xref: /netbsd-src/sys/net/if_arcsubr.c (revision 21e37cc72a480a47828990a439cde7ac9ffaf0c6)
1 /*	$NetBSD: if_arcsubr.c,v 1.45 2004/03/25 10:53:46 is Exp $	*/
2 
3 /*
4  * Copyright (c) 1994, 1995 Ignatios Souvatzis
5  * Copyright (c) 1982, 1989, 1993
6  *	The Regents of the University of California.  All rights reserved.
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. Neither the name of the University nor the names of its contributors
17  *    may be used to endorse or promote products derived from this software
18  *    without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30  * SUCH DAMAGE.
31  *
32  * from: NetBSD: if_ethersubr.c,v 1.9 1994/06/29 06:36:11 cgd Exp
33  *       @(#)if_ethersubr.c	8.1 (Berkeley) 6/10/93
34  *
35  */
36 
37 #include <sys/cdefs.h>
38 __KERNEL_RCSID(0, "$NetBSD: if_arcsubr.c,v 1.45 2004/03/25 10:53:46 is Exp $");
39 
40 #include "opt_inet.h"
41 
42 #include "bpfilter.h"
43 
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/kernel.h>
47 #include <sys/malloc.h>
48 #include <sys/mbuf.h>
49 #include <sys/protosw.h>
50 #include <sys/socket.h>
51 #include <sys/ioctl.h>
52 #include <sys/errno.h>
53 #include <sys/syslog.h>
54 
55 #include <machine/cpu.h>
56 
57 #include <net/if.h>
58 #include <net/netisr.h>
59 #include <net/route.h>
60 #include <net/if_dl.h>
61 #include <net/if_types.h>
62 #include <net/if_arc.h>
63 #include <net/if_arp.h>
64 #include <net/if_ether.h>
65 
66 #if NBPFILTER > 0
67 #include <net/bpf.h>
68 #endif
69 
70 #ifdef INET
71 #include <netinet/in.h>
72 #include <netinet/in_var.h>
73 #include <netinet/if_inarp.h>
74 #endif
75 
76 #ifdef INET6
77 #ifndef INET
78 #include <netinet/in.h>
79 #endif
80 #include <netinet6/in6_var.h>
81 #include <netinet6/nd6.h>
82 #endif
83 
84 #define ARCNET_ALLOW_BROKEN_ARP
85 
86 #ifndef ARC_IPMTU
87 #define ARC_IPMTU	1500
88 #endif
89 
90 static struct mbuf *arc_defrag __P((struct ifnet *, struct mbuf *));
91 
92 /*
93  * RC1201 requires us to have this configurable. We have it only per
94  * machine at the moment... there is no generic "set mtu" ioctl, AFAICS.
95  * Anyway, it is possible to binpatch this or set it per kernel config
96  * option.
97  */
98 #if ARC_IPMTU > 60480
99 ERROR: The arc_ipmtu is ARC_IPMTU, but must not exceed 60480.
100 #endif
101 int arc_ipmtu = ARC_IPMTU;
102 u_int8_t  arcbroadcastaddr = 0;
103 
104 #define senderr(e) { error = (e); goto bad;}
105 #define SIN(s) ((struct sockaddr_in *)s)
106 
107 static	int arc_output __P((struct ifnet *, struct mbuf *,
108 	    struct sockaddr *, struct rtentry *));
109 static	void arc_input __P((struct ifnet *, struct mbuf *));
110 
111 /*
112  * ARCnet output routine.
113  * Encapsulate a packet of type family for the local net.
114  * Assumes that ifp is actually pointer to arccom structure.
115  */
116 static int
117 arc_output(ifp, m0, dst, rt0)
118 	struct ifnet *ifp;
119 	struct mbuf *m0;
120 	struct sockaddr *dst;
121 	struct rtentry *rt0;
122 {
123 	struct mbuf		*m, *m1, *mcopy;
124 	struct rtentry		*rt;
125 	struct arccom		*ac;
126 	struct arc_header	*ah;
127 	struct arphdr		*arph;
128 	int			s, error, newencoding, len;
129 	u_int8_t		atype, adst, myself;
130 	int			tfrags, sflag, fsflag, rsflag;
131 	ALTQ_DECL(struct altq_pktattr pktattr;)
132 
133 	if ((ifp->if_flags & (IFF_UP|IFF_RUNNING)) != (IFF_UP|IFF_RUNNING))
134 		return (ENETDOWN); /* m, m1 aren't initialized yet */
135 
136 	error = newencoding = 0;
137 	ac = (struct arccom *)ifp;
138 	m = m0;
139 	mcopy = m1 = NULL;
140 
141 	myself = *LLADDR(ifp->if_sadl);
142 
143 	if ((rt = rt0)) {
144 		if ((rt->rt_flags & RTF_UP) == 0) {
145 			if ((rt0 = rt = rtalloc1(dst, 1)))
146 				rt->rt_refcnt--;
147 			else
148 				senderr(EHOSTUNREACH);
149 		}
150 		if (rt->rt_flags & RTF_GATEWAY) {
151 			if (rt->rt_gwroute == 0)
152 				goto lookup;
153 			if (((rt = rt->rt_gwroute)->rt_flags & RTF_UP) == 0) {
154 				rtfree(rt); rt = rt0;
155 			lookup: rt->rt_gwroute = rtalloc1(rt->rt_gateway, 1);
156 				if ((rt = rt->rt_gwroute) == 0)
157 					senderr(EHOSTUNREACH);
158 			}
159 		}
160 		if (rt->rt_flags & RTF_REJECT)
161 			if (rt->rt_rmx.rmx_expire == 0 ||
162 			    time.tv_sec < rt->rt_rmx.rmx_expire)
163 				senderr(rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
164 	}
165 
166 	/*
167 	 * if the queueing discipline needs packet classification,
168 	 * do it before prepending link headers.
169 	 */
170 	IFQ_CLASSIFY(&ifp->if_snd, m, dst->sa_family, &pktattr);
171 
172 	switch (dst->sa_family) {
173 #ifdef INET
174 	case AF_INET:
175 
176 		/*
177 		 * For now, use the simple IP addr -> ARCnet addr mapping
178 		 */
179 		if (m->m_flags & (M_BCAST|M_MCAST))
180 			adst = arcbroadcastaddr; /* ARCnet broadcast address */
181 		else if (ifp->if_flags & IFF_NOARP)
182 			adst = ntohl(SIN(dst)->sin_addr.s_addr) & 0xFF;
183 		else if (!arpresolve(ifp, rt, m, dst, &adst))
184 			return 0;	/* not resolved yet */
185 
186 		/* If broadcasting on a simplex interface, loopback a copy */
187 		if ((m->m_flags & (M_BCAST|M_MCAST)) &&
188 		    (ifp->if_flags & IFF_SIMPLEX))
189 			mcopy = m_copy(m, 0, (int)M_COPYALL);
190 		if (ifp->if_flags & IFF_LINK0) {
191 			atype = ARCTYPE_IP;
192 			newencoding = 1;
193 		} else {
194 			atype = ARCTYPE_IP_OLD;
195 			newencoding = 0;
196 		}
197 		break;
198 
199 	case AF_ARP:
200 		arph = mtod(m, struct arphdr *);
201 		if (m->m_flags & M_BCAST)
202 			adst = arcbroadcastaddr;
203 		else
204 			adst = *ar_tha(arph);
205 
206 		arph->ar_hrd = htons(ARPHRD_ARCNET);
207 
208 		switch (ntohs(arph->ar_op)) {
209 		case ARPOP_REVREQUEST:
210 		case ARPOP_REVREPLY:
211 			if (!(ifp->if_flags & IFF_LINK0)) {
212 				printf("%s: can't handle af%d\n",
213 				    ifp->if_xname, dst->sa_family);
214 				senderr(EAFNOSUPPORT);
215 			}
216 
217 			atype = htons(ARCTYPE_REVARP);
218 			newencoding = 1;
219 			break;
220 
221 		case ARPOP_REQUEST:
222 		case ARPOP_REPLY:
223 		default:
224 			if (ifp->if_flags & IFF_LINK0) {
225 				atype = htons(ARCTYPE_ARP);
226 				newencoding = 1;
227 			} else {
228 				atype = htons(ARCTYPE_ARP_OLD);
229 				newencoding = 0;
230 			}
231 		}
232 #ifdef ARCNET_ALLOW_BROKEN_ARP
233 		/*
234 		 * XXX It's not clear per RFC826 if this is needed, but
235 		 * "assigned numbers" say this is wrong.
236 		 * However, e.g., AmiTCP 3.0Beta used it... we make this
237 		 * switchable for emergency cases. Not perfect, but...
238 		 */
239 		if (ifp->if_flags & IFF_LINK2)
240 			arph->ar_pro = atype - 1;
241 #endif
242 		break;
243 #endif
244 #ifdef INET6
245 	case AF_INET6:
246 		if (!nd6_storelladdr(ifp, rt, m, dst, (u_char *)&adst))
247 			return (0); /* it must be impossible, but... */
248 		atype = htons(ARCTYPE_INET6);
249 		newencoding = 1;
250 		break;
251 #endif
252 
253 	case AF_UNSPEC:
254 		ah = (struct arc_header *)dst->sa_data;
255  		adst = ah->arc_dhost;
256 		atype = ah->arc_type;
257 		break;
258 
259 	default:
260 		printf("%s: can't handle af%d\n", ifp->if_xname,
261 		    dst->sa_family);
262 		senderr(EAFNOSUPPORT);
263 	}
264 
265 	if (mcopy)
266 		(void) looutput(ifp, mcopy, dst, rt);
267 
268 	/*
269 	 * Add local net header.  If no space in first mbuf,
270 	 * allocate another.
271 	 *
272 	 * For ARCnet, this is just symbolic. The header changes
273 	 * form and position on its way into the hardware and out of
274 	 * the wire.  At this point, it contains source, destination and
275 	 * packet type.
276 	 */
277 	if (newencoding) {
278 		++ac->ac_seqid; /* make the seqid unique */
279 
280 		tfrags = (m->m_pkthdr.len + 503) / 504;
281 		fsflag = 2 * tfrags - 3;
282 		sflag = 0;
283 		rsflag = fsflag;
284 
285 		while (sflag < fsflag) {
286 			/* we CAN'T have short packets here */
287 			m1 = m_split(m, 504, M_DONTWAIT);
288 			if (m1 == 0)
289 				senderr(ENOBUFS);
290 
291 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
292 			if (m == 0)
293 				senderr(ENOBUFS);
294 			ah = mtod(m, struct arc_header *);
295 			ah->arc_type = atype;
296 			ah->arc_dhost = adst;
297 			ah->arc_shost = myself;
298 			ah->arc_flag = rsflag;
299 			ah->arc_seqid = ac->ac_seqid;
300 
301 			len = m->m_pkthdr.len;
302 			s = splnet();
303 			/*
304 			 * Queue message on interface, and start output if
305 			 * interface not yet active.
306 			 */
307 			IFQ_ENQUEUE(&ifp->if_snd, m, &pktattr, error);
308 			if (error) {
309 				/* mbuf is already freed */
310 				splx(s);
311 				return (error);
312 			}
313 			ifp->if_obytes += len;
314 			if ((ifp->if_flags & IFF_OACTIVE) == 0)
315 				(*ifp->if_start)(ifp);
316 			splx(s);
317 
318 			m = m1;
319 			sflag += 2;
320 			rsflag = sflag;
321 		}
322 		m1 = NULL;
323 
324 
325 		/* here we can have small, especially forbidden packets */
326 
327 		if ((m->m_pkthdr.len >=
328 		    ARC_MIN_FORBID_LEN - ARC_HDRNEWLEN + 2) &&
329 		    (m->m_pkthdr.len <=
330 		    ARC_MAX_FORBID_LEN - ARC_HDRNEWLEN + 2)) {
331 
332 			M_PREPEND(m, ARC_HDRNEWLEN_EXC, M_DONTWAIT);
333 			if (m == 0)
334 				senderr(ENOBUFS);
335 			ah = mtod(m, struct arc_header *);
336 			ah->arc_flag = 0xFF;
337 			ah->arc_seqid = 0xFFFF;
338 			ah->arc_type2 = atype;
339 			ah->arc_flag2 = sflag;
340 			ah->arc_seqid2 = ac->ac_seqid;
341 		} else {
342 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
343 			if (m == 0)
344 				senderr(ENOBUFS);
345 			ah = mtod(m, struct arc_header *);
346 			ah->arc_flag = sflag;
347 			ah->arc_seqid = ac->ac_seqid;
348 		}
349 
350 		ah->arc_dhost = adst;
351 		ah->arc_shost = myself;
352 		ah->arc_type = atype;
353 	} else {
354 		M_PREPEND(m, ARC_HDRLEN, M_DONTWAIT);
355 		if (m == 0)
356 			senderr(ENOBUFS);
357 		ah = mtod(m, struct arc_header *);
358 		ah->arc_type = atype;
359 		ah->arc_dhost = adst;
360 		ah->arc_shost = myself;
361 	}
362 
363 	len = m->m_pkthdr.len;
364 	s = splnet();
365 	/*
366 	 * Queue message on interface, and start output if interface
367 	 * not yet active.
368 	 */
369 	IFQ_ENQUEUE(&ifp->if_snd, m, &pktattr, error);
370 	if (error) {
371 		/* mbuf is already freed */
372 		splx(s);
373 		return (error);
374 	}
375 	ifp->if_obytes += len;
376 	if ((ifp->if_flags & IFF_OACTIVE) == 0)
377 		(*ifp->if_start)(ifp);
378 	splx(s);
379 
380 	return (error);
381 
382 bad:
383 	if (m1)
384 		m_freem(m1);
385 	if (m)
386 		m_freem(m);
387 	return (error);
388 }
389 
390 /*
391  * Defragmenter. Returns mbuf if last packet found, else
392  * NULL. frees imcoming mbuf as necessary.
393  */
394 
395 __inline struct mbuf *
396 arc_defrag(ifp, m)
397 	struct ifnet *ifp;
398 	struct mbuf *m;
399 {
400 	struct arc_header *ah, *ah1;
401 	struct arccom *ac;
402 	struct ac_frag *af;
403 	struct mbuf *m1;
404 	char *s;
405 	int newflen;
406 	u_char src, dst, typ;
407 
408 	ac = (struct arccom *)ifp;
409 
410 	if (m->m_len < ARC_HDRNEWLEN) {
411 		m = m_pullup(m, ARC_HDRNEWLEN);
412 		if (m == NULL) {
413 			++ifp->if_ierrors;
414 			return NULL;
415 		}
416 	}
417 
418 	ah = mtod(m, struct arc_header *);
419 	typ = ah->arc_type;
420 
421 	if (!arc_isphds(typ))
422 		return m;
423 
424 	src = ah->arc_shost;
425 	dst = ah->arc_dhost;
426 
427 	if (ah->arc_flag == 0xff) {
428 		m_adj(m, 4);
429 
430 		if (m->m_len < ARC_HDRNEWLEN) {
431 			m = m_pullup(m, ARC_HDRNEWLEN);
432 			if (m == NULL) {
433 				++ifp->if_ierrors;
434 				return NULL;
435 			}
436 		}
437 
438 		ah = mtod(m, struct arc_header *);
439 	}
440 
441 	af = &ac->ac_fragtab[src];
442 	m1 = af->af_packet;
443 	s = "debug code error";
444 
445 	if (ah->arc_flag & 1) {
446 		/*
447 		 * first fragment. We always initialize, which is
448 		 * about the right thing to do, as we only want to
449 		 * accept one fragmented packet per src at a time.
450 		 */
451 		if (m1 != NULL)
452 			m_freem(m1);
453 
454 		af->af_packet = m;
455 		m1 = m;
456 		af->af_maxflag = ah->arc_flag;
457 		af->af_lastseen = 0;
458 		af->af_seqid = ah->arc_seqid;
459 
460 		return NULL;
461 		/* notreached */
462 	} else {
463 		/* check for unfragmented packet */
464 		if (ah->arc_flag == 0)
465 			return m;
466 
467 		/* do we have a first packet from that src? */
468 		if (m1 == NULL) {
469 			s = "no first frag";
470 			goto outofseq;
471 		}
472 
473 		ah1 = mtod(m1, struct arc_header *);
474 
475 		if (ah->arc_seqid != ah1->arc_seqid) {
476 			s = "seqid differs";
477 			goto outofseq;
478 		}
479 
480 		if (typ != ah1->arc_type) {
481 			s = "type differs";
482 			goto outofseq;
483 		}
484 
485 		if (dst != ah1->arc_dhost) {
486 			s = "dest host differs";
487 			goto outofseq;
488 		}
489 
490 		/* typ, seqid and dst are ok here. */
491 
492 		if (ah->arc_flag == af->af_lastseen) {
493 			m_freem(m);
494 			return NULL;
495 		}
496 
497 		if (ah->arc_flag == af->af_lastseen + 2) {
498 			/* ok, this is next fragment */
499 			af->af_lastseen = ah->arc_flag;
500 			m_adj(m, ARC_HDRNEWLEN);
501 
502 			/*
503 			 * m_cat might free the first mbuf (with pkthdr)
504 			 * in 2nd chain; therefore:
505 			 */
506 
507 			newflen = m->m_pkthdr.len;
508 
509 			m_cat(m1, m);
510 
511 			m1->m_pkthdr.len += newflen;
512 
513 			/* is it the last one? */
514 			if (af->af_lastseen > af->af_maxflag) {
515 				af->af_packet = NULL;
516 				return (m1);
517 			} else
518 				return NULL;
519 		}
520 		s = "other reason";
521 		/* if all else fails, it is out of sequence, too */
522 	}
523 outofseq:
524 	if (m1) {
525 		m_freem(m1);
526 		af->af_packet = NULL;
527 	}
528 
529 	if (m)
530 		m_freem(m);
531 
532 	log(LOG_INFO,"%s: got out of seq. packet: %s\n",
533 	    ifp->if_xname, s);
534 
535 	return NULL;
536 }
537 
538 /*
539  * return 1 if Packet Header Definition Standard, else 0.
540  * For now: old IP, old ARP aren't obviously. Lacking correct information,
541  * we guess that besides new IP and new ARP also IPX and APPLETALK are PHDS.
542  * (Apple and Novell corporations were involved, among others, in PHDS work).
543  * Easiest is to assume that everybody else uses that, too.
544  */
545 int
546 arc_isphds(type)
547 	u_int8_t type;
548 {
549 	return (type != ARCTYPE_IP_OLD &&
550 		type != ARCTYPE_ARP_OLD &&
551 		type != ARCTYPE_DIAGNOSE);
552 }
553 
554 /*
555  * Process a received Arcnet packet;
556  * the packet is in the mbuf chain m with
557  * the ARCnet header.
558  */
559 static void
560 arc_input(ifp, m)
561 	struct ifnet *ifp;
562 	struct mbuf *m;
563 {
564 	struct arc_header *ah;
565 	struct ifqueue *inq;
566 	u_int8_t atype;
567 	int s;
568 
569 	if ((ifp->if_flags & IFF_UP) == 0) {
570 		m_freem(m);
571 		return;
572 	}
573 
574 	/* possibly defragment: */
575 	m = arc_defrag(ifp, m);
576 	if (m == NULL)
577 		return;
578 
579 	ah = mtod(m, struct arc_header *);
580 
581 	ifp->if_ibytes += m->m_pkthdr.len;
582 
583 	if (arcbroadcastaddr == ah->arc_dhost) {
584 		m->m_flags |= M_BCAST|M_MCAST;
585 		ifp->if_imcasts++;
586 	}
587 
588 	atype = ah->arc_type;
589 	switch (atype) {
590 #ifdef INET
591 	case ARCTYPE_IP:
592 		m_adj(m, ARC_HDRNEWLEN);
593 		schednetisr(NETISR_IP);
594 		inq = &ipintrq;
595 		break;
596 
597 	case ARCTYPE_IP_OLD:
598 		m_adj(m, ARC_HDRLEN);
599 		schednetisr(NETISR_IP);
600 		inq = &ipintrq;
601 		break;
602 
603 	case ARCTYPE_ARP:
604 		m_adj(m, ARC_HDRNEWLEN);
605 		schednetisr(NETISR_ARP);
606 		inq = &arpintrq;
607 #ifdef ARCNET_ALLOW_BROKEN_ARP
608 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
609 #endif
610 		break;
611 
612 	case ARCTYPE_ARP_OLD:
613 		m_adj(m, ARC_HDRLEN);
614 		schednetisr(NETISR_ARP);
615 		inq = &arpintrq;
616 #ifdef ARCNET_ALLOW_BROKEN_ARP
617 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
618 #endif
619 		break;
620 #endif
621 #ifdef INET6
622 	case ARCTYPE_INET6:
623 		m_adj(m, ARC_HDRNEWLEN);
624 		schednetisr(NETISR_IPV6);
625 		inq = &ip6intrq;
626 		break;
627 #endif
628 	default:
629 		m_freem(m);
630 		return;
631 	}
632 
633 	s = splnet();
634 	if (IF_QFULL(inq)) {
635 		IF_DROP(inq);
636 		m_freem(m);
637 	} else
638 		IF_ENQUEUE(inq, m);
639 	splx(s);
640 }
641 
642 /*
643  * Convert Arcnet address to printable (loggable) representation.
644  */
645 static char digits[] = "0123456789abcdef";
646 char *
647 arc_sprintf(ap)
648 	u_int8_t *ap;
649 {
650 	static char arcbuf[3];
651 	char *cp = arcbuf;
652 
653 	*cp++ = digits[*ap >> 4];
654 	*cp++ = digits[*ap++ & 0xf];
655 	*cp   = 0;
656 	return (arcbuf);
657 }
658 
659 /*
660  * Register (new) link level address.
661  */
662 void
663 arc_storelladdr(ifp, lla)
664 	struct ifnet *ifp;
665 	u_int8_t lla;
666 {
667 
668 	*(LLADDR(ifp->if_sadl)) = lla;
669 	ifp->if_mtu = ARC_PHDS_MAXMTU;
670 }
671 
672 /*
673  * Perform common duties while attaching to interface list
674  */
675 void
676 arc_ifattach(ifp, lla)
677 	struct ifnet *ifp;
678 	u_int8_t lla;
679 {
680 	struct arccom *ac;
681 
682 	ifp->if_type = IFT_ARCNET;
683 	ifp->if_addrlen = 1;
684 	ifp->if_hdrlen = ARC_HDRLEN;
685 	ifp->if_dlt = DLT_ARCNET;
686 	if (ifp->if_flags & IFF_BROADCAST)
687 		ifp->if_flags |= IFF_MULTICAST|IFF_ALLMULTI;
688 	if (ifp->if_flags & IFF_LINK0 && arc_ipmtu > ARC_PHDS_MAXMTU)
689 		log(LOG_ERR,
690 		    "%s: arc_ipmtu is %d, but must not exceed %d",
691 		    ifp->if_xname, arc_ipmtu, ARC_PHDS_MAXMTU);
692 
693 	ifp->if_output = arc_output;
694 	ifp->if_input = arc_input;
695 	ac = (struct arccom *)ifp;
696 	ac->ac_seqid = (time.tv_sec) & 0xFFFF; /* try to make seqid unique */
697 	if (lla == 0) {
698 		/* XXX this message isn't entirely clear, to me -- cgd */
699 		log(LOG_ERR,"%s: link address 0 reserved for broadcasts.  Please change it and ifconfig %s down up\n",
700 		   ifp->if_xname, ifp->if_xname);
701 	}
702 	if_attach(ifp);
703 	if_alloc_sadl(ifp);
704 	arc_storelladdr(ifp, lla);
705 
706 	ifp->if_broadcastaddr = &arcbroadcastaddr;
707 
708 #if NBPFILTER > 0
709 	bpfattach(ifp, DLT_ARCNET, ARC_HDRLEN);
710 #endif
711 }
712