src/tundev.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * Portions of this code derived and modified from:
   4  *  Copyright 1998-2000 Maxim Krasnyansky <max_mk@yahoo.com>
   5  *  VTun has been derived from VPPP package by Maxim Krasnyansky.
   6  *  Subject to the GPL, version 2.
   7  * By Daniel Borkmann <daniel@netsniff-ng.org>
   8  * Copyright 2011 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,
   9  * Swiss federal institute of technology (ETH Zurich)
  10  * Subject to the GPL.
  11  */
  12
  13 #include <fcntl.h>
  14 #include <unistd.h>
  15 #include <sys/ioctl.h>
  16 #include <sys/socket.h>
  17 #include <sys/types.h>
  18 #include <sys/stat.h>
  19 #include <linux/if.h>
  20 #include <linux/if_tun.h>
  21
  22 #include "tundev.h"
  23 #include "die.h"
  24
  25 static int __tun_open_or_die(void)
  26 {
  27         int i, fd;
  28         char tunname[IFNAMSIZ];
  29
  30         for (i = 0; i < 255; ++i) {
  31                 memset(tunname, 0, sizeof(tunname));
  32                 sprintf(tunname, "/dev/tun%d", i);
  33
  34                 fd = open(tunname, O_RDWR);
  35                 if (fd > 0)
  36                         return fd;
  37         }
  38
  39         panic("Cannot open tunnel device!\n");
  40         return 0; /* never reached, but to suppress compiler warning */
  41 }
  42
  43 #ifndef OTUNSETIFF
  44 # define OTUNSETIFF (('T' << 8) | 202)
  45 #endif
  46
  47 int tun_open_or_die(void)
  48 {
  49         int fd, ret;
  50         struct ifreq ifr;
  51
  52         fd = open("/dev/net/tun", O_RDWR);
  53         if (fd < 0)
  54                 return __tun_open_or_die();
  55
  56         memset(&ifr, 0, sizeof(ifr));
  57         ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
  58
  59         ret = ioctl(fd, TUNSETIFF, &ifr);
  60         if (ret < 0) {
  61                 if (errno == EBADFD) {
  62                         ret = ioctl(fd, OTUNSETIFF, &ifr);
  63                         if (ret < 0)
  64                                 panic("ioctl screwed up 1!\n");
  65                 } else
  66                         panic("ioctl screwed up 2!\n");
  67         }
  68
  69         return fd;
  70 }
  71
  72 ssize_t tun_write(int fd, const void *buf, size_t count)
  73 {
  74         return write(fd, buf, count);
  75 }
  76
  77 ssize_t tun_read(int fd, void *buf, size_t count)
  78 {
  79         return read(fd, buf, count);
  80 }
  81
  82 void tun_close(int fd)
  83 {
  84         close(fd);
  85 }
  86