xref: /freebsd/usr.sbin/rtsold/rtsold.c (revision 77a0943ded95b9e6438f7db70c4a28e4d93946d4) 
1 /*	$KAME: rtsold.c,v 1.26 2000/08/13 18:17:15 itojun Exp $	*/
2 
3 /*
4  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. Neither the name of the project nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  *
31  * $FreeBSD$
32  */
33 
34 #include <sys/types.h>
35 #include <sys/time.h>
36 #include <sys/socket.h>
37 
38 #include <net/if.h>
39 #include <net/if_dl.h>
40 
41 #include <netinet/in.h>
42 #include <netinet/icmp6.h>
43 
44 #include <signal.h>
45 #include <unistd.h>
46 #include <syslog.h>
47 #include <string.h>
48 #include <stdlib.h>
49 #include <stdio.h>
50 #include <errno.h>
51 #include <err.h>
52 #include <stdarg.h>
53 #include <ifaddrs.h>
54 #include "rtsold.h"
55 
56 struct ifinfo *iflist;
57 struct timeval tm_max =	{0x7fffffff, 0x7fffffff};
58 int aflag = 0;
59 int dflag = 0;
60 static int log_upto = 999;
61 static int fflag = 0;
62 
63 /* protocol constatns */
64 #define MAX_RTR_SOLICITATION_DELAY	1 /* second */
65 #define RTR_SOLICITATION_INTERVAL	4 /* seconds */
66 #define MAX_RTR_SOLICITATIONS		3 /* times */
67 
68 /* implementation dependent constants */
69 #define PROBE_INTERVAL 60	/* secondes XXX: should be configurable */
70 
71 /* utility macros */
72 /* a < b */
73 #define TIMEVAL_LT(a, b) (((a).tv_sec < (b).tv_sec) ||\
74 			  (((a).tv_sec == (b).tv_sec) && \
75 			    ((a).tv_usec < (b).tv_usec)))
76 
77 /* a <= b */
78 #define TIMEVAL_LEQ(a, b) (((a).tv_sec < (b).tv_sec) ||\
79 			   (((a).tv_sec == (b).tv_sec) &&\
80  			    ((a).tv_usec <= (b).tv_usec)))
81 
82 /* a == b */
83 #define TIMEVAL_EQ(a, b) (((a).tv_sec==(b).tv_sec) && ((a).tv_usec==(b).tv_usec))
84 
85 int main __P((int argc, char *argv[]));
86 
87 /* static variables and functions */
88 static int mobile_node = 0;
89 static int do_dump;
90 static char *dumpfilename = "/var/run/rtsold.dump"; /* XXX: should be configurable */
91 static char *pidfilename = "/var/run/rtsold.pid"; /* should be configurable */
92 
93 static int ifconfig __P((char *ifname));
94 #if 0
95 static int ifreconfig __P((char *ifname));
96 #endif
97 static int make_packet __P((struct ifinfo *ifinfo));
98 static struct timeval *rtsol_check_timer __P((void));
99 static void TIMEVAL_ADD __P((struct timeval *a, struct timeval *b,
100 			     struct timeval *result));
101 static void TIMEVAL_SUB __P((struct timeval *a, struct timeval *b,
102 			     struct timeval *result));
103 
104 static void rtsold_set_dump_file __P((void));
105 static void usage __P((char *progname));
106 static char **autoifprobe __P((void));
107 
108 int
109 main(argc, argv)
110 	int argc;
111 	char *argv[];
112 {
113 	int s, ch;
114 	int once = 0;
115 	struct timeval *timeout;
116 	struct fd_set fdset;
117 	char *argv0;
118 	char *opts;
119 
120 	/*
121 	 * Initialization
122 	 */
123 	argv0 = argv[0];
124 
125 	/* get option */
126 	if (argv0 && argv0[strlen(argv0) - 1] != 'd') {
127 		fflag = 1;
128 		once = 1;
129 		opts = "adD";
130 	} else
131 		opts = "adDfm1";
132 
133 	while ((ch = getopt(argc, argv, opts)) != -1) {
134 		switch (ch) {
135 		case 'a':
136 			aflag = 1;
137 			break;
138 		case 'd':
139 			dflag = 1;
140 			break;
141 		case 'D':
142 			dflag = 2;
143 			break;
144 		case 'f':
145 			fflag = 1;
146 			break;
147 		case 'm':
148 			mobile_node = 1;
149 			break;
150 		case '1':
151 			once = 1;
152 			break;
153 		default:
154 			usage(argv0);
155 			/*NOTREACHED*/
156 		}
157 	}
158 	argc -= optind;
159 	argv += optind;
160 
161 	if (aflag) {
162 		int i;
163 
164 		if (argc != 0) {
165 			usage(argv0);
166 			/*NOTREACHED*/
167 		}
168 
169 		argv = autoifprobe();
170 		if (!argv) {
171 			errx(1, "could not autoprobe interface");
172 			/*NOTREACHED*/
173 		}
174 
175 		for (i = 0; argv[i]; i++)
176 			;
177 		argc = i;
178 	}
179 	if (argc == 0) {
180 		usage(argv0);
181 		/*NOTREACHED*/
182 	}
183 
184 	/* set log level */
185 	if (dflag == 0)
186 		log_upto = LOG_NOTICE;
187 	if (!fflag) {
188 		char *ident;
189 		ident = strrchr(argv0, '/');
190 		if (!ident)
191 			ident = argv0;
192 		else
193 			ident++;
194 		openlog(ident, LOG_NDELAY|LOG_PID, LOG_DAEMON);
195 		if (log_upto >= 0)
196 			setlogmask(LOG_UPTO(log_upto));
197 	}
198 
199 #ifndef HAVE_ARC4RANDOM
200 	/* random value initilization */
201 	srandom((u_long)time(NULL));
202 #endif
203 
204 	/* warn if accept_rtadv is down */
205 	if (!getinet6sysctl(IPV6CTL_ACCEPT_RTADV))
206 		warnx("kernel is configured not to accept RAs");
207 	/* warn if forwarding is up */
208 	if (getinet6sysctl(IPV6CTL_FORWARDING))
209 		warnx("kernel is configured as a router, not a host");
210 
211 	/* initialization to dump internal status to a file */
212 	if (signal(SIGUSR1, (void *)rtsold_set_dump_file) < 0) {
213 		errx(1, "failed to set signal for dump status");
214 		/*NOTREACHED*/
215 	}
216 
217 	/*
218 	 * Open a socket for sending RS and receiving RA.
219 	 * This should be done before calling ifinit(), since the function
220 	 * uses the socket.
221 	 */
222 	if ((s = sockopen()) < 0) {
223 		errx(1, "failed to open a socket");
224 		/*NOTREACHED*/
225 	}
226 
227 	/* configuration per interface */
228 	if (ifinit()) {
229 		errx(1, "failed to initilizatoin interfaces");
230 		/*NOTREACHED*/
231 	}
232 	while (argc--) {
233 		if (ifconfig(*argv)) {
234 			errx(1, "failed to initialize %s", *argv);
235 			/*NOTREACHED*/
236 		}
237 		argv++;
238 	}
239 
240 	/* setup for probing default routers */
241 	if (probe_init()) {
242 		errx(1, "failed to setup for probing routers");
243 		/*NOTREACHED*/
244 	}
245 
246 	if (!fflag)
247 		daemon(0, 0);		/* act as a daemon */
248 
249 	/* dump the current pid */
250 	if (!once) {
251 		pid_t pid = getpid();
252 		FILE *fp;
253 
254 		if ((fp = fopen(pidfilename, "w")) == NULL)
255 			warnmsg(LOG_ERR, __FUNCTION__,
256 				"failed to open a log file(%s): %s",
257 				pidfilename, strerror(errno));
258 		else {
259 			fprintf(fp, "%d\n", pid);
260 			fclose(fp);
261 		}
262 	}
263 
264 	FD_ZERO(&fdset);
265 	FD_SET(s, &fdset);
266 	while (1) {		/* main loop */
267 		int e;
268 		struct fd_set select_fd = fdset;
269 
270 		if (do_dump) {	/* SIGUSR1 */
271 			do_dump = 0;
272 			rtsold_dump_file(dumpfilename);
273 		}
274 
275 		timeout = rtsol_check_timer();
276 
277 		if (once) {
278 			struct ifinfo *ifi;
279 
280 			/* if we have no timeout, we are done (or failed) */
281 			if (timeout == NULL)
282 				break;
283 
284 			/* if all interfaces have got RA packet, we are done */
285 			for (ifi = iflist; ifi; ifi = ifi->next) {
286 				if (ifi->state != IFS_DOWN && ifi->racnt == 0)
287 					break;
288 			}
289 			if (ifi == NULL)
290 				break;
291 		}
292 
293 		if ((e = select(s + 1, &select_fd, NULL, NULL, timeout)) < 1) {
294 			if (e < 0 && errno != EINTR) {
295 				warnmsg(LOG_ERR, __FUNCTION__, "select: %s",
296 				       strerror(errno));
297 			}
298 			continue;
299 		}
300 
301 		/* packet reception */
302 		if (FD_ISSET(s, &fdset))
303 			rtsol_input(s);
304 	}
305 	/* NOTREACHED */
306 
307 	return 0;
308 }
309 
310 static int
311 ifconfig(char *ifname)
312 {
313 	struct ifinfo *ifinfo;
314 	struct sockaddr_dl *sdl;
315 	int flags;
316 
317 	if ((sdl = if_nametosdl(ifname)) == NULL) {
318 		warnmsg(LOG_ERR, __FUNCTION__,
319 		       "failed to get link layer information for %s", ifname);
320 		return(-1);
321 	}
322 	if (find_ifinfo(sdl->sdl_index)) {
323 		warnmsg(LOG_ERR, __FUNCTION__,
324 			"interface %s was already cofigured", ifname);
325 		free(sdl);
326 		return(-1);
327 	}
328 
329 	if ((ifinfo = malloc(sizeof(*ifinfo))) == NULL) {
330 		warnmsg(LOG_ERR, __FUNCTION__, "memory allocation failed");
331 		free(sdl);
332 		return(-1);
333 	}
334 	memset(ifinfo, 0, sizeof(*ifinfo));
335 	ifinfo->sdl = sdl;
336 
337 	strncpy(ifinfo->ifname, ifname, sizeof(ifinfo->ifname));
338 
339 	/* construct a router solicitation message */
340 	if (make_packet(ifinfo))
341 		goto bad;
342 
343 	/*
344 	 * check if the interface is available.
345 	 * also check if SIOCGIFMEDIA ioctl is OK on the interface.
346 	 */
347 	ifinfo->mediareqok = 1;
348 	ifinfo->active = interface_status(ifinfo);
349 	if (!ifinfo->mediareqok) {
350 		/*
351 		 * probe routers periodically even if the link status
352 		 * does not change.
353 		 */
354 		ifinfo->probeinterval = PROBE_INTERVAL;
355 	}
356 
357 	/* activate interface: interface_up returns 0 on success */
358 	flags = interface_up(ifinfo->ifname);
359 	if (flags == 0)
360 		ifinfo->state = IFS_DELAY;
361 	else if (flags == IFS_TENTATIVE)
362 		ifinfo->state = IFS_TENTATIVE;
363 	else
364 		ifinfo->state = IFS_DOWN;
365 
366 	rtsol_timer_update(ifinfo);
367 
368 	/* link into chain */
369 	if (iflist)
370 		ifinfo->next = iflist;
371 	iflist = ifinfo;
372 
373 	return(0);
374 
375   bad:
376 	free(ifinfo->sdl);
377 	free(ifinfo);
378 	return(-1);
379 }
380 
381 #if 0
382 static int
383 ifreconfig(char *ifname)
384 {
385 	struct ifinfo *ifi, *prev;
386 	int rv;
387 
388 	prev = NULL;
389 	for (ifi = iflist; ifi; ifi = ifi->next) {
390 		if (strncmp(ifi->ifname, ifname, sizeof(ifi->ifname)) == 0)
391 			break;
392 		prev = ifi;
393 	}
394 	prev->next = ifi->next;
395 
396 	rv = ifconfig(ifname);
397 
398 	/* reclaim it after ifconfig() in case ifname is pointer inside ifi */
399 	if (ifi->rs_data)
400 		free(ifi->rs_data);
401 	free(ifi->sdl);
402 	free(ifi);
403 
404 	return rv;
405 }
406 #endif
407 
408 struct ifinfo *
409 find_ifinfo(int ifindex)
410 {
411 	struct ifinfo *ifi;
412 
413 	for (ifi = iflist; ifi; ifi = ifi->next)
414 		if (ifi->sdl->sdl_index == ifindex)
415 			return(ifi);
416 
417 	return(NULL);
418 }
419 
420 static int
421 make_packet(struct ifinfo *ifinfo)
422 {
423 	char *buf;
424 	struct nd_router_solicit *rs;
425 	size_t packlen = sizeof(struct nd_router_solicit), lladdroptlen = 0;
426 
427 	if ((lladdroptlen = lladdropt_length(ifinfo->sdl)) == 0) {
428 		warnmsg(LOG_INFO, __FUNCTION__,
429 			"link-layer address option has null length"
430 		       " on %s. Treat as not included.", ifinfo->ifname);
431 	}
432 	packlen += lladdroptlen;
433 	ifinfo->rs_datalen = packlen;
434 
435 	/* allocate buffer */
436 	if ((buf = malloc(packlen)) == NULL) {
437 		warnmsg(LOG_ERR, __FUNCTION__,
438 			"memory allocation failed for %s", ifinfo->ifname);
439 		return(-1);
440 	}
441 	ifinfo->rs_data = buf;
442 
443 	/* fill in the message */
444 	rs = (struct nd_router_solicit *)buf;
445 	rs->nd_rs_type = ND_ROUTER_SOLICIT;
446 	rs->nd_rs_code = 0;
447 	rs->nd_rs_cksum = 0;
448 	rs->nd_rs_reserved = 0;
449 	buf += sizeof(*rs);
450 
451 	/* fill in source link-layer address option */
452 	if (lladdroptlen)
453 		lladdropt_fill(ifinfo->sdl, (struct nd_opt_hdr *)buf);
454 
455 	return(0);
456 }
457 
458 static struct timeval *
459 rtsol_check_timer()
460 {
461 	static struct timeval returnval;
462 	struct timeval now, rtsol_timer;
463 	struct ifinfo *ifinfo;
464 	int flags;
465 
466 	gettimeofday(&now, NULL);
467 
468 	rtsol_timer = tm_max;
469 
470 	for (ifinfo = iflist; ifinfo; ifinfo = ifinfo->next) {
471 		if (TIMEVAL_LEQ(ifinfo->expire, now)) {
472 			if (dflag > 1)
473 				warnmsg(LOG_DEBUG, __FUNCTION__,
474 					"timer expiration on %s, "
475 				       "state = %d", ifinfo->ifname,
476 				       ifinfo->state);
477 
478 			switch (ifinfo->state) {
479 			case IFS_DOWN:
480 			case IFS_TENTATIVE:
481 				/* interface_up returns 0 on success */
482 				flags = interface_up(ifinfo->ifname);
483 				if (flags == 0)
484 					ifinfo->state = IFS_DELAY;
485 				else if (flags == IFS_TENTATIVE)
486 					ifinfo->state = IFS_TENTATIVE;
487 				else
488 					ifinfo->state = IFS_DOWN;
489 				break;
490 			case IFS_IDLE:
491 			{
492 				int oldstatus = ifinfo->active;
493 				int probe = 0;
494 
495 				ifinfo->active =
496 					interface_status(ifinfo);
497 
498 				if (oldstatus != ifinfo->active) {
499 					warnmsg(LOG_DEBUG, __FUNCTION__,
500 						"%s status is changed"
501 						" from %d to %d",
502 						ifinfo->ifname,
503 						oldstatus, ifinfo->active);
504 					probe = 1;
505 					ifinfo->state = IFS_DELAY;
506 				}
507 				else if (ifinfo->probeinterval &&
508 					 (ifinfo->probetimer -=
509 					  ifinfo->timer.tv_sec) <= 0) {
510 					/* probe timer expired */
511 					ifinfo->probetimer =
512 						ifinfo->probeinterval;
513 					probe = 1;
514 					ifinfo->state = IFS_PROBE;
515 				}
516 
517 				if (probe && mobile_node)
518 					defrouter_probe(ifinfo->sdl->sdl_index);
519 				break;
520 			}
521 			case IFS_DELAY:
522 				ifinfo->state = IFS_PROBE;
523 				sendpacket(ifinfo);
524 				break;
525 			case IFS_PROBE:
526 				if (ifinfo->probes < MAX_RTR_SOLICITATIONS)
527 					sendpacket(ifinfo);
528 				else {
529 					warnmsg(LOG_INFO, __FUNCTION__,
530 						"No answer "
531 						"after sending %d RSs",
532 						ifinfo->probes);
533 					ifinfo->probes = 0;
534 					ifinfo->state = IFS_IDLE;
535 				}
536 				break;
537 			}
538 			rtsol_timer_update(ifinfo);
539 		}
540 
541 		if (TIMEVAL_LT(ifinfo->expire, rtsol_timer))
542 			rtsol_timer = ifinfo->expire;
543 	}
544 
545 	if (TIMEVAL_EQ(rtsol_timer, tm_max)) {
546 		warnmsg(LOG_DEBUG, __FUNCTION__, "there is no timer");
547 		return(NULL);
548 	}
549 	else if (TIMEVAL_LT(rtsol_timer, now))
550 		/* this may occur when the interval is too small */
551 		returnval.tv_sec = returnval.tv_usec = 0;
552 	else
553 		TIMEVAL_SUB(&rtsol_timer, &now, &returnval);
554 
555 	if (dflag > 1)
556 		warnmsg(LOG_DEBUG, __FUNCTION__, "New timer is %ld:%08ld",
557 			(long)returnval.tv_sec, (long)returnval.tv_usec);
558 
559 	return(&returnval);
560 }
561 
562 void
563 rtsol_timer_update(struct ifinfo *ifinfo)
564 {
565 #define MILLION 1000000
566 #define DADRETRY 10		/* XXX: adhoc */
567 	long interval;
568 	struct timeval now;
569 
570 	bzero(&ifinfo->timer, sizeof(ifinfo->timer));
571 
572 	switch (ifinfo->state) {
573 	case IFS_DOWN:
574 	case IFS_TENTATIVE:
575 		if (++ifinfo->dadcount > DADRETRY) {
576 			ifinfo->dadcount = 0;
577 			ifinfo->timer.tv_sec = PROBE_INTERVAL;
578 		}
579 		else
580 			ifinfo->timer.tv_sec = 1;
581 		break;
582 	case IFS_IDLE:
583 		if (mobile_node) {
584 			/* XXX should be configurable */
585 			ifinfo->timer.tv_sec = 3;
586 		}
587 		else
588 			ifinfo->timer = tm_max;	/* stop timer(valid?) */
589 		break;
590 	case IFS_DELAY:
591 #ifndef HAVE_ARC4RANDOM
592 		interval = random() % (MAX_RTR_SOLICITATION_DELAY * MILLION);
593 #else
594 		interval = arc4random() % (MAX_RTR_SOLICITATION_DELAY * MILLION);
595 #endif
596 		ifinfo->timer.tv_sec = interval / MILLION;
597 		ifinfo->timer.tv_usec = interval % MILLION;
598 		break;
599 	case IFS_PROBE:
600 		ifinfo->timer.tv_sec = RTR_SOLICITATION_INTERVAL;
601 		break;
602 	default:
603 		warnmsg(LOG_ERR, __FUNCTION__,
604 			"illegal interface state(%d) on %s",
605 			ifinfo->state, ifinfo->ifname);
606 		return;
607 	}
608 
609 	/* reset the timer */
610 	if (TIMEVAL_EQ(ifinfo->timer, tm_max)) {
611 		ifinfo->expire = tm_max;
612 		warnmsg(LOG_DEBUG, __FUNCTION__,
613 			"stop timer for %s", ifinfo->ifname);
614 	}
615 	else {
616 		gettimeofday(&now, NULL);
617 		TIMEVAL_ADD(&now, &ifinfo->timer, &ifinfo->expire);
618 
619 		if (dflag > 1)
620 			warnmsg(LOG_DEBUG, __FUNCTION__,
621 				"set timer for %s to %d:%d", ifinfo->ifname,
622 			       (int)ifinfo->timer.tv_sec,
623 			       (int)ifinfo->timer.tv_usec);
624 	}
625 
626 #undef MILLION
627 }
628 
629 /* timer related utility functions */
630 #define MILLION 1000000
631 
632 /* result = a + b */
633 static void
634 TIMEVAL_ADD(struct timeval *a, struct timeval *b, struct timeval *result)
635 {
636 	long l;
637 
638 	if ((l = a->tv_usec + b->tv_usec) < MILLION) {
639 		result->tv_usec = l;
640 		result->tv_sec = a->tv_sec + b->tv_sec;
641 	}
642 	else {
643 		result->tv_usec = l - MILLION;
644 		result->tv_sec = a->tv_sec + b->tv_sec + 1;
645 	}
646 }
647 
648 /*
649  * result = a - b
650  * XXX: this function assumes that a >= b.
651  */
652 void
653 TIMEVAL_SUB(struct timeval *a, struct timeval *b, struct timeval *result)
654 {
655 	long l;
656 
657 	if ((l = a->tv_usec - b->tv_usec) >= 0) {
658 		result->tv_usec = l;
659 		result->tv_sec = a->tv_sec - b->tv_sec;
660 	}
661 	else {
662 		result->tv_usec = MILLION + l;
663 		result->tv_sec = a->tv_sec - b->tv_sec - 1;
664 	}
665 }
666 
667 static void
668 rtsold_set_dump_file()
669 {
670 	do_dump = 1;
671 }
672 
673 static void
674 usage(char *progname)
675 {
676 	if (progname && progname[strlen(progname) - 1] != 'd') {
677 		fprintf(stderr, "usage: rtsol [-dD] interfaces...\n");
678 		fprintf(stderr, "usage: rtsol [-dD] -a\n");
679 	} else {
680 		fprintf(stderr, "usage: rtsold [-adDfm1] interfaces...\n");
681 		fprintf(stderr, "usage: rtsold [-dDfm1] -a\n");
682 	}
683 	exit(1);
684 }
685 
686 void
687 #if __STDC__
688 warnmsg(int priority, const char *func, const char *msg, ...)
689 #else
690 warnmsg(priority, func, msg, va_alist)
691 	int priority;
692 	const char *func;
693 	const char *msg;
694 	va_dcl
695 #endif
696 {
697 	va_list ap;
698 	char buf[BUFSIZ];
699 
700 	va_start(ap, msg);
701 	if (fflag) {
702 		if (priority <= log_upto) {
703 			(void)vfprintf(stderr, msg, ap);
704 			(void)fprintf(stderr, "\n");
705 		}
706 	} else {
707 		snprintf(buf, sizeof(buf), "<%s> %s", func, msg);
708 		msg = buf;
709 		vsyslog(priority, msg, ap);
710 	}
711 	va_end(ap);
712 }
713 
714 static char **
715 autoifprobe()
716 {
717 #ifndef HAVE_GETIFADDRS
718 	errx(1, "-a is not available with the configuration");
719 #else
720 	static char ifname[IFNAMSIZ + 1];
721 	static char *argv[2];
722 	struct ifaddrs *ifap, *ifa, *target;
723 
724 	if (getifaddrs(&ifap) != 0)
725 		return NULL;
726 
727 	target = NULL;
728 	/* find an ethernet */
729 	for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
730 		if ((ifa->ifa_flags & IFF_UP) == 0)
731 			continue;
732 		if ((ifa->ifa_flags & IFF_POINTOPOINT) != 0)
733 			continue;
734 		if ((ifa->ifa_flags & IFF_LOOPBACK) != 0)
735 			continue;
736 		if ((ifa->ifa_flags & IFF_MULTICAST) == 0)
737 			continue;
738 
739 		if (ifa->ifa_addr->sa_family != AF_INET6)
740 			continue;
741 
742 		if (target && strcmp(target->ifa_name, ifa->ifa_name) == 0)
743 			continue;
744 
745 		if (!target)
746 			target = ifa;
747 		else {
748 			/* if we find multiple candidates, failure. */
749 			if (dflag > 1)
750 				warnx("multiple interfaces found");
751 			target = NULL;
752 			break;
753 		}
754 	}
755 
756 	if (target) {
757 		strncpy(ifname, target->ifa_name, sizeof(ifname) - 1);
758 		ifname[sizeof(ifname) - 1] = '\0';
759 		argv[0] = ifname;
760 		argv[1] = NULL;
761 
762 		if (dflag > 0)
763 			warnx("probing %s", argv[0]);
764 	}
765 	freeifaddrs(ifap);
766 	if (target)
767 		return argv;
768 	else
769 		return (char **)NULL;
770 #endif
771 }
772