src/cypherpunks.ru/govpn/tap_android.go

   1 /*
   2 GoVPN -- simple secure free software virtual private network daemon
   3 Copyright (C) 2016-2017 Bruno Clermont <bruno@robotinfra.com>
   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 govpn
  20
  21 import (
  22         "os"
  23         "syscall"
  24         "time"
  25
  26         "github.com/Sirupsen/logrus"
  27 )
  28
  29 func TapListenFileDescriptor(fd uintptr, ifaceName string, mtu int) *TAP {
  30         tap, exists := taps[ifaceName]
  31         if exists {
  32                 return tap
  33         }
  34
  35         tap = &TAP{
  36                 Name: ifaceName,
  37                 dev:  os.NewFile(fd, ifaceName),
  38                 Sink: make(chan []byte),
  39         }
  40         go func() {
  41                 var n int
  42                 var err error
  43                 var buf []byte
  44                 buf0 := make([]byte, mtu)
  45                 buf1 := make([]byte, mtu)
  46                 bufZ := false
  47                 for {
  48                         if bufZ {
  49                                 buf = buf0
  50                         } else {
  51                                 buf = buf1
  52                         }
  53                         bufZ = !bufZ
  54                         n, err = tap.dev.Read(buf)
  55                         if err != nil {
  56                                 if tap.closed {
  57                                         return
  58                                 }
  59
  60                                 e, ok := err.(*os.PathError)
  61                                 if ok && e.Err == syscall.EAGAIN {
  62                                         time.Sleep(time.Millisecond * 20)
  63                                         continue
  64                                 }
  65
  66                                 logger.WithError(err).WithFields(logrus.Fields{
  67                                         "func", logFuncPrefix + "TUN read sink loop",
  68                                         "name": tap.Name,
  69                                         "mtu":  mtu,
  70                                 }).Error("Can not read interface, stop")
  71                                 return
  72                                 // TODO: need a way to warn consumer that something is wrong
  73                                 // TODO: to force peer to just disconnect
  74                                 // TODO: use the client/server error channel?
  75                         } else {
  76                                 tap.Sink <- buf[:n]
  77                         }
  78                 }
  79         }()
  80         taps[ifaceName] = tap
  81         return tap
  82 }