arp.c revision 36285 
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 1.27.2.15 1998/05/01 19:23:46 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 "ipcp.h"
57#include "filter.h"
58#include "descriptor.h"
59#include "lqr.h"
60#include "hdlc.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 arpmsg_valid;
91
92int
93arp_SetProxy(struct bundle *bundle, struct in_addr addr, int s)
94{
95  int routes;
96
97  /*
98   * Get the hardware address of an interface on the same subnet as our local
99   * address.
100   */
101  memset(&arpmsg, 0, sizeof arpmsg);
102  if (!get_ether_addr(s, addr, &arpmsg.hwa)) {
103    log_Printf(LogERROR, "Cannot determine ethernet address for proxy ARP\n");
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 = RTM_ADD;
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  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
126    log_Printf(LogERROR, "Add proxy arp entry: %s\n", strerror(errno));
127    close(routes);
128    return 0;
129  }
130  close(routes);
131  arpmsg_valid = 1;
132  return 1;
133}
134
135/*
136 * arp_ClearProxy - Delete the proxy ARP entry for the peer.
137 */
138int
139arp_ClearProxy(struct bundle *bundle, struct in_addr addr, int s)
140{
141  int routes;
142
143  if (!arpmsg_valid)
144    return 0;
145  arpmsg_valid = 0;
146
147  arpmsg.hdr.rtm_type = RTM_DELETE;
148  arpmsg.hdr.rtm_seq = ++bundle->routing_seq;
149
150  routes = ID0socket(PF_ROUTE, SOCK_RAW, AF_INET);
151  if (routes < 0) {
152    log_Printf(LogERROR, "arp_SetProxy: opening routing socket: %s\n",
153	      strerror(errno));
154    return 0;
155  }
156  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
157    log_Printf(LogERROR, "Delete proxy arp entry: %s\n", strerror(errno));
158    close(routes);
159    return 0;
160  }
161  close(routes);
162  return 1;
163}
164
165#else				/* RTM_VERSION */
166
167/*
168 * arp_SetProxy - Make a proxy ARP entry for the peer.
169 */
170int
171arp_SetProxy(struct bundle *bundle, struct in_addr addr, int s)
172{
173  struct arpreq arpreq;
174  struct {
175    struct sockaddr_dl sdl;
176    char space[128];
177  }      dls;
178
179  memset(&arpreq, '\0', sizeof arpreq);
180
181  /*
182   * Get the hardware address of an interface on the same subnet as our local
183   * address.
184   */
185  if (!get_ether_addr(s, addr, &dls.sdl)) {
186    log_Printf(LOG_PHASE_BIT, "Cannot determine ethernet address for proxy ARP\n");
187    return 0;
188  }
189  arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
190  arpreq.arp_ha.sa_family = AF_UNSPEC;
191  memcpy(arpreq.arp_ha.sa_data, LLADDR(&dls.sdl), dls.sdl.sdl_alen);
192  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
193  ((struct sockaddr_in *)&arpreq.arp_pa)->sin_addr.s_addr = addr.s_addr;
194  arpreq.arp_flags = ATF_PERM | ATF_PUBL;
195  if (ID0ioctl(s, SIOCSARP, (caddr_t) & arpreq) < 0) {
196    log_Printf(LogERROR, "arp_SetProxy: ioctl(SIOCSARP): %s\n", strerror(errno));
197    return 0;
198  }
199  return 1;
200}
201
202/*
203 * arp_ClearProxy - Delete the proxy ARP entry for the peer.
204 */
205int
206arp_ClearProxy(struct bundle *bundle, struct in_addr addr, int s)
207{
208  struct arpreq arpreq;
209
210  memset(&arpreq, '\0', sizeof arpreq);
211  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
212  ((struct sockaddr_in *)&arpreq.arp_pa)->sin_addr.s_addr = addr.s_addr;
213  if (ID0ioctl(s, SIOCDARP, (caddr_t) & arpreq) < 0) {
214    log_Printf(LogERROR, "arp_ClearProxy: ioctl(SIOCDARP): %s\n", strerror(errno));
215    return 0;
216  }
217  return 1;
218}
219
220#endif				/* RTM_VERSION */
221
222
223/*
224 * get_ether_addr - get the hardware address of an interface on the
225 * the same subnet as ipaddr.
226 */
227
228int
229get_ether_addr(int s, struct in_addr ipaddr, struct sockaddr_dl *hwaddr)
230{
231  int mib[6], sa_len, skip, b;
232  size_t needed;
233  char *buf, *ptr, *end;
234  struct if_msghdr *ifm;
235  struct ifa_msghdr *ifam;
236  struct sockaddr *sa;
237  struct sockaddr_dl *dl;
238  struct sockaddr_in *ifa, *mask;
239
240  mib[0] = CTL_NET;
241  mib[1] = PF_ROUTE;
242  mib[2] = 0;
243  mib[3] = 0;
244  mib[4] = NET_RT_IFLIST;
245  mib[5] = 0;
246
247  if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) {
248    log_Printf(LogERROR, "get_ether_addr: sysctl: estimate: %s\n",
249              strerror(errno));
250    return 0;
251  }
252
253  if ((buf = malloc(needed)) == NULL)
254    return 0;
255
256  if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
257    free(buf);
258    return 0;
259  }
260  end = buf + needed;
261
262  ptr = buf;
263  while (ptr < end) {
264    ifm = (struct if_msghdr *)ptr;		/* On if_msghdr */
265    if (ifm->ifm_type != RTM_IFINFO)
266      break;
267    dl = (struct sockaddr_dl *)(ifm + 1);	/* Single _dl at end */
268    skip = (ifm->ifm_flags & (IFF_UP | IFF_BROADCAST | IFF_POINTOPOINT |
269            IFF_NOARP | IFF_LOOPBACK)) != (IFF_UP | IFF_BROADCAST);
270    ptr += ifm->ifm_msglen;			/* First ifa_msghdr */
271    while (ptr < end) {
272      ifam = (struct ifa_msghdr *)ptr;	/* Next ifa_msghdr (alias) */
273      if (ifam->ifam_type != RTM_NEWADDR)	/* finished ? */
274        break;
275      sa = (struct sockaddr *)(ifam+1);	/* pile of sa's at end */
276      ptr += ifam->ifam_msglen;
277      if (skip || (ifam->ifam_addrs & (RTA_NETMASK|RTA_IFA)) !=
278          (RTA_NETMASK|RTA_IFA))
279        continue;
280      /* Found a candidate.  Do the addresses match ? */
281      if (log_IsKept(LogDEBUG) &&
282          ptr == (char *)ifm + ifm->ifm_msglen + ifam->ifam_msglen)
283        log_Printf(LogDEBUG, "%.*s interface is a candidate for proxy\n",
284                  dl->sdl_nlen, dl->sdl_data);
285      b = 1;
286      ifa = mask = NULL;
287      while (b < (RTA_NETMASK|RTA_IFA) && sa < (struct sockaddr *)ptr) {
288        switch (b) {
289        case RTA_IFA:
290          ifa = (struct sockaddr_in *)sa;
291          break;
292        case RTA_NETMASK:
293          /*
294           * Careful here !  this sockaddr doesn't have sa_family set to
295           * AF_INET, and is only 8 bytes big !  I have no idea why !
296           */
297          mask = (struct sockaddr_in *)sa;
298          break;
299        }
300        if (ifam->ifam_addrs & b) {
301#define ALN sizeof(ifa->sin_addr.s_addr)
302          sa_len = sa->sa_len > 0 ? ((sa->sa_len-1)|(ALN-1))+1 : ALN;
303          sa = (struct sockaddr *)((char *)sa + sa_len);
304        }
305        b <<= 1;
306      }
307      if (log_IsKept(LogDEBUG)) {
308        char a[16];
309        strncpy(a, inet_ntoa(mask->sin_addr), sizeof a - 1);
310        a[sizeof a - 1] = '\0';
311        log_Printf(LogDEBUG, "Check addr %s, mask %s\n",
312                  inet_ntoa(ifa->sin_addr), a);
313      }
314      if (ifa->sin_family == AF_INET &&
315          (ifa->sin_addr.s_addr & mask->sin_addr.s_addr) ==
316          (ipaddr.s_addr & mask->sin_addr.s_addr)) {
317        log_Printf(LogPHASE, "Found interface %.*s for %s\n",
318                  dl->sdl_alen, dl->sdl_data, inet_ntoa(ipaddr));
319        memcpy(hwaddr, dl, dl->sdl_len);
320        free(buf);
321        return 1;
322      }
323    }
324  }
325  free(buf);
326
327  return 0;
328}
329