arp.c revision 28679 
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 1.12 1997/06/09 03:27:11 brian Exp $
21 *
22 */
23
24/*
25 * TODO:
26 */
27
28#include <sys/ioctl.h>
29#include <sys/types.h>
30#include <sys/uio.h>
31#include <sys/socket.h>
32#include <sys/time.h>
33#include <sys/errno.h>
34#include <unistd.h>
35#include <string.h>
36
37#include <net/if.h>
38#include <net/if_var.h>
39#include <net/route.h>
40#include <net/if_dl.h>
41#include <netinet/in.h>
42#include <stdio.h>
43#include <fcntl.h>
44#ifdef __bsdi__
45#include <kvm.h>
46#endif
47#include <net/if_types.h>
48#include <netinet/in_var.h>
49#include <netinet/if_ether.h>
50#include "log.h"
51
52#if RTM_VERSION >= 3
53#include <netinet/if_ether.h>
54#endif
55
56static int rtm_seq;
57
58static int get_ether_addr(int, u_long, struct sockaddr_dl *);
59
60#define BCOPY(s, d, l)		memcpy(d, s, l)
61#define BZERO(s, n)		memset(s, 0, n)
62/*
63 * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
64 * if it exists.
65 */
66#define SET_SA_FAMILY(addr, family)		\
67    BZERO((char *) &(addr), sizeof(addr));	\
68    addr.sa_family = (family); 			\
69    addr.sa_len = sizeof(addr);
70
71
72#if RTM_VERSION >= 3
73
74/*
75 * sifproxyarp - Make a proxy ARP entry for the peer.
76 */
77static struct {
78  struct rt_msghdr hdr;
79  struct sockaddr_inarp dst;
80  struct sockaddr_dl hwa;
81  char extra[128];
82}      arpmsg;
83
84static int arpmsg_valid;
85
86int
87sifproxyarp(int unit, u_long hisaddr)
88{
89  int routes;
90
91  /*
92   * Get the hardware address of an interface on the same subnet as our local
93   * address.
94   */
95  memset(&arpmsg, 0, sizeof(arpmsg));
96  if (!get_ether_addr(unit, hisaddr, &arpmsg.hwa)) {
97    LogPrintf(LogERROR, "Cannot determine ethernet address"
98	      " for proxy ARP\n");
99    return 0;
100  }
101  if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
102    LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
103	      strerror(errno));
104    return 0;
105  }
106  arpmsg.hdr.rtm_type = RTM_ADD;
107  arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
108  arpmsg.hdr.rtm_version = RTM_VERSION;
109  arpmsg.hdr.rtm_seq = ++rtm_seq;
110  arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
111  arpmsg.hdr.rtm_inits = RTV_EXPIRE;
112  arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
113  arpmsg.dst.sin_family = AF_INET;
114  arpmsg.dst.sin_addr.s_addr = hisaddr;
115  arpmsg.dst.sin_other = SIN_PROXY;
116
117  arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
118    + arpmsg.hwa.sdl_len;
119  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
120    LogPrintf(LogERROR, "Add proxy arp entry: %s\n", strerror(errno));
121    close(routes);
122    return 0;
123  }
124  close(routes);
125  arpmsg_valid = 1;
126  return 1;
127}
128
129/*
130 * cifproxyarp - Delete the proxy ARP entry for the peer.
131 */
132int
133cifproxyarp(int unit, u_long hisaddr)
134{
135  int routes;
136
137  if (!arpmsg_valid)
138    return 0;
139  arpmsg_valid = 0;
140
141  arpmsg.hdr.rtm_type = RTM_DELETE;
142  arpmsg.hdr.rtm_seq = ++rtm_seq;
143
144  if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
145    LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
146	      strerror(errno));
147    return 0;
148  }
149  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
150    LogPrintf(LogERROR, "Delete proxy arp entry: %s\n", strerror(errno));
151    close(routes);
152    return 0;
153  }
154  close(routes);
155  return 1;
156}
157
158#else				/* RTM_VERSION */
159
160/*
161 * sifproxyarp - Make a proxy ARP entry for the peer.
162 */
163int
164sifproxyarp(int unit, u_long hisaddr)
165{
166  struct arpreq arpreq;
167  struct {
168    struct sockaddr_dl sdl;
169    char space[128];
170  }      dls;
171
172  BZERO(&arpreq, sizeof(arpreq));
173
174  /*
175   * Get the hardware address of an interface on the same subnet as our local
176   * address.
177   */
178  if (!get_ether_addr(unit, hisaddr, &dls.sdl)) {
179    LogPrintf(LOG_PHASE_BIT, "Cannot determine ethernet address for proxy ARP\n");
180    return 0;
181  }
182  arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
183  arpreq.arp_ha.sa_family = AF_UNSPEC;
184  BCOPY(LLADDR(&dls.sdl), arpreq.arp_ha.sa_data, dls.sdl.sdl_alen);
185  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
186  ((struct sockaddr_in *) & arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
187  arpreq.arp_flags = ATF_PERM | ATF_PUBL;
188  if (ioctl(unit, SIOCSARP, (caddr_t) & arpreq) < 0) {
189    LogPrintf(LogERROR, "sifproxyarp: ioctl(SIOCSARP): \n");
190    return 0;
191  }
192  return 1;
193}
194
195/*
196 * cifproxyarp - Delete the proxy ARP entry for the peer.
197 */
198int
199cifproxyarp(int unit, u_long hisaddr)
200{
201  struct arpreq arpreq;
202
203  BZERO(&arpreq, sizeof(arpreq));
204  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
205  ((struct sockaddr_in *) & arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
206  if (ioctl(unit, SIOCDARP, (caddr_t) & arpreq) < 0) {
207    LogPrintf(LogERROR, "cifproxyarp: ioctl(SIOCDARP): \n");
208    return 0;
209  }
210  return 1;
211}
212
213#endif				/* RTM_VERSION */
214
215
216/*
217 * get_ether_addr - get the hardware address of an interface on the
218 * the same subnet as ipaddr.
219 */
220#define MAX_IFS		32
221
222int
223get_ether_addr(int s, u_long ipaddr, struct sockaddr_dl * hwaddr)
224{
225  struct ifreq *ifr, *ifend, *ifp;
226  u_long ina, mask;
227  struct sockaddr_dl *dla;
228  struct ifreq ifreq;
229  struct ifconf ifc;
230  struct ifreq ifs[MAX_IFS];
231
232  ifc.ifc_len = sizeof(ifs);
233  ifc.ifc_req = ifs;
234  if (ioctl(s, SIOCGIFCONF, &ifc) < 0) {
235    LogPrintf(LogERROR, "get_ether_addr: ioctl(SIOCGIFCONF): \n");
236    return 0;
237  }
238
239  /*
240   * Scan through looking for an interface with an Internet address on the
241   * same subnet as `ipaddr'.
242   */
243  ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
244  for (ifr = ifc.ifc_req; ifr < ifend;) {
245    if (ifr->ifr_addr.sa_family == AF_INET) {
246      ina = ((struct sockaddr_in *) & ifr->ifr_addr)->sin_addr.s_addr;
247      strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name));
248      ifreq.ifr_name[sizeof(ifreq.ifr_name) - 1] = '\0';
249
250      /*
251       * Check that the interface is up, and not point-to-point or loopback.
252       */
253      if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0)
254	continue;
255      if ((ifreq.ifr_flags &
256      (IFF_UP | IFF_BROADCAST | IFF_POINTOPOINT | IFF_LOOPBACK | IFF_NOARP))
257	  != (IFF_UP | IFF_BROADCAST))
258	goto nextif;
259
260      /*
261       * Get its netmask and check that it's on the right subnet.
262       */
263      if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0)
264	continue;
265      mask = ((struct sockaddr_in *) & ifreq.ifr_addr)->sin_addr.s_addr;
266      if ((ipaddr & mask) != (ina & mask))
267	goto nextif;
268
269      break;
270    }
271nextif:
272    ifr = (struct ifreq *) ((char *) &ifr->ifr_addr + ifr->ifr_addr.sa_len);
273  }
274
275  if (ifr >= ifend)
276    return 0;
277  LogPrintf(LogPHASE, "Found interface %s for proxy arp\n", ifr->ifr_name);
278
279  /*
280   * Now scan through again looking for a link-level address for this
281   * interface.
282   */
283  ifp = ifr;
284  for (ifr = ifc.ifc_req; ifr < ifend;) {
285    if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
286	&& ifr->ifr_addr.sa_family == AF_LINK) {
287
288      /*
289       * Found the link-level address - copy it out
290       */
291      dla = (struct sockaddr_dl *) & ifr->ifr_addr;
292#ifdef __bsdi__
293      if (dla->sdl_alen == 0)
294	kmemgetether(ifr->ifr_name, dla);
295#endif
296      BCOPY(dla, hwaddr, dla->sdl_len);
297      return 1;
298    }
299    ifr = (struct ifreq *) ((char *) &ifr->ifr_addr + ifr->ifr_addr.sa_len);
300  }
301
302  return 0;
303}
304
305#ifdef __bsdi__
306#include <nlist.h>
307
308struct nlist nl[] = {
309#define N_IFNET		0
310  {"_ifnet"},
311  "",
312};
313
314
315kvm_t *kvmd;
316
317/*
318 * Read kernel memory, return 0 on success.
319 */
320int
321kread(u_long addr, char *buf, int size)
322{
323  if (kvm_read(kvmd, addr, buf, size) != size) {
324    /* XXX this duplicates kvm_read's error printout */
325    LogPrintf(LogERROR, "kvm_read %s\n", kvm_geterr(kvmd));
326    return -1;
327  }
328  return 0;
329}
330
331void
332kmemgetether(char *ifname, struct sockaddr_dl * dlo)
333{
334  struct ifnet ifnet;
335  int n;
336  u_long addr, ifaddraddr, ifnetfound, ifaddrfound;
337  char name[16 + 32];
338  struct sockaddr *sa;
339  char *cp;
340  struct sockaddr_dl *sdl;
341  union {
342    struct ifaddr ifa;
343    struct in_ifaddr in;
344  }     ifaddr;
345  struct arpcom ac;
346
347  kvmd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL);
348  if (kvmd) {
349    n = kvm_nlist(kvmd, nl);
350    if (n >= 0) {
351      addr = nl[N_IFNET].n_value;
352      kread(addr, (char *) &addr, sizeof(addr));
353      ifaddraddr = ifnetfound = 0;
354      while (addr || ifaddraddr) {
355	ifnetfound = addr;
356	if (ifaddraddr == 0) {
357	  if (kread(addr, (char *) &ifnet, sizeof(ifnet)) ||
358	      kread((u_long) ifnet.if_name, name, 16))
359	    return;
360	  name[15] = 0;
361	  addr = (u_long) ifnet.if_next;
362	  cp = (char *) index(name, '\0');
363	  cp += sprintf(cp, "%d", ifnet.if_unit);
364	  *cp = '\0';
365	  ifaddraddr = (u_long) ifnet.if_addrlist;
366	}
367	ifaddrfound = ifaddraddr;
368	if (ifaddraddr) {
369	  if (kread(ifaddraddr, (char *) &ifaddr, sizeof ifaddr)) {
370	    ifaddraddr = 0;
371	    continue;
372	  }
373#define CP(x) ((char *)(x))
374	  cp = (CP(ifaddr.ifa.ifa_addr) - CP(ifaddraddr)) + CP(&ifaddr);
375	  sa = (struct sockaddr *) cp;
376	  if (sa->sa_family == AF_LINK && strcmp(ifname, name) == 0) {
377	    sdl = (struct sockaddr_dl *) sa;
378	    cp = (char *) LLADDR(sdl);
379	    n = sdl->sdl_alen;
380	    if (ifnet.if_type == IFT_ETHER) {
381	      if (n == 0) {
382		kread(ifnetfound, (char *) &ac, sizeof(ac));
383		cp = (char *) LLADDR(sdl);
384		bcopy((char *) ac.ac_enaddr, cp, 6);
385		sdl->sdl_alen = 6;
386	      }
387	      bcopy(sdl, dlo, sizeof(*sdl));
388	      return;
389	    }
390	  }
391	  ifaddraddr = (u_long) ifaddr.ifa.ifa_next;
392	}
393      }
394    }
395  }
396}
397
398#endif
399
400#ifdef DEBUG
401main()
402{
403  u_long ipaddr;
404  int s;
405
406  s = socket(AF_INET, SOCK_DGRAM, 0);
407  ipaddr = inet_addr("192.168.1.32");
408  sifproxyarp(s, ipaddr);
409  close(s);
410}
411
412#endif
413