rtsold.c revision 118914 
1/*	$KAME: rtsold.c,v 1.31 2001/05/22 06:03:06 jinmei 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: head/usr.sbin/rtsold/rtsold.c 118914 2003-08-14 18:13:34Z ume $
32 */
33
34#include <sys/types.h>
35#include <sys/time.h>
36#include <sys/socket.h>
37#include <sys/param.h>
38
39#include <net/if.h>
40#include <net/if_dl.h>
41
42#include <netinet/in.h>
43#include <netinet/icmp6.h>
44
45#include <signal.h>
46#include <unistd.h>
47#include <syslog.h>
48#include <string.h>
49#include <stdlib.h>
50#include <stdio.h>
51#include <errno.h>
52#include <err.h>
53#include <stdarg.h>
54#include <ifaddrs.h>
55
56#include "rtsold.h"
57
58struct ifinfo *iflist;
59struct timeval tm_max =	{0x7fffffff, 0x7fffffff};
60static int log_upto = 999;
61static int fflag = 0;
62
63int aflag = 0;
64int dflag = 0;
65
66char *otherconf_script;
67
68/* protocol constatns */
69#define MAX_RTR_SOLICITATION_DELAY	1 /* second */
70#define RTR_SOLICITATION_INTERVAL	4 /* seconds */
71#define MAX_RTR_SOLICITATIONS		3 /* times */
72
73/*
74 * implementation dependent constants in seconds
75 * XXX: should be configurable
76 */
77#define PROBE_INTERVAL 60
78
79/* utility macros */
80/* a < b */
81#define TIMEVAL_LT(a, b) (((a).tv_sec < (b).tv_sec) ||\
82			  (((a).tv_sec == (b).tv_sec) && \
83			    ((a).tv_usec < (b).tv_usec)))
84
85/* a <= b */
86#define TIMEVAL_LEQ(a, b) (((a).tv_sec < (b).tv_sec) ||\
87			   (((a).tv_sec == (b).tv_sec) &&\
88			    ((a).tv_usec <= (b).tv_usec)))
89
90/* a == b */
91#define TIMEVAL_EQ(a, b) (((a).tv_sec==(b).tv_sec) && ((a).tv_usec==(b).tv_usec))
92
93int main __P((int, char **));
94
95/* static variables and functions */
96static int mobile_node = 0;
97static int do_dump;
98static char *dumpfilename = "/var/run/rtsold.dump"; /* XXX: should be configurable */
99static char *pidfilename = "/var/run/rtsold.pid"; /* should be configurable */
100
101static int ifconfig __P((char *));
102#if 0
103static int ifreconfig __P((char *));
104#endif
105static int make_packet __P((struct ifinfo *));
106static struct timeval *rtsol_check_timer __P((void));
107static void TIMEVAL_ADD __P((struct timeval *, struct timeval *,
108	struct timeval *));
109static void TIMEVAL_SUB __P((struct timeval *, struct timeval *,
110	struct timeval *));
111
112static void rtsold_set_dump_file __P((int));
113static void usage __P((char *));
114static char **autoifprobe __P((void));
115
116int
117main(argc, argv)
118	int argc;
119	char **argv;
120{
121	int s, ch, once = 0;
122	struct timeval *timeout;
123	char *argv0, *opts;
124	fd_set *fdsetp, *selectfdp;
125	int fdmasks;
126	int maxfd;
127	int rtsock;
128
129	/*
130	 * Initialization
131	 */
132	argv0 = argv[0];
133
134	/* get option */
135	if (argv0 && argv0[strlen(argv0) - 1] != 'd') {
136		fflag = 1;
137		once = 1;
138		opts = "adDO:";
139	} else
140		opts = "adDfm1O:";
141
142	while ((ch = getopt(argc, argv, opts)) != -1) {
143		switch (ch) {
144		case 'a':
145			aflag = 1;
146			break;
147		case 'd':
148			dflag = 1;
149			break;
150		case 'D':
151			dflag = 2;
152			break;
153		case 'f':
154			fflag = 1;
155			break;
156		case 'm':
157			mobile_node = 1;
158			break;
159		case '1':
160			once = 1;
161			break;
162		case 'O':
163			otherconf_script = optarg;
164			break;
165		default:
166			usage(argv0);
167			/*NOTREACHED*/
168		}
169	}
170	argc -= optind;
171	argv += optind;
172
173	if (aflag) {
174		int i;
175
176		if (argc != 0) {
177			usage(argv0);
178			/*NOTREACHED*/
179		}
180
181		argv = autoifprobe();
182		if (!argv) {
183			errx(1, "could not autoprobe interface");
184			/*NOTREACHED*/
185		}
186
187		for (i = 0; argv[i]; i++)
188			;
189		argc = i;
190	}
191	if (argc == 0) {
192		usage(argv0);
193		/*NOTREACHED*/
194	}
195
196	/* set log level */
197	if (dflag == 0)
198		log_upto = LOG_NOTICE;
199	if (!fflag) {
200		char *ident;
201
202		ident = strrchr(argv0, '/');
203		if (!ident)
204			ident = argv0;
205		else
206			ident++;
207		openlog(ident, LOG_NDELAY|LOG_PID, LOG_DAEMON);
208		if (log_upto >= 0)
209			setlogmask(LOG_UPTO(log_upto));
210	}
211
212	if (otherconf_script && *otherconf_script != '/') {
213		errx(1, "configuration script (%s) must be an absolute path",
214		    otherconf_script);
215	}
216
217#ifndef HAVE_ARC4RANDOM
218	/* random value initialization */
219	srandom((u_long)time(NULL));
220#endif
221
222	/* warn if accept_rtadv is down */
223	if (!getinet6sysctl(IPV6CTL_ACCEPT_RTADV))
224		warnx("kernel is configured not to accept RAs");
225	/* warn if forwarding is up */
226	if (getinet6sysctl(IPV6CTL_FORWARDING))
227		warnx("kernel is configured as a router, not a host");
228
229	/* initialization to dump internal status to a file */
230	signal(SIGUSR1, rtsold_set_dump_file);
231
232	if (!fflag)
233		daemon(0, 0);		/* act as a daemon */
234
235	/*
236	 * Open a socket for sending RS and receiving RA.
237	 * This should be done before calling ifinit(), since the function
238	 * uses the socket.
239	 */
240	if ((s = sockopen()) < 0) {
241		warnmsg(LOG_ERR, __func__, "failed to open a socket");
242		exit(1);
243		/*NOTREACHED*/
244	}
245	maxfd = s;
246	if ((rtsock = rtsock_open()) < 0) {
247		warnmsg(LOG_ERR, __func__, "failed to open a socket");
248		exit(1);
249		/*NOTREACHED*/
250	}
251	if (rtsock > maxfd)
252		maxfd = rtsock;
253
254	fdmasks = howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask);
255	if ((fdsetp = malloc(fdmasks)) == NULL) {
256		err(1, "malloc");
257		/*NOTREACHED*/
258	}
259	if ((selectfdp = malloc(fdmasks)) == NULL) {
260		err(1, "malloc");
261		/*NOTREACHED*/
262	}
263
264	/* configuration per interface */
265	if (ifinit()) {
266		warnmsg(LOG_ERR, __func__,
267		    "failed to initilizatoin interfaces");
268		exit(1);
269		/*NOTREACHED*/
270	}
271	while (argc--) {
272		if (ifconfig(*argv)) {
273			warnmsg(LOG_ERR, __func__,
274			    "failed to initialize %s", *argv);
275			exit(1);
276			/*NOTREACHED*/
277		}
278		argv++;
279	}
280
281	/* setup for probing default routers */
282	if (probe_init()) {
283		warnmsg(LOG_ERR, __func__,
284		    "failed to setup for probing routers");
285		exit(1);
286		/*NOTREACHED*/
287	}
288
289	/* dump the current pid */
290	if (!once) {
291		pid_t pid = getpid();
292		FILE *fp;
293
294		if ((fp = fopen(pidfilename, "w")) == NULL)
295			warnmsg(LOG_ERR, __func__,
296			    "failed to open a pid log file(%s): %s",
297			    pidfilename, strerror(errno));
298		else {
299			fprintf(fp, "%d\n", pid);
300			fclose(fp);
301		}
302	}
303
304	memset(fdsetp, 0, fdmasks);
305	FD_SET(s, fdsetp);
306	FD_SET(rtsock, fdsetp);
307	while (1) {		/* main loop */
308		int e;
309
310		memcpy(selectfdp, fdsetp, fdmasks);
311
312		if (do_dump) {	/* SIGUSR1 */
313			do_dump = 0;
314			rtsold_dump_file(dumpfilename);
315		}
316
317		timeout = rtsol_check_timer();
318
319		if (once) {
320			struct ifinfo *ifi;
321
322			/* if we have no timeout, we are done (or failed) */
323			if (timeout == NULL)
324				break;
325
326			/* if all interfaces have got RA packet, we are done */
327			for (ifi = iflist; ifi; ifi = ifi->next) {
328				if (ifi->state != IFS_DOWN && ifi->racnt == 0)
329					break;
330			}
331			if (ifi == NULL)
332				break;
333		}
334		e = select(maxfd + 1, selectfdp, NULL, NULL, timeout);
335		if (e < 1) {
336			if (e < 0 && errno != EINTR) {
337				warnmsg(LOG_ERR, __func__, "select: %s",
338				    strerror(errno));
339			}
340			continue;
341		}
342
343		/* packet reception */
344		if (FD_ISSET(rtsock, selectfdp))
345			rtsock_input(rtsock);
346		if (FD_ISSET(s, selectfdp))
347			rtsol_input(s);
348	}
349	/* NOTREACHED */
350
351	return 0;
352}
353
354static int
355ifconfig(char *ifname)
356{
357	struct ifinfo *ifinfo;
358	struct sockaddr_dl *sdl;
359	int flags;
360
361	if ((sdl = if_nametosdl(ifname)) == NULL) {
362		warnmsg(LOG_ERR, __func__,
363		    "failed to get link layer information for %s", ifname);
364		return(-1);
365	}
366	if (find_ifinfo(sdl->sdl_index)) {
367		warnmsg(LOG_ERR, __func__,
368		    "interface %s was already configured", ifname);
369		free(sdl);
370		return(-1);
371	}
372
373	if ((ifinfo = malloc(sizeof(*ifinfo))) == NULL) {
374		warnmsg(LOG_ERR, __func__, "memory allocation failed");
375		free(sdl);
376		return(-1);
377	}
378	memset(ifinfo, 0, sizeof(*ifinfo));
379	ifinfo->sdl = sdl;
380
381	strlcpy(ifinfo->ifname, ifname, sizeof(ifinfo->ifname));
382
383	/* construct a router solicitation message */
384	if (make_packet(ifinfo))
385		goto bad;
386
387	/*
388	 * check if the interface is available.
389	 * also check if SIOCGIFMEDIA ioctl is OK on the interface.
390	 */
391	ifinfo->mediareqok = 1;
392	ifinfo->active = interface_status(ifinfo);
393	if (!ifinfo->mediareqok) {
394		/*
395		 * probe routers periodically even if the link status
396		 * does not change.
397		 */
398		ifinfo->probeinterval = PROBE_INTERVAL;
399	}
400
401	/* activate interface: interface_up returns 0 on success */
402	flags = interface_up(ifinfo->ifname);
403	if (flags == 0)
404		ifinfo->state = IFS_DELAY;
405	else if (flags == IFS_TENTATIVE)
406		ifinfo->state = IFS_TENTATIVE;
407	else
408		ifinfo->state = IFS_DOWN;
409
410	rtsol_timer_update(ifinfo);
411
412	/* link into chain */
413	if (iflist)
414		ifinfo->next = iflist;
415	iflist = ifinfo;
416
417	return(0);
418
419bad:
420	free(ifinfo->sdl);
421	free(ifinfo);
422	return(-1);
423}
424
425#if 0
426static int
427ifreconfig(char *ifname)
428{
429	struct ifinfo *ifi, *prev;
430	int rv;
431
432	prev = NULL;
433	for (ifi = iflist; ifi; ifi = ifi->next) {
434		if (strncmp(ifi->ifname, ifname, sizeof(ifi->ifname)) == 0)
435			break;
436		prev = ifi;
437	}
438	prev->next = ifi->next;
439
440	rv = ifconfig(ifname);
441
442	/* reclaim it after ifconfig() in case ifname is pointer inside ifi */
443	if (ifi->rs_data)
444		free(ifi->rs_data);
445	free(ifi->sdl);
446	free(ifi);
447	return rv;
448}
449#endif
450
451struct ifinfo *
452find_ifinfo(int ifindex)
453{
454	struct ifinfo *ifi;
455
456	for (ifi = iflist; ifi; ifi = ifi->next)
457		if (ifi->sdl->sdl_index == ifindex)
458			return(ifi);
459	return(NULL);
460}
461
462static int
463make_packet(struct ifinfo *ifinfo)
464{
465	size_t packlen = sizeof(struct nd_router_solicit), lladdroptlen = 0;
466	struct nd_router_solicit *rs;
467	char *buf;
468
469	if ((lladdroptlen = lladdropt_length(ifinfo->sdl)) == 0) {
470		warnmsg(LOG_INFO, __func__,
471		    "link-layer address option has null length"
472		    " on %s. Treat as not included.", ifinfo->ifname);
473	}
474	packlen += lladdroptlen;
475	ifinfo->rs_datalen = packlen;
476
477	/* allocate buffer */
478	if ((buf = malloc(packlen)) == NULL) {
479		warnmsg(LOG_ERR, __func__,
480		    "memory allocation failed for %s", ifinfo->ifname);
481		return(-1);
482	}
483	ifinfo->rs_data = buf;
484
485	/* fill in the message */
486	rs = (struct nd_router_solicit *)buf;
487	rs->nd_rs_type = ND_ROUTER_SOLICIT;
488	rs->nd_rs_code = 0;
489	rs->nd_rs_cksum = 0;
490	rs->nd_rs_reserved = 0;
491	buf += sizeof(*rs);
492
493	/* fill in source link-layer address option */
494	if (lladdroptlen)
495		lladdropt_fill(ifinfo->sdl, (struct nd_opt_hdr *)buf);
496
497	return(0);
498}
499
500static struct timeval *
501rtsol_check_timer()
502{
503	static struct timeval returnval;
504	struct timeval now, rtsol_timer;
505	struct ifinfo *ifinfo;
506	int flags;
507
508	gettimeofday(&now, NULL);
509
510	rtsol_timer = tm_max;
511
512	for (ifinfo = iflist; ifinfo; ifinfo = ifinfo->next) {
513		if (TIMEVAL_LEQ(ifinfo->expire, now)) {
514			if (dflag > 1)
515				warnmsg(LOG_DEBUG, __func__,
516				    "timer expiration on %s, "
517				    "state = %d", ifinfo->ifname,
518				    ifinfo->state);
519
520			switch (ifinfo->state) {
521			case IFS_DOWN:
522			case IFS_TENTATIVE:
523				/* interface_up returns 0 on success */
524				flags = interface_up(ifinfo->ifname);
525				if (flags == 0)
526					ifinfo->state = IFS_DELAY;
527				else if (flags == IFS_TENTATIVE)
528					ifinfo->state = IFS_TENTATIVE;
529				else
530					ifinfo->state = IFS_DOWN;
531				break;
532			case IFS_IDLE:
533			{
534				int oldstatus = ifinfo->active;
535				int probe = 0;
536
537				ifinfo->active = interface_status(ifinfo);
538
539				if (oldstatus != ifinfo->active) {
540					warnmsg(LOG_DEBUG, __func__,
541					    "%s status is changed"
542					    " from %d to %d",
543					    ifinfo->ifname,
544					    oldstatus, ifinfo->active);
545					probe = 1;
546					ifinfo->state = IFS_DELAY;
547				} else if (ifinfo->probeinterval &&
548				    (ifinfo->probetimer -=
549				    ifinfo->timer.tv_sec) <= 0) {
550					/* probe timer expired */
551					ifinfo->probetimer =
552					    ifinfo->probeinterval;
553					probe = 1;
554					ifinfo->state = IFS_PROBE;
555				}
556
557				/*
558				 * If we need a probe, clear the previous
559				 * status wrt the "other" configuration.
560				 */
561				if (probe)
562					ifinfo->otherconfig = 0;
563
564				if (probe && mobile_node)
565					defrouter_probe(ifinfo->sdl->sdl_index);
566				break;
567			}
568			case IFS_DELAY:
569				ifinfo->state = IFS_PROBE;
570				sendpacket(ifinfo);
571				break;
572			case IFS_PROBE:
573				if (ifinfo->probes < MAX_RTR_SOLICITATIONS)
574					sendpacket(ifinfo);
575				else {
576					warnmsg(LOG_INFO, __func__,
577					    "No answer after sending %d RSs",
578					    ifinfo->probes);
579					ifinfo->probes = 0;
580					ifinfo->state = IFS_IDLE;
581				}
582				break;
583			}
584			rtsol_timer_update(ifinfo);
585		}
586
587		if (TIMEVAL_LT(ifinfo->expire, rtsol_timer))
588			rtsol_timer = ifinfo->expire;
589	}
590
591	if (TIMEVAL_EQ(rtsol_timer, tm_max)) {
592		warnmsg(LOG_DEBUG, __func__, "there is no timer");
593		return(NULL);
594	} else if (TIMEVAL_LT(rtsol_timer, now))
595		/* this may occur when the interval is too small */
596		returnval.tv_sec = returnval.tv_usec = 0;
597	else
598		TIMEVAL_SUB(&rtsol_timer, &now, &returnval);
599
600	if (dflag > 1)
601		warnmsg(LOG_DEBUG, __func__, "New timer is %ld:%08ld",
602		    (long)returnval.tv_sec, (long)returnval.tv_usec);
603
604	return(&returnval);
605}
606
607void
608rtsol_timer_update(struct ifinfo *ifinfo)
609{
610#define MILLION 1000000
611#define DADRETRY 10		/* XXX: adhoc */
612	long interval;
613	struct timeval now;
614
615	bzero(&ifinfo->timer, sizeof(ifinfo->timer));
616
617	switch (ifinfo->state) {
618	case IFS_DOWN:
619	case IFS_TENTATIVE:
620		if (++ifinfo->dadcount > DADRETRY) {
621			ifinfo->dadcount = 0;
622			ifinfo->timer.tv_sec = PROBE_INTERVAL;
623		} else
624			ifinfo->timer.tv_sec = 1;
625		break;
626	case IFS_IDLE:
627		if (mobile_node) {
628			/* XXX should be configurable */
629			ifinfo->timer.tv_sec = 3;
630		}
631		else
632			ifinfo->timer = tm_max;	/* stop timer(valid?) */
633		break;
634	case IFS_DELAY:
635#ifndef HAVE_ARC4RANDOM
636		interval = random() % (MAX_RTR_SOLICITATION_DELAY * MILLION);
637#else
638		interval = arc4random() % (MAX_RTR_SOLICITATION_DELAY * MILLION);
639#endif
640		ifinfo->timer.tv_sec = interval / MILLION;
641		ifinfo->timer.tv_usec = interval % MILLION;
642		break;
643	case IFS_PROBE:
644		if (ifinfo->probes < MAX_RTR_SOLICITATIONS)
645			ifinfo->timer.tv_sec = RTR_SOLICITATION_INTERVAL;
646		else {
647			/*
648			 * After sending MAX_RTR_SOLICITATIONS solicitations,
649			 * we're just waiting for possible replies; there
650			 * will be no more solicatation.  Thus, we change
651			 * the timer value to MAX_RTR_SOLICITATION_DELAY based
652			 * on RFC 2461, Section 6.3.7.
653			 */
654			ifinfo->timer.tv_sec = MAX_RTR_SOLICITATION_DELAY;
655		}
656		break;
657	default:
658		warnmsg(LOG_ERR, __func__,
659		    "illegal interface state(%d) on %s",
660		    ifinfo->state, ifinfo->ifname);
661		return;
662	}
663
664	/* reset the timer */
665	if (TIMEVAL_EQ(ifinfo->timer, tm_max)) {
666		ifinfo->expire = tm_max;
667		warnmsg(LOG_DEBUG, __func__,
668		    "stop timer for %s", ifinfo->ifname);
669	} else {
670		gettimeofday(&now, NULL);
671		TIMEVAL_ADD(&now, &ifinfo->timer, &ifinfo->expire);
672
673		if (dflag > 1)
674			warnmsg(LOG_DEBUG, __func__,
675			    "set timer for %s to %d:%d", ifinfo->ifname,
676			    (int)ifinfo->timer.tv_sec,
677			    (int)ifinfo->timer.tv_usec);
678	}
679
680#undef MILLION
681}
682
683/* timer related utility functions */
684#define MILLION 1000000
685
686/* result = a + b */
687static void
688TIMEVAL_ADD(struct timeval *a, struct timeval *b, struct timeval *result)
689{
690	long l;
691
692	if ((l = a->tv_usec + b->tv_usec) < MILLION) {
693		result->tv_usec = l;
694		result->tv_sec = a->tv_sec + b->tv_sec;
695	} else {
696		result->tv_usec = l - MILLION;
697		result->tv_sec = a->tv_sec + b->tv_sec + 1;
698	}
699}
700
701/*
702 * result = a - b
703 * XXX: this function assumes that a >= b.
704 */
705void
706TIMEVAL_SUB(struct timeval *a, struct timeval *b, struct timeval *result)
707{
708	long l;
709
710	if ((l = a->tv_usec - b->tv_usec) >= 0) {
711		result->tv_usec = l;
712		result->tv_sec = a->tv_sec - b->tv_sec;
713	} else {
714		result->tv_usec = MILLION + l;
715		result->tv_sec = a->tv_sec - b->tv_sec - 1;
716	}
717}
718
719static void
720rtsold_set_dump_file(sig)
721	int sig;
722{
723	do_dump = 1;
724}
725
726static void
727usage(char *progname)
728{
729	if (progname && progname[strlen(progname) - 1] != 'd') {
730		fprintf(stderr, "usage: rtsol [-dD] interfaces...\n");
731		fprintf(stderr, "usage: rtsol [-dD] -a\n");
732	} else {
733		fprintf(stderr, "usage: rtsold [-adDfm1] interfaces...\n");
734		fprintf(stderr, "usage: rtsold [-dDfm1] -a\n");
735	}
736	exit(1);
737}
738
739void
740#if __STDC__
741warnmsg(int priority, const char *func, const char *msg, ...)
742#else
743warnmsg(priority, func, msg, va_alist)
744	int priority;
745	const char *func;
746	const char *msg;
747	va_dcl
748#endif
749{
750	va_list ap;
751	char buf[BUFSIZ];
752
753	va_start(ap, msg);
754	if (fflag) {
755		if (priority <= log_upto) {
756			(void)vfprintf(stderr, msg, ap);
757			(void)fprintf(stderr, "\n");
758		}
759	} else {
760		snprintf(buf, sizeof(buf), "<%s> %s", func, msg);
761		msg = buf;
762		vsyslog(priority, msg, ap);
763	}
764	va_end(ap);
765}
766
767static char **
768autoifprobe()
769{
770	static char ifname[IFNAMSIZ + 1];
771	static char *argv[2];
772	struct ifaddrs *ifap, *ifa, *target;
773
774	if (getifaddrs(&ifap) != 0)
775		return NULL;
776
777	target = NULL;
778	/* find an ethernet */
779	for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
780		if ((ifa->ifa_flags & IFF_UP) == 0)
781			continue;
782		if ((ifa->ifa_flags & IFF_POINTOPOINT) != 0)
783			continue;
784		if ((ifa->ifa_flags & IFF_LOOPBACK) != 0)
785			continue;
786		if ((ifa->ifa_flags & IFF_MULTICAST) == 0)
787			continue;
788
789		if (ifa->ifa_addr->sa_family != AF_INET6)
790			continue;
791
792		if (target && strcmp(target->ifa_name, ifa->ifa_name) == 0)
793			continue;
794
795		if (!target)
796			target = ifa;
797		else {
798			/* if we find multiple candidates, failure. */
799			if (dflag > 1)
800				warnx("multiple interfaces found");
801			target = NULL;
802			break;
803		}
804	}
805
806	if (target) {
807		strncpy(ifname, target->ifa_name, sizeof(ifname) - 1);
808		ifname[sizeof(ifname) - 1] = '\0';
809		argv[0] = ifname;
810		argv[1] = NULL;
811
812		if (dflag > 0)
813			warnx("probing %s", argv[0]);
814	}
815	freeifaddrs(ifap);
816	if (target)
817		return argv;
818	else
819		return (char **)NULL;
820}
821