Implement remote side buffer control.

README.md

@@ -119,9 +119,14 @@ This field also has no effect if `AdminUID` isn't a valid UID or is empty.
 upstream proxy server. Zero or negative value disables it. Default is 0 (disabled).
 
 `LoopbackTcpSendBuffer` is the number of bytes to use for the tcp loopback send buffer. Use a low value like 4096 for a server-to-server bridge.
+
 `LoopbackTcpReceiveBuffer` is the number of bytes to use for the tcp loopback receive buffer. Use a low value like 4096 for a server-to-server bridge.
 
-These 2 options are not normally needed except when setting up a tcp server-to-server bridge using a shadowsocks or similar tcp server in the `ProxyBook` to reduce tcp performance degradation due to bufferbloat across the bridge.
+`RemoteTcpSendBuffer` is the number of bytes to use for the tcp remote send buffer. Use a low value like 4096 for a server-to-server bridge.
+
+`RemoteTcpReceiveBuffer` is the number of bytes to use for the tcp remote receive buffer. Use a low value like 4096 for a server-to-server bridge.
+
+These 4 options are not normally needed except when setting up a tcp server-to-server bridge using a shadowsocks or similar tcp server in the `ProxyBook` to reduce tcp performance degradation due to bufferbloat across the bridge.
 
 
 ### Client

internal/client/connector.go

@@ -32,6 +32,9 @@ func MakeSession(connConfig RemoteConnConfig, authInfo AuthInfo, dialer common.D
 				goto makeconn
 			}
 
+			sendBufferSize := connConfig.TcpSendBuffer
+			receiveBufferSize := connConfig.TcpReceiveBuffer
+
 			tcpConn, ok := remoteConn.(*net.TCPConn)
 			if ok {
 				syscallConn, err := tcpConn.SyscallConn()
@@ -40,6 +43,22 @@ func MakeSession(connConfig RemoteConnConfig, authInfo AuthInfo, dialer common.D
 				}
 
 				err = syscallConn.Control(func(fd uintptr) {
+					if sendBufferSize > 0 {
+						log.Debugf("Setting remote connection tcp send buffer: %d", sendBufferSize)
+						err := syscall.SetsockoptInt(common.Platformfd(fd), syscall.SOL_SOCKET, syscall.SO_SNDBUF, sendBufferSize)
+						if err != nil {
+							log.Errorf("setsocketopt SO_SNDBUF: %s\n", err)
+						}
+					}
+
+					if receiveBufferSize > 0 {
+						log.Debugf("Setting remote connection tcp receive buffer: %d", receiveBufferSize)
+						err = syscall.SetsockoptInt(common.Platformfd(fd), syscall.SOL_SOCKET, syscall.SO_RCVBUF, receiveBufferSize)
+						if err != nil {
+							log.Errorf("setsocketopt SO_RCVBUF: %s\n", err)
+						}
+					}
+
 					err = syscall.SetsockoptInt(common.Platformfd(fd), syscall.IPPROTO_TCP, syscall.TCP_NODELAY, 1)
 					if err != nil {
 						log.Errorf("setsocketopt TCP_NODELAY: %s\n", err)

internal/client/state.go

@@ -42,14 +42,18 @@ type RawConfig struct {
 	KeepAlive                int    // nullable
 	LoopbackTcpSendBuffer    int    // nullable
 	LoopbackTcpReceiveBuffer int    // nullable
+	RemoteTcpSendBuffer      int    // nullable
+	RemoteTcpReceiveBuffer   int    // nullable
 }
 
 type RemoteConnConfig struct {
-	Singleplex     bool
-	NumConn        int
-	KeepAlive      time.Duration
-	RemoteAddr     string
-	TransportMaker func() Transport
+	Singleplex       bool
+	NumConn          int
+	KeepAlive        time.Duration
+	RemoteAddr       string
+	TransportMaker   func() Transport
+	TcpSendBuffer    int
+	TcpReceiveBuffer int
 }
 
 type LocalConnConfig struct {
@@ -291,5 +295,13 @@ func (raw *RawConfig) ProcessRawConfig(worldState common.WorldState) (local Loca
 		local.TcpReceiveBuffer = raw.LoopbackTcpReceiveBuffer
 	}
 
+	if raw.RemoteTcpSendBuffer > 0 {
+		remote.TcpSendBuffer = raw.RemoteTcpSendBuffer
+	}
+
+	if raw.RemoteTcpReceiveBuffer > 0 {
+		remote.TcpReceiveBuffer = raw.RemoteTcpReceiveBuffer
+	}
+
 	return
 }