arp.c revision 23114 
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 1.9 1997/02/22 16:09:56 peter 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 <osreldate.h>
39#if __FreeBSD_version >= 199702
40#include <net/if_var.h>
41#endif
42#include <net/route.h>
43#include <net/if_dl.h>
44#include <netinet/in.h>
45#include <stdio.h>
46#include <fcntl.h>
47#ifdef __bsdi__
48#include <kvm.h>
49#endif
50#include <net/if_types.h>
51#include <netinet/in_var.h>
52#include <netinet/if_ether.h>
53#include "log.h"
54
55#if RTM_VERSION >= 3
56#include <netinet/if_ether.h>
57#endif
58
59static int rtm_seq;
60
61static int get_ether_addr __P((int, u_long, struct sockaddr_dl *));
62
63#define BCOPY(s, d, l)		memcpy(d, s, l)
64#define BZERO(s, n)		memset(s, 0, n)
65/*
66 * SET_SA_FAMILY - set the sa_family field of a struct sockaddr,
67 * if it exists.
68 */
69#define SET_SA_FAMILY(addr, family)		\
70    BZERO((char *) &(addr), sizeof(addr));	\
71    addr.sa_family = (family); 			\
72    addr.sa_len = sizeof(addr);
73
74
75#if RTM_VERSION >= 3
76
77/*
78 * sifproxyarp - Make a proxy ARP entry for the peer.
79 */
80static struct {
81    struct rt_msghdr		hdr;
82    struct sockaddr_inarp	dst;
83    struct sockaddr_dl		hwa;
84    char			extra[128];
85} arpmsg;
86
87static int arpmsg_valid;
88
89int
90sifproxyarp(unit, hisaddr)
91    int unit;
92    u_long hisaddr;
93{
94    int routes;
95
96    /*
97     * Get the hardware address of an interface on the same subnet
98     * as our local address.
99     */
100    memset(&arpmsg, 0, sizeof(arpmsg));
101    if (!get_ether_addr(unit, hisaddr, &arpmsg.hwa)) {
102	logprintf("Cannot determine ethernet address for proxy ARP\n");
103	return 0;
104    }
105
106    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
107	logprintf("sifproxyarp: opening routing socket: \n");
108	return 0;
109    }
110
111    arpmsg.hdr.rtm_type = RTM_ADD;
112    arpmsg.hdr.rtm_flags = RTF_ANNOUNCE | RTF_HOST | RTF_STATIC;
113    arpmsg.hdr.rtm_version = RTM_VERSION;
114    arpmsg.hdr.rtm_seq = ++rtm_seq;
115    arpmsg.hdr.rtm_addrs = RTA_DST | RTA_GATEWAY;
116    arpmsg.hdr.rtm_inits = RTV_EXPIRE;
117    arpmsg.dst.sin_len = sizeof(struct sockaddr_inarp);
118    arpmsg.dst.sin_family = AF_INET;
119    arpmsg.dst.sin_addr.s_addr = hisaddr;
120    arpmsg.dst.sin_other = SIN_PROXY;
121
122    arpmsg.hdr.rtm_msglen = (char *) &arpmsg.hwa - (char *) &arpmsg
123	+ arpmsg.hwa.sdl_len;
124    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
125	logprintf("add proxy arp entry: \n");
126	close(routes);
127	return 0;
128    }
129
130    close(routes);
131    arpmsg_valid = 1;
132    return 1;
133}
134
135/*
136 * cifproxyarp - Delete the proxy ARP entry for the peer.
137 */
138int
139cifproxyarp(unit, hisaddr)
140    int unit;
141    u_long hisaddr;
142{
143    int routes;
144
145    if (!arpmsg_valid)
146	return 0;
147    arpmsg_valid = 0;
148
149    arpmsg.hdr.rtm_type = RTM_DELETE;
150    arpmsg.hdr.rtm_seq = ++rtm_seq;
151
152    if ((routes = socket(PF_ROUTE, SOCK_RAW, AF_INET)) < 0) {
153	logprintf("sifproxyarp: opening routing socket: \n");
154	return 0;
155    }
156
157    if (write(routes, &arpmsg, arpmsg.hdr.rtm_msglen) < 0) {
158	logprintf("delete proxy arp entry: \n");
159	close(routes);
160	return 0;
161    }
162
163    close(routes);
164    return 1;
165}
166
167#else	/* RTM_VERSION */
168
169/*
170 * sifproxyarp - Make a proxy ARP entry for the peer.
171 */
172int
173sifproxyarp(unit, hisaddr)
174    int unit;
175    u_long hisaddr;
176{
177    struct arpreq arpreq;
178    struct {
179	struct sockaddr_dl	sdl;
180	char			space[128];
181    } dls;
182
183    BZERO(&arpreq, sizeof(arpreq));
184
185    /*
186     * Get the hardware address of an interface on the same subnet
187     * as our local address.
188     */
189    if (!get_ether_addr(unit, hisaddr, &dls.sdl)) {
190	LogPrintf(LOG_PHASE_BIT, "Cannot determine ethernet address for proxy ARP\n");
191	return 0;
192    }
193
194    arpreq.arp_ha.sa_len = sizeof(struct sockaddr);
195    arpreq.arp_ha.sa_family = AF_UNSPEC;
196    BCOPY(LLADDR(&dls.sdl), arpreq.arp_ha.sa_data, dls.sdl.sdl_alen);
197    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
198    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
199    arpreq.arp_flags = ATF_PERM | ATF_PUBL;
200    if (ioctl(unit, SIOCSARP, (caddr_t)&arpreq) < 0) {
201	fprintf(stderr, "ioctl(SIOCSARP): \n");
202	return 0;
203    }
204
205    return 1;
206}
207
208/*
209 * cifproxyarp - Delete the proxy ARP entry for the peer.
210 */
211int
212cifproxyarp(unit, hisaddr)
213    int unit;
214    u_long hisaddr;
215{
216    struct arpreq arpreq;
217
218    BZERO(&arpreq, sizeof(arpreq));
219    SET_SA_FAMILY(arpreq.arp_pa, AF_INET);
220    ((struct sockaddr_in *) &arpreq.arp_pa)->sin_addr.s_addr = hisaddr;
221    if (ioctl(unit, SIOCDARP, (caddr_t)&arpreq) < 0) {
222	fprintf(stderr, "ioctl(SIOCDARP): \n");
223	return 0;
224    }
225    return 1;
226}
227#endif	/* RTM_VERSION */
228
229
230/*
231 * get_ether_addr - get the hardware address of an interface on the
232 * the same subnet as ipaddr.
233 */
234#define MAX_IFS		32
235
236int
237get_ether_addr(s, ipaddr, hwaddr)
238    int    s;
239    u_long ipaddr;
240    struct sockaddr_dl *hwaddr;
241{
242    struct ifreq *ifr, *ifend, *ifp;
243    u_long ina, mask;
244    struct sockaddr_dl *dla;
245    struct ifreq ifreq;
246    struct ifconf ifc;
247    struct ifreq ifs[MAX_IFS];
248
249    ifc.ifc_len = sizeof(ifs);
250    ifc.ifc_req = ifs;
251    if (ioctl(s, SIOCGIFCONF, &ifc) < 0) {
252	fprintf(stderr, "ioctl(SIOCGIFCONF): \n");
253	return 0;
254    }
255
256    /*
257     * Scan through looking for an interface with an Internet
258     * address on the same subnet as `ipaddr'.
259     */
260    ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
261    for (ifr = ifc.ifc_req; ifr < ifend; ) {
262	if (ifr->ifr_addr.sa_family == AF_INET) {
263	    ina = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr.s_addr;
264	    strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name));
265	    ifreq.ifr_name[sizeof(ifreq.ifr_name)-1]='\0';
266	    /*
267	     * Check that the interface is up, and not point-to-point
268	     * or loopback.
269	     */
270	    if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0)
271		continue;
272	    if ((ifreq.ifr_flags &
273		 (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|IFF_LOOPBACK|IFF_NOARP))
274		 != (IFF_UP|IFF_BROADCAST))
275		goto nextif;
276	    /*
277	     * Get its netmask and check that it's on the right subnet.
278	     */
279	    if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0)
280		continue;
281	    mask = ((struct sockaddr_in *) &ifreq.ifr_addr)->sin_addr.s_addr;
282	    if ((ipaddr & mask) != (ina & mask))
283		goto nextif;
284
285	    break;
286	}
287nextif:
288	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
289    }
290
291    if (ifr >= ifend)
292	return 0;
293    LogPrintf(LOG_PHASE_BIT, "found interface %s for proxy arp\n", ifr->ifr_name);
294
295    /*
296     * Now scan through again looking for a link-level address
297     * for this interface.
298     */
299    ifp = ifr;
300    for (ifr = ifc.ifc_req; ifr < ifend; ) {
301	if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
302	    && ifr->ifr_addr.sa_family == AF_LINK) {
303	    /*
304	     * Found the link-level address - copy it out
305	     */
306	    dla = (struct sockaddr_dl *) &ifr->ifr_addr;
307#ifdef __bsdi__
308	    if (dla->sdl_alen == 0)
309	      kmemgetether(ifr->ifr_name, dla);
310#endif
311	    BCOPY(dla, hwaddr, dla->sdl_len);
312	    return 1;
313	}
314	ifr = (struct ifreq *) ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
315    }
316
317    return 0;
318}
319
320#ifdef __bsdi__
321#include <nlist.h>
322
323struct nlist nl[] = {
324#define N_IFNET		0
325	{ "_ifnet" },
326	"",
327};
328
329
330kvm_t *kvmd;
331
332/*
333 * Read kernel memory, return 0 on success.
334 */
335int
336kread(addr, buf, size)
337  u_long addr;
338  char *buf;
339  int size;
340{
341
342	if (kvm_read(kvmd, addr, buf, size) != size) {
343		/* XXX this duplicates kvm_read's error printout */
344		(void)fprintf(stderr, "kvm_read %s\n",
345			kvm_geterr(kvmd));
346		return (-1);
347	}
348	return (0);
349}
350
351kmemgetether(ifname, dlo)
352char *ifname;
353struct sockaddr_dl *dlo;
354{
355  struct ifnet ifnet;
356  int n;
357  u_long addr, ifaddraddr, ifnetfound, ifaddrfound;
358  char name[16+32];
359  struct sockaddr *sa;
360  char *cp;
361  struct sockaddr_dl *sdl;
362  union {
363	  struct ifaddr ifa;
364	  struct in_ifaddr in;
365  } ifaddr;
366  struct arpcom ac;
367
368  kvmd = kvm_open(NULL, NULL, NULL, O_RDONLY, NULL);
369  if (kvmd) {
370    n = kvm_nlist(kvmd, nl);
371    if (n >= 0) {
372      addr = nl[N_IFNET].n_value;
373      kread(addr, (char *)&addr, sizeof(addr));
374      ifaddraddr = ifnetfound = 0;
375      while (addr || ifaddraddr) {
376	ifnetfound = addr;
377	if (ifaddraddr == 0) {
378	  if (kread(addr, (char *)&ifnet, sizeof(ifnet)) ||
379	      kread((u_long)ifnet.if_name, name, 16))
380		return;
381	  name[15] = 0;
382	  addr = (u_long) ifnet.if_next;
383	  cp = (char *)index(name, '\0');
384	  cp += sprintf(cp, "%d", ifnet.if_unit);
385	  *cp = '\0';
386	  ifaddraddr = (u_long)ifnet.if_addrlist;
387	}
388	ifaddrfound = ifaddraddr;
389	if (ifaddraddr) {
390	  if (kread(ifaddraddr, (char *)&ifaddr, sizeof ifaddr)) {
391	    ifaddraddr = 0;
392	    continue;
393	  }
394#define CP(x) ((char *)(x))
395	  cp = (CP(ifaddr.ifa.ifa_addr) - CP(ifaddraddr)) + CP(&ifaddr);
396	  sa = (struct sockaddr *)cp;
397	  if (sa->sa_family == AF_LINK && strcmp(ifname, name) == 0) {
398	    sdl = (struct sockaddr_dl *)sa;
399	    cp = (char *)LLADDR(sdl);
400	    n = sdl->sdl_alen;
401	    if (ifnet.if_type == IFT_ETHER) {
402		if (n == 0) {
403		  kread(ifnetfound, (char *)&ac, sizeof(ac));
404	    	  cp = (char *)LLADDR(sdl);
405		  bcopy((char *)ac.ac_enaddr, cp, 6);
406		  sdl->sdl_alen = 6;
407		}
408		bcopy(sdl, dlo, sizeof(*sdl));
409		return;
410	    }
411	  }
412	  ifaddraddr = (u_long)ifaddr.ifa.ifa_next;
413	}
414      }
415    }
416  }
417}
418#endif
419
420#ifdef DEBUG
421main()
422{
423    u_long ipaddr;
424    int s;
425
426    s = socket(AF_INET, SOCK_DGRAM, 0);
427    ipaddr = inet_addr("192.168.1.32");
428    sifproxyarp(s, ipaddr);
429    close(s);
430}
431#endif
432