p1 net.Conn, ctrl *generic.CopyControl, quiet bool) {
 	logln := func(v ...interface{}) {
 		if !quiet {
 			log.Println(v...)
@@ -54,36 +54,29 @@ func handleClient(mux generic.Mux, p1 net.Conn, quiet bool) {
 	}
 
 	// start tunnel & wait for tunnel termination
-	streamCopy := func(dst io.Writer, src io.ReadCloser) chan struct{} {
-		die := make(chan struct{})
-		go func() {
-			buf := xmitBuf.Get().([]byte)
-			if _, err := generic.CopyBuffer(dst, src, buf); err != nil {
-				if s2, ok := p2.(generic.Stream); ok {
-					// verbose error handling
-					cause := err
-					if e, ok := err.(interface{ Cause() error }); ok {
-						cause = e.Cause()
-					}
+	streamCopy := func(dst io.Writer, src io.ReadCloser) {
+		if _, err := generic.Copy(dst, src, ctrl); err != nil {
+			if s2, ok := p2.(generic.Stream); ok {
+				// verbose error handling
+				cause := err
+				if e, ok := err.(interface{ Cause() error }); ok {
+					cause = e.Cause()
+				}
 
-					switch cause {
-					case smux.ErrInvalidProtocol:
-						log.Println("smux version:1", err, "in:", p1.RemoteAddr(), "out:", fmt.Sprint(s2.RemoteAddr(), "(", s2.ID(), ")"))
-					case smuxv2.ErrInvalidProtocol:
-						log.Println("smux version:2", err, "in:", p1.RemoteAddr(), "out:", fmt.Sprint(s2.RemoteAddr(), "(", s2.ID(), ")"))
-					}
+				switch cause {
+				case smux.ErrInvalidProtocol:
+					log.Println("smux version:1", err, "in:", p1.RemoteAddr(), "out:", fmt.Sprint(s2.RemoteAddr(), "(", s2.ID(), ")"))
+				case smuxv2.ErrInvalidProtocol:
+					log.Println("smux version:2", err, "in:", p1.RemoteAddr(), "out:", fmt.Sprint(s2.RemoteAddr(), "(", s2.ID(), ")"))
 				}
 			}
-			xmitBuf.Put(buf)
-			close(die)
-		}()
-		return die
+		}
+		p1.Close()
+		p2.Close()
 	}
 
-	select {
-	case <-streamCopy(p1, p2):
-	case <-streamCopy(p2, p1):
-	}
+	go streamCopy(p1, p2)
+	streamCopy(p2, p1)
 }
 
 func checkError(err error) {
@@ -99,9 +92,6 @@ func main() {
 		// add more log flags for debugging
 		log.SetFlags(log.LstdFlags | log.Lshortfile)
 	}
-	xmitBuf.New = func() interface{} {
-		return make([]byte, 32768)
-	}
 
 	myApp := cli.NewApp()
 	myApp.Name = "kcptun"
@@ -464,11 +454,13 @@ func main() {
 		muxes := make([]struct {
 			session generic.Mux
 			ttl     time.Time
+			ctrl    *generic.CopyControl // for control of memory in copying
 		}, numconn)
 
 		for k := range muxes {
 			muxes[k].session = waitConn()
 			muxes[k].ttl = time.Now().Add(time.Duration(config.AutoExpire) * time.Second)
+			muxes[k].ctrl = &generic.CopyControl{Buffer: make([]byte, bufSize)}
 		}
 
 		chScavenger := make(chan generic.Mux, 128)
@@ -487,9 +479,10 @@ func main() {
 				chScavenger <- muxes[idx].session
 				muxes[idx].session = waitConn()
 				muxes[idx].ttl = time.Now().Add(time.Duration(config.AutoExpire) * time.Second)
+				muxes[idx].ctrl = &generic.CopyControl{Buffer: make([]byte, bufSize)}
 			}
 
-			go handleClient(muxes[idx].session, p1, config.Quiet)
+			go handleClient(muxes[idx].session, p1, muxes[idx].ctrl, config.Quiet)
 			rr++
 		}
 	}

generic/copy.go

@@ -1,36 +1,40 @@
 package generic
 
-import "io"
+import (
+	"io"
+	"net"
+	"sync"
+)
 
-// io.CopyBuffer has extra tests for interface like io.ReaderFrom and io.WriterTo
-// which is not efficient in memory management from tests
-func CopyBuffer(dst io.Writer, src io.Reader, buf []byte) (written int64, err error) {
-	if buf != nil && len(buf) == 0 {
-		panic("empty buffer in copyBuffer")
-	}
+const bufSize = 4096
 
-	for {
-		nr, er := src.Read(buf)
-		if nr > 0 {
-			nw, ew := dst.Write(buf[0:nr])
-			if nw > 0 {
-				written += int64(nw)
-			}
-			if ew != nil {
-				err = ew
-				break
-			}
-			if nr != nw {
-				err = io.ErrShortWrite
-				break
-			}
-		}
-		if er != nil {
-			if er != io.EOF {
-				err = er
-			}
-			break
+type CopyControl struct {
+	Buffer []byte // shared buffer for copying controlled by mutex
+	sync.Mutex
+}
+
+// Memory optimized io.Copy function specified for this library
+func Copy(dst io.Writer, src io.Reader, ctrl *CopyControl) (written int64, err error) {
+	// If the reader has a WriteTo method, use it to do the copy.
+	// Avoids an allocation and a copy.
+	if wt, ok := src.(io.WriterTo); ok {
+		return wt.WriteTo(dst)
+	}
+	// Similarly, if the writer has a ReadFrom method, use it to do the copy.
+	if rt, ok := dst.(io.ReaderFrom); ok {
+		return rt.ReadFrom(src)
+	}
+
+	// if src is net.TCPConn, and dst is a multiplexed connection
+	// reading can be controlled by writable events of smux
+	// and make the reading serialized
+	if tcpconn, ok := src.(*net.TCPConn); ok {
+		if ctrl != nil {
+			return rawCopy(dst, tcpconn, ctrl)
 		}
 	}
-	return written, err
+
+	// fallback to standard io.CopyBuffer
+	buf := make([]byte, bufSize)
+	return io.CopyBuffer(dst, src, buf)
 }

generic/rawcopy_unix.go

@@ -0,0 +1,83 @@
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package generic
+
+import (
+	"io"
+	"net"
+
+	"syscall"
+)
+
+// rawCopy can fan in N src into 1 dst with only 1 shared buffer
+func rawCopy(dst io.Writer, src *net.TCPConn, ctrl *CopyControl) (written int64, err error) {
+	c, err := src.SyscallConn()
+	if err != nil {
+		return 0, err
+	}
+
+	buf := ctrl.Buffer
+	var locked bool
+	for {
+		var er error
+		var nr int
+		rr := c.Read(func(s uintptr) bool {
+			// if the 'src' readable, acquire the shared lock first
+			// to make sure no other writers to 'dst' are blocked on dst.Write.
+			// With such design, we only need 1 buffer for a specific 'dst',
+			// especially when 'dst' is a multiplexed connection.
+			ctrl.Lock()
+			locked = true
+			nr, er = syscall.Read(int(s), buf)
+			if er == syscall.EAGAIN {
+				ctrl.Unlock()
+				locked = false
+				return false
+			}
+			// keep the lock on the shared buffer
+			// for the following dst.Write
+			return true
+		})
+
+		// read EOF
+		if nr == 0 && er == nil {
+			break
+		}
+
+		if nr > 0 {
+			nw, ew := dst.Write(buf[0:nr])
+			ctrl.Unlock()
+			locked = false
+
+			if nw > 0 {
+				written += int64(nw)
+			}
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != nw {
+				err = io.ErrShortWrite
+				break
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				err = er
+			}
+			break
+		}
+		if rr != nil {
+			if rr != io.EOF {
+				err = rr
+			}
+			break
+		}
+	}
+
+	if locked {
+		ctrl.Unlock()
+	}
+
+	return written, err
+}

generic/rawcopy_windows.go

@@ -0,0 +1,14 @@
+// +build windows
+
+package generic
+
+import (
+	"io"
+	"net"
+)
+
+func rawCopy(dst io.Writer, src *net.TCPConn, ctrl *CopyControl) (written int64, err error) {
+	// fallback to standard io.CopyBuffer
+	buf := make([]byte, bufSize)
+	return io.CopyBuffer(dst, src, buf)
+}

go.mod

@@ -4,21 +4,21 @@ require (
 	github.com/coreos/go-iptables v0.4.2 // indirect
 	github.com/golang/snappy v0.0.1
 	github.com/google/gopacket v1.1.17 // indirect
-	github.com/klauspost/cpuid v1.2.1 // indirect
-	github.com/klauspost/reedsolomon v1.9.2 // indirect
+	github.com/klauspost/cpuid v1.2.2 // indirect
+	github.com/klauspost/reedsolomon v1.9.3 // indirect
 	github.com/pkg/errors v0.8.1
 	github.com/templexxx/cpufeat v0.0.0-20180724012125-cef66df7f161 // indirect
-	github.com/templexxx/xor v0.0.0-20181023030647-4e92f724b73b // indirect
+	github.com/templexxx/xor v0.0.0-20191217153810-f85b25db303b // indirect
 	github.com/tjfoc/gmsm v1.0.1 // indirect
 	github.com/urfave/cli v1.21.0
-	github.com/xtaci/kcp-go v5.4.16+incompatible
+	github.com/xtaci/kcp-go v5.4.20+incompatible
 	github.com/xtaci/lossyconn v0.0.0-20190602105132-8df528c0c9ae // indirect
-	github.com/xtaci/smux v1.4.4
-	github.com/xtaci/smux/v2 v2.0.11
+	github.com/xtaci/smux v1.4.8
+	github.com/xtaci/smux/v2 v2.0.18
 	github.com/xtaci/tcpraw v1.2.25
-	golang.org/x/crypto v0.0.0-20190909091759-094676da4a83
-	golang.org/x/net v0.0.0-20190909003024-a7b16738d86b // indirect
-	golang.org/x/sys v0.0.0-20190910064555-bbd175535a8b // indirect
+	golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413
+	golang.org/x/net v0.0.0-20191209160850-c0dbc17a3553 // indirect
+	golang.org/x/sys v0.0.0-20191218084908-4a24b4065292 // indirect
 )
 
 go 1.13

go.sum

@@ -5,47 +5,49 @@ github.com/golang/snappy v0.0.1 h1:Qgr9rKW7uDUkrbSmQeiDsGa8SjGyCOGtuasMWwvp2P4=
 github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/google/gopacket v1.1.17 h1:rMrlX2ZY2UbvT+sdz3+6J+pp2z+msCq9MxTU6ymxbBY=
 github.com/google/gopacket v1.1.17/go.mod h1:UdDNZ1OO62aGYVnPhxT1U6aI7ukYtA/kB8vaU0diBUM=
-github.com/klauspost/cpuid v1.2.1 h1:vJi+O/nMdFt0vqm8NZBI6wzALWdA2X+egi0ogNyrC/w=
-github.com/klauspost/cpuid v1.2.1/go.mod h1:Pj4uuM528wm8OyEC2QMXAi2YiTZ96dNQPGgoMS4s3ek=
-github.com/klauspost/reedsolomon v1.9.2 h1:E9CMS2Pqbv+C7tsrYad4YC9MfhnMVWhMRsTi7U0UB18=
-github.com/klauspost/reedsolomon v1.9.2/go.mod h1:CwCi+NUr9pqSVktrkN+Ondf06rkhYZ/pcNv7fu+8Un4=
+github.com/klauspost/cpuid v1.2.2 h1:1xAgYebNnsb9LKCdLOvFWtAxGU/33mjJtyOVbmUa0Us=
+github.com/klauspost/cpuid v1.2.2/go.mod h1:Pj4uuM528wm8OyEC2QMXAi2YiTZ96dNQPGgoMS4s3ek=
+github.com/klauspost/reedsolomon v1.9.3 h1:N/VzgeMfHmLc+KHMD1UL/tNkfXAt8FnUqlgXGIduwAY=
+github.com/klauspost/reedsolomon v1.9.3/go.mod h1:CwCi+NUr9pqSVktrkN+Ondf06rkhYZ/pcNv7fu+8Un4=
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/templexxx/cpufeat v0.0.0-20180724012125-cef66df7f161 h1:89CEmDvlq/F7SJEOqkIdNDGJXrQIhuIx9D2DBXjavSU=
 github.com/templexxx/cpufeat v0.0.0-20180724012125-cef66df7f161/go.mod h1:wM7WEvslTq+iOEAMDLSzhVuOt5BRZ05WirO+b09GHQU=
-github.com/templexxx/xor v0.0.0-20181023030647-4e92f724b73b h1:mnG1fcsIB1d/3vbkBak2MM0u+vhGhlQwpeimUi7QncM=
-github.com/templexxx/xor v0.0.0-20181023030647-4e92f724b73b/go.mod h1:5XA7W9S6mni3h5uvOC75dA3m9CCCaS83lltmc0ukdi4=
+github.com/templexxx/xor v0.0.0-20191217153810-f85b25db303b h1:fj5tQ8acgNUr6O8LEplsxDhUIe2573iLkJc+PqnzZTI=
+github.com/templexxx/xor v0.0.0-20191217153810-f85b25db303b/go.mod h1:5XA7W9S6mni3h5uvOC75dA3m9CCCaS83lltmc0ukdi4=
 github.com/tjfoc/gmsm v1.0.1 h1:R11HlqhXkDospckjZEihx9SW/2VW0RgdwrykyWMFOQU=
 github.com/tjfoc/gmsm v1.0.1/go.mod h1:XxO4hdhhrzAd+G4CjDqaOkd0hUzmtPR/d3EiBBMn/wc=
 github.com/urfave/cli v1.21.0 h1:wYSSj06510qPIzGSua9ZqsncMmWE3Zr55KBERygyrxE=
 github.com/urfave/cli v1.21.0/go.mod h1:lxDj6qX9Q6lWQxIrbrT0nwecwUtRnhVZAJjJZrVUZZQ=
-github.com/xtaci/kcp-go v5.4.13+incompatible h1:s6ba2XTw8lAj+s6AQNob25dCvWDgwE+U1QpEVBUoYy8=
-github.com/xtaci/kcp-go v5.4.13+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.14+incompatible h1:kQZr/ngKQtYrgXSUxwF4A59mTMzUp0BDmtWIRuXYoqg=
-github.com/xtaci/kcp-go v5.4.14+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.15+incompatible h1:QLDulPaKjT4k4cGeviyC1mt00gwJ3r5epx8yCw6ACEc=
-github.com/xtaci/kcp-go v5.4.15+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
-github.com/xtaci/kcp-go v5.4.16+incompatible h1:/L7UP4P4H/oXpMnrb2W9oOxCMVpjPi3FJeMJmgN+SUE=
-github.com/xtaci/kcp-go v5.4.16+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
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 github.com/xtaci/lossyconn v0.0.0-20190602105132-8df528c0c9ae h1:J0GxkO96kL4WF+AIT3M4mfUVinOCPgf2uUWYFUzN0sM=
 github.com/xtaci/lossyconn v0.0.0-20190602105132-8df528c0c9ae/go.mod h1:gXtu8J62kEgmN++bm9BVICuT/e8yiLI2KFobd/TRFsE=
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-github.com/xtaci/smux/v2 v2.0.11 h1:thVWmgGRciZ8iaATwpY2B/51aHzmMI6wrF7DfcJSckU=
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+github.com/xtaci/smux/v2 v2.0.17/go.mod h1:Iqy5a3Gax2p7WCKHOHkSNo/COthNFXd3/vqrcKNtzqI=
+github.com/xtaci/smux/v2 v2.0.18 h1:Sa+W8IMR0dv3Tj9XxDUqovEFYGtU8Upydmmpez7IZgA=
+github.com/xtaci/smux/v2 v2.0.18/go.mod h1:Iqy5a3Gax2p7WCKHOHkSNo/COthNFXd3/vqrcKNtzqI=
 github.com/xtaci/tcpraw v1.2.25 h1:VDlqo0op17JeXBM6e2G9ocCNLOJcw9mZbobMbJjo0vk=
 github.com/xtaci/tcpraw v1.2.25/go.mod h1:dKyZ2V75s0cZ7cbgJYdxPvms7af0joIeOyx1GgJQbLk=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20190909091759-094676da4a83 h1:mgAKeshyNqWKdENOnQsg+8dRTwZFIwFaO3HNl52sweA=
-golang.org/x/crypto v0.0.0-20190909091759-094676da4a83/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
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+golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190909003024-a7b16738d86b h1:XfVGCX+0T4WOStkaOsJRllbsiImhB2jgVBGc9L0lPGc=
-golang.org/x/net v0.0.0-20190909003024-a7b16738d86b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20191209160850-c0dbc17a3553 h1:efeOvDhwQ29Dj3SdAV/MJf8oukgn+8D8WgaCaRMchF8=
+golang.org/x/net v0.0.0-20191209160850-c0dbc17a3553/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190405154228-4b34438f7a67/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20190910064555-bbd175535a8b h1:3S2h5FadpNr0zUUCVZjlKIEYF+KaX/OBplTGo89CYHI=
-golang.org/x/sys v0.0.0-20190910064555-bbd175535a8b/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191218084908-4a24b4065292 h1:Y8q0zsdcgAd+JU8VUA8p8Qv2YhuY9zevDG2ORt5qBUI=
+golang.org/x/sys v0.0.0-20191218084908-4a24b4065292/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

server/main.go

@@ -23,18 +23,18 @@ import (
 	"github.com/xtaci/tcpraw"
 )
 
-// SALT is use for pbkdf2 key expansion
-const SALT = "kcp-go"
-
-// maximum supported smux version
-const maxSmuxVer = 2
+const (
+	// SALT is use for pbkdf2 key expansion
+	SALT = "kcp-go"
+	// maximum supported smux version
+	maxSmuxVer = 2
+	// stream copy buffer size
+	bufSize = 4096
+)
 
 // VERSION is injected by buildflags
 var VERSION = "SELFBUILD"
 
-// A pool for stream copying
-var xmitBuf sync.Pool
-
 // handle multiplex-ed connection
 func handleMux(conn net.Conn, config *Config) {
 	// check if target is unix domain socket
@@ -76,6 +76,9 @@ func handleMux(conn net.Conn, config *Config) {
 		panic("incorrect smux version")
 	}
 
+	// copy to stream control
+	copyControl := &generic.CopyControl{Buffer: make([]byte, bufSize)}
+
 	for {
 		stream, err := muxer.Accept()
 		if err != nil {
@@ -97,12 +100,12 @@ func handleMux(conn net.Conn, config *Config) {
 				p1.Close()
 				return
 			}
-			handleClient(p1, p2, config.Quiet)
+			handleClient(p1, p2, copyControl, config.Quiet)
 		}(stream)
 	}
 }
 
-func handleClient(p1 io.ReadWriteCloser, p2 net.Conn, quiet bool) {
+func handleClient(p1 io.ReadWriteCloser, p2 net.Conn, ctrl *generic.CopyControl, quiet bool) {
 	logln := func(v ...interface{}) {
 		if !quiet {
 			log.Println(v...)
@@ -118,36 +121,29 @@ func handleClient(p1 io.ReadWriteCloser, p2 net.Conn, quiet bool) {
 	}
 
 	// start tunnel & wait for tunnel termination
-	streamCopy := func(dst io.Writer, src io.ReadCloser) chan struct{} {
-		die := make(chan struct{})
-		go func() {
-			buf := xmitBuf.Get().([]byte)
-			if _, err := generic.CopyBuffer(dst, src, buf); err != nil {
-				if s1, ok := p1.(generic.Stream); ok {
-					// verbose error handling
-					cause := err
-					if e, ok := err.(interface{ Cause() error }); ok {
-						cause = e.Cause()
-					}
+	streamCopy := func(dst io.Writer, src io.ReadCloser) {
+		if _, err := generic.Copy(dst, src, ctrl); err != nil {
+			if s1, ok := p1.(generic.Stream); ok {
+				// verbose error handling
+				cause := err
+				if e, ok := err.(interface{ Cause() error }); ok {
+					cause = e.Cause()
+				}
 
-					switch cause {
-					case smux.ErrInvalidProtocol:
-						log.Println("smux version:1", err, "in:", fmt.Sprint(s1.RemoteAddr(), "(", s1.ID(), ")"), "out:", p2.RemoteAddr())
-					case smuxv2.ErrInvalidProtocol:
-						log.Println("smux version:2", err, "in:", fmt.Sprint(s1.RemoteAddr(), "(", s1.ID(), ")"), "out:", p2.RemoteAddr())
-					}
+				switch cause {
+				case smux.ErrInvalidProtocol:
+					log.Println("smux version:1", err, "in:", fmt.Sprint(s1.RemoteAddr(), "(", s1.ID(), ")"), "out:", p2.RemoteAddr())
+				case smuxv2.ErrInvalidProtocol:
+					log.Println("smux version:2", err, "in:", fmt.Sprint(s1.RemoteAddr(), "(", s1.ID(), ")"), "out:", p2.RemoteAddr())
 				}
 			}
-			xmitBuf.Put(buf)
-			close(die)
-		}()
-		return die
+		}
+		p1.Close()
+		p2.Close()
 	}
 
-	select {
-	case <-streamCopy(p1, p2):
-	case <-streamCopy(p2, p1):
-	}
+	go streamCopy(p2, p1)
+	streamCopy(p1, p2)
 }
 
 func checkError(err error) {
@@ -163,9 +159,6 @@ func main() {
 		// add more log flags for debugging
 		log.SetFlags(log.LstdFlags | log.Lshortfile)
 	}
-	xmitBuf.New = func() interface{} {
-		return make([]byte, 32768)
-	}
 
 	myApp := cli.NewApp()
 	myApp.Name = "kcptun"