arp.c revision 40665 
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 1.30 1998/08/26 17:39:36 brian Exp $
21 *
22 */
23
24/*
25 * TODO:
26 */
27
28#include <sys/types.h>
29#include <sys/socket.h>
30#include <net/if.h>
31#include <net/route.h>
32#include <net/if_dl.h>
33#include <netinet/in.h>
34#include <netinet/if_ether.h>
35#include <arpa/inet.h>
36#include <netinet/in_systm.h>
37#include <netinet/ip.h>
38#include <sys/un.h>
39
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <sys/errno.h>
44#include <sys/sysctl.h>
45#include <unistd.h>
46
47#include "mbuf.h"
48#include "log.h"
49#include "id.h"
50#include "timer.h"
51#include "fsm.h"
52#include "defs.h"
53#include "iplist.h"
54#include "throughput.h"
55#include "slcompress.h"
56#include "lqr.h"
57#include "hdlc.h"
58#include "ipcp.h"
59#include "filter.h"
60#include "descriptor.h"
61#include "lcp.h"
62#include "ccp.h"
63#include "link.h"
64#include "mp.h"
65#include "bundle.h"
66#include "arp.h"
67
68/*
69 * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
70 * if it exists.
71 */
72#define SET_SA_FAMILY(addr, family)		\
73    memset((char *) &(addr), '\0', sizeof(addr));	\
74    addr.sa_family = (family); 			\
75    addr.sa_len = sizeof(addr);
76
77
78#if RTM_VERSION >= 3
79
80/*
81 * arp_SetProxy - Make a proxy ARP entry for the peer.
82 */
83static struct {
84  struct rt_msghdr hdr;
85  struct sockaddr_inarp dst;
86  struct sockaddr_dl hwa;
87  char extra[128];
88} arpmsg;
89
90static int
91arp_ProxySub(struct bundle *bundle, struct in_addr addr, int add, int s)
92{
93  int routes;
94
95  /*
96   * Get the hardware address of an interface on the same subnet as our local
97   * address.
98   */
99
100  memset(&arpmsg, 0, sizeof arpmsg);
101  if (!get_ether_addr(s, addr, &arpmsg.hwa)) {
102    log_Printf(LogWARN, "%s: Cannot determine ethernet address for proxy ARP\n",
103	       inet_ntoa(addr));
104    return 0;
105  }
106  routes = ID0socket(PF_ROUTE, SOCK_RAW, AF_INET);
107  if (routes < 0) {
108    log_Printf(LogERROR, "arp_SetProxy: opening routing socket: %s\n",
109	      strerror(errno));
110    return 0;
111  }
112  arpmsg.hdr.rtm_type = add ? RTM_ADD : RTM_DELETE;
113  arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
114  arpmsg.hdr.rtm_version = RTM_VERSION;
115  arpmsg.hdr.rtm_seq = ++bundle->routing_seq;
116  arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
117  arpmsg.hdr.rtm_inits = RTV_EXPIRE;
118  arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
119  arpmsg.dst.sin_family = AF_INET;
120  arpmsg.dst.sin_addr.s_addr = addr.s_addr;
121  arpmsg.dst.sin_other = SIN_PROXY;
122
123  arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
124    + arpmsg.hwa.sdl_len;
125
126
127  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0 &&
128      !(!add && errno == ESRCH)) {
129    log_Printf(LogERROR, "%s proxy arp entry %s: %s\n",
130	add ? "Add" : "Delete", inet_ntoa(addr), strerror(errno));
131    close(routes);
132    return 0;
133  }
134  close(routes);
135  return 1;
136}
137
138int
139arp_SetProxy(struct bundle *bundle, struct in_addr addr, int s)
140{
141
142  return (arp_ProxySub(bundle, addr, 1, s));
143}
144
145/*
146 * arp_ClearProxy - Delete the proxy ARP entry for the peer.
147 */
148int
149arp_ClearProxy(struct bundle *bundle, struct in_addr addr, int s)
150{
151
152  return (arp_ProxySub(bundle, addr, 0, s));
153}
154
155#else				/* RTM_VERSION */
156
157/*
158 * arp_SetProxy - Make a proxy ARP entry for the peer.
159 */
160int
161arp_SetProxy(struct bundle *bundle, struct in_addr addr, int s)
162{
163  struct arpreq arpreq;
164  struct {
165    struct sockaddr_dl sdl;
166    char space[128];
167  }      dls;
168
169  memset(&arpreq, '\0', sizeof arpreq);
170
171  /*
172   * Get the hardware address of an interface on the same subnet as our local
173   * address.
174   */
175  if (!get_ether_addr(s, addr, &dls.sdl)) {
176    log_Printf(LOG_PHASE_BIT, "Cannot determine ethernet address for proxy ARP\n");
177    return 0;
178  }
179  arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
180  arpreq.arp_ha.sa_family = AF_UNSPEC;
181  memcpy(arpreq.arp_ha.sa_data, LLADDR(&dls.sdl), dls.sdl.sdl_alen);
182  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
183  ((struct sockaddr_in *)&arpreq.arp_pa)->sin_addr.s_addr = addr.s_addr;
184  arpreq.arp_flags = ATF_PERM | ATF_PUBL;
185  if (ID0ioctl(s, SIOCSARP, (caddr_t) & arpreq) < 0) {
186    log_Printf(LogERROR, "arp_SetProxy: ioctl(SIOCSARP): %s\n",
187               strerror(errno));
188    return 0;
189  }
190  return 1;
191}
192
193/*
194 * arp_ClearProxy - Delete the proxy ARP entry for the peer.
195 */
196int
197arp_ClearProxy(struct bundle *bundle, struct in_addr addr, int s)
198{
199  struct arpreq arpreq;
200
201  memset(&arpreq, '\0', sizeof arpreq);
202  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
203  ((struct sockaddr_in *)&arpreq.arp_pa)->sin_addr.s_addr = addr.s_addr;
204  if (ID0ioctl(s, SIOCDARP, (caddr_t) & arpreq) < 0) {
205    log_Printf(LogERROR, "arp_ClearProxy: ioctl(SIOCDARP): %s\n",
206               strerror(errno));
207    return 0;
208  }
209  return 1;
210}
211
212#endif				/* RTM_VERSION */
213
214
215/*
216 * get_ether_addr - get the hardware address of an interface on the
217 * the same subnet as ipaddr.
218 */
219
220int
221get_ether_addr(int s, struct in_addr ipaddr, struct sockaddr_dl *hwaddr)
222{
223  int mib[6], sa_len, skip, b;
224  size_t needed;
225  char *buf, *ptr, *end;
226  struct if_msghdr *ifm;
227  struct ifa_msghdr *ifam;
228  struct sockaddr *sa;
229  struct sockaddr_dl *dl;
230  struct sockaddr_in *ifa, *mask;
231
232  mib[0] = CTL_NET;
233  mib[1] = PF_ROUTE;
234  mib[2] = 0;
235  mib[3] = 0;
236  mib[4] = NET_RT_IFLIST;
237  mib[5] = 0;
238
239  if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) {
240    log_Printf(LogERROR, "get_ether_addr: sysctl: estimate: %s\n",
241              strerror(errno));
242    return 0;
243  }
244
245  if ((buf = malloc(needed)) == NULL)
246    return 0;
247
248  if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
249    free(buf);
250    return 0;
251  }
252  end = buf + needed;
253
254  ptr = buf;
255  while (ptr < end) {
256    ifm = (struct if_msghdr *)ptr;		/* On if_msghdr */
257    if (ifm->ifm_type != RTM_IFINFO)
258      break;
259    dl = (struct sockaddr_dl *)(ifm + 1);	/* Single _dl at end */
260    skip = (ifm->ifm_flags & (IFF_UP | IFF_BROADCAST | IFF_POINTOPOINT |
261            IFF_NOARP | IFF_LOOPBACK)) != (IFF_UP | IFF_BROADCAST);
262    ptr += ifm->ifm_msglen;			/* First ifa_msghdr */
263    while (ptr < end) {
264      ifam = (struct ifa_msghdr *)ptr;	/* Next ifa_msghdr (alias) */
265      if (ifam->ifam_type != RTM_NEWADDR)	/* finished ? */
266        break;
267      sa = (struct sockaddr *)(ifam+1);	/* pile of sa's at end */
268      ptr += ifam->ifam_msglen;
269      if (skip || (ifam->ifam_addrs & (RTA_NETMASK|RTA_IFA)) !=
270          (RTA_NETMASK|RTA_IFA))
271        continue;
272      /* Found a candidate.  Do the addresses match ? */
273      if (log_IsKept(LogDEBUG) &&
274          ptr == (char *)ifm + ifm->ifm_msglen + ifam->ifam_msglen)
275        log_Printf(LogDEBUG, "%.*s interface is a candidate for proxy\n",
276                  dl->sdl_nlen, dl->sdl_data);
277      b = 1;
278      ifa = mask = NULL;
279      while (b < (RTA_NETMASK|RTA_IFA) && sa < (struct sockaddr *)ptr) {
280        switch (b) {
281        case RTA_IFA:
282          ifa = (struct sockaddr_in *)sa;
283          break;
284        case RTA_NETMASK:
285          /*
286           * Careful here !  this sockaddr doesn't have sa_family set to
287           * AF_INET, and is only 8 bytes big !  I have no idea why !
288           */
289          mask = (struct sockaddr_in *)sa;
290          break;
291        }
292        if (ifam->ifam_addrs & b) {
293#define ALN sizeof(ifa->sin_addr.s_addr)
294          sa_len = sa->sa_len > 0 ? ((sa->sa_len-1)|(ALN-1))+1 : ALN;
295          sa = (struct sockaddr *)((char *)sa + sa_len);
296        }
297        b <<= 1;
298      }
299      if (log_IsKept(LogDEBUG)) {
300        char a[16];
301        strncpy(a, inet_ntoa(mask->sin_addr), sizeof a - 1);
302        a[sizeof a - 1] = '\0';
303        log_Printf(LogDEBUG, "Check addr %s, mask %s\n",
304                  inet_ntoa(ifa->sin_addr), a);
305      }
306      if (ifa->sin_family == AF_INET &&
307          (ifa->sin_addr.s_addr & mask->sin_addr.s_addr) ==
308          (ipaddr.s_addr & mask->sin_addr.s_addr)) {
309        log_Printf(LogPHASE, "Found interface %.*s for %s\n",
310                  dl->sdl_alen, dl->sdl_data, inet_ntoa(ipaddr));
311        memcpy(hwaddr, dl, dl->sdl_len);
312        free(buf);
313        return 1;
314      }
315    }
316  }
317  free(buf);
318
319  return 0;
320}
321