src/govpn/cmd/govpn-server/tcp.go

   1 /*
   2 GoVPN -- simple secure free software virtual private network daemon
   3 Copyright (C) 2014-2015 Sergey Matveev <stargrave@stargrave.org>
   4
   5 This program is free software: you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation, either version 3 of the License, or
   8 (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19 package main
  20
  21 import (
  22         "encoding/binary"
  23         "log"
  24         "net"
  25
  26         "govpn"
  27 )
  28
  29 type TCPSender struct {
  30         conn *net.TCPConn
  31 }
  32
  33 func (c TCPSender) Write(data []byte) (int, error) {
  34         size := make([]byte, 2)
  35         binary.BigEndian.PutUint16(size, uint16(len(data)))
  36         return c.conn.Write(append(size, data...))
  37 }
  38
  39 func startTCP(sink *chan Pkt) {
  40         bind, err := net.ResolveTCPAddr("tcp", *bindAddr)
  41         if err != nil {
  42                 log.Fatalln("Can not resolve bind address:", err)
  43         }
  44         listener, err := net.ListenTCP("tcp", bind)
  45         if err != nil {
  46                 log.Fatalln("Can not listen on TCP:", err)
  47         }
  48         log.Println("Listening on TCP", *bindAddr)
  49         go func() {
  50                 for {
  51                         conn, _ := listener.AcceptTCP()
  52                         ready := make(chan struct{}, 1)
  53                         go func(conn *net.TCPConn, ready chan struct{}) {
  54                                 addr := conn.RemoteAddr().String()
  55                                 var err error
  56                                 var n int
  57                                 var sizeNbuf int
  58                                 sizeBuf := make([]byte, 2)
  59                                 var sizeNeed uint16
  60                                 var bufN uint16
  61                                 buf := make([]byte, govpn.MTU)
  62                                 for {
  63                                         <-ready
  64                                         if sizeNbuf != 2 {
  65                                                 n, err = conn.Read(sizeBuf[sizeNbuf:2])
  66                                                 if err != nil {
  67                                                         break
  68                                                 }
  69                                                 sizeNbuf += n
  70                                                 if sizeNbuf == 2 {
  71                                                         sizeNeed = binary.BigEndian.Uint16(sizeBuf)
  72                                                         if sizeNeed > uint16(govpn.MTU)-2 {
  73                                                                 log.Println("Invalid TCP size, skipping")
  74                                                                 sizeNbuf = 0
  75                                                                 *sink <- Pkt{ready: ready}
  76                                                                 continue
  77                                                         }
  78                                                         bufN = 0
  79                                                 }
  80                                         }
  81                                 ReadMore:
  82                                         if sizeNeed != bufN {
  83                                                 n, err = conn.Read(buf[bufN:sizeNeed])
  84                                                 if err != nil {
  85                                                         break
  86                                                 }
  87                                                 bufN += uint16(n)
  88                                                 goto ReadMore
  89                                         }
  90                                         sizeNbuf = 0
  91                                         *sink <- Pkt{
  92                                                 addr,
  93                                                 TCPSender{conn},
  94                                                 buf[:sizeNeed],
  95                                                 ready,
  96                                         }
  97                                 }
  98                         }(conn, ready)
  99                         ready <- struct{}{}
 100                 }
 101         }()
 102 }