Optionally use TCP_CORK on client-side

TCP_CORK/TCP_NOPUSH coalesces salt+address+initial data in one packet

main.go

@@ -21,6 +21,7 @@ import (
 var config struct {
 	Verbose    bool
 	UDPTimeout time.Duration
+	TCPCork    bool
 }
 
 func main() {
@@ -61,6 +62,7 @@ func main() {
 	flag.StringVar(&flags.PluginOpts, "plugin-opts", "", "Set SIP003 plugin options. (e.g., \"server;tls;host=mydomain.me\")")
 	flag.BoolVar(&flags.UDP, "udp", false, "(server-only) enable UDP support")
 	flag.BoolVar(&flags.UDP, "tcp", true, "(server-only) enable TCP support")
+	flag.BoolVar(&config.TCPCork, "tcpcork", false, "(client-only) enable TCP_CORK (Linux) or TCP_NOPUSH (BSD) for the first few packets")
 	flag.DurationVar(&config.UDPTimeout, "udptimeout", 5*time.Minute, "UDP tunnel timeout")
 	flag.Parse()
 

tcp.go

@@ -70,7 +70,11 @@ func tcpLocal(addr, server string, shadow func(net.Conn) net.Conn, getAddr func(
 				return
 			}
 			defer rc.Close()
-			rc.(*net.TCPConn).SetKeepAlive(true)
+			tc := rc.(*net.TCPConn)
+			tc.SetKeepAlive(true)
+			if config.TCPCork {
+				timedCork(tc, 10*time.Millisecond)
+			}
 			rc = shadow(rc)
 
 			if _, err = rc.Write(tgt); err != nil {

tcp_darwin.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"net"
+	"syscall"
+	"time"
 
 	"github.com/shadowsocks/go-shadowsocks2/pfutil"
 	"github.com/shadowsocks/go-shadowsocks2/socks"
@@ -22,3 +24,18 @@ func natLookup(c net.Conn) (socks.Addr, error) {
 	}
 	panic("not TCP connection")
 }
+
+func timedCork(c *net.TCPConn, d time.Duration) error {
+	rc, err := c.SyscallConn()
+	if err != nil {
+		return err
+	}
+	rc.Control(func(fd uintptr) { err = syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, syscall.TCP_NOPUSH, 1) })
+	if err != nil {
+		return err
+	}
+	time.AfterFunc(d, func() {
+		rc.Control(func(fd uintptr) { syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, syscall.TCP_NOPUSH, 0) })
+	})
+	return nil
+}

tcp_linux.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"net"
+	"syscall"
+	"time"
 
 	"github.com/shadowsocks/go-shadowsocks2/nfutil"
 	"github.com/shadowsocks/go-shadowsocks2/socks"
@@ -26,3 +28,18 @@ func redir6Local(addr, server string, shadow func(net.Conn) net.Conn) {
 	logf("TCP6 redirect %s <-> %s", addr, server)
 	tcpLocal(addr, server, shadow, func(c net.Conn) (socks.Addr, error) { return getOrigDst(c, true) })
 }
+
+func timedCork(c *net.TCPConn, d time.Duration) error {
+	rc, err := c.SyscallConn()
+	if err != nil {
+		return err
+	}
+	rc.Control(func(fd uintptr) { err = syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, syscall.TCP_CORK, 1) })
+	if err != nil {
+		return err
+	}
+	time.AfterFunc(d, func() {
+		rc.Control(func(fd uintptr) { syscall.SetsockoptInt(int(fd), syscall.IPPROTO_TCP, syscall.TCP_CORK, 0) })
+	})
+	return nil
+}

tcp_other.go

@@ -2,7 +2,10 @@
 
 package main
 
-import "net"
+import (
+	"net"
+	"time"
+)
 
 func redirLocal(addr, server string, shadow func(net.Conn) net.Conn) {
 	logf("TCP redirect not supported")
@@ -11,3 +14,5 @@ func redirLocal(addr, server string, shadow func(net.Conn) net.Conn) {
 func redir6Local(addr, server string, shadow func(net.Conn) net.Conn) {
 	logf("TCP6 redirect not supported")
 }
+
+func timedCork(c *net.TCPConn, d time.Duration) error { return nil }