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.Conn
  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 (c TCPSender) Reorderable() bool {
  40         return false
  41 }
  42
  43 func startTCP(sink chan Pkt) {
  44         bind, err := net.ResolveTCPAddr("tcp", *bindAddr)
  45         if err != nil {
  46                 log.Fatalln("Can not resolve bind address:", err)
  47         }
  48         listener, err := net.ListenTCP("tcp", bind)
  49         if err != nil {
  50                 log.Fatalln("Can not listen on TCP:", err)
  51         }
  52         log.Println("Listening on TCP", *bindAddr)
  53         go func() {
  54                 for {
  55                         conn, _ := listener.AcceptTCP()
  56                         ready := make(chan struct{}, 1)
  57                         go handleTCP(conn, sink, ready)
  58                         ready <- struct{}{}
  59                 }
  60         }()
  61 }
  62
  63 func handleTCP(conn net.Conn, sink chan Pkt, ready chan struct{}) {
  64         addr := conn.RemoteAddr().String()
  65         var err error
  66         var n int
  67         var sizeNbuf int
  68         sizeBuf := make([]byte, 2)
  69         var sizeNeed uint16
  70         var bufN uint16
  71         buf := make([]byte, govpn.MTU)
  72         for {
  73                 <-ready
  74                 if sizeNbuf != 2 {
  75                         n, err = conn.Read(sizeBuf[sizeNbuf:2])
  76                         if err != nil {
  77                                 break
  78                         }
  79                         sizeNbuf += n
  80                         if sizeNbuf != 2 {
  81                                 sink <- Pkt{ready: ready}
  82                                 continue
  83                         }
  84                         sizeNeed = binary.BigEndian.Uint16(sizeBuf)
  85                         if int(sizeNeed) > govpn.MTU-2 {
  86                                 log.Println("Invalid TCP size, skipping")
  87                                 sizeNbuf = 0
  88                                 sink <- Pkt{ready: ready}
  89                                 continue
  90                         }
  91                         bufN = 0
  92                 }
  93         ReadMore:
  94                 if sizeNeed != bufN {
  95                         n, err = conn.Read(buf[bufN:sizeNeed])
  96                         if err != nil {
  97                                 break
  98                         }
  99                         bufN += uint16(n)
 100                         goto ReadMore
 101                 }
 102                 sizeNbuf = 0
 103                 sink <- Pkt{
 104                         addr,
 105                         TCPSender{conn},
 106                         buf[:sizeNeed],
 107                         ready,
 108                 }
 109         }
 110 }