arp.c revision 32627 
1/*
2 * sys-bsd.c - System-dependent procedures for setting up
3 * PPP interfaces on bsd-4.4-ish systems (including 386BSD, NetBSD, etc.)
4 *
5 * Copyright (c) 1989 Carnegie Mellon University.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms are permitted
9 * provided that the above copyright notice and this paragraph are
10 * duplicated in all such forms and that any documentation,
11 * advertising materials, and other materials related to such
12 * distribution and use acknowledge that the software was developed
13 * by Carnegie Mellon University.  The name of the
14 * University may not be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
18 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19 *
20 * $Id: arp.c,v 1.22 1998/01/19 02:59:32 brian Exp $
21 *
22 */
23
24/*
25 * TODO:
26 */
27
28#include <sys/param.h>
29#include <sys/time.h>
30#include <sys/socket.h>
31#include <net/if.h>
32#include <net/route.h>
33#include <net/if_dl.h>
34#include <netinet/in.h>
35#include <net/if_types.h>
36#include <netinet/if_ether.h>
37
38#include <fcntl.h>
39#include <stdio.h>
40#include <stdlib.h>
41#include <string.h>
42#include <sys/errno.h>
43#include <sys/ioctl.h>
44#include <sys/sysctl.h>
45#include <sys/uio.h>
46#include <unistd.h>
47
48#include "command.h"
49#include "mbuf.h"
50#include "log.h"
51#include "id.h"
52#include "route.h"
53#include "arp.h"
54
55#ifdef DEBUG
56/*
57 * To test the proxy arp stuff, put the following in your Makefile:
58 *
59 * arp-test: arp.c
60 * 	cp ${.CURDIR}/arp.c arp-test.c
61 * 	echo 'const char *' >>arp-test.c
62 * 	awk '/^Index2Nam/,/^}/' ${.CURDIR}/route.c >>arp-test.c
63 * 	cc -I${.CURDIR} -DDEBUG arp-test.c -o arp-test
64 *
65 * and type ``make arp-test''.
66 *
67 */
68#define LogIsKept(x) 0
69#define LogPrintf fprintf
70#undef LogDEBUG
71#define LogDEBUG stderr
72#undef LogERROR
73#define LogERROR stderr
74#undef LogPHASE
75#define LogPHASE stdout
76#define ID0socket socket
77#define ID0ioctl ioctl
78#endif
79
80static int rtm_seq;
81
82static int get_ether_addr(int, struct in_addr, struct sockaddr_dl *);
83
84/*
85 * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
86 * if it exists.
87 */
88#define SET_SA_FAMILY(addr, family)		\
89    memset((char *) &(addr), '\0', sizeof(addr));	\
90    addr.sa_family = (family); 			\
91    addr.sa_len = sizeof(addr);
92
93
94#if RTM_VERSION >= 3
95
96/*
97 * sifproxyarp - Make a proxy ARP entry for the peer.
98 */
99static struct {
100  struct rt_msghdr hdr;
101  struct sockaddr_inarp dst;
102  struct sockaddr_dl hwa;
103  char extra[128];
104} arpmsg;
105
106static int arpmsg_valid;
107
108int
109sifproxyarp(int unit, struct in_addr hisaddr)
110{
111  int routes;
112
113  /*
114   * Get the hardware address of an interface on the same subnet as our local
115   * address.
116   */
117  memset(&arpmsg, 0, sizeof arpmsg);
118  if (!get_ether_addr(unit, hisaddr, &arpmsg.hwa)) {
119    LogPrintf(LogERROR, "Cannot determine ethernet address for proxy ARP\n");
120    return 0;
121  }
122  routes = ID0socket(PF_ROUTE, SOCK_RAW, AF_INET);
123  if (routes < 0) {
124    LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
125	      strerror(errno));
126    return 0;
127  }
128  arpmsg.hdr.rtm_type = RTM_ADD;
129  arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
130  arpmsg.hdr.rtm_version = RTM_VERSION;
131  arpmsg.hdr.rtm_seq = ++rtm_seq;
132  arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
133  arpmsg.hdr.rtm_inits = RTV_EXPIRE;
134  arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
135  arpmsg.dst.sin_family = AF_INET;
136  arpmsg.dst.sin_addr.s_addr = hisaddr.s_addr;
137  arpmsg.dst.sin_other = SIN_PROXY;
138
139  arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
140    + arpmsg.hwa.sdl_len;
141  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
142    LogPrintf(LogERROR, "Add proxy arp entry: %s\n", strerror(errno));
143    close(routes);
144    return 0;
145  }
146  close(routes);
147  arpmsg_valid = 1;
148  return 1;
149}
150
151/*
152 * cifproxyarp - Delete the proxy ARP entry for the peer.
153 */
154int
155cifproxyarp(int unit, struct in_addr hisaddr)
156{
157  int routes;
158
159  if (!arpmsg_valid)
160    return 0;
161  arpmsg_valid = 0;
162
163  arpmsg.hdr.rtm_type = RTM_DELETE;
164  arpmsg.hdr.rtm_seq = ++rtm_seq;
165
166  routes = ID0socket(PF_ROUTE, SOCK_RAW, AF_INET);
167  if (routes < 0) {
168    LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
169	      strerror(errno));
170    return 0;
171  }
172  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
173    LogPrintf(LogERROR, "Delete proxy arp entry: %s\n", strerror(errno));
174    close(routes);
175    return 0;
176  }
177  close(routes);
178  return 1;
179}
180
181#else				/* RTM_VERSION */
182
183/*
184 * sifproxyarp - Make a proxy ARP entry for the peer.
185 */
186int
187sifproxyarp(int unit, struct in_addr hisaddr)
188{
189  struct arpreq arpreq;
190  struct {
191    struct sockaddr_dl sdl;
192    char space[128];
193  }      dls;
194
195  memset(&arpreq, '\0', sizeof arpreq);
196
197  /*
198   * Get the hardware address of an interface on the same subnet as our local
199   * address.
200   */
201  if (!get_ether_addr(unit, hisaddr, &dls.sdl)) {
202    LogPrintf(LOG_PHASE_BIT, "Cannot determine ethernet address for proxy ARP\n");
203    return 0;
204  }
205  arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
206  arpreq.arp_ha.sa_family = AF_UNSPEC;
207  memcpy(arpreq.arp_ha.sa_data, LLADDR(&dls.sdl), dls.sdl.sdl_alen);
208  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
209  ((struct sockaddr_in *) & arpreq.arp_pa)->sin_addr.s_addr = hisaddr.s_addr;
210  arpreq.arp_flags = ATF_PERM | ATF_PUBL;
211  if (ID0ioctl(unit, SIOCSARP, (caddr_t) & arpreq) < 0) {
212    LogPrintf(LogERROR, "sifproxyarp: ioctl(SIOCSARP): %s\n", strerror(errno));
213    return 0;
214  }
215  return 1;
216}
217
218/*
219 * cifproxyarp - Delete the proxy ARP entry for the peer.
220 */
221int
222cifproxyarp(int unit, struct in_addr hisaddr)
223{
224  struct arpreq arpreq;
225
226  memset(&arpreq, '\0', sizeof arpreq);
227  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
228  ((struct sockaddr_in *) & arpreq.arp_pa)->sin_addr.s_addr = hisaddr.s_addr;
229  if (ID0ioctl(unit, SIOCDARP, (caddr_t) & arpreq) < 0) {
230    LogPrintf(LogERROR, "cifproxyarp: ioctl(SIOCDARP): %s\n", strerror(errno));
231    return 0;
232  }
233  return 1;
234}
235
236#endif				/* RTM_VERSION */
237
238
239/*
240 * get_ether_addr - get the hardware address of an interface on the
241 * the same subnet as ipaddr.
242 */
243#define MAX_IFS		32
244
245static int
246get_ether_addr(int s, struct in_addr ipaddr, struct sockaddr_dl *hwaddr)
247{
248  int idx;
249  const char *got;
250  char *sp, *ep, *cp, *wp;
251  struct ifreq ifrq;
252  struct in_addr addr, mask;
253  struct rt_msghdr *rtm;
254  struct sockaddr *sa_dst, *sa_gw;
255  struct sockaddr_dl *dl;
256  size_t needed;
257  int mib[6];
258
259  idx = 1;
260  while (strcmp(got = Index2Nam(idx), "???")) {
261    strncpy(ifrq.ifr_name, got, sizeof ifrq.ifr_name - 1);
262    ifrq.ifr_name[sizeof ifrq.ifr_name - 1] = '\0';
263    if (ID0ioctl(s, SIOCGIFADDR, &ifrq) == 0 &&
264        ifrq.ifr_addr.sa_family == AF_INET) {
265      addr = ((struct sockaddr_in *)&ifrq.ifr_addr)->sin_addr;
266      if (ID0ioctl(s, SIOCGIFNETMASK, &ifrq) == 0) {
267        mask = ((struct sockaddr_in *)&ifrq.ifr_broadaddr)->sin_addr;
268        if ((ipaddr.s_addr & mask.s_addr) == (addr.s_addr & mask.s_addr))
269          break;
270      }
271    }
272    idx++;
273  }
274
275  if (!strcmp(got, "???"))
276    return 0;
277
278  LogPrintf(LogPHASE, "Found interface %s for proxy arp\n", got);
279
280  mib[0] = CTL_NET;
281  mib[1] = PF_ROUTE;
282  mib[2] = 0;
283  mib[3] = 0;
284  mib[4] = NET_RT_DUMP;
285  mib[5] = 0;
286  if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) {
287    LogPrintf(LogERROR, "get_ether_addr: sysctl: estimate: %s\n",
288              strerror(errno));
289    return 0;
290  }
291  if (needed < 0)
292    return 0;
293  if ((sp = malloc(needed)) == NULL)
294    return 0;
295  if (sysctl(mib, 6, sp, &needed, NULL, 0) < 0) {
296    LogPrintf(LogERROR, "ShowRoute: sysctl: getroute: %s\n", strerror(errno));
297    free(sp);
298    return (1);
299  }
300  ep = sp + needed;
301
302  for (cp = sp; cp < ep; cp += rtm->rtm_msglen) {
303    rtm = (struct rt_msghdr *) cp;
304    if (rtm->rtm_index == idx) {
305      wp = (char *)(rtm+1);
306
307      if (rtm->rtm_addrs & RTA_DST) {
308        sa_dst = (struct sockaddr *)wp;
309        wp += sa_dst->sa_len;
310      } else
311        sa_dst = NULL;
312
313      if (rtm->rtm_addrs & RTA_GATEWAY) {
314        sa_gw = (struct sockaddr *)wp;
315        if (sa_gw->sa_family == AF_LINK) {
316          dl = (struct sockaddr_dl *)wp;
317          if (dl->sdl_alen && dl->sdl_type == IFT_ETHER) {
318            memcpy(hwaddr, dl, dl->sdl_len);
319            free(sp);
320            return 1;
321          }
322        }
323      }
324    }
325  }
326  free(sp);
327  return 0;
328}
329
330#ifdef DEBUG
331int
332main(int argc, char **argv)
333{
334  struct in_addr ipaddr;
335  int s, f;
336
337  s = socket(AF_INET, SOCK_DGRAM, 0);
338  for (f = 1; f < argc; f++) {
339    if (inet_aton(argv[f], &ipaddr))
340      sifproxyarp(s, ipaddr);
341  }
342  close(s);
343}
344#endif
345