arp.c revision 29265 
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 1.14 1997/08/31 22:59:12 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#if RTM_VERSION >= 3
50#include <netinet/if_ether.h>
51#endif
52#include "log.h"
53
54static int rtm_seq;
55
56static int get_ether_addr(int, u_long, struct sockaddr_dl *);
57
58#define BCOPY(s, d, l)		memcpy(d, s, l)
59#define BZERO(s, n)		memset(s, 0, n)
60/*
61 * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
62 * if it exists.
63 */
64#define SET_SA_FAMILY(addr, family)		\
65    BZERO((char *) &(addr), sizeof(addr));	\
66    addr.sa_family = (family); 			\
67    addr.sa_len = sizeof(addr);
68
69
70#if RTM_VERSION >= 3
71
72/*
73 * sifproxyarp - Make a proxy ARP entry for the peer.
74 */
75static struct {
76  struct rt_msghdr hdr;
77  struct sockaddr_inarp dst;
78  struct sockaddr_dl hwa;
79  char extra[128];
80}      arpmsg;
81
82static int arpmsg_valid;
83
84int
85sifproxyarp(int unit, u_long hisaddr)
86{
87  int routes;
88
89  /*
90   * Get the hardware address of an interface on the same subnet as our local
91   * address.
92   */
93  memset(&arpmsg, 0, sizeof(arpmsg));
94  if (!get_ether_addr(unit, hisaddr, &arpmsg.hwa)) {
95    LogPrintf(LogERROR, "Cannot determine ethernet address for proxy ARP\n");
96    return 0;
97  }
98  if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
99    LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
100	      strerror(errno));
101    return 0;
102  }
103  arpmsg.hdr.rtm_type = RTM_ADD;
104  arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
105  arpmsg.hdr.rtm_version = RTM_VERSION;
106  arpmsg.hdr.rtm_seq = ++rtm_seq;
107  arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
108  arpmsg.hdr.rtm_inits = RTV_EXPIRE;
109  arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
110  arpmsg.dst.sin_family = AF_INET;
111  arpmsg.dst.sin_addr.s_addr = hisaddr;
112  arpmsg.dst.sin_other = SIN_PROXY;
113
114  arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
115    + arpmsg.hwa.sdl_len;
116  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
117    LogPrintf(LogERROR, "Add proxy arp entry: %s\n", strerror(errno));
118    close(routes);
119    return 0;
120  }
121  close(routes);
122  arpmsg_valid = 1;
123  return 1;
124}
125
126/*
127 * cifproxyarp - Delete the proxy ARP entry for the peer.
128 */
129int
130cifproxyarp(int unit, u_long hisaddr)
131{
132  int routes;
133
134  if (!arpmsg_valid)
135    return 0;
136  arpmsg_valid = 0;
137
138  arpmsg.hdr.rtm_type = RTM_DELETE;
139  arpmsg.hdr.rtm_seq = ++rtm_seq;
140
141  if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
142    LogPrintf(LogERROR, "sifproxyarp: opening routing socket: %s\n",
143	      strerror(errno));
144    return 0;
145  }
146  if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
147    LogPrintf(LogERROR, "Delete proxy arp entry: %s\n", strerror(errno));
148    close(routes);
149    return 0;
150  }
151  close(routes);
152  return 1;
153}
154
155#else				/* RTM_VERSION */
156
157/*
158 * sifproxyarp - Make a proxy ARP entry for the peer.
159 */
160int
161sifproxyarp(int unit, u_long hisaddr)
162{
163  struct arpreq arpreq;
164  struct {
165    struct sockaddr_dl sdl;
166    char space[128];
167  }      dls;
168
169  BZERO(&arpreq, 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(unit, hisaddr, &dls.sdl)) {
176    LogPrintf(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  BCOPY(LLADDR(&dls.sdl), arpreq.arp_ha.sa_data, dls.sdl.sdl_alen);
182  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
183  ((struct sockaddr_in *) & arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
184  arpreq.arp_flags = ATF_PERM | ATF_PUBL;
185  if (ioctl(unit, SIOCSARP, (caddr_t) & arpreq) < 0) {
186    LogPrintf(LogERROR, "sifproxyarp: ioctl(SIOCSARP): %s\n", strerror(errno));
187    return 0;
188  }
189  return 1;
190}
191
192/*
193 * cifproxyarp - Delete the proxy ARP entry for the peer.
194 */
195int
196cifproxyarp(int unit, u_long hisaddr)
197{
198  struct arpreq arpreq;
199
200  BZERO(&arpreq, sizeof(arpreq));
201  SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
202  ((struct sockaddr_in *) & arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
203  if (ioctl(unit, SIOCDARP, (caddr_t) & arpreq) < 0) {
204    LogPrintf(LogERROR, "cifproxyarp: ioctl(SIOCDARP): %s\n", strerror(errno));
205    return 0;
206  }
207  return 1;
208}
209
210#endif				/* RTM_VERSION */
211
212
213/*
214 * get_ether_addr - get the hardware address of an interface on the
215 * the same subnet as ipaddr.
216 */
217#define MAX_IFS		32
218
219int
220get_ether_addr(int s, u_long ipaddr, struct sockaddr_dl * hwaddr)
221{
222  struct ifreq *ifr, *ifend, *ifp;
223  u_long ina, mask;
224  struct sockaddr_dl *dla;
225  struct ifreq ifreq;
226  struct ifconf ifc;
227  struct ifreq ifs[MAX_IFS];
228
229  ifc.ifc_len = sizeof(ifs);
230  ifc.ifc_req = ifs;
231  if (ioctl(s, SIOCGIFCONF, &ifc) < 0) {
232    LogPrintf(LogERROR, "get_ether_addr: ioctl(SIOCGIFCONF): %s\n",
233	      strerror(errno));
234    return 0;
235  }
236
237  /*
238   * Scan through looking for an interface with an Internet address on the
239   * same subnet as `ipaddr'.
240   */
241  ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
242  for (ifr = ifc.ifc_req; ifr < ifend;) {
243    if (ifr->ifr_addr.sa_family == AF_INET) {
244      ina = ((struct sockaddr_in *) & ifr->ifr_addr)->sin_addr.s_addr;
245      strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name));
246      ifreq.ifr_name[sizeof(ifreq.ifr_name) - 1] = '\0';
247
248      /*
249       * Check that the interface is up, and not point-to-point or loopback.
250       */
251      if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0)
252	continue;
253      if ((ifreq.ifr_flags &
254      (IFF_UP | IFF_BROADCAST | IFF_POINTOPOINT | IFF_LOOPBACK | IFF_NOARP))
255	  != (IFF_UP | IFF_BROADCAST))
256	goto nextif;
257
258      /*
259       * Get its netmask and check that it's on the right subnet.
260       */
261      if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0)
262	continue;
263      mask = ((struct sockaddr_in *) & ifreq.ifr_addr)->sin_addr.s_addr;
264      if ((ipaddr & mask) != (ina & mask))
265	goto nextif;
266
267      break;
268    }
269nextif:
270    ifr = (struct ifreq *) ((char *) &ifr->ifr_addr + ifr->ifr_addr.sa_len);
271  }
272
273  if (ifr >= ifend)
274    return 0;
275  LogPrintf(LogPHASE, "Found interface %s for proxy arp\n", ifr->ifr_name);
276
277  /*
278   * Now scan through again looking for a link-level address for this
279   * interface.
280   */
281  ifp = ifr;
282  for (ifr = ifc.ifc_req; ifr < ifend;) {
283    if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
284	&& ifr->ifr_addr.sa_family == AF_LINK) {
285
286      /*
287       * Found the link-level address - copy it out
288       */
289      dla = (struct sockaddr_dl *) & ifr->ifr_addr;
290#ifdef __bsdi__
291      if (dla->sdl_alen == 0)
292	kmemgetether(ifr->ifr_name, dla);
293#endif
294      BCOPY(dla, hwaddr, dla->sdl_len);
295      return 1;
296    }
297    ifr = (struct ifreq *) ((char *) &ifr->ifr_addr + ifr->ifr_addr.sa_len);
298  }
299
300  return 0;
301}
302
303#ifdef __bsdi__
304#include <nlist.h>
305
306struct nlist nl[] = {
307#define N_IFNET		0
308  {"_ifnet"},
309  "",
310};
311
312
313kvm_t *kvmd;
314
315/*
316 * Read kernel memory, return 0 on success.
317 */
318int
319kread(u_long addr, char *buf, int size)
320{
321  if (kvm_read(kvmd, addr, buf, size) != size) {
322    /* XXX this duplicates kvm_read's error printout */
323    LogPrintf(LogERROR, "kvm_read %s\n", kvm_geterr(kvmd));
324    return -1;
325  }
326  return 0;
327}
328
329void
330kmemgetether(char *ifname, struct sockaddr_dl * dlo)
331{
332  struct ifnet ifnet;
333  int n;
334  u_long addr, ifaddraddr, ifnetfound, ifaddrfound;
335  char name[16 + 32];
336  struct sockaddr *sa;
337  char *cp;
338  struct sockaddr_dl *sdl;
339  union {
340    struct ifaddr ifa;
341    struct in_ifaddr in;
342  }     ifaddr;
343  struct arpcom ac;
344
345  kvmd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL);
346  if (kvmd) {
347    n = kvm_nlist(kvmd, nl);
348    if (n >= 0) {
349      addr = nl[N_IFNET].n_value;
350      kread(addr, (char *) &addr, sizeof(addr));
351      ifaddraddr = ifnetfound = 0;
352      while (addr || ifaddraddr) {
353	ifnetfound = addr;
354	if (ifaddraddr == 0) {
355	  if (kread(addr, (char *) &ifnet, sizeof(ifnet)) ||
356	      kread((u_long) ifnet.if_name, name, 16))
357	    return;
358	  name[15] = 0;
359	  addr = (u_long) ifnet.if_next;
360	  cp = (char *) index(name, '\0');
361	  cp += sprintf(cp, "%d", ifnet.if_unit);
362	  *cp = '\0';
363	  ifaddraddr = (u_long) ifnet.if_addrlist;
364	}
365	ifaddrfound = ifaddraddr;
366	if (ifaddraddr) {
367	  if (kread(ifaddraddr, (char *) &ifaddr, sizeof ifaddr)) {
368	    ifaddraddr = 0;
369	    continue;
370	  }
371#define CP(x) ((char *)(x))
372	  cp = (CP(ifaddr.ifa.ifa_addr) - CP(ifaddraddr)) + CP(&ifaddr);
373	  sa = (struct sockaddr *) cp;
374	  if (sa->sa_family == AF_LINK && strcmp(ifname, name) == 0) {
375	    sdl = (struct sockaddr_dl *) sa;
376	    cp = (char *) LLADDR(sdl);
377	    n = sdl->sdl_alen;
378	    if (ifnet.if_type == IFT_ETHER) {
379	      if (n == 0) {
380		kread(ifnetfound, (char *) &ac, sizeof(ac));
381		cp = (char *) LLADDR(sdl);
382		bcopy((char *) ac.ac_enaddr, cp, 6);
383		sdl->sdl_alen = 6;
384	      }
385	      bcopy(sdl, dlo, sizeof(*sdl));
386	      return;
387	    }
388	  }
389	  ifaddraddr = (u_long) ifaddr.ifa.ifa_next;
390	}
391      }
392    }
393  }
394}
395
396#endif
397
398#ifdef DEBUG
399main()
400{
401  u_long ipaddr;
402  int s;
403
404  s = socket(AF_INET, SOCK_DGRAM, 0);
405  ipaddr = inet_addr("192.168.1.32");
406  sifproxyarp(s, ipaddr);
407  close(s);
408}
409
410#endif
411