nos-tun.c revision 37669 
1/*
2 * Copyright (c) 1996, Nickolay Dudorov
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice unmodified, this list of conditions, and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 */
28
29/*
30 *  'nos_tun' program configure tunN interface as a point-to-point
31 *  connection with two "pseudo"-addresses between this host and
32 *  'target'.
33 *
34 *  It uses Ip-over-Ip incapsulation ( protocol number 94 - IPIP)
35 *  (known as NOS-incapsulation in CISCO-routers' terminology).
36 *
37 *  'nos_tun' can works with itself and CISCO-routers.
38 *  (It may also work with Linux 'nos_tun's, but
39 *  I have no Linux system here to test with).
40 *
41 *  BUGS (or features ?):
42 *  - you must specify ONE of the target host's addresses
43 *    ( nos_tun sends and accepts packets only to/from this
44 *      address )
45 *  - there can be only ONE tunnel between two hosts,
46 *    more precisely - between given host and (one of)
47 *    target hosts' address(es)
48 *    (and why do you want more ?)
49 */
50
51#ifndef lint
52static const char rcsid[] =
53	"$Id$";
54#endif /* not lint */
55
56#include <fcntl.h>
57#include <netdb.h>
58#include <stdio.h>
59#include <stdlib.h>
60#include <string.h>
61#include <syslog.h>
62#include <sys/signal.h>
63#include <sys/socket.h>
64#include <sys/ioctl.h>
65#include <netinet/in.h>
66#include <netinet/in_systm.h>
67#include <netinet/ip.h>
68#include <net/if.h>
69#include <arpa/inet.h>
70#include <unistd.h>
71
72/* Tunnel interface configuration stuff */
73static struct ifaliasreq ifra;
74static struct ifreq ifrq;
75
76/* Global descriptors */
77int net;                          /* socket descriptor */
78int tun;                          /* tunnel descriptor */
79
80static void usage __P((void));
81
82int Set_address(char *addr, struct sockaddr_in *sin)
83{
84  struct hostent *hp;
85
86  bzero((char *)sin, sizeof(struct sockaddr));
87  sin->sin_family = AF_INET;
88  if((sin->sin_addr.s_addr = inet_addr(addr)) == (u_long)-1) {
89    hp = gethostbyname(addr);
90    if (!hp) {
91      syslog(LOG_ERR,"unknown host %s", addr);
92      return 1;
93    }
94    sin->sin_family = hp->h_addrtype;
95    bcopy(hp->h_addr, (caddr_t)&sin->sin_addr, hp->h_length);
96  }
97  return 0;
98}
99
100int tun_open(char *devname, struct sockaddr *ouraddr, char *theiraddr)
101{
102  int s;
103  struct sockaddr_in *sin;
104
105  /* Open tun device */
106  tun = open (devname, O_RDWR);
107  if (tun < 0) {
108    syslog(LOG_ERR,"can't open %s - %m",devname);
109    return(1);
110  }
111
112  /*
113   * At first, name the interface.
114   */
115  bzero((char *)&ifra, sizeof(ifra));
116  bzero((char *)&ifrq, sizeof(ifrq));
117
118  strncpy(ifrq.ifr_name, devname+5, IFNAMSIZ);
119  strncpy(ifra.ifra_name, devname+5, IFNAMSIZ);
120
121  s = socket(AF_INET, SOCK_DGRAM, 0);
122  if (s < 0) {
123    syslog(LOG_ERR,"can't open socket - %M");
124    goto tunc_return;
125  }
126
127  /*
128   *  Delete (previous) adresses for interface
129   *
130   *  !!!!
131   *  On FreeBSD this ioctl returns error
132   *  when tunN have no addresses, so - log and ignore it.
133   *
134   */
135  if (ioctl(s, SIOCDIFADDR, &ifra) < 0) {
136    syslog(LOG_ERR,"SIOCDIFADDR - %m");
137  }
138
139  /*
140   *  Set interface address
141   */
142  sin = (struct sockaddr_in *)&(ifra.ifra_addr);
143  bcopy(ouraddr, sin, sizeof(struct sockaddr_in));
144  sin->sin_len = sizeof(*sin);
145
146  /*
147   *  Set destination address
148   */
149  sin = (struct sockaddr_in *)&(ifra.ifra_broadaddr);
150  if(Set_address(theiraddr,sin)) {
151    syslog(LOG_ERR,"bad destination address: %s",theiraddr);
152    goto stunc_return;
153  }
154  sin->sin_len = sizeof(*sin);
155
156  if (ioctl(s, SIOCAIFADDR, &ifra) < 0) {
157    syslog(LOG_ERR,"can't set interface address - %m");
158    goto stunc_return;
159  }
160
161  /*
162   *  Now, bring up the interface.
163   */
164  if (ioctl(s, SIOCGIFFLAGS, &ifrq) < 0) {
165    syslog(LOG_ERR,"can't get interface flags - %m");
166    goto stunc_return;
167  }
168
169  ifrq.ifr_flags |= IFF_UP;
170  if (!(ioctl(s, SIOCSIFFLAGS, &ifrq) < 0)) {
171    close(s);
172    return(0);
173  }
174  syslog(LOG_ERR,"can't set interface UP - %m");
175stunc_return:
176  close(s);
177tunc_return:
178  close(tun);
179  return(1);
180}
181
182void Finish(int signum)
183{
184  int s;
185
186  syslog(LOG_INFO,"exiting");
187
188  close(net);
189
190  s = socket(AF_INET, SOCK_DGRAM, 0);
191  if (s < 0) {
192    syslog(LOG_ERR,"can't open socket - %m");
193    goto closing_tun;
194  }
195
196  /*
197   *  Shut down interface.
198   */
199  if (ioctl(s, SIOCGIFFLAGS, &ifrq) < 0) {
200    syslog(LOG_ERR,"can't get interface flags - %m");
201    goto closing_fds;
202  }
203
204  ifrq.ifr_flags &= ~(IFF_UP|IFF_RUNNING);
205  if (ioctl(s, SIOCSIFFLAGS, &ifrq) < 0) {
206    syslog(LOG_ERR,"can't set interface DOWN - %m");
207    goto closing_fds;
208  }
209
210  /*
211   *  Delete adresses for interface
212   */
213  bzero(&ifra.ifra_addr, sizeof(ifra.ifra_addr));
214  bzero(&ifra.ifra_broadaddr, sizeof(ifra.ifra_addr));
215  bzero(&ifra.ifra_mask, sizeof(ifra.ifra_addr));
216  if (ioctl(s, SIOCDIFADDR, &ifra) < 0) {
217    syslog(LOG_ERR,"can't delete interface's addresses - %m");
218  }
219closing_fds:
220  close(s);
221closing_tun:
222  close(tun);
223  closelog();
224  exit(signum);
225}
226
227int main (int argc, char **argv)
228{
229  int  c, len, ipoff;
230
231  char *devname = NULL;
232  char *point_to = NULL;
233  char *to_point = NULL;
234  char *target;
235
236  struct sockaddr t_laddr;          /* Source address of tunnel */
237  struct sockaddr whereto;          /* Destination of tunnel */
238  struct sockaddr_in *to;
239
240  char buf[0x2000];                 /* Packets buffer */
241  struct ip *ip = (struct ip *)buf;
242
243  fd_set rfds, wfds, efds;          /* File descriptors for select() */
244  int nfds;                         /* Return from select() */
245
246
247  while ((c = getopt(argc, argv, "d:s:t:")) != -1) {
248    switch (c) {
249    case 'd':
250      to_point = optarg;
251      break;
252    case 's':
253      point_to = optarg;
254      break;
255    case 't':
256      devname = optarg;
257      break;
258    }
259  }
260  argc -= optind;
261  argv += optind;
262
263  if (argc != 1 || (devname == NULL) ||
264      (point_to == NULL) || (to_point == NULL)) {
265    usage();
266  }
267
268  target = *argv;
269
270  /* Establish logging through 'syslog' */
271  openlog("nos_tun", LOG_PID, LOG_DAEMON);
272
273  if(Set_address(point_to, (struct sockaddr_in *)&t_laddr)) {
274    closelog();
275    exit(2);
276  }
277
278  if(tun_open(devname, &t_laddr, to_point)) {
279    closelog();
280    exit(3);
281  }
282
283  to = (struct sockaddr_in *)&whereto;
284  if(Set_address(target, to))
285    Finish(4);
286
287  if ((net = socket(AF_INET, SOCK_RAW, 94)) < 0) {
288    syslog(LOG_ERR,"can't open socket - %m");
289    Finish(5);
290  }
291
292  if (connect(net,&whereto,sizeof(struct sockaddr_in)) < 0 ) {
293    syslog(LOG_ERR,"can't connect to target - %m");
294    close(net);
295    Finish(6);
296  }
297
298  /*  Demonize it */
299  daemon(0,0);
300
301  /* Install signal handlers */
302  (void)signal(SIGHUP,Finish);
303  (void)signal(SIGINT,Finish);
304  (void)signal(SIGTERM,Finish);
305
306  for (;;) {
307    /* Set file descriptors for select() */
308    FD_ZERO(&rfds); FD_ZERO(&wfds); FD_ZERO(&efds);
309    FD_SET(tun,&rfds); FD_SET(net,&rfds);
310
311    nfds = select(net+10,&rfds,&wfds,&efds,NULL);
312    if(nfds < 0) {
313      syslog(LOG_ERR,"interrupted select");
314      close(net);
315      Finish(7);
316    }
317    if(nfds == 0) {         /* Impossible ? */
318      syslog(LOG_ERR,"timeout in select");
319      close(net);
320      Finish(8);
321    }
322
323
324    if(FD_ISSET(net,&rfds)) {
325      /* Read from socket ... */
326      len = read(net, buf, sizeof(buf));
327      /* Check if this is "our" packet */
328      if((ip->ip_src).s_addr == (to->sin_addr).s_addr) {
329	/* ... skip encapsulation headers ... */
330	ipoff = (ip->ip_hl << 2);
331	/* ... and write to tun-device */
332	write(tun,buf+ipoff,len-ipoff);
333      }
334    }
335
336    if(FD_ISSET(tun,&rfds)) {
337      /* Read from tun ... */
338      len = read(tun, buf, sizeof(buf));
339      /* ... and send to network */
340      if(send(net, buf, len,0) <= 0) {
341	syslog(LOG_ERR,"can't send - %m");
342      }
343    }
344  }
345}
346
347static void
348usage()
349{
350	fprintf(stderr,
351"usage: nos_tun -t <tun_name> -s <source_addr> -d <dest_addr> <target_addr>\n");
352	exit(1);
353}
354
355