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if_arcsubr.c revision 1.58
      1 /*	$NetBSD: if_arcsubr.c,v 1.58 2007/12/25 23:31:26 he 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 1.58 2007/12/25 23:31:26 he 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 <sys/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(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 
    106 static	int arc_output(struct ifnet *, struct mbuf *,
    107 	    const struct sockaddr *, struct rtentry *);
    108 static	void arc_input(struct ifnet *, struct mbuf *);
    109 
    110 /*
    111  * ARCnet output routine.
    112  * Encapsulate a packet of type family for the local net.
    113  * Assumes that ifp is actually pointer to arccom structure.
    114  */
    115 static int
    116 arc_output(struct ifnet *ifp, struct mbuf *m0, const struct sockaddr *dst,
    117     struct rtentry *rt0)
    118 {
    119 	struct mbuf		*m, *m1, *mcopy;
    120 	struct rtentry		*rt;
    121 	struct arccom		*ac;
    122 	const struct arc_header	*cah;
    123 	struct arc_header	*ah;
    124 	struct arphdr		*arph;
    125 	int			error, newencoding;
    126 	u_int8_t		atype, adst, myself;
    127 	int			tfrags, sflag, fsflag, rsflag;
    128 	ALTQ_DECL(struct altq_pktattr pktattr;)
    129 
    130 	if ((ifp->if_flags & (IFF_UP|IFF_RUNNING)) != (IFF_UP|IFF_RUNNING))
    131 		return (ENETDOWN); /* m, m1 aren't initialized yet */
    132 
    133 	error = newencoding = 0;
    134 	ac = (struct arccom *)ifp;
    135 	m = m0;
    136 	mcopy = m1 = NULL;
    137 
    138 	myself = *CLLADDR(ifp->if_sadl);
    139 
    140 	if ((rt = rt0)) {
    141 		if ((rt->rt_flags & RTF_UP) == 0) {
    142 			if ((rt0 = rt = rtalloc1(dst, 1)))
    143 				rt->rt_refcnt--;
    144 			else
    145 				senderr(EHOSTUNREACH);
    146 		}
    147 		if (rt->rt_flags & RTF_GATEWAY) {
    148 			if (rt->rt_gwroute == 0)
    149 				goto lookup;
    150 			if (((rt = rt->rt_gwroute)->rt_flags & RTF_UP) == 0) {
    151 				rtfree(rt); rt = rt0;
    152 			lookup: rt->rt_gwroute = rtalloc1(rt->rt_gateway, 1);
    153 				if ((rt = rt->rt_gwroute) == 0)
    154 					senderr(EHOSTUNREACH);
    155 			}
    156 		}
    157 		if (rt->rt_flags & RTF_REJECT)
    158 			if (rt->rt_rmx.rmx_expire == 0 ||
    159 			    time_second < rt->rt_rmx.rmx_expire)
    160 				senderr(rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
    161 	}
    162 
    163 	/*
    164 	 * if the queueing discipline needs packet classification,
    165 	 * do it before prepending link headers.
    166 	 */
    167 	IFQ_CLASSIFY(&ifp->if_snd, m, dst->sa_family, &pktattr);
    168 
    169 	switch (dst->sa_family) {
    170 #ifdef INET
    171 	case AF_INET:
    172 
    173 		/*
    174 		 * For now, use the simple IP addr -> ARCnet addr mapping
    175 		 */
    176 		if (m->m_flags & (M_BCAST|M_MCAST))
    177 			adst = arcbroadcastaddr; /* ARCnet broadcast address */
    178 		else if (ifp->if_flags & IFF_NOARP)
    179 			adst = ntohl(satocsin(dst)->sin_addr.s_addr) & 0xFF;
    180 		else if (!arpresolve(ifp, rt, m, dst, &adst))
    181 			return 0;	/* not resolved yet */
    182 
    183 		/* If broadcasting on a simplex interface, loopback a copy */
    184 		if ((m->m_flags & (M_BCAST|M_MCAST)) &&
    185 		    (ifp->if_flags & IFF_SIMPLEX))
    186 			mcopy = m_copy(m, 0, (int)M_COPYALL);
    187 		if (ifp->if_flags & IFF_LINK0) {
    188 			atype = ARCTYPE_IP;
    189 			newencoding = 1;
    190 		} else {
    191 			atype = ARCTYPE_IP_OLD;
    192 			newencoding = 0;
    193 		}
    194 		break;
    195 
    196 	case AF_ARP:
    197 		arph = mtod(m, struct arphdr *);
    198 		if (m->m_flags & M_BCAST)
    199 			adst = arcbroadcastaddr;
    200 		else
    201 			adst = *ar_tha(arph);
    202 
    203 		arph->ar_hrd = htons(ARPHRD_ARCNET);
    204 
    205 		switch (ntohs(arph->ar_op)) {
    206 		case ARPOP_REVREQUEST:
    207 		case ARPOP_REVREPLY:
    208 			if (!(ifp->if_flags & IFF_LINK0)) {
    209 				printf("%s: can't handle af%d\n",
    210 				    ifp->if_xname, dst->sa_family);
    211 				senderr(EAFNOSUPPORT);
    212 			}
    213 
    214 			atype = htons(ARCTYPE_REVARP);
    215 			newencoding = 1;
    216 			break;
    217 
    218 		case ARPOP_REQUEST:
    219 		case ARPOP_REPLY:
    220 		default:
    221 			if (ifp->if_flags & IFF_LINK0) {
    222 				atype = htons(ARCTYPE_ARP);
    223 				newencoding = 1;
    224 			} else {
    225 				atype = htons(ARCTYPE_ARP_OLD);
    226 				newencoding = 0;
    227 			}
    228 		}
    229 #ifdef ARCNET_ALLOW_BROKEN_ARP
    230 		/*
    231 		 * XXX It's not clear per RFC826 if this is needed, but
    232 		 * "assigned numbers" say this is wrong.
    233 		 * However, e.g., AmiTCP 3.0Beta used it... we make this
    234 		 * switchable for emergency cases. Not perfect, but...
    235 		 */
    236 		if (ifp->if_flags & IFF_LINK2)
    237 			arph->ar_pro = atype - 1;
    238 #endif
    239 		break;
    240 #endif
    241 #ifdef INET6
    242 	case AF_INET6:
    243 		if (!nd6_storelladdr(ifp, rt, m, dst, &adst, sizeof(adst)))
    244 			return (0); /* it must be impossible, but... */
    245 		atype = htons(ARCTYPE_INET6);
    246 		newencoding = 1;
    247 		break;
    248 #endif
    249 
    250 	case AF_UNSPEC:
    251 		cah = (const struct arc_header *)dst->sa_data;
    252  		adst = cah->arc_dhost;
    253 		atype = cah->arc_type;
    254 		break;
    255 
    256 	default:
    257 		printf("%s: can't handle af%d\n", ifp->if_xname,
    258 		    dst->sa_family);
    259 		senderr(EAFNOSUPPORT);
    260 	}
    261 
    262 	if (mcopy)
    263 		(void) looutput(ifp, mcopy, dst, rt);
    264 
    265 	/*
    266 	 * Add local net header.  If no space in first mbuf,
    267 	 * allocate another.
    268 	 *
    269 	 * For ARCnet, this is just symbolic. The header changes
    270 	 * form and position on its way into the hardware and out of
    271 	 * the wire.  At this point, it contains source, destination and
    272 	 * packet type.
    273 	 */
    274 	if (newencoding) {
    275 		++ac->ac_seqid; /* make the seqid unique */
    276 
    277 		tfrags = (m->m_pkthdr.len + 503) / 504;
    278 		fsflag = 2 * tfrags - 3;
    279 		sflag = 0;
    280 		rsflag = fsflag;
    281 
    282 		while (sflag < fsflag) {
    283 			/* we CAN'T have short packets here */
    284 			m1 = m_split(m, 504, M_DONTWAIT);
    285 			if (m1 == 0)
    286 				senderr(ENOBUFS);
    287 
    288 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
    289 			if (m == 0)
    290 				senderr(ENOBUFS);
    291 			ah = mtod(m, struct arc_header *);
    292 			ah->arc_type = atype;
    293 			ah->arc_dhost = adst;
    294 			ah->arc_shost = myself;
    295 			ah->arc_flag = rsflag;
    296 			ah->arc_seqid = ac->ac_seqid;
    297 
    298 			if ((error = ifq_enqueue(ifp, m ALTQ_COMMA
    299 			    ALTQ_DECL(&pktattr))) != 0)
    300 				return (error);
    301 
    302 			m = m1;
    303 			sflag += 2;
    304 			rsflag = sflag;
    305 		}
    306 		m1 = NULL;
    307 
    308 
    309 		/* here we can have small, especially forbidden packets */
    310 
    311 		if ((m->m_pkthdr.len >=
    312 		    ARC_MIN_FORBID_LEN - ARC_HDRNEWLEN + 2) &&
    313 		    (m->m_pkthdr.len <=
    314 		    ARC_MAX_FORBID_LEN - ARC_HDRNEWLEN + 2)) {
    315 
    316 			M_PREPEND(m, ARC_HDRNEWLEN_EXC, M_DONTWAIT);
    317 			if (m == 0)
    318 				senderr(ENOBUFS);
    319 			ah = mtod(m, struct arc_header *);
    320 			ah->arc_flag = 0xFF;
    321 			ah->arc_seqid = 0xFFFF;
    322 			ah->arc_type2 = atype;
    323 			ah->arc_flag2 = sflag;
    324 			ah->arc_seqid2 = ac->ac_seqid;
    325 		} else {
    326 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
    327 			if (m == 0)
    328 				senderr(ENOBUFS);
    329 			ah = mtod(m, struct arc_header *);
    330 			ah->arc_flag = sflag;
    331 			ah->arc_seqid = ac->ac_seqid;
    332 		}
    333 
    334 		ah->arc_dhost = adst;
    335 		ah->arc_shost = myself;
    336 		ah->arc_type = atype;
    337 	} else {
    338 		M_PREPEND(m, ARC_HDRLEN, M_DONTWAIT);
    339 		if (m == 0)
    340 			senderr(ENOBUFS);
    341 		ah = mtod(m, struct arc_header *);
    342 		ah->arc_type = atype;
    343 		ah->arc_dhost = adst;
    344 		ah->arc_shost = myself;
    345 	}
    346 
    347 	return ifq_enqueue(ifp, m ALTQ_COMMA ALTQ_DECL(&pktattr));
    348 
    349 bad:
    350 	if (m1)
    351 		m_freem(m1);
    352 	if (m)
    353 		m_freem(m);
    354 	return (error);
    355 }
    356 
    357 /*
    358  * Defragmenter. Returns mbuf if last packet found, else
    359  * NULL. frees imcoming mbuf as necessary.
    360  */
    361 
    362 static struct mbuf *
    363 arc_defrag(struct ifnet *ifp, struct mbuf *m)
    364 {
    365 	struct arc_header *ah, *ah1;
    366 	struct arccom *ac;
    367 	struct ac_frag *af;
    368 	struct mbuf *m1;
    369 	const char *s;
    370 	int newflen;
    371 	u_char src, dst, typ;
    372 
    373 	ac = (struct arccom *)ifp;
    374 
    375 	if (m->m_len < ARC_HDRNEWLEN) {
    376 		m = m_pullup(m, ARC_HDRNEWLEN);
    377 		if (m == NULL) {
    378 			++ifp->if_ierrors;
    379 			return NULL;
    380 		}
    381 	}
    382 
    383 	ah = mtod(m, struct arc_header *);
    384 	typ = ah->arc_type;
    385 
    386 	if (!arc_isphds(typ))
    387 		return m;
    388 
    389 	src = ah->arc_shost;
    390 	dst = ah->arc_dhost;
    391 
    392 	if (ah->arc_flag == 0xff) {
    393 		m_adj(m, 4);
    394 
    395 		if (m->m_len < ARC_HDRNEWLEN) {
    396 			m = m_pullup(m, ARC_HDRNEWLEN);
    397 			if (m == NULL) {
    398 				++ifp->if_ierrors;
    399 				return NULL;
    400 			}
    401 		}
    402 
    403 		ah = mtod(m, struct arc_header *);
    404 	}
    405 
    406 	af = &ac->ac_fragtab[src];
    407 	m1 = af->af_packet;
    408 	s = "debug code error";
    409 
    410 	if (ah->arc_flag & 1) {
    411 		/*
    412 		 * first fragment. We always initialize, which is
    413 		 * about the right thing to do, as we only want to
    414 		 * accept one fragmented packet per src at a time.
    415 		 */
    416 		if (m1 != NULL)
    417 			m_freem(m1);
    418 
    419 		af->af_packet = m;
    420 		m1 = m;
    421 		af->af_maxflag = ah->arc_flag;
    422 		af->af_lastseen = 0;
    423 		af->af_seqid = ah->arc_seqid;
    424 
    425 		return NULL;
    426 		/* notreached */
    427 	} else {
    428 		/* check for unfragmented packet */
    429 		if (ah->arc_flag == 0)
    430 			return m;
    431 
    432 		/* do we have a first packet from that src? */
    433 		if (m1 == NULL) {
    434 			s = "no first frag";
    435 			goto outofseq;
    436 		}
    437 
    438 		ah1 = mtod(m1, struct arc_header *);
    439 
    440 		if (ah->arc_seqid != ah1->arc_seqid) {
    441 			s = "seqid differs";
    442 			goto outofseq;
    443 		}
    444 
    445 		if (typ != ah1->arc_type) {
    446 			s = "type differs";
    447 			goto outofseq;
    448 		}
    449 
    450 		if (dst != ah1->arc_dhost) {
    451 			s = "dest host differs";
    452 			goto outofseq;
    453 		}
    454 
    455 		/* typ, seqid and dst are ok here. */
    456 
    457 		if (ah->arc_flag == af->af_lastseen) {
    458 			m_freem(m);
    459 			return NULL;
    460 		}
    461 
    462 		if (ah->arc_flag == af->af_lastseen + 2) {
    463 			/* ok, this is next fragment */
    464 			af->af_lastseen = ah->arc_flag;
    465 			m_adj(m, ARC_HDRNEWLEN);
    466 
    467 			/*
    468 			 * m_cat might free the first mbuf (with pkthdr)
    469 			 * in 2nd chain; therefore:
    470 			 */
    471 
    472 			newflen = m->m_pkthdr.len;
    473 
    474 			m_cat(m1, m);
    475 
    476 			m1->m_pkthdr.len += newflen;
    477 
    478 			/* is it the last one? */
    479 			if (af->af_lastseen > af->af_maxflag) {
    480 				af->af_packet = NULL;
    481 				return (m1);
    482 			} else
    483 				return NULL;
    484 		}
    485 		s = "other reason";
    486 		/* if all else fails, it is out of sequence, too */
    487 	}
    488 outofseq:
    489 	if (m1) {
    490 		m_freem(m1);
    491 		af->af_packet = NULL;
    492 	}
    493 
    494 	if (m)
    495 		m_freem(m);
    496 
    497 	log(LOG_INFO,"%s: got out of seq. packet: %s\n",
    498 	    ifp->if_xname, s);
    499 
    500 	return NULL;
    501 }
    502 
    503 /*
    504  * return 1 if Packet Header Definition Standard, else 0.
    505  * For now: old IP, old ARP aren't obviously. Lacking correct information,
    506  * we guess that besides new IP and new ARP also IPX and APPLETALK are PHDS.
    507  * (Apple and Novell corporations were involved, among others, in PHDS work).
    508  * Easiest is to assume that everybody else uses that, too.
    509  */
    510 int
    511 arc_isphds(uint8_t type)
    512 {
    513 	return (type != ARCTYPE_IP_OLD &&
    514 		type != ARCTYPE_ARP_OLD &&
    515 		type != ARCTYPE_DIAGNOSE);
    516 }
    517 
    518 /*
    519  * Process a received Arcnet packet;
    520  * the packet is in the mbuf chain m with
    521  * the ARCnet header.
    522  */
    523 static void
    524 arc_input(struct ifnet *ifp, struct mbuf *m)
    525 {
    526 	struct arc_header *ah;
    527 	struct ifqueue *inq;
    528 	u_int8_t atype;
    529 	int s;
    530 
    531 	if ((ifp->if_flags & IFF_UP) == 0) {
    532 		m_freem(m);
    533 		return;
    534 	}
    535 
    536 	/* possibly defragment: */
    537 	m = arc_defrag(ifp, m);
    538 	if (m == NULL)
    539 		return;
    540 
    541 	ah = mtod(m, struct arc_header *);
    542 
    543 	ifp->if_ibytes += m->m_pkthdr.len;
    544 
    545 	if (arcbroadcastaddr == ah->arc_dhost) {
    546 		m->m_flags |= M_BCAST|M_MCAST;
    547 		ifp->if_imcasts++;
    548 	}
    549 
    550 	atype = ah->arc_type;
    551 	switch (atype) {
    552 #ifdef INET
    553 	case ARCTYPE_IP:
    554 		m_adj(m, ARC_HDRNEWLEN);
    555 		schednetisr(NETISR_IP);
    556 		inq = &ipintrq;
    557 		break;
    558 
    559 	case ARCTYPE_IP_OLD:
    560 		m_adj(m, ARC_HDRLEN);
    561 		schednetisr(NETISR_IP);
    562 		inq = &ipintrq;
    563 		break;
    564 
    565 	case ARCTYPE_ARP:
    566 		m_adj(m, ARC_HDRNEWLEN);
    567 		schednetisr(NETISR_ARP);
    568 		inq = &arpintrq;
    569 #ifdef ARCNET_ALLOW_BROKEN_ARP
    570 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
    571 #endif
    572 		break;
    573 
    574 	case ARCTYPE_ARP_OLD:
    575 		m_adj(m, ARC_HDRLEN);
    576 		schednetisr(NETISR_ARP);
    577 		inq = &arpintrq;
    578 #ifdef ARCNET_ALLOW_BROKEN_ARP
    579 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
    580 #endif
    581 		break;
    582 #endif
    583 #ifdef INET6
    584 	case ARCTYPE_INET6:
    585 		m_adj(m, ARC_HDRNEWLEN);
    586 		schednetisr(NETISR_IPV6);
    587 		inq = &ip6intrq;
    588 		break;
    589 #endif
    590 	default:
    591 		m_freem(m);
    592 		return;
    593 	}
    594 
    595 	s = splnet();
    596 	if (IF_QFULL(inq)) {
    597 		IF_DROP(inq);
    598 		m_freem(m);
    599 	} else
    600 		IF_ENQUEUE(inq, m);
    601 	splx(s);
    602 }
    603 
    604 /*
    605  * Convert Arcnet address to printable (loggable) representation.
    606  */
    607 char *
    608 arc_sprintf(uint8_t *ap)
    609 {
    610 	static char arcbuf[3];
    611 	char *cp = arcbuf;
    612 
    613 	*cp++ = hexdigits[*ap >> 4];
    614 	*cp++ = hexdigits[*ap++ & 0xf];
    615 	*cp   = 0;
    616 	return (arcbuf);
    617 }
    618 
    619 /*
    620  * Perform common duties while attaching to interface list
    621  */
    622 void
    623 arc_ifattach(struct ifnet *ifp, uint8_t lla)
    624 {
    625 	struct arccom *ac;
    626 
    627 	ifp->if_type = IFT_ARCNET;
    628 	ifp->if_addrlen = 1;
    629 	ifp->if_hdrlen = ARC_HDRLEN;
    630 	ifp->if_dlt = DLT_ARCNET;
    631 	if (ifp->if_flags & IFF_BROADCAST)
    632 		ifp->if_flags |= IFF_MULTICAST|IFF_ALLMULTI;
    633 	if (ifp->if_flags & IFF_LINK0 && arc_ipmtu > ARC_PHDS_MAXMTU)
    634 		log(LOG_ERR,
    635 		    "%s: arc_ipmtu is %d, but must not exceed %d",
    636 		    ifp->if_xname, arc_ipmtu, ARC_PHDS_MAXMTU);
    637 
    638 	ifp->if_output = arc_output;
    639 	ifp->if_input = arc_input;
    640 	ac = (struct arccom *)ifp;
    641 	ac->ac_seqid = (time_second) & 0xFFFF; /* try to make seqid unique */
    642 	if (lla == 0) {
    643 		/* XXX this message isn't entirely clear, to me -- cgd */
    644 		log(LOG_ERR,"%s: link address 0 reserved for broadcasts.  Please change it and ifconfig %s down up\n",
    645 		   ifp->if_xname, ifp->if_xname);
    646 	}
    647 	if_attach(ifp);
    648 	if_set_sadl(ifp, &lla, sizeof(lla));
    649 
    650 	ifp->if_broadcastaddr = &arcbroadcastaddr;
    651 
    652 #if NBPFILTER > 0
    653 	bpfattach(ifp, DLT_ARCNET, ARC_HDRLEN);
    654 #endif
    655 }
    656