xref: /freebsd/usr.sbin/arp/arp.c (revision 61afd5bb22d787b0641523e7b9b95c964d669bd5)
1 /*
2  * Copyright (c) 1984, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Sun Microsystems, Inc.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. All advertising materials mentioning features or use of this software
17  *    must display the following acknowledgement:
18  *	This product includes software developed by the University of
19  *	California, Berkeley and its contributors.
20  * 4. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  */
36 
37 #ifndef lint
38 static char const copyright[] =
39 "@(#) Copyright (c) 1984, 1993\n\
40 	The Regents of the University of California.  All rights reserved.\n";
41 #endif /* not lint */
42 
43 #ifndef lint
44 static char const sccsid[] = "@(#)from: arp.c	8.2 (Berkeley) 1/2/94";
45 static char const freebsdid[] = "$Id: arp.c,v 1.6 1996/12/19 19:33:10 nate Exp $";
46 #endif /* not lint */
47 
48 /*
49  * arp - display, set, and delete arp table entries
50  */
51 
52 
53 #include <sys/param.h>
54 #include <sys/file.h>
55 #include <sys/socket.h>
56 #include <sys/sockio.h>
57 #include <sys/sysctl.h>
58 #include <sys/ioctl.h>
59 #include <sys/time.h>
60 
61 #include <net/if.h>
62 #include <net/if_var.h>
63 #include <net/if_dl.h>
64 #include <net/if_types.h>
65 #include <net/route.h>
66 
67 #include <netinet/in.h>
68 #include <netinet/if_ether.h>
69 
70 #include <arpa/inet.h>
71 
72 #include <netdb.h>
73 #include <errno.h>
74 #include <nlist.h>
75 #include <stdio.h>
76 #include <stdlib.h>
77 #include <unistd.h>
78 #include <strings.h>
79 #include <paths.h>
80 
81 void dump(u_long addr);
82 int delete(char *host, char *info);
83 void ether_print(u_char *cp);
84 void usage(void);
85 int set(int argc, char **argv);
86 void get(char *host);
87 int file(char *name);
88 void getsocket(void);
89 int my_ether_aton(char *a, u_char *n);
90 int rtmsg(int cmd);
91 void quit(char *msg);
92 int get_ether_addr(u_long ipaddr, u_char *hwaddr);
93 
94 static int pid;
95 static int nflag;
96 static int s = -1;
97 
98 int
99 main(argc, argv)
100 	int argc;
101 	char **argv;
102 {
103 	int ch;
104 
105 	pid = getpid();
106 	while ((ch = getopt(argc, argv, "andfsS")) != EOF)
107 		switch((char)ch) {
108 		case 'a':
109 			dump(0);
110 			exit(0);
111 		case 'd':
112 			if (argc < 3 || argc > 4)
113 				usage();
114 			delete(argv[2], argv[3]);
115 			exit(0);
116 		case 'n':
117 			nflag = 1;
118 			continue;
119 		case 'S':
120 			delete(argv[2], NULL);
121 			/* FALL THROUGH */
122 		case 's':
123 			if (argc < 4 || argc > 7)
124 				usage();
125 			exit(set(argc-2, &argv[2]) ? 1 : 0);
126 		case 'f' :
127 			if (argc != 3)
128 				usage();
129 			return (file(argv[2]));
130 		case '?':
131 		default:
132 			usage();
133 		}
134 	if (argc != 2)
135 		usage();
136 	get(argv[1]);
137 	exit(0);
138 }
139 
140 /*
141  * Process a file to set standard arp entries
142  */
143 int
144 file(char *name)
145 {
146 	FILE *fp;
147 	int i, retval;
148 	char line[100], arg[5][50], *args[5];
149 
150 	if ((fp = fopen(name, "r")) == NULL) {
151 		fprintf(stderr, "arp: cannot open %s\n", name);
152 		exit(1);
153 	}
154 	args[0] = &arg[0][0];
155 	args[1] = &arg[1][0];
156 	args[2] = &arg[2][0];
157 	args[3] = &arg[3][0];
158 	args[4] = &arg[4][0];
159 	retval = 0;
160 	while(fgets(line, 100, fp) != NULL) {
161 		i = sscanf(line, "%s %s %s %s %s", arg[0], arg[1], arg[2],
162 		    arg[3], arg[4]);
163 		if (i < 2) {
164 			fprintf(stderr, "arp: bad line: %s\n", line);
165 			retval = 1;
166 			continue;
167 		}
168 		if (set(i, args))
169 			retval = 1;
170 	}
171 	fclose(fp);
172 	return (retval);
173 }
174 
175 void
176 getsocket(void)
177 {
178 	if (s < 0) {
179 		s = socket(PF_ROUTE, SOCK_RAW, 0);
180 		if (s < 0) {
181 			perror("arp: socket");
182 			exit(1);
183 		}
184 	}
185 }
186 
187 struct	sockaddr_in so_mask = {8, 0, 0, { 0xffffffff}};
188 struct	sockaddr_inarp blank_sin = {sizeof(blank_sin), AF_INET }, sin_m;
189 struct	sockaddr_dl blank_sdl = {sizeof(blank_sdl), AF_LINK }, sdl_m;
190 int	expire_time, flags, export_only, doing_proxy, found_entry;
191 struct	{
192 	struct	rt_msghdr m_rtm;
193 	char	m_space[512];
194 }	m_rtmsg;
195 
196 /*
197  * Set an individual arp entry
198  */
199 int
200 set(int argc, char **argv)
201 {
202 	struct hostent *hp;
203 	register struct sockaddr_inarp *sin = &sin_m;
204 	register struct sockaddr_dl *sdl;
205 	register struct rt_msghdr *rtm = &(m_rtmsg.m_rtm);
206 	u_char *ea;
207 	char *host = argv[0], *eaddr = argv[1];
208 
209 	getsocket();
210 	argc -= 2;
211 	argv += 2;
212 	sdl_m = blank_sdl;
213 	sin_m = blank_sin;
214 	sin->sin_addr.s_addr = inet_addr(host);
215 	if (sin->sin_addr.s_addr == -1) {
216 		if (!(hp = gethostbyname(host))) {
217 			fprintf(stderr, "arp: %s: ", host);
218 			herror((char *)NULL);
219 			return (1);
220 		}
221 		bcopy((char *)hp->h_addr, (char *)&sin->sin_addr,
222 		    sizeof sin->sin_addr);
223 	}
224 	doing_proxy = flags = export_only = expire_time = 0;
225 	while (argc-- > 0) {
226 		if (strncmp(argv[0], "temp", 4) == 0) {
227 			struct timeval time;
228 			gettimeofday(&time, 0);
229 			expire_time = time.tv_sec + 20 * 60;
230 		}
231 		else if (strncmp(argv[0], "pub", 3) == 0) {
232 			flags |= RTF_ANNOUNCE;
233 			doing_proxy = SIN_PROXY;
234 		} else if (strncmp(argv[0], "trail", 5) == 0) {
235 			printf("%s: Sending trailers is no longer supported\n",
236 				host);
237 		}
238 		argv++;
239 	}
240 	ea = (u_char *)LLADDR(&sdl_m);
241 	if (doing_proxy && !strcmp(eaddr, "auto")) {
242 		if (!get_ether_addr(sin->sin_addr.s_addr, ea)) {
243 			return (1);
244 		}
245 		sdl_m.sdl_alen = 6;
246 	} else {
247 		if (my_ether_aton(eaddr, ea) == 0)
248 			sdl_m.sdl_alen = 6;
249 	}
250 tryagain:
251 	if (rtmsg(RTM_GET) < 0) {
252 		perror(host);
253 		return (1);
254 	}
255 	sin = (struct sockaddr_inarp *)(rtm + 1);
256 	sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
257 	if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
258 		if (sdl->sdl_family == AF_LINK &&
259 		    (rtm->rtm_flags & RTF_LLINFO) &&
260 		    !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
261 		case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
262 		case IFT_ISO88024: case IFT_ISO88025:
263 			goto overwrite;
264 		}
265 		if (doing_proxy == 0) {
266 			printf("set: can only proxy for %s\n", host);
267 			return (1);
268 		}
269 		if (sin_m.sin_other & SIN_PROXY) {
270 			printf("set: proxy entry exists for non 802 device\n");
271 			return(1);
272 		}
273 		sin_m.sin_other = SIN_PROXY;
274 		export_only = 1;
275 		goto tryagain;
276 	}
277 overwrite:
278 	if (sdl->sdl_family != AF_LINK) {
279 		printf("cannot intuit interface index and type for %s\n", host);
280 		return (1);
281 	}
282 	sdl_m.sdl_type = sdl->sdl_type;
283 	sdl_m.sdl_index = sdl->sdl_index;
284 	return (rtmsg(RTM_ADD));
285 }
286 
287 /*
288  * Display an individual arp entry
289  */
290 void
291 get(char *host)
292 {
293 	struct hostent *hp;
294 	struct sockaddr_inarp *sin = &sin_m;
295 
296 	sin_m = blank_sin;
297 	sin->sin_addr.s_addr = inet_addr(host);
298 	if (sin->sin_addr.s_addr == -1) {
299 		if (!(hp = gethostbyname(host))) {
300 			fprintf(stderr, "arp: %s: ", host);
301 			herror((char *)NULL);
302 			exit(1);
303 		}
304 		bcopy((char *)hp->h_addr, (char *)&sin->sin_addr,
305 		    sizeof sin->sin_addr);
306 	}
307 	dump(sin->sin_addr.s_addr);
308 	if (found_entry == 0) {
309 		printf("%s (%s) -- no entry\n",
310 		    host, inet_ntoa(sin->sin_addr));
311 		exit(1);
312 	}
313 }
314 
315 /*
316  * Delete an arp entry
317  */
318 int
319 delete(char *host, char *info)
320 {
321 	struct hostent *hp;
322 	register struct sockaddr_inarp *sin = &sin_m;
323 	register struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
324 	struct sockaddr_dl *sdl;
325 
326 	if (info && strncmp(info, "pro", 3) )
327 		export_only = 1;
328 	getsocket();
329 	sin_m = blank_sin;
330 	sin->sin_addr.s_addr = inet_addr(host);
331 	if (sin->sin_addr.s_addr == -1) {
332 		if (!(hp = gethostbyname(host))) {
333 			fprintf(stderr, "arp: %s: ", host);
334 			herror((char *)NULL);
335 			return (1);
336 		}
337 		bcopy((char *)hp->h_addr, (char *)&sin->sin_addr,
338 		    sizeof sin->sin_addr);
339 	}
340 tryagain:
341 	if (rtmsg(RTM_GET) < 0) {
342 		perror(host);
343 		return (1);
344 	}
345 	sin = (struct sockaddr_inarp *)(rtm + 1);
346 	sdl = (struct sockaddr_dl *)(sin->sin_len + (char *)sin);
347 	if (sin->sin_addr.s_addr == sin_m.sin_addr.s_addr) {
348 		if (sdl->sdl_family == AF_LINK &&
349 		    (rtm->rtm_flags & RTF_LLINFO) &&
350 		    !(rtm->rtm_flags & RTF_GATEWAY)) switch (sdl->sdl_type) {
351 		case IFT_ETHER: case IFT_FDDI: case IFT_ISO88023:
352 		case IFT_ISO88024: case IFT_ISO88025:
353 			goto delete;
354 		}
355 	}
356 	if (sin_m.sin_other & SIN_PROXY) {
357 		fprintf(stderr, "delete: can't locate %s\n",host);
358 		return (1);
359 	} else {
360 		sin_m.sin_other = SIN_PROXY;
361 		goto tryagain;
362 	}
363 delete:
364 	if (sdl->sdl_family != AF_LINK) {
365 		printf("cannot locate %s\n", host);
366 		return (1);
367 	}
368 	if (rtmsg(RTM_DELETE) == 0) {
369 		printf("%s (%s) deleted\n", host, inet_ntoa(sin->sin_addr));
370 		return (0);
371 	}
372 	return (1);
373 }
374 
375 /*
376  * Dump the entire arp table
377  */
378 void
379 dump(u_long addr)
380 {
381 	int mib[6];
382 	size_t needed;
383 	char *host, *malloc(), *lim, *buf, *next;
384 	struct rt_msghdr *rtm;
385 	struct sockaddr_inarp *sin;
386 	struct sockaddr_dl *sdl;
387 	extern int h_errno;
388 	struct hostent *hp;
389 
390 	mib[0] = CTL_NET;
391 	mib[1] = PF_ROUTE;
392 	mib[2] = 0;
393 	mib[3] = AF_INET;
394 	mib[4] = NET_RT_FLAGS;
395 	mib[5] = RTF_LLINFO;
396 	if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
397 		quit("route-sysctl-estimate");
398 	if ((buf = malloc(needed)) == NULL)
399 		quit("malloc");
400 	if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0)
401 		quit("actual retrieval of routing table");
402 	lim = buf + needed;
403 	for (next = buf; next < lim; next += rtm->rtm_msglen) {
404 		rtm = (struct rt_msghdr *)next;
405 		sin = (struct sockaddr_inarp *)(rtm + 1);
406 		sdl = (struct sockaddr_dl *)(sin + 1);
407 		if (addr) {
408 			if (addr != sin->sin_addr.s_addr)
409 				continue;
410 			found_entry = 1;
411 		}
412 		if (nflag == 0)
413 			hp = gethostbyaddr((caddr_t)&(sin->sin_addr),
414 			    sizeof sin->sin_addr, AF_INET);
415 		else
416 			hp = 0;
417 		if (hp)
418 			host = hp->h_name;
419 		else {
420 			host = "?";
421 			if (h_errno == TRY_AGAIN)
422 				nflag = 1;
423 		}
424 		printf("%s (%s) at ", host, inet_ntoa(sin->sin_addr));
425 		if (sdl->sdl_alen)
426 			ether_print(LLADDR(sdl));
427 		else
428 			printf("(incomplete)");
429 		if (rtm->rtm_rmx.rmx_expire == 0)
430 			printf(" permanent");
431 		if (sin->sin_other & SIN_PROXY)
432 			printf(" published (proxy only)");
433 		if (rtm->rtm_addrs & RTA_NETMASK) {
434 			sin = (struct sockaddr_inarp *)
435 				(sdl->sdl_len + (char *)sdl);
436 			if (sin->sin_addr.s_addr == 0xffffffff)
437 				printf(" published");
438 			if (sin->sin_len != 8)
439 				printf("(wierd)");
440 		}
441 		printf("\n");
442 	}
443 }
444 
445 void
446 ether_print(u_char *cp)
447 {
448 	printf("%x:%x:%x:%x:%x:%x", cp[0], cp[1], cp[2], cp[3], cp[4], cp[5]);
449 }
450 
451 int
452 my_ether_aton(char *a, u_char *n)
453 {
454 	int i, o[6];
455 
456 	i = sscanf(a, "%x:%x:%x:%x:%x:%x", &o[0], &o[1], &o[2],
457 					   &o[3], &o[4], &o[5]);
458 	if (i != 6) {
459 		fprintf(stderr, "arp: invalid Ethernet address '%s'\n", a);
460 		return (1);
461 	}
462 	for (i=0; i<6; i++)
463 		n[i] = o[i];
464 	return (0);
465 }
466 
467 void
468 usage(void)
469 {
470 	printf("usage: arp hostname\n");
471 	printf("       arp -a [kernel] [kernel_memory]\n");
472 	printf("       arp -d hostname\n");
473 	printf("       arp -s hostname ether_addr [temp] [pub]\n");
474 	printf("       arp -S hostname ether_addr [temp] [pub]\n");
475 	printf("       arp -f filename\n");
476 	exit(1);
477 }
478 
479 int
480 rtmsg(int cmd)
481 {
482 	static int seq;
483 	int rlen;
484 	register struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
485 	register char *cp = m_rtmsg.m_space;
486 	register int l;
487 
488 	errno = 0;
489 	if (cmd == RTM_DELETE)
490 		goto doit;
491 	bzero((char *)&m_rtmsg, sizeof(m_rtmsg));
492 	rtm->rtm_flags = flags;
493 	rtm->rtm_version = RTM_VERSION;
494 
495 	switch (cmd) {
496 	default:
497 		fprintf(stderr, "arp: internal wrong cmd\n");
498 		exit(1);
499 	case RTM_ADD:
500 		rtm->rtm_addrs |= RTA_GATEWAY;
501 		rtm->rtm_rmx.rmx_expire = expire_time;
502 		rtm->rtm_inits = RTV_EXPIRE;
503 		rtm->rtm_flags |= (RTF_HOST | RTF_STATIC);
504 		sin_m.sin_other = 0;
505 		if (doing_proxy) {
506 			if (export_only)
507 				sin_m.sin_other = SIN_PROXY;
508 			else {
509 				rtm->rtm_addrs |= RTA_NETMASK;
510 				rtm->rtm_flags &= ~RTF_HOST;
511 			}
512 		}
513 		/* FALLTHROUGH */
514 	case RTM_GET:
515 		rtm->rtm_addrs |= RTA_DST;
516 	}
517 #define NEXTADDR(w, s) \
518 	if (rtm->rtm_addrs & (w)) { \
519 		bcopy((char *)&s, cp, sizeof(s)); cp += sizeof(s);}
520 
521 	NEXTADDR(RTA_DST, sin_m);
522 	NEXTADDR(RTA_GATEWAY, sdl_m);
523 	NEXTADDR(RTA_NETMASK, so_mask);
524 
525 	rtm->rtm_msglen = cp - (char *)&m_rtmsg;
526 doit:
527 	l = rtm->rtm_msglen;
528 	rtm->rtm_seq = ++seq;
529 	rtm->rtm_type = cmd;
530 	if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
531 		if (errno != ESRCH || cmd != RTM_DELETE) {
532 			perror("writing to routing socket");
533 			return (-1);
534 		}
535 	}
536 	do {
537 		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
538 	} while (l > 0 && (rtm->rtm_seq != seq || rtm->rtm_pid != pid));
539 	if (l < 0)
540 		(void) fprintf(stderr, "arp: read from routing socket: %s\n",
541 		    strerror(errno));
542 	return (0);
543 }
544 
545 void
546 quit(char *msg)
547 {
548 	fprintf(stderr, "%s\n", msg);
549 	exit(1);
550 }
551 
552 /*
553  * get_ether_addr - get the hardware address of an interface on the
554  * the same subnet as ipaddr.
555  */
556 #define MAX_IFS		32
557 
558 int
559 get_ether_addr(u_long ipaddr, u_char *hwaddr)
560 {
561 	struct ifreq *ifr, *ifend, *ifp;
562 	u_long ina, mask;
563 	struct sockaddr_dl *dla;
564 	struct ifreq ifreq;
565 	struct ifconf ifc;
566 	struct ifreq ifs[MAX_IFS];
567 	int s;
568 
569 	s = socket(AF_INET, SOCK_DGRAM, 0);
570 	if (s < 0) {
571 		perror("socket");
572 		exit(1);
573 	}
574 
575 	ifc.ifc_len = sizeof(ifs);
576 	ifc.ifc_req = ifs;
577 	if (ioctl(s, SIOCGIFCONF, &ifc) < 0) {
578 		fprintf(stderr, "ioctl(SIOCGIFCONF): \n");
579 		close(s);
580 		return 0;
581 	}
582 
583 	/*
584 	* Scan through looking for an interface with an Internet
585 	* address on the same subnet as `ipaddr'.
586 	*/
587 	ifend = (struct ifreq *) (ifc.ifc_buf + ifc.ifc_len);
588 	for (ifr = ifc.ifc_req; ifr < ifend; ) {
589 		if (ifr->ifr_addr.sa_family == AF_INET) {
590 			ina = ((struct sockaddr_in *)
591 				&ifr->ifr_addr)->sin_addr.s_addr;
592 			strncpy(ifreq.ifr_name, ifr->ifr_name,
593 				sizeof(ifreq.ifr_name));
594 			/*
595 			 * Check that the interface is up,
596 			 * and not point-to-point or loopback.
597 			 */
598 			if (ioctl(s, SIOCGIFFLAGS, &ifreq) < 0)
599 				continue;
600 			if ((ifreq.ifr_flags &
601 			     (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|
602 					IFF_LOOPBACK|IFF_NOARP))
603 			     != (IFF_UP|IFF_BROADCAST))
604 				goto nextif;
605 			/*
606 			 * Get its netmask and check that it's on
607 			 * the right subnet.
608 			 */
609 			if (ioctl(s, SIOCGIFNETMASK, &ifreq) < 0)
610 				continue;
611 			mask = ((struct sockaddr_in *)
612 				&ifreq.ifr_addr)->sin_addr.s_addr;
613 			if ((ipaddr & mask) != (ina & mask))
614 				goto nextif;
615 			break;
616 		}
617 nextif:
618 		ifr = (struct ifreq *)
619 		    ((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
620 	}
621 
622 	if (ifr >= ifend) {
623 		close(s);
624 		return 0;
625 	}
626 
627 	/*
628 	* Now scan through again looking for a link-level address
629 	* for this interface.
630 	*/
631 	ifp = ifr;
632 	for (ifr = ifc.ifc_req; ifr < ifend; ) {
633 		if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0
634 		    && ifr->ifr_addr.sa_family == AF_LINK) {
635 			/*
636 			 * Found the link-level address - copy it out
637 			 */
638 		 	dla = (struct sockaddr_dl *) &ifr->ifr_addr;
639 			memcpy(hwaddr,  LLADDR(dla), dla->sdl_alen);
640 			close (s);
641 			printf("using interface %s for proxy with address ",
642 				ifp->ifr_name);
643 			ether_print(hwaddr);
644 			printf("\n");
645 			return dla->sdl_alen;
646 		}
647 		ifr = (struct ifreq *)
648 			((char *)&ifr->ifr_addr + ifr->ifr_addr.sa_len);
649 	}
650 	return 0;
651 }
652