xref: /netbsd-src/sys/net/if_arcsubr.c (revision 4472dbe5e3bd91ef2540bada7a7ca7384627ff9b)
1 /*	$NetBSD: if_arcsubr.c,v 1.31 2000/04/12 10:36:38 itojun 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. All advertising materials mentioning features or use of this software
17  *    must display the following acknowledgement:
18  *	This product includes software developed by the University of
19  *	California, Berkeley and its contributors.
20  * 4. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  *
36  * from: NetBSD: if_ethersubr.c,v 1.9 1994/06/29 06:36:11 cgd Exp
37  *       @(#)if_ethersubr.c	8.1 (Berkeley) 6/10/93
38  *
39  */
40 #include "opt_inet.h"
41 
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
45 #include <sys/malloc.h>
46 #include <sys/mbuf.h>
47 #include <sys/protosw.h>
48 #include <sys/socket.h>
49 #include <sys/ioctl.h>
50 #include <sys/errno.h>
51 #include <sys/syslog.h>
52 
53 #include <machine/cpu.h>
54 
55 #include <net/if.h>
56 #include <net/netisr.h>
57 #include <net/route.h>
58 #include <net/if_dl.h>
59 #include <net/if_types.h>
60 #include <net/if_arc.h>
61 #include <net/if_arp.h>
62 #include <net/if_ether.h>
63 
64 #ifdef INET
65 #include <netinet/in.h>
66 #include <netinet/in_var.h>
67 #include <netinet/if_inarp.h>
68 #endif
69 
70 #ifdef INET6
71 #ifndef INET
72 #include <netinet/in.h>
73 #endif
74 #include <netinet6/in6_var.h>
75 #include <netinet6/nd6.h>
76 #endif
77 
78 #define ARCNET_ALLOW_BROKEN_ARP
79 
80 #ifndef ARC_IPMTU
81 #define ARC_IPMTU	1500
82 #endif
83 
84 static struct mbuf *arc_defrag __P((struct ifnet *, struct mbuf *));
85 
86 /*
87  * RC1201 requires us to have this configurable. We have it only per
88  * machine at the moment... there is no generic "set mtu" ioctl, AFAICS.
89  * Anyway, it is possible to binpatch this or set it per kernel config
90  * option.
91  */
92 #if ARC_IPMTU > 60480
93 ERROR: The arc_ipmtu is ARC_IPMTU, but must not exceed 60480.
94 #endif
95 int arc_ipmtu = ARC_IPMTU;
96 u_int8_t  arcbroadcastaddr = 0;
97 
98 #define senderr(e) { error = (e); goto bad;}
99 #define SIN(s) ((struct sockaddr_in *)s)
100 
101 static	int arc_output __P((struct ifnet *, struct mbuf *,
102 	    struct sockaddr *, struct rtentry *));
103 static	void arc_input __P((struct ifnet *, struct mbuf *));
104 
105 /*
106  * ARCnet output routine.
107  * Encapsulate a packet of type family for the local net.
108  * Assumes that ifp is actually pointer to arccom structure.
109  */
110 static int
111 arc_output(ifp, m0, dst, rt0)
112 	struct ifnet *ifp;
113 	struct mbuf *m0;
114 	struct sockaddr *dst;
115 	struct rtentry *rt0;
116 {
117 	struct mbuf		*m, *m1, *mcopy;
118 	struct rtentry		*rt;
119 	struct arccom		*ac;
120 	struct arc_header	*ah;
121 	struct arphdr		*arph;
122 	int			s, error, newencoding;
123 	u_int8_t		atype, adst, myself;
124 	int			tfrags, sflag, fsflag, rsflag;
125 
126 	if ((ifp->if_flags & (IFF_UP|IFF_RUNNING)) != (IFF_UP|IFF_RUNNING))
127 		return(ENETDOWN); /* m, m1 aren't initialized yet */
128 
129 	error = newencoding = 0;
130 	ac = (struct arccom *)ifp;
131 	m = m0;
132 	mcopy = m1 = NULL;
133 
134 	myself = *LLADDR(ifp->if_sadl);
135 
136 	ifp->if_lastchange = time;
137 	if ((rt = rt0)) {
138 		if ((rt->rt_flags & RTF_UP) == 0) {
139 			if ((rt0 = rt = rtalloc1(dst, 1)))
140 				rt->rt_refcnt--;
141 			else
142 				senderr(EHOSTUNREACH);
143 		}
144 		if (rt->rt_flags & RTF_GATEWAY) {
145 			if (rt->rt_gwroute == 0)
146 				goto lookup;
147 			if (((rt = rt->rt_gwroute)->rt_flags & RTF_UP) == 0) {
148 				rtfree(rt); rt = rt0;
149 			lookup: rt->rt_gwroute = rtalloc1(rt->rt_gateway, 1);
150 				if ((rt = rt->rt_gwroute) == 0)
151 					senderr(EHOSTUNREACH);
152 			}
153 		}
154 		if (rt->rt_flags & RTF_REJECT)
155 			if (rt->rt_rmx.rmx_expire == 0 ||
156 			    time.tv_sec < rt->rt_rmx.rmx_expire)
157 				senderr(rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
158 	}
159 
160 	switch (dst->sa_family) {
161 #ifdef INET
162 	case AF_INET:
163 
164 		/*
165 		 * For now, use the simple IP addr -> ARCnet addr mapping
166 		 */
167 		if (m->m_flags & (M_BCAST|M_MCAST))
168 			adst = arcbroadcastaddr; /* ARCnet broadcast address */
169 		else if (ifp->if_flags & IFF_NOARP)
170 			adst = ntohl(SIN(dst)->sin_addr.s_addr) & 0xFF;
171 		else if (!arpresolve(ifp, rt, m, dst, &adst))
172 			return 0;	/* not resolved yet */
173 
174 		/* If broadcasting on a simplex interface, loopback a copy */
175 		if ((m->m_flags & (M_BCAST|M_MCAST)) &&
176 		    (ifp->if_flags & IFF_SIMPLEX))
177 			mcopy = m_copy(m, 0, (int)M_COPYALL);
178 		if (ifp->if_flags & IFF_LINK0) {
179 			atype = ARCTYPE_IP;
180 			newencoding = 1;
181 		} else {
182 			atype = ARCTYPE_IP_OLD;
183 			newencoding = 0;
184 		}
185 		break;
186 
187 	case AF_ARP:
188 		arph = mtod(m, struct arphdr *);
189 		if (m->m_flags & M_BCAST)
190 			adst = arcbroadcastaddr;
191 		else
192 			adst = *ar_tha(arph);
193 
194 		arph->ar_hrd = htons(ARPHRD_ARCNET);
195 
196 		switch(ntohs(arph->ar_op)) {
197 
198 		case ARPOP_REVREQUEST:
199 		case ARPOP_REVREPLY:
200 			if (!(ifp->if_flags & IFF_LINK0)) {
201 				printf("%s: can't handle af%d\n",
202 				    ifp->if_xname, dst->sa_family);
203 				senderr(EAFNOSUPPORT);
204 			}
205 
206 			atype = htons(ARCTYPE_REVARP);
207 			newencoding = 1;
208 			break;
209 
210 		case ARPOP_REQUEST:
211 		case ARPOP_REPLY:
212 		default:
213 			if (ifp->if_flags & IFF_LINK0) {
214 				atype = htons(ARCTYPE_ARP);
215 				newencoding = 1;
216 			} else {
217 				atype = htons(ARCTYPE_ARP_OLD);
218 				newencoding = 0;
219 			}
220 		}
221 #ifdef ARCNET_ALLOW_BROKEN_ARP
222 		/*
223 		 * XXX It's not clear per RFC826 if this is needed, but
224 		 * "assigned numbers" say this is wrong.
225 		 * However, e.g., AmiTCP 3.0Beta used it... we make this
226 		 * switchable for emergency cases. Not perfect, but...
227 		 */
228 		if (ifp->if_flags & IFF_LINK2)
229 			arph->ar_pro = atype - 1;
230 #endif
231 		break;
232 #endif
233 #ifdef INET6
234 	case AF_INET6:
235 #ifdef OLDIP6OUTPUT
236 		if (!nd6_resolve(ifp, rt, m, dst, (u_char *)&adst))
237 			return(0);	/* if not yet resolves */
238 #else
239 		if (!nd6_storelladdr(ifp, rt, m, dst, (u_char *)&adst))
240 			return(0); /* it must be impossible, but... */
241 #endif /* OLDIP6OUTPUT */
242 		atype = htons(ARCTYPE_INET6);
243 		newencoding = 1;
244 		break;
245 #endif
246 
247 	case AF_UNSPEC:
248 		ah = (struct arc_header *)dst->sa_data;
249  		adst = ah->arc_dhost;
250 		atype = ah->arc_type;
251 		break;
252 
253 	default:
254 		printf("%s: can't handle af%d\n", ifp->if_xname,
255 		    dst->sa_family);
256 		senderr(EAFNOSUPPORT);
257 	}
258 
259 	if (mcopy)
260 		(void) looutput(ifp, mcopy, dst, rt);
261 
262 	/*
263 	 * Add local net header.  If no space in first mbuf,
264 	 * allocate another.
265 	 *
266 	 * For ARCnet, this is just symbolic. The header changes
267 	 * form and position on its way into the hardware and out of
268 	 * the wire.  At this point, it contains source, destination and
269 	 * packet type.
270 	 */
271 	if (newencoding) {
272 		++ac->ac_seqid; /* make the seqid unique */
273 
274 		tfrags = (m->m_pkthdr.len + 503) / 504;
275 		fsflag = 2 * tfrags - 3;
276 		sflag = 0;
277 		rsflag = fsflag;
278 
279 		while (sflag < fsflag) {
280 			/* we CAN'T have short packets here */
281 			m1 = m_split(m, 504, M_DONTWAIT);
282 			if (m1 == 0)
283 				senderr(ENOBUFS);
284 
285 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
286 			if (m == 0)
287 				senderr(ENOBUFS);
288 			ah = mtod(m, struct arc_header *);
289 			ah->arc_type = atype;
290 			ah->arc_dhost = adst;
291 			ah->arc_shost = myself;
292 			ah->arc_flag = rsflag;
293 			ah->arc_seqid = ac->ac_seqid;
294 
295 			s = splimp();
296 			/*
297 			 * Queue message on interface, and start output if
298 			 * interface not yet active.
299 			 */
300 			if (IF_QFULL(&ifp->if_snd)) {
301 				IF_DROP(&ifp->if_snd);
302 				splx(s);
303 				senderr(ENOBUFS);
304 			}
305 			ifp->if_obytes += m->m_pkthdr.len;
306 			IF_ENQUEUE(&ifp->if_snd, m);
307 			if ((ifp->if_flags & IFF_OACTIVE) == 0)
308 				(*ifp->if_start)(ifp);
309 			splx(s);
310 
311 			m = m1;
312 			sflag += 2;
313 			rsflag = sflag;
314 		}
315 		m1 = NULL;
316 
317 
318 		/* here we can have small, especially forbidden packets */
319 
320 		if ((m->m_pkthdr.len >=
321 		    ARC_MIN_FORBID_LEN - ARC_HDRNEWLEN + 2) &&
322 		    (m->m_pkthdr.len <=
323 		    ARC_MAX_FORBID_LEN - ARC_HDRNEWLEN + 2)) {
324 
325 			M_PREPEND(m, ARC_HDRNEWLEN_EXC, M_DONTWAIT);
326 			if (m == 0)
327 				senderr(ENOBUFS);
328 			ah = mtod(m, struct arc_header *);
329 			ah->arc_flag = 0xFF;
330 			ah->arc_seqid = 0xFFFF;
331 			ah->arc_type2 = atype;
332 			ah->arc_flag2 = sflag;
333 			ah->arc_seqid2 = ac->ac_seqid;
334 		} else {
335 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
336 			if (m == 0)
337 				senderr(ENOBUFS);
338 			ah = mtod(m, struct arc_header *);
339 			ah->arc_flag = sflag;
340 			ah->arc_seqid = ac->ac_seqid;
341 		}
342 
343 		ah->arc_dhost = adst;
344 		ah->arc_shost = myself;
345 		ah->arc_type = atype;
346 	} else {
347 		M_PREPEND(m, ARC_HDRLEN, M_DONTWAIT);
348 		if (m == 0)
349 			senderr(ENOBUFS);
350 		ah = mtod(m, struct arc_header *);
351 		ah->arc_type = atype;
352 		ah->arc_dhost = adst;
353 		ah->arc_shost = myself;
354 	}
355 	s = splimp();
356 	/*
357 	 * Queue message on interface, and start output if interface
358 	 * not yet active.
359 	 */
360 	if (IF_QFULL(&ifp->if_snd)) {
361 		IF_DROP(&ifp->if_snd);
362 		splx(s);
363 		senderr(ENOBUFS);
364 	}
365 	ifp->if_obytes += m->m_pkthdr.len;
366 	IF_ENQUEUE(&ifp->if_snd, m);
367 	if ((ifp->if_flags & IFF_OACTIVE) == 0)
368 		(*ifp->if_start)(ifp);
369 	splx(s);
370 
371 	return (error);
372 
373 bad:
374 	if (m1)
375 		m_freem(m1);
376 	if (m)
377 		m_freem(m);
378 	return (error);
379 }
380 
381 /*
382  * Defragmenter. Returns mbuf if last packet found, else
383  * NULL. frees imcoming mbuf as necessary.
384  */
385 
386 __inline struct mbuf *
387 arc_defrag(ifp, m)
388 	struct ifnet *ifp;
389 	struct mbuf *m;
390 {
391 	struct arc_header *ah, *ah1;
392 	struct arccom *ac;
393 	struct ac_frag *af;
394 	struct mbuf *m1;
395 	char *s;
396 	int newflen;
397 	u_char src,dst,typ;
398 
399 	ac = (struct arccom *)ifp;
400 
401 	if (m->m_len < ARC_HDRNEWLEN) {
402 		m = m_pullup(m, ARC_HDRNEWLEN);
403 		if (m == NULL) {
404 			++ifp->if_ierrors;
405 			return NULL;
406 		}
407 	}
408 
409 	ah = mtod(m, struct arc_header *);
410 	typ = ah->arc_type;
411 
412 	if (!arc_isphds(typ))
413 		return m;
414 
415 	src = ah->arc_shost;
416 	dst = ah->arc_dhost;
417 
418 	if (ah->arc_flag == 0xff) {
419 		m_adj(m, 4);
420 
421 		if (m->m_len < ARC_HDRNEWLEN) {
422 			m = m_pullup(m, ARC_HDRNEWLEN);
423 			if (m == NULL) {
424 				++ifp->if_ierrors;
425 				return NULL;
426 			}
427 		}
428 
429 		ah = mtod(m, struct arc_header *);
430 	}
431 
432 	af = &ac->ac_fragtab[src];
433 	m1 = af->af_packet;
434 	s = "debug code error";
435 
436 	if (ah->arc_flag & 1) {
437 		/*
438 		 * first fragment. We always initialize, which is
439 		 * about the right thing to do, as we only want to
440 		 * accept one fragmented packet per src at a time.
441 		 */
442 		if (m1 != NULL)
443 			m_freem(m1);
444 
445 		af->af_packet = m;
446 		m1 = m;
447 		af->af_maxflag = ah->arc_flag;
448 		af->af_lastseen = 0;
449 		af->af_seqid = ah->arc_seqid;
450 
451 		return NULL;
452 		/* notreached */
453 	} else {
454 		/* check for unfragmented packet */
455 		if (ah->arc_flag == 0)
456 			return m;
457 
458 		/* do we have a first packet from that src? */
459 		if (m1 == NULL) {
460 			s = "no first frag";
461 			goto outofseq;
462 		}
463 
464 		ah1 = mtod(m1, struct arc_header *);
465 
466 		if (ah->arc_seqid != ah1->arc_seqid) {
467 			s = "seqid differs";
468 			goto outofseq;
469 		}
470 
471 		if (typ != ah1->arc_type) {
472 			s = "type differs";
473 			goto outofseq;
474 		}
475 
476 		if (dst != ah1->arc_dhost) {
477 			s = "dest host differs";
478 			goto outofseq;
479 		}
480 
481 		/* typ, seqid and dst are ok here. */
482 
483 		if (ah->arc_flag == af->af_lastseen) {
484 			m_freem(m);
485 			return NULL;
486 		}
487 
488 		if (ah->arc_flag == af->af_lastseen + 2) {
489 			/* ok, this is next fragment */
490 			af->af_lastseen = ah->arc_flag;
491 			m_adj(m,ARC_HDRNEWLEN);
492 
493 			/*
494 			 * m_cat might free the first mbuf (with pkthdr)
495 			 * in 2nd chain; therefore:
496 			 */
497 
498 			newflen = m->m_pkthdr.len;
499 
500 			m_cat(m1,m);
501 
502 			m1->m_pkthdr.len += newflen;
503 
504 			/* is it the last one? */
505 			if (af->af_lastseen > af->af_maxflag) {
506 				af->af_packet = NULL;
507 				return(m1);
508 			} else
509 				return NULL;
510 		}
511 		s = "other reason";
512 		/* if all else fails, it is out of sequence, too */
513 	}
514 outofseq:
515 	if (m1) {
516 		m_freem(m1);
517 		af->af_packet = NULL;
518 	}
519 
520 	if (m)
521 		m_freem(m);
522 
523 	log(LOG_INFO,"%s: got out of seq. packet: %s\n",
524 	    ifp->if_xname, s);
525 
526 	return NULL;
527 }
528 
529 /*
530  * return 1 if Packet Header Definition Standard, else 0.
531  * For now: old IP, old ARP aren't obviously. Lacking correct information,
532  * we guess that besides new IP and new ARP also IPX and APPLETALK are PHDS.
533  * (Apple and Novell corporations were involved, among others, in PHDS work).
534  * Easiest is to assume that everybody else uses that, too.
535  */
536 int
537 arc_isphds(type)
538 	u_int8_t type;
539 {
540 	return (type != ARCTYPE_IP_OLD &&
541 		type != ARCTYPE_ARP_OLD &&
542 		type != ARCTYPE_DIAGNOSE);
543 }
544 
545 /*
546  * Process a received Arcnet packet;
547  * the packet is in the mbuf chain m with
548  * the ARCnet header.
549  */
550 static void
551 arc_input(ifp, m)
552 	struct ifnet *ifp;
553 	struct mbuf *m;
554 {
555 	struct arc_header *ah;
556 	struct ifqueue *inq;
557 	u_int8_t atype;
558 	int s;
559 	struct arphdr *arph;
560 
561 	if ((ifp->if_flags & IFF_UP) == 0) {
562 		m_freem(m);
563 		return;
564 	}
565 
566 	/* possibly defragment: */
567 	m = arc_defrag(ifp, m);
568 	if (m == NULL)
569 		return;
570 
571 	ah = mtod(m, struct arc_header *);
572 
573 	ifp->if_lastchange = time;
574 	ifp->if_ibytes += m->m_pkthdr.len;
575 
576 	if (arcbroadcastaddr == ah->arc_dhost) {
577 		m->m_flags |= M_BCAST|M_MCAST;
578 		ifp->if_imcasts++;
579 	}
580 
581 	atype = ah->arc_type;
582 	switch (atype) {
583 #ifdef INET
584 	case ARCTYPE_IP:
585 		m_adj(m, ARC_HDRNEWLEN);
586 		schednetisr(NETISR_IP);
587 		inq = &ipintrq;
588 		break;
589 
590 	case ARCTYPE_IP_OLD:
591 		m_adj(m, ARC_HDRLEN);
592 		schednetisr(NETISR_IP);
593 		inq = &ipintrq;
594 		break;
595 
596 	case ARCTYPE_ARP:
597 		m_adj(m, ARC_HDRNEWLEN);
598 		schednetisr(NETISR_ARP);
599 		inq = &arpintrq;
600 #ifdef ARCNET_ALLOW_BROKEN_ARP
601 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
602 #endif
603 		break;
604 
605 	case ARCTYPE_ARP_OLD:
606 		m_adj(m, ARC_HDRLEN);
607 		schednetisr(NETISR_ARP);
608 		inq = &arpintrq;
609 		arph = mtod(m, struct arphdr *);
610 #ifdef ARCNET_ALLOW_BROKEN_ARP
611 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
612 #endif
613 		break;
614 #endif
615 #ifdef INET6
616 	case ARCTYPE_INET6:
617 		m_adj(m, ARC_HDRNEWLEN);
618 		schednetisr(NETISR_IPV6);
619 		inq = &ip6intrq;
620 		break;
621 #endif
622 	default:
623 		m_freem(m);
624 		return;
625 	}
626 
627 	s = splimp();
628 	if (IF_QFULL(inq)) {
629 		IF_DROP(inq);
630 		m_freem(m);
631 	} else
632 		IF_ENQUEUE(inq, m);
633 	splx(s);
634 }
635 
636 /*
637  * Convert Arcnet address to printable (loggable) representation.
638  */
639 static char digits[] = "0123456789abcdef";
640 char *
641 arc_sprintf(ap)
642 	u_int8_t *ap;
643 {
644 	static char arcbuf[3];
645 	char *cp = arcbuf;
646 
647 	*cp++ = digits[*ap >> 4];
648 	*cp++ = digits[*ap++ & 0xf];
649 	*cp   = 0;
650 	return (arcbuf);
651 }
652 
653 /*
654  * Register (new) link level address.
655  */
656 void
657 arc_storelladdr(ifp, lla)
658 	struct ifnet *ifp;
659 	u_int8_t lla;
660 {
661 	struct sockaddr_dl *sdl;
662 	if ((sdl = ifp->if_sadl) &&
663 	   sdl->sdl_family == AF_LINK) {
664 		sdl->sdl_type = IFT_ARCNET;
665 		sdl->sdl_alen = ifp->if_addrlen;
666 		*(LLADDR(sdl)) = lla;
667 	}
668 	ifp->if_mtu = ARC_PHDS_MAXMTU;
669 }
670 
671 /*
672  * Perform common duties while attaching to interface list
673  */
674 void
675 arc_ifattach(ifp, lla)
676 	struct ifnet *ifp;
677 	u_int8_t lla;
678 {
679 	struct arccom *ac;
680 
681 	ifp->if_type = IFT_ARCNET;
682 	ifp->if_addrlen = 1;
683 	ifp->if_hdrlen = ARC_HDRLEN;
684 	if (ifp->if_flags & IFF_BROADCAST)
685 		ifp->if_flags |= IFF_MULTICAST|IFF_ALLMULTI;
686 	if (ifp->if_flags & IFF_LINK0 && arc_ipmtu > ARC_PHDS_MAXMTU)
687 		log(LOG_ERR,
688 		    "%s: arc_ipmtu is %d, but must not exceed %d",
689 		    ifp->if_xname, arc_ipmtu, ARC_PHDS_MAXMTU);
690 
691 	ifp->if_output = arc_output;
692 	ifp->if_input = arc_input;
693 	ac = (struct arccom *)ifp;
694 	ac->ac_seqid = (time.tv_sec) & 0xFFFF; /* try to make seqid unique */
695 	if (lla == 0) {
696 		/* XXX this message isn't entirely clear, to me -- cgd */
697 		log(LOG_ERR,"%s: link address 0 reserved for broadcasts.  Please change it and ifconfig %s down up\n",
698 		   ifp->if_xname, ifp->if_xname);
699 	}
700 	if_attach(ifp);
701 	arc_storelladdr(ifp, lla);
702 
703 	ifp->if_broadcastaddr = &arcbroadcastaddr;
704 }
705