xref: /netbsd-src/sys/net/if_ethersubr.c (revision d9158b13b5dfe46201430699a3f7a235ecf28df3)
1 /*
2  * Copyright (c) 1982, 1989, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  *	@(#)if_ethersubr.c	8.1 (Berkeley) 6/10/93
34  */
35 
36 #include <sys/param.h>
37 #include <sys/systm.h>
38 #include <sys/kernel.h>
39 #include <sys/malloc.h>
40 #include <sys/mbuf.h>
41 #include <sys/protosw.h>
42 #include <sys/socket.h>
43 #include <sys/ioctl.h>
44 #include <sys/errno.h>
45 #include <sys/syslog.h>
46 
47 #include <machine/cpu.h>
48 
49 #include <net/if.h>
50 #include <net/netisr.h>
51 #include <net/route.h>
52 #include <net/if_llc.h>
53 #include <net/if_dl.h>
54 #include <net/if_types.h>
55 
56 #ifdef INET
57 #include <netinet/in.h>
58 #include <netinet/in_var.h>
59 #endif
60 #include <netinet/if_ether.h>
61 
62 #ifdef NS
63 #include <netns/ns.h>
64 #include <netns/ns_if.h>
65 #endif
66 
67 #ifdef ISO
68 #include <netiso/argo_debug.h>
69 #include <netiso/iso.h>
70 #include <netiso/iso_var.h>
71 #include <netiso/iso_snpac.h>
72 #endif
73 
74 #ifdef LLC
75 #include <netccitt/dll.h>
76 #include <netccitt/llc_var.h>
77 #endif
78 
79 #if defined(LLC) && defined(CCITT)
80 extern struct ifqueue pkintrq;
81 #endif
82 
83 u_char	etherbroadcastaddr[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
84 extern	struct ifnet loif;
85 #define senderr(e) { error = (e); goto bad;}
86 
87 /*
88  * Ethernet output routine.
89  * Encapsulate a packet of type family for the local net.
90  * Use trailer local net encapsulation if enough data in first
91  * packet leaves a multiple of 512 bytes of data in remainder.
92  * Assumes that ifp is actually pointer to arpcom structure.
93  */
94 int
95 ether_output(ifp, m0, dst, rt0)
96 	register struct ifnet *ifp;
97 	struct mbuf *m0;
98 	struct sockaddr *dst;
99 	struct rtentry *rt0;
100 {
101 	u_short etype;
102 	int s, error = 0;
103  	u_char edst[6];
104 	register struct mbuf *m = m0;
105 	register struct rtentry *rt;
106 	struct mbuf *mcopy = (struct mbuf *)0;
107 	register struct ether_header *eh;
108 	int off, len = m->m_pkthdr.len;
109 	struct arpcom *ac = (struct arpcom *)ifp;
110 
111 	if ((ifp->if_flags & (IFF_UP|IFF_RUNNING)) != (IFF_UP|IFF_RUNNING))
112 		senderr(ENETDOWN);
113 	ifp->if_lastchange = time;
114 	if (rt = rt0) {
115 		if ((rt->rt_flags & RTF_UP) == 0) {
116 			if (rt0 = rt = rtalloc1(dst, 1))
117 				rt->rt_refcnt--;
118 			else
119 				senderr(EHOSTUNREACH);
120 		}
121 		if (rt->rt_flags & RTF_GATEWAY) {
122 			if (rt->rt_gwroute == 0)
123 				goto lookup;
124 			if (((rt = rt->rt_gwroute)->rt_flags & RTF_UP) == 0) {
125 				rtfree(rt); rt = rt0;
126 			lookup: rt->rt_gwroute = rtalloc1(rt->rt_gateway, 1);
127 				if ((rt = rt->rt_gwroute) == 0)
128 					senderr(EHOSTUNREACH);
129 			}
130 		}
131 		if (rt->rt_flags & RTF_REJECT)
132 			if (rt->rt_rmx.rmx_expire == 0 ||
133 			    time.tv_sec < rt->rt_rmx.rmx_expire)
134 				senderr(rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
135 	}
136 	switch (dst->sa_family) {
137 
138 #ifdef INET
139 	case AF_INET:
140 		if (!arpresolve(ac, rt, m, dst, edst))
141 			return (0);	/* if not yet resolved */
142 		/* If broadcasting on a simplex interface, loopback a copy */
143 		if ((m->m_flags & M_BCAST) && (ifp->if_flags & IFF_SIMPLEX))
144 			mcopy = m_copy(m, 0, (int)M_COPYALL);
145 		off = m->m_pkthdr.len - m->m_len;
146 		etype = ETHERTYPE_IP;
147 		break;
148 #endif
149 #ifdef NS
150 	case AF_NS:
151 		etype = ETHERTYPE_NS;
152  		bcopy((caddr_t)&(((struct sockaddr_ns *)dst)->sns_addr.x_host),
153 		    (caddr_t)edst, sizeof (edst));
154 		if (!bcmp((caddr_t)edst, (caddr_t)&ns_thishost, sizeof(edst)))
155 			return (looutput(ifp, m, dst, rt));
156 		/* If broadcasting on a simplex interface, loopback a copy */
157 		if ((m->m_flags & M_BCAST) && (ifp->if_flags & IFF_SIMPLEX))
158 			mcopy = m_copy(m, 0, (int)M_COPYALL);
159 		break;
160 #endif
161 #ifdef	ISO
162 	case AF_ISO: {
163 		int	snpalen;
164 		struct	llc *l;
165 		register struct sockaddr_dl *sdl;
166 
167 		if (rt && (sdl = (struct sockaddr_dl *)rt->rt_gateway) &&
168 		    sdl->sdl_family == AF_LINK && sdl->sdl_alen > 0) {
169 			bcopy(LLADDR(sdl), (caddr_t)edst, sizeof(edst));
170 		} else if (error =
171 			    iso_snparesolve(ifp, (struct sockaddr_iso *)dst,
172 					    (char *)edst, &snpalen))
173 			goto bad; /* Not Resolved */
174 		/* If broadcasting on a simplex interface, loopback a copy */
175 		if (*edst & 1)
176 			m->m_flags |= (M_BCAST|M_MCAST);
177 		if ((m->m_flags & M_BCAST) && (ifp->if_flags & IFF_SIMPLEX) &&
178 		    (mcopy = m_copy(m, 0, (int)M_COPYALL))) {
179 			M_PREPEND(mcopy, sizeof (*eh), M_DONTWAIT);
180 			if (mcopy) {
181 				eh = mtod(mcopy, struct ether_header *);
182 				bcopy((caddr_t)edst,
183 				      (caddr_t)eh->ether_dhost, sizeof (edst));
184 				bcopy((caddr_t)ac->ac_enaddr,
185 				      (caddr_t)eh->ether_shost, sizeof (edst));
186 			}
187 		}
188 		M_PREPEND(m, 3, M_DONTWAIT);
189 		if (m == NULL)
190 			return (0);
191 		etype = m->m_pkthdr.len;
192 		l = mtod(m, struct llc *);
193 		l->llc_dsap = l->llc_ssap = LLC_ISO_LSAP;
194 		l->llc_control = LLC_UI;
195 		len += 3;
196 		IFDEBUG(D_ETHER)
197 			int i;
198 			printf("unoutput: sending pkt to: ");
199 			for (i=0; i<6; i++)
200 				printf("%x ", edst[i] & 0xff);
201 			printf("\n");
202 		ENDDEBUG
203 		} break;
204 #endif /* ISO */
205 #ifdef	LLC
206 /*	case AF_NSAP: */
207 	case AF_CCITT: {
208 		register struct sockaddr_dl *sdl =
209 			(struct sockaddr_dl *) rt -> rt_gateway;
210 
211 		if (sdl && sdl->sdl_family == AF_LINK
212 		    && sdl->sdl_alen > 0) {
213 			bcopy(LLADDR(sdl), (char *)edst,
214 				sizeof(edst));
215 		} else goto bad; /* Not a link interface ? Funny ... */
216 		if ((ifp->if_flags & IFF_SIMPLEX) && (*edst & 1) &&
217 		    (mcopy = m_copy(m, 0, (int)M_COPYALL))) {
218 			M_PREPEND(mcopy, sizeof (*eh), M_DONTWAIT);
219 			if (mcopy) {
220 				eh = mtod(mcopy, struct ether_header *);
221 				bcopy((caddr_t)edst,
222 				      (caddr_t)eh->ether_dhost, sizeof (edst));
223 				bcopy((caddr_t)ac->ac_enaddr,
224 				      (caddr_t)eh->ether_shost, sizeof (edst));
225 			}
226 		}
227 		etype = m->m_pkthdr.len;
228 #ifdef LLC_DEBUG
229 		{
230 			int i;
231 			register struct llc *l = mtod(m, struct llc *);
232 
233 			printf("ether_output: sending LLC2 pkt to: ");
234 			for (i=0; i<6; i++)
235 				printf("%x ", edst[i] & 0xff);
236 			printf(" len 0x%x dsap 0x%x ssap 0x%x control 0x%x\n",
237 			       etype & 0xff, l->llc_dsap & 0xff, l->llc_ssap &0xff,
238 			       l->llc_control & 0xff);
239 
240 		}
241 #endif /* LLC_DEBUG */
242 		} break;
243 #endif /* LLC */
244 
245 	case AF_UNSPEC:
246 		eh = (struct ether_header *)dst->sa_data;
247  		bcopy((caddr_t)eh->ether_dhost, (caddr_t)edst, sizeof (edst));
248 		/* AF_UNSPEC doesn't swap the byte order of the ether_type. */
249 		etype = ntohs(eh->ether_type);
250 		break;
251 
252 	default:
253 		printf("%s%d: can't handle af%d\n", ifp->if_name, ifp->if_unit,
254 			dst->sa_family);
255 		senderr(EAFNOSUPPORT);
256 	}
257 
258 
259 	if (mcopy)
260 		(void) looutput(ifp, mcopy, dst, rt);
261 	/*
262 	 * Add local net header.  If no space in first mbuf,
263 	 * allocate another.
264 	 */
265 	M_PREPEND(m, sizeof (struct ether_header), M_DONTWAIT);
266 	if (m == 0)
267 		senderr(ENOBUFS);
268 	eh = mtod(m, struct ether_header *);
269 	etype = htons(etype);
270 	bcopy((caddr_t)&etype,(caddr_t)&eh->ether_type,
271 		sizeof(eh->ether_type));
272  	bcopy((caddr_t)edst, (caddr_t)eh->ether_dhost, sizeof (edst));
273  	bcopy((caddr_t)ac->ac_enaddr, (caddr_t)eh->ether_shost,
274 	    sizeof(eh->ether_shost));
275 	s = splimp();
276 	/*
277 	 * Queue message on interface, and start output if interface
278 	 * not yet active.
279 	 */
280 	if (IF_QFULL(&ifp->if_snd)) {
281 		IF_DROP(&ifp->if_snd);
282 		splx(s);
283 		senderr(ENOBUFS);
284 	}
285 	IF_ENQUEUE(&ifp->if_snd, m);
286 	if ((ifp->if_flags & IFF_OACTIVE) == 0)
287 		(*ifp->if_start)(ifp);
288 	splx(s);
289 	ifp->if_obytes += len + sizeof (struct ether_header);
290 	if (m->m_flags & M_MCAST)
291 		ifp->if_omcasts++;
292 	return (error);
293 
294 bad:
295 	if (m)
296 		m_freem(m);
297 	return (error);
298 }
299 
300 /*
301  * Process a received Ethernet packet;
302  * the packet is in the mbuf chain m without
303  * the ether header, which is provided separately.
304  */
305 void
306 ether_input(ifp, eh, m)
307 	struct ifnet *ifp;
308 	register struct ether_header *eh;
309 	struct mbuf *m;
310 {
311 	register struct ifqueue *inq;
312 	register struct llc *l;
313 	u_short etype;
314 	struct arpcom *ac = (struct arpcom *)ifp;
315 	int s;
316 
317 	if ((ifp->if_flags & IFF_UP) == 0) {
318 		m_freem(m);
319 		return;
320 	}
321 	ifp->if_lastchange = time;
322 	ifp->if_ibytes += m->m_pkthdr.len + sizeof (*eh);
323 	if (eh->ether_dhost[0] & 1) {
324 		if (bcmp((caddr_t)etherbroadcastaddr, (caddr_t)eh->ether_dhost,
325 		    sizeof(etherbroadcastaddr)) == 0)
326 			m->m_flags |= M_BCAST;
327 		else
328 			m->m_flags |= M_MCAST;
329 	}
330 	if (m->m_flags & (M_BCAST|M_MCAST))
331 		ifp->if_imcasts++;
332 
333 	etype = ntohs(eh->ether_type);
334 	switch (etype) {
335 #ifdef INET
336 	case ETHERTYPE_IP:
337 		schednetisr(NETISR_IP);
338 		inq = &ipintrq;
339 		break;
340 
341 	case ETHERTYPE_ARP:
342 		schednetisr(NETISR_ARP);
343 		inq = &arpintrq;
344 		break;
345 
346 	case ETHERTYPE_REVARP:
347 		revarpinput(m);	/* XXX queue? */
348 		return;
349 #endif
350 #ifdef NS
351 	case ETHERTYPE_NS:
352 		schednetisr(NETISR_NS);
353 		inq = &nsintrq;
354 		break;
355 
356 #endif
357 	default:
358 #if defined (ISO) || defined (LLC)
359 		if (eh->ether_type > ETHERMTU)
360 			goto dropanyway;
361 		l = mtod(m, struct llc *);
362 		switch (l->llc_dsap) {
363 #ifdef	ISO
364 		case LLC_ISO_LSAP:
365 			switch (l->llc_control) {
366 			case LLC_UI:
367 				/* LLC_UI_P forbidden in class 1 service */
368 				if ((l->llc_dsap == LLC_ISO_LSAP) &&
369 				    (l->llc_ssap == LLC_ISO_LSAP)) {
370 					/* LSAP for ISO */
371 					if (m->m_pkthdr.len > eh->ether_type)
372 						m_adj(m, eh->ether_type - m->m_pkthdr.len);
373 					m->m_data += 3;		/* XXX */
374 					m->m_len -= 3;		/* XXX */
375 					m->m_pkthdr.len -= 3;	/* XXX */
376 					M_PREPEND(m, sizeof *eh, M_DONTWAIT);
377 					if (m == 0)
378 						return;
379 					*mtod(m, struct ether_header *) = *eh;
380 					IFDEBUG(D_ETHER)
381 						printf("clnp packet");
382 					ENDDEBUG
383 					schednetisr(NETISR_ISO);
384 					inq = &clnlintrq;
385 					break;
386 				}
387 				goto dropanyway;
388 
389 			case LLC_XID:
390 			case LLC_XID_P:
391 				if(m->m_len < 6)
392 					goto dropanyway;
393 				l->llc_window = 0;
394 				l->llc_fid = 9;
395 				l->llc_class = 1;
396 				l->llc_dsap = l->llc_ssap = 0;
397 				/* Fall through to */
398 			case LLC_TEST:
399 			case LLC_TEST_P:
400 			{
401 				struct sockaddr sa;
402 				register struct ether_header *eh2;
403 				int i;
404 				u_char c = l->llc_dsap;
405 
406 				l->llc_dsap = l->llc_ssap;
407 				l->llc_ssap = c;
408 				if (m->m_flags & (M_BCAST | M_MCAST))
409 					bcopy((caddr_t)ac->ac_enaddr,
410 					      (caddr_t)eh->ether_dhost, 6);
411 				sa.sa_family = AF_UNSPEC;
412 				sa.sa_len = sizeof(sa);
413 				eh2 = (struct ether_header *)sa.sa_data;
414 				for (i = 0; i < 6; i++) {
415 					eh2->ether_shost[i] = c = eh->ether_dhost[i];
416 					eh2->ether_dhost[i] =
417 						eh->ether_dhost[i] = eh->ether_shost[i];
418 					eh->ether_shost[i] = c;
419 				}
420 				ifp->if_output(ifp, m, &sa, NULL);
421 				return;
422 			}
423 			default:
424 				m_freem(m);
425 				return;
426 			}
427 			break;
428 #endif /* ISO */
429 #ifdef LLC
430 		case LLC_X25_LSAP:
431 		{
432 			if (m->m_pkthdr.len > eh->ether_type)
433 				m_adj(m, eh->ether_type - m->m_pkthdr.len);
434 			M_PREPEND(m, sizeof(struct sdl_hdr) , M_DONTWAIT);
435 			if (m == 0)
436 				return;
437 			if ( !sdl_sethdrif(ifp, eh->ether_shost, LLC_X25_LSAP,
438 					    eh->ether_dhost, LLC_X25_LSAP, 6,
439 					    mtod(m, struct sdl_hdr *)))
440 				panic("ETHER cons addr failure");
441 			mtod(m, struct sdl_hdr *)->sdlhdr_len = eh->ether_type;
442 #ifdef LLC_DEBUG
443 				printf("llc packet\n");
444 #endif /* LLC_DEBUG */
445 			schednetisr(NETISR_CCITT);
446 			inq = &llcintrq;
447 			break;
448 		}
449 #endif /* LLC */
450 		dropanyway:
451 		default:
452 			m_freem(m);
453 			return;
454 		}
455 #else /* ISO || LLC */
456 	    m_freem(m);
457 	    return;
458 #endif /* ISO || LLC */
459 	}
460 
461 	s = splimp();
462 	if (IF_QFULL(inq)) {
463 		IF_DROP(inq);
464 		m_freem(m);
465 	} else
466 		IF_ENQUEUE(inq, m);
467 	splx(s);
468 }
469 
470 /*
471  * Convert Ethernet address to printable (loggable) representation.
472  */
473 static char digits[] = "0123456789abcdef";
474 char *
475 ether_sprintf(ap)
476 	register u_char *ap;
477 {
478 	register i;
479 	static char etherbuf[18];
480 	register char *cp = etherbuf;
481 
482 	for (i = 0; i < 6; i++) {
483 		*cp++ = digits[*ap >> 4];
484 		*cp++ = digits[*ap++ & 0xf];
485 		*cp++ = ':';
486 	}
487 	*--cp = 0;
488 	return (etherbuf);
489 }
490 
491 /*
492  * Perform common duties while attaching to interface list
493  */
494 void
495 ether_ifattach(ifp)
496 	register struct ifnet *ifp;
497 {
498 	register struct ifaddr *ifa;
499 	register struct sockaddr_dl *sdl;
500 
501 	ifp->if_type = IFT_ETHER;
502 	ifp->if_addrlen = 6;
503 	ifp->if_hdrlen = 14;
504 	ifp->if_mtu = ETHERMTU;
505 	for (ifa = ifp->if_addrlist; ifa; ifa = ifa->ifa_next)
506 		if ((sdl = (struct sockaddr_dl *)ifa->ifa_addr) &&
507 		    sdl->sdl_family == AF_LINK) {
508 			sdl->sdl_type = IFT_ETHER;
509 			sdl->sdl_alen = ifp->if_addrlen;
510 			bcopy((caddr_t)((struct arpcom *)ifp)->ac_enaddr,
511 			      LLADDR(sdl), ifp->if_addrlen);
512 			break;
513 		}
514 }
515 
516 u_char	ether_ipmulticast_min[6] = { 0x01, 0x00, 0x5e, 0x00, 0x00, 0x00 };
517 u_char	ether_ipmulticast_max[6] = { 0x01, 0x00, 0x5e, 0x7f, 0xff, 0xff };
518 /*
519  * Add an Ethernet multicast address or range of addresses to the list for a
520  * given interface.
521  */
522 int
523 ether_addmulti(ifr, ac)
524 	struct ifreq *ifr;
525 	register struct arpcom *ac;
526 {
527 	register struct ether_multi *enm;
528 	struct sockaddr_in *sin;
529 	u_char addrlo[6];
530 	u_char addrhi[6];
531 	int s = splimp();
532 
533 	switch (ifr->ifr_addr.sa_family) {
534 
535 	case AF_UNSPEC:
536 		bcopy(ifr->ifr_addr.sa_data, addrlo, 6);
537 		bcopy(addrlo, addrhi, 6);
538 		break;
539 
540 #ifdef INET
541 	case AF_INET:
542 		sin = (struct sockaddr_in *)&(ifr->ifr_addr);
543 		if (sin->sin_addr.s_addr == INADDR_ANY) {
544 			/*
545 			 * An IP address of INADDR_ANY means listen to all
546 			 * of the Ethernet multicast addresses used for IP.
547 			 * (This is for the sake of IP multicast routers.)
548 			 */
549 			bcopy(ether_ipmulticast_min, addrlo, 6);
550 			bcopy(ether_ipmulticast_max, addrhi, 6);
551 		}
552 		else {
553 			ETHER_MAP_IP_MULTICAST(&sin->sin_addr, addrlo);
554 			bcopy(addrlo, addrhi, 6);
555 		}
556 		break;
557 #endif
558 
559 	default:
560 		splx(s);
561 		return (EAFNOSUPPORT);
562 	}
563 
564 	/*
565 	 * Verify that we have valid Ethernet multicast addresses.
566 	 */
567 	if ((addrlo[0] & 0x01) != 1 || (addrhi[0] & 0x01) != 1) {
568 		splx(s);
569 		return (EINVAL);
570 	}
571 	/*
572 	 * See if the address range is already in the list.
573 	 */
574 	ETHER_LOOKUP_MULTI(addrlo, addrhi, ac, enm);
575 	if (enm != NULL) {
576 		/*
577 		 * Found it; just increment the reference count.
578 		 */
579 		++enm->enm_refcount;
580 		splx(s);
581 		return (0);
582 	}
583 	/*
584 	 * New address or range; malloc a new multicast record
585 	 * and link it into the interface's multicast list.
586 	 */
587 	enm = (struct ether_multi *)malloc(sizeof(*enm), M_IFMADDR, M_NOWAIT);
588 	if (enm == NULL) {
589 		splx(s);
590 		return (ENOBUFS);
591 	}
592 	bcopy(addrlo, enm->enm_addrlo, 6);
593 	bcopy(addrhi, enm->enm_addrhi, 6);
594 	enm->enm_ac = ac;
595 	enm->enm_refcount = 1;
596 	enm->enm_next = ac->ac_multiaddrs;
597 	ac->ac_multiaddrs = enm;
598 	ac->ac_multicnt++;
599 	splx(s);
600 	/*
601 	 * Return ENETRESET to inform the driver that the list has changed
602 	 * and its reception filter should be adjusted accordingly.
603 	 */
604 	return (ENETRESET);
605 }
606 
607 /*
608  * Delete a multicast address record.
609  */
610 int
611 ether_delmulti(ifr, ac)
612 	struct ifreq *ifr;
613 	register struct arpcom *ac;
614 {
615 	register struct ether_multi *enm;
616 	register struct ether_multi **p;
617 	struct sockaddr_in *sin;
618 	u_char addrlo[6];
619 	u_char addrhi[6];
620 	int s = splimp();
621 
622 	switch (ifr->ifr_addr.sa_family) {
623 
624 	case AF_UNSPEC:
625 		bcopy(ifr->ifr_addr.sa_data, addrlo, 6);
626 		bcopy(addrlo, addrhi, 6);
627 		break;
628 
629 #ifdef INET
630 	case AF_INET:
631 		sin = (struct sockaddr_in *)&(ifr->ifr_addr);
632 		if (sin->sin_addr.s_addr == INADDR_ANY) {
633 			/*
634 			 * An IP address of INADDR_ANY means stop listening
635 			 * to the range of Ethernet multicast addresses used
636 			 * for IP.
637 			 */
638 			bcopy(ether_ipmulticast_min, addrlo, 6);
639 			bcopy(ether_ipmulticast_max, addrhi, 6);
640 		}
641 		else {
642 			ETHER_MAP_IP_MULTICAST(&sin->sin_addr, addrlo);
643 			bcopy(addrlo, addrhi, 6);
644 		}
645 		break;
646 #endif
647 
648 	default:
649 		splx(s);
650 		return (EAFNOSUPPORT);
651 	}
652 
653 	/*
654 	 * Look up the address in our list.
655 	 */
656 	ETHER_LOOKUP_MULTI(addrlo, addrhi, ac, enm);
657 	if (enm == NULL) {
658 		splx(s);
659 		return (ENXIO);
660 	}
661 	if (--enm->enm_refcount != 0) {
662 		/*
663 		 * Still some claims to this record.
664 		 */
665 		splx(s);
666 		return (0);
667 	}
668 	/*
669 	 * No remaining claims to this record; unlink and free it.
670 	 */
671 	for (p = &enm->enm_ac->ac_multiaddrs;
672 	     *p != enm;
673 	     p = &(*p)->enm_next)
674 		continue;
675 	*p = (*p)->enm_next;
676 	free(enm, M_IFMADDR);
677 	ac->ac_multicnt--;
678 	splx(s);
679 	/*
680 	 * Return ENETRESET to inform the driver that the list has changed
681 	 * and its reception filter should be adjusted accordingly.
682 	 */
683 	return (ENETRESET);
684 }
685