1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1984, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Sun Microsystems, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#if 0
36#ifndef lint
37static char const copyright[] =
38"@(#) Copyright (c) 1984, 1993\n\
39	The Regents of the University of California.  All rights reserved.\n";
40#endif /* not lint */
41
42#ifndef lint
43static char const sccsid[] = "@(#)from: arp.c	8.2 (Berkeley) 1/2/94";
44#endif /* not lint */
45#endif
46#include <sys/cdefs.h>
47__FBSDID("$FreeBSD$");
48
49/*
50 * arp - display, set, and delete arp table entries
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_dl.h>
63#include <net/if_types.h>
64#include <net/route.h>
65
66#include <netinet/in.h>
67#include <netinet/if_ether.h>
68
69#include <arpa/inet.h>
70
71#include <ctype.h>
72#include <err.h>
73#include <errno.h>
74#include <netdb.h>
75#include <nlist.h>
76#include <paths.h>
77#include <stdio.h>
78#include <stdlib.h>
79#include <string.h>
80#include <strings.h>
81#include <unistd.h>
82#include <libxo/xo.h>
83
84typedef void (action_fn)(struct sockaddr_dl *sdl, struct sockaddr_in *s_in,
85    struct rt_msghdr *rtm);
86
87static int search(u_long addr, action_fn *action);
88static action_fn print_entry;
89static action_fn nuke_entry;
90
91static int delete(char *host);
92static void usage(void);
93static int set(int argc, char **argv);
94static int get(char *host);
95static int file(char *name);
96static struct rt_msghdr *rtmsg(int cmd,
97    struct sockaddr_in *dst, struct sockaddr_dl *sdl);
98static int get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr);
99static struct sockaddr_in *getaddr(char *host);
100static int valid_type(int type);
101
102static int nflag;	/* no reverse dns lookups */
103static char *rifname;
104
105static time_t	expire_time;
106static int	flags, doing_proxy;
107
108struct if_nameindex *ifnameindex;
109
110/* which function we're supposed to do */
111#define F_GET		1
112#define F_SET		2
113#define F_FILESET	3
114#define F_REPLACE	4
115#define F_DELETE	5
116
117#define SETFUNC(f)	{ if (func) usage(); func = (f); }
118
119#define ARP_XO_VERSION	"1"
120
121int
122main(int argc, char *argv[])
123{
124	int ch, func = 0;
125	int rtn = 0;
126	int aflag = 0;	/* do it for all entries */
127
128	argc = xo_parse_args(argc, argv);
129	if (argc < 0)
130		exit(1);
131
132	while ((ch = getopt(argc, argv, "andfsSi:")) != -1)
133		switch(ch) {
134		case 'a':
135			aflag = 1;
136			break;
137		case 'd':
138			SETFUNC(F_DELETE);
139			break;
140		case 'n':
141			nflag = 1;
142			break;
143		case 'S':
144			SETFUNC(F_REPLACE);
145			break;
146		case 's':
147			SETFUNC(F_SET);
148			break;
149		case 'f' :
150			SETFUNC(F_FILESET);
151			break;
152		case 'i':
153			rifname = optarg;
154			break;
155		case '?':
156		default:
157			usage();
158		}
159	argc -= optind;
160	argv += optind;
161
162	if (!func)
163		func = F_GET;
164	if (rifname) {
165		if (func != F_GET && !(func == F_DELETE && aflag))
166			xo_errx(1, "-i not applicable to this operation");
167		if (if_nametoindex(rifname) == 0) {
168			if (errno == ENXIO)
169				xo_errx(1, "interface %s does not exist",
170				    rifname);
171			else
172				xo_err(1, "if_nametoindex(%s)", rifname);
173		}
174	}
175	switch (func) {
176	case F_GET:
177		if (aflag) {
178			if (argc != 0)
179				usage();
180
181			xo_set_version(ARP_XO_VERSION);
182			xo_open_container("arp");
183			xo_open_list("arp-cache");
184
185			search(0, print_entry);
186
187			xo_close_list("arp-cache");
188			xo_close_container("arp");
189			xo_finish();
190		} else {
191			if (argc != 1)
192				usage();
193			rtn = get(argv[0]);
194		}
195		break;
196	case F_SET:
197	case F_REPLACE:
198		if (argc < 2 || argc > 6)
199			usage();
200		if (func == F_REPLACE)
201			(void)delete(argv[0]);
202		rtn = set(argc, argv) ? 1 : 0;
203		break;
204	case F_DELETE:
205		if (aflag) {
206			if (argc != 0)
207				usage();
208			search(0, nuke_entry);
209		} else {
210			if (argc != 1)
211				usage();
212			rtn = delete(argv[0]);
213		}
214		break;
215	case F_FILESET:
216		if (argc != 1)
217			usage();
218		rtn = file(argv[0]);
219		break;
220	}
221
222	if (ifnameindex != NULL)
223		if_freenameindex(ifnameindex);
224
225	return (rtn);
226}
227
228/*
229 * Process a file to set standard arp entries
230 */
231static int
232file(char *name)
233{
234	FILE *fp;
235	int i, retval;
236	char line[100], arg[5][50], *args[5], *p;
237
238	if ((fp = fopen(name, "r")) == NULL)
239		xo_err(1, "cannot open %s", name);
240	args[0] = &arg[0][0];
241	args[1] = &arg[1][0];
242	args[2] = &arg[2][0];
243	args[3] = &arg[3][0];
244	args[4] = &arg[4][0];
245	retval = 0;
246	while(fgets(line, sizeof(line), fp) != NULL) {
247		if ((p = strchr(line, '#')) != NULL)
248			*p = '\0';
249		for (p = line; isblank(*p); p++);
250		if (*p == '\n' || *p == '\0')
251			continue;
252		i = sscanf(p, "%49s %49s %49s %49s %49s", arg[0], arg[1],
253		    arg[2], arg[3], arg[4]);
254		if (i < 2) {
255			xo_warnx("bad line: %s", line);
256			retval = 1;
257			continue;
258		}
259		if (set(i, args))
260			retval = 1;
261	}
262	fclose(fp);
263	return (retval);
264}
265
266/*
267 * Given a hostname, fills up a (static) struct sockaddr_in with
268 * the address of the host and returns a pointer to the
269 * structure.
270 */
271static struct sockaddr_in *
272getaddr(char *host)
273{
274	struct hostent *hp;
275	static struct sockaddr_in reply;
276
277	bzero(&reply, sizeof(reply));
278	reply.sin_len = sizeof(reply);
279	reply.sin_family = AF_INET;
280	reply.sin_addr.s_addr = inet_addr(host);
281	if (reply.sin_addr.s_addr == INADDR_NONE) {
282		if (!(hp = gethostbyname(host))) {
283			xo_warnx("%s: %s", host, hstrerror(h_errno));
284			return (NULL);
285		}
286		bcopy((char *)hp->h_addr, (char *)&reply.sin_addr,
287			sizeof reply.sin_addr);
288	}
289	return (&reply);
290}
291
292/*
293 * Returns true if the type is a valid one for ARP.
294 */
295static int
296valid_type(int type)
297{
298
299	switch (type) {
300	case IFT_ETHER:
301	case IFT_FDDI:
302	case IFT_INFINIBAND:
303	case IFT_ISO88023:
304	case IFT_ISO88024:
305	case IFT_L2VLAN:
306	case IFT_BRIDGE:
307		return (1);
308	default:
309		return (0);
310	}
311}
312
313/*
314 * Set an individual arp entry
315 */
316static int
317set(int argc, char **argv)
318{
319	struct sockaddr_in *addr;
320	struct sockaddr_in *dst;	/* what are we looking for */
321	struct sockaddr_dl *sdl;
322	struct rt_msghdr *rtm;
323	struct ether_addr *ea;
324	char *host = argv[0], *eaddr = argv[1];
325	struct sockaddr_dl sdl_m;
326
327	argc -= 2;
328	argv += 2;
329
330	bzero(&sdl_m, sizeof(sdl_m));
331	sdl_m.sdl_len = sizeof(sdl_m);
332	sdl_m.sdl_family = AF_LINK;
333
334	dst = getaddr(host);
335	if (dst == NULL)
336		return (1);
337	doing_proxy = flags = expire_time = 0;
338	while (argc-- > 0) {
339		if (strcmp(argv[0], "temp") == 0) {
340			struct timespec tp;
341			int max_age;
342			size_t len = sizeof(max_age);
343
344			clock_gettime(CLOCK_MONOTONIC, &tp);
345			if (sysctlbyname("net.link.ether.inet.max_age",
346			    &max_age, &len, NULL, 0) != 0)
347				xo_err(1, "sysctlbyname");
348			expire_time = tp.tv_sec + max_age;
349		} else if (strcmp(argv[0], "pub") == 0) {
350			flags |= RTF_ANNOUNCE;
351			doing_proxy = 1;
352			if (argc && strcmp(argv[1], "only") == 0) {
353				/*
354				 * Compatibility: in pre FreeBSD 8 times
355				 * the "only" keyword used to mean that
356				 * an ARP entry should be announced, but
357				 * not installed into routing table.
358				 */
359				argc--; argv++;
360			}
361		} else if (strcmp(argv[0], "blackhole") == 0) {
362			if (flags & RTF_REJECT) {
363				xo_errx(1, "Choose one of blackhole or reject, "
364				    "not both.");
365			}
366			flags |= RTF_BLACKHOLE;
367		} else if (strcmp(argv[0], "reject") == 0) {
368			if (flags & RTF_BLACKHOLE) {
369				xo_errx(1, "Choose one of blackhole or reject, "
370				    "not both.");
371			}
372			flags |= RTF_REJECT;
373		} else {
374			xo_warnx("Invalid parameter '%s'", argv[0]);
375			usage();
376		}
377		argv++;
378	}
379	ea = (struct ether_addr *)LLADDR(&sdl_m);
380	if (doing_proxy && !strcmp(eaddr, "auto")) {
381		if (!get_ether_addr(dst->sin_addr.s_addr, ea)) {
382			xo_warnx("no interface found for %s",
383			       inet_ntoa(dst->sin_addr));
384			return (1);
385		}
386		sdl_m.sdl_alen = ETHER_ADDR_LEN;
387	} else {
388		struct ether_addr *ea1 = ether_aton(eaddr);
389
390		if (ea1 == NULL) {
391			xo_warnx("invalid Ethernet address '%s'", eaddr);
392			return (1);
393		} else {
394			*ea = *ea1;
395			sdl_m.sdl_alen = ETHER_ADDR_LEN;
396		}
397	}
398
399	/*
400	 * In the case a proxy-arp entry is being added for
401	 * a remote end point, the RTF_ANNOUNCE flag in the
402	 * RTM_GET command is an indication to the kernel
403	 * routing code that the interface associated with
404	 * the prefix route covering the local end of the
405	 * PPP link should be returned, on which ARP applies.
406	 */
407	rtm = rtmsg(RTM_GET, dst, NULL);
408	if (rtm == NULL) {
409		xo_warn("%s", host);
410		return (1);
411	}
412	addr = (struct sockaddr_in *)(rtm + 1);
413	sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr);
414
415	if ((sdl->sdl_family != AF_LINK) ||
416	    (rtm->rtm_flags & RTF_GATEWAY) ||
417	    !valid_type(sdl->sdl_type)) {
418		xo_warnx("cannot intuit interface index and type for %s", host);
419		return (1);
420	}
421	sdl_m.sdl_type = sdl->sdl_type;
422	sdl_m.sdl_index = sdl->sdl_index;
423	return (rtmsg(RTM_ADD, dst, &sdl_m) == NULL);
424}
425
426/*
427 * Display an individual arp entry
428 */
429static int
430get(char *host)
431{
432	struct sockaddr_in *addr;
433	int found;
434
435	addr = getaddr(host);
436	if (addr == NULL)
437		return (1);
438
439	xo_set_version(ARP_XO_VERSION);
440	xo_open_container("arp");
441	xo_open_list("arp-cache");
442
443	found = search(addr->sin_addr.s_addr, print_entry);
444
445	if (found == 0) {
446		xo_emit("{d:hostname/%s} ({d:ip-address/%s}) -- no entry",
447		    host, inet_ntoa(addr->sin_addr));
448		if (rifname)
449			xo_emit(" on {d:interface/%s}", rifname);
450		xo_emit("\n");
451	}
452
453	xo_close_list("arp-cache");
454	xo_close_container("arp");
455	xo_finish();
456
457	return (found == 0);
458}
459
460/*
461 * Delete an arp entry
462 */
463static int
464delete(char *host)
465{
466	struct sockaddr_in *addr, *dst;
467	struct rt_msghdr *rtm;
468	struct sockaddr_dl *sdl;
469
470	dst = getaddr(host);
471	if (dst == NULL)
472		return (1);
473
474	/*
475	 * Perform a regular entry delete first.
476	 */
477	flags &= ~RTF_ANNOUNCE;
478
479	for (;;) {	/* try twice */
480		rtm = rtmsg(RTM_GET, dst, NULL);
481		if (rtm == NULL) {
482			xo_warn("%s", host);
483			return (1);
484		}
485		addr = (struct sockaddr_in *)(rtm + 1);
486		sdl = (struct sockaddr_dl *)(SA_SIZE(addr) + (char *)addr);
487
488		/*
489		 * With the new L2/L3 restructure, the route
490		 * returned is a prefix route. The important
491		 * piece of information from the previous
492		 * RTM_GET is the interface index. In the
493		 * case of ECMP, the kernel will traverse
494		 * the route group for the given entry.
495		 */
496		if (sdl->sdl_family == AF_LINK &&
497		    !(rtm->rtm_flags & RTF_GATEWAY) &&
498		    valid_type(sdl->sdl_type) ) {
499			addr->sin_addr.s_addr = dst->sin_addr.s_addr;
500			break;
501		}
502
503		/*
504		 * Regular entry delete failed, now check if there
505		 * is a proxy-arp entry to remove.
506		 */
507		if (flags & RTF_ANNOUNCE) {
508			xo_warnx("delete: cannot locate %s", host);
509			return (1);
510		}
511
512		flags |= RTF_ANNOUNCE;
513	}
514	rtm->rtm_flags |= RTF_LLDATA;
515	if (rtmsg(RTM_DELETE, dst, NULL) != NULL) {
516		printf("%s (%s) deleted\n", host, inet_ntoa(addr->sin_addr));
517		return (0);
518	}
519	return (1);
520}
521
522
523/*
524 * Search the arp table and do some action on matching entries
525 */
526static int
527search(u_long addr, action_fn *action)
528{
529	int mib[6];
530	size_t needed;
531	char *lim, *buf, *next;
532	struct rt_msghdr *rtm;
533	struct sockaddr_in *sin2;
534	struct sockaddr_dl *sdl;
535	char ifname[IF_NAMESIZE];
536	int st, found_entry = 0;
537
538	mib[0] = CTL_NET;
539	mib[1] = PF_ROUTE;
540	mib[2] = 0;
541	mib[3] = AF_INET;
542	mib[4] = NET_RT_FLAGS;
543#ifdef RTF_LLINFO
544	mib[5] = RTF_LLINFO;
545#else
546	mib[5] = 0;
547#endif
548	if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
549		xo_err(1, "route-sysctl-estimate");
550	if (needed == 0)	/* empty table */
551		return 0;
552	buf = NULL;
553	for (;;) {
554		buf = reallocf(buf, needed);
555		if (buf == NULL)
556			xo_errx(1, "could not reallocate memory");
557		st = sysctl(mib, 6, buf, &needed, NULL, 0);
558		if (st == 0 || errno != ENOMEM)
559			break;
560		needed += needed / 8;
561	}
562	if (st == -1)
563		xo_err(1, "actual retrieval of routing table");
564	lim = buf + needed;
565	for (next = buf; next < lim; next += rtm->rtm_msglen) {
566		rtm = (struct rt_msghdr *)next;
567		sin2 = (struct sockaddr_in *)(rtm + 1);
568		sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2));
569		if (rifname && if_indextoname(sdl->sdl_index, ifname) &&
570		    strcmp(ifname, rifname))
571			continue;
572		if (addr) {
573			if (addr != sin2->sin_addr.s_addr)
574				continue;
575			found_entry = 1;
576		}
577		(*action)(sdl, sin2, rtm);
578	}
579	free(buf);
580	return (found_entry);
581}
582
583/*
584 * Display an arp entry
585 */
586
587static void
588print_entry(struct sockaddr_dl *sdl,
589	struct sockaddr_in *addr, struct rt_msghdr *rtm)
590{
591	const char *host;
592	struct hostent *hp;
593	struct if_nameindex *p;
594
595	if (ifnameindex == NULL)
596		if ((ifnameindex = if_nameindex()) == NULL)
597			xo_err(1, "cannot retrieve interface names");
598
599	xo_open_instance("arp-cache");
600
601	if (nflag == 0)
602		hp = gethostbyaddr((caddr_t)&(addr->sin_addr),
603		    sizeof addr->sin_addr, AF_INET);
604	else
605		hp = 0;
606	if (hp)
607		host = hp->h_name;
608	else {
609		host = "?";
610		if (h_errno == TRY_AGAIN)
611			nflag = 1;
612	}
613	xo_emit("{:hostname/%s} ({:ip-address/%s}) at ", host,
614	    inet_ntoa(addr->sin_addr));
615	if (sdl->sdl_alen) {
616		if ((sdl->sdl_type == IFT_ETHER ||
617		    sdl->sdl_type == IFT_L2VLAN ||
618		    sdl->sdl_type == IFT_BRIDGE) &&
619		    sdl->sdl_alen == ETHER_ADDR_LEN)
620			xo_emit("{:mac-address/%s}",
621			    ether_ntoa((struct ether_addr *)LLADDR(sdl)));
622		else {
623			int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0;
624
625			xo_emit("{:mac-address/%s}", link_ntoa(sdl) + n);
626		}
627	} else
628		xo_emit("{d:/(incomplete)}{en:incomplete/true}");
629
630	for (p = ifnameindex; p && ifnameindex->if_index &&
631	    ifnameindex->if_name; p++) {
632		if (p->if_index == sdl->sdl_index) {
633			xo_emit(" on {:interface/%s}", p->if_name);
634			break;
635		}
636	}
637
638	if (rtm->rtm_rmx.rmx_expire == 0)
639		xo_emit("{d:/ permanent}{en:permanent/true}");
640	else {
641		static struct timespec tp;
642		if (tp.tv_sec == 0)
643			clock_gettime(CLOCK_MONOTONIC, &tp);
644		if ((expire_time = rtm->rtm_rmx.rmx_expire - tp.tv_sec) > 0)
645			xo_emit(" expires in {:expires/%d} seconds",
646			    (int)expire_time);
647		else
648			xo_emit("{d:/ expired}{en:expired/true}");
649	}
650
651	if (rtm->rtm_flags & RTF_ANNOUNCE)
652		xo_emit("{d:/ published}{en:published/true}");
653
654	switch(sdl->sdl_type) {
655	case IFT_ETHER:
656		xo_emit(" [{:type/ethernet}]");
657		break;
658	case IFT_FDDI:
659		xo_emit(" [{:type/fddi}]");
660		break;
661	case IFT_ATM:
662		xo_emit(" [{:type/atm}]");
663		break;
664	case IFT_L2VLAN:
665		xo_emit(" [{:type/vlan}]");
666		break;
667	case IFT_IEEE1394:
668		xo_emit(" [{:type/firewire}]");
669		break;
670	case IFT_BRIDGE:
671		xo_emit(" [{:type/bridge}]");
672		break;
673	case IFT_INFINIBAND:
674		xo_emit(" [{:type/infiniband}]");
675		break;
676	default:
677		break;
678	}
679
680	xo_emit("\n");
681
682	xo_close_instance("arp-cache");
683}
684
685/*
686 * Nuke an arp entry
687 */
688static void
689nuke_entry(struct sockaddr_dl *sdl __unused,
690	struct sockaddr_in *addr, struct rt_msghdr *rtm)
691{
692	char ip[20];
693
694	if (rtm->rtm_flags & RTF_PINNED)
695		return;
696
697	snprintf(ip, sizeof(ip), "%s", inet_ntoa(addr->sin_addr));
698	delete(ip);
699}
700
701static void
702usage(void)
703{
704	fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n",
705	    "usage: arp [-n] [-i interface] hostname",
706	    "       arp [-n] [-i interface] -a",
707	    "       arp -d hostname [pub]",
708	    "       arp -d [-i interface] -a",
709	    "       arp -s hostname ether_addr [temp] [reject | blackhole] [pub [only]]",
710	    "       arp -S hostname ether_addr [temp] [reject | blackhole] [pub [only]]",
711	    "       arp -f filename");
712	exit(1);
713}
714
715static struct rt_msghdr *
716rtmsg(int cmd, struct sockaddr_in *dst, struct sockaddr_dl *sdl)
717{
718	static int seq;
719	int rlen;
720	int l;
721	struct sockaddr_in so_mask, *som = &so_mask;
722	static int s = -1;
723	static pid_t pid;
724
725	static struct	{
726		struct	rt_msghdr m_rtm;
727		char	m_space[512];
728	}	m_rtmsg;
729
730	struct rt_msghdr *rtm = &m_rtmsg.m_rtm;
731	char *cp = m_rtmsg.m_space;
732
733	if (s < 0) {	/* first time: open socket, get pid */
734		s = socket(PF_ROUTE, SOCK_RAW, 0);
735		if (s < 0)
736			xo_err(1, "socket");
737		pid = getpid();
738	}
739	bzero(&so_mask, sizeof(so_mask));
740	so_mask.sin_len = 8;
741	so_mask.sin_addr.s_addr = 0xffffffff;
742
743	errno = 0;
744	/*
745	 * XXX RTM_DELETE relies on a previous RTM_GET to fill the buffer
746	 * appropriately.
747	 */
748	if (cmd == RTM_DELETE)
749		goto doit;
750	bzero((char *)&m_rtmsg, sizeof(m_rtmsg));
751	rtm->rtm_flags = flags;
752	rtm->rtm_version = RTM_VERSION;
753
754	switch (cmd) {
755	default:
756		xo_errx(1, "internal wrong cmd");
757	case RTM_ADD:
758		rtm->rtm_addrs |= RTA_GATEWAY;
759		rtm->rtm_rmx.rmx_expire = expire_time;
760		rtm->rtm_inits = RTV_EXPIRE;
761		rtm->rtm_flags |= (RTF_HOST | RTF_STATIC | RTF_LLDATA);
762		if (doing_proxy) {
763			rtm->rtm_addrs |= RTA_NETMASK;
764			rtm->rtm_flags &= ~RTF_HOST;
765		}
766		/* FALLTHROUGH */
767	case RTM_GET:
768		rtm->rtm_addrs |= RTA_DST;
769	}
770#define NEXTADDR(w, s)						\
771	do {							\
772		if ((s) != NULL && rtm->rtm_addrs & (w)) {	\
773			bcopy((s), cp, sizeof(*(s)));		\
774			cp += SA_SIZE(s);			\
775		}						\
776	} while (0)
777
778	NEXTADDR(RTA_DST, dst);
779	NEXTADDR(RTA_GATEWAY, sdl);
780	NEXTADDR(RTA_NETMASK, som);
781
782	rtm->rtm_msglen = cp - (char *)&m_rtmsg;
783doit:
784	l = rtm->rtm_msglen;
785	rtm->rtm_seq = ++seq;
786	rtm->rtm_type = cmd;
787	if ((rlen = write(s, (char *)&m_rtmsg, l)) < 0) {
788		if (errno != ESRCH || cmd != RTM_DELETE) {
789			xo_warn("writing to routing socket");
790			return (NULL);
791		}
792	}
793	do {
794		l = read(s, (char *)&m_rtmsg, sizeof(m_rtmsg));
795	} while (l > 0 && (rtm->rtm_type != cmd || rtm->rtm_seq != seq ||
796	    rtm->rtm_pid != pid));
797	if (l < 0)
798		xo_warn("read from routing socket");
799	return (rtm);
800}
801
802/*
803 * get_ether_addr - get the hardware address of an interface on the
804 * the same subnet as ipaddr.
805 */
806#define MAX_IFS		32
807
808static int
809get_ether_addr(in_addr_t ipaddr, struct ether_addr *hwaddr)
810{
811	struct ifreq *ifr, *ifend, *ifp;
812	in_addr_t ina, mask;
813	struct sockaddr_dl *dla;
814	struct ifreq ifreq;
815	struct ifconf ifc;
816	struct ifreq ifs[MAX_IFS];
817	int sock;
818	int retval = 0;
819
820	sock = socket(AF_INET, SOCK_DGRAM, 0);
821	if (sock < 0)
822		xo_err(1, "socket");
823
824	ifc.ifc_len = sizeof(ifs);
825	ifc.ifc_req = ifs;
826	if (ioctl(sock, SIOCGIFCONF, &ifc) < 0) {
827		xo_warnx("ioctl(SIOCGIFCONF)");
828		goto done;
829	}
830
831#define NEXTIFR(i)						\
832	((struct ifreq *)((char *)&(i)->ifr_addr		\
833	+ MAX((i)->ifr_addr.sa_len, sizeof((i)->ifr_addr))) )
834
835	/*
836	 * Scan through looking for an interface with an Internet
837	 * address on the same subnet as `ipaddr'.
838	 */
839	ifend = (struct ifreq *)(ifc.ifc_buf + ifc.ifc_len);
840	for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr) ) {
841		if (ifr->ifr_addr.sa_family != AF_INET)
842			continue;
843		strncpy(ifreq.ifr_name, ifr->ifr_name,
844			sizeof(ifreq.ifr_name));
845		ifreq.ifr_addr = ifr->ifr_addr;
846		/*
847		 * Check that the interface is up,
848		 * and not point-to-point or loopback.
849		 */
850		if (ioctl(sock, SIOCGIFFLAGS, &ifreq) < 0)
851			continue;
852		if ((ifreq.ifr_flags &
853		    (IFF_UP|IFF_BROADCAST|IFF_POINTOPOINT|
854		    IFF_LOOPBACK|IFF_NOARP)) != (IFF_UP|IFF_BROADCAST))
855			continue;
856		/* Get its netmask and check that it's on the right subnet. */
857		if (ioctl(sock, SIOCGIFNETMASK, &ifreq) < 0)
858			continue;
859		mask = ((struct sockaddr_in *)
860			&ifreq.ifr_addr)->sin_addr.s_addr;
861		ina = ((struct sockaddr_in *)
862			&ifr->ifr_addr)->sin_addr.s_addr;
863		if ((ipaddr & mask) == (ina & mask))
864			break; /* ok, we got it! */
865	}
866
867	if (ifr >= ifend)
868		goto done;
869
870	/*
871	 * Now scan through again looking for a link-level address
872	 * for this interface.
873	 */
874	ifp = ifr;
875	for (ifr = ifc.ifc_req; ifr < ifend; ifr = NEXTIFR(ifr))
876		if (strcmp(ifp->ifr_name, ifr->ifr_name) == 0 &&
877		    ifr->ifr_addr.sa_family == AF_LINK)
878			break;
879	if (ifr >= ifend)
880		goto done;
881	/*
882	 * Found the link-level address - copy it out
883	 */
884	dla = (struct sockaddr_dl *) &ifr->ifr_addr;
885	memcpy(hwaddr,  LLADDR(dla), dla->sdl_alen);
886	printf("using interface %s for proxy with address %s\n", ifp->ifr_name,
887	    ether_ntoa(hwaddr));
888	retval = dla->sdl_alen;
889done:
890	close(sock);
891	return (retval);
892}
893