Support setting send/receive buffers for the IP sockets

protocol/gateway.go

@@ -2,13 +2,17 @@ package protocol
 
 import (
 	"context"
+	"errors"
 	"github.com/bolkedebruin/rdpgw/common"
 	"github.com/bolkedebruin/rdpgw/transport"
 	"github.com/gorilla/websocket"
 	"github.com/patrickmn/go-cache"
 	"github.com/prometheus/client_golang/prometheus"
 	"log"
+	"net"
 	"net/http"
+	"reflect"
+	"syscall"
 	"time"
 )
 
@@ -81,12 +85,76 @@ func (g *Gateway) HandleGatewayProtocol(w http.ResponseWriter, r *http.Request)
 		}
 		defer conn.Close()
 
+		err = g.setSendReceiveBuffers(conn.UnderlyingConn())
+		if err != nil {
+			log.Printf("Cannot set send/receive buffers: %s", err)
+		}
+
 		g.handleWebsocketProtocol(ctx, conn, s)
 	} else if r.Method == MethodRDGIN {
 		g.handleLegacyProtocol(w, r.WithContext(ctx), s)
 	}
 }
 
+func (g *Gateway) setSendReceiveBuffers(conn net.Conn) error {
+	if g.ServerConf.SendBuf < 1 && g.ServerConf.ReceiveBuf < 1 {
+		return nil
+	}
+
+	// conn == tls.Conn
+	ptr := reflect.ValueOf(conn)
+	val := reflect.Indirect(ptr)
+
+	if val.Kind() != reflect.Struct {
+		return errors.New("didn't get a struct from conn")
+	}
+
+	// this gets net.Conn -> *net.TCPConn -> net.TCPConn
+	ptrConn := val.FieldByName("conn")
+	valConn := reflect.Indirect(ptrConn)
+	if !valConn.IsValid() {
+		return errors.New("cannot find conn field")
+	}
+	valConn = valConn.Elem().Elem()
+
+	// net.FD
+	ptrNetFd := valConn.FieldByName("fd")
+	valNetFd := reflect.Indirect(ptrNetFd)
+	if !valNetFd.IsValid() {
+		return errors.New("cannot find fd field")
+	}
+
+	// pfd member
+	ptrPfd := valNetFd.FieldByName("pfd")
+	valPfd := reflect.Indirect(ptrPfd)
+	if !valPfd.IsValid() {
+		return errors.New("cannot find pfd field")
+	}
+
+	// finally the exported Sysfd
+	ptrSysFd := valPfd.FieldByName("Sysfd")
+	if !ptrSysFd.IsValid() {
+		return errors.New("cannot find Sysfd field")
+	}
+	fd := int(ptrSysFd.Int())
+
+	if g.ServerConf.ReceiveBuf > 0 {
+		err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_RCVBUF, g.ServerConf.ReceiveBuf)
+		if err != nil {
+			return wrapSyscallError("setsockopt", err)
+		}
+	}
+
+	if g.ServerConf.SendBuf > 0 {
+		err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_SNDBUF, g.ServerConf.SendBuf)
+		if err != nil {
+			return wrapSyscallError("setsockopt", err)
+		}
+	}
+
+	return nil
+}
+
 func (g *Gateway) handleWebsocketProtocol(ctx context.Context, c *websocket.Conn, s *SessionInfo) {
 	websocketConnections.Inc()
 	defer websocketConnections.Dec()