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if_arcsubr.c revision 1.63
      1 /*	$NetBSD: if_arcsubr.c,v 1.63 2010/04/05 07:22:22 joerg 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 1.63 2010/04/05 07:22:22 joerg Exp $");
     39 
     40 #include "opt_inet.h"
     41 
     42 
     43 #include <sys/param.h>
     44 #include <sys/systm.h>
     45 #include <sys/kernel.h>
     46 #include <sys/malloc.h>
     47 #include <sys/mbuf.h>
     48 #include <sys/protosw.h>
     49 #include <sys/socket.h>
     50 #include <sys/ioctl.h>
     51 #include <sys/errno.h>
     52 #include <sys/syslog.h>
     53 
     54 #include <sys/cpu.h>
     55 
     56 #include <net/if.h>
     57 #include <net/netisr.h>
     58 #include <net/route.h>
     59 #include <net/if_dl.h>
     60 #include <net/if_types.h>
     61 #include <net/if_arc.h>
     62 #include <net/if_arp.h>
     63 #include <net/if_ether.h>
     64 
     65 #include <net/bpf.h>
     66 
     67 #ifdef INET
     68 #include <netinet/in.h>
     69 #include <netinet/in_var.h>
     70 #include <netinet/if_inarp.h>
     71 #endif
     72 
     73 #ifdef INET6
     74 #ifndef INET
     75 #include <netinet/in.h>
     76 #endif
     77 #include <netinet6/in6_var.h>
     78 #include <netinet6/nd6.h>
     79 #endif
     80 
     81 #define ARCNET_ALLOW_BROKEN_ARP
     82 
     83 #ifndef ARC_IPMTU
     84 #define ARC_IPMTU	1500
     85 #endif
     86 
     87 static struct mbuf *arc_defrag(struct ifnet *, struct mbuf *);
     88 
     89 /*
     90  * RC1201 requires us to have this configurable. We have it only per
     91  * machine at the moment... there is no generic "set mtu" ioctl, AFAICS.
     92  * Anyway, it is possible to binpatch this or set it per kernel config
     93  * option.
     94  */
     95 #if ARC_IPMTU > 60480
     96 ERROR: The arc_ipmtu is ARC_IPMTU, but must not exceed 60480.
     97 #endif
     98 int arc_ipmtu = ARC_IPMTU;
     99 uint8_t  arcbroadcastaddr = 0;
    100 
    101 #define senderr(e) { error = (e); goto bad;}
    102 
    103 static	int arc_output(struct ifnet *, struct mbuf *,
    104 	    const struct sockaddr *, struct rtentry *);
    105 static	void arc_input(struct ifnet *, struct mbuf *);
    106 
    107 /*
    108  * ARCnet output routine.
    109  * Encapsulate a packet of type family for the local net.
    110  * Assumes that ifp is actually pointer to arccom structure.
    111  */
    112 static int
    113 arc_output(struct ifnet *ifp, struct mbuf *m0, const struct sockaddr *dst,
    114     struct rtentry *rt0)
    115 {
    116 	struct mbuf		*m, *m1, *mcopy;
    117 	struct rtentry		*rt;
    118 	struct arccom		*ac;
    119 	const struct arc_header	*cah;
    120 	struct arc_header	*ah;
    121 	struct arphdr		*arph;
    122 	int			error, newencoding;
    123 	uint8_t			atype, adst, myself;
    124 	int			tfrags, sflag, fsflag, rsflag;
    125 	ALTQ_DECL(struct altq_pktattr pktattr;)
    126 
    127 	if ((ifp->if_flags & (IFF_UP|IFF_RUNNING)) != (IFF_UP|IFF_RUNNING))
    128 		return (ENETDOWN); /* m, m1 aren't initialized yet */
    129 
    130 	error = newencoding = 0;
    131 	ac = (struct arccom *)ifp;
    132 	m = m0;
    133 	mcopy = m1 = NULL;
    134 
    135 	myself = *CLLADDR(ifp->if_sadl);
    136 
    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_second < rt->rt_rmx.rmx_expire)
    157 				senderr(rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
    158 	}
    159 
    160 	/*
    161 	 * if the queueing discipline needs packet classification,
    162 	 * do it before prepending link headers.
    163 	 */
    164 	IFQ_CLASSIFY(&ifp->if_snd, m, dst->sa_family, &pktattr);
    165 
    166 	switch (dst->sa_family) {
    167 #ifdef INET
    168 	case AF_INET:
    169 
    170 		/*
    171 		 * For now, use the simple IP addr -> ARCnet addr mapping
    172 		 */
    173 		if (m->m_flags & (M_BCAST|M_MCAST))
    174 			adst = arcbroadcastaddr; /* ARCnet broadcast address */
    175 		else if (ifp->if_flags & IFF_NOARP)
    176 			adst = ntohl(satocsin(dst)->sin_addr.s_addr) & 0xFF;
    177 		else if (!arpresolve(ifp, rt, m, dst, &adst))
    178 			return 0;	/* not resolved yet */
    179 
    180 		/* If broadcasting on a simplex interface, loopback a copy */
    181 		if ((m->m_flags & (M_BCAST|M_MCAST)) &&
    182 		    (ifp->if_flags & IFF_SIMPLEX))
    183 			mcopy = m_copy(m, 0, (int)M_COPYALL);
    184 		if (ifp->if_flags & IFF_LINK0) {
    185 			atype = ARCTYPE_IP;
    186 			newencoding = 1;
    187 		} else {
    188 			atype = ARCTYPE_IP_OLD;
    189 			newencoding = 0;
    190 		}
    191 		break;
    192 
    193 	case AF_ARP:
    194 		arph = mtod(m, struct arphdr *);
    195 		if (m->m_flags & M_BCAST)
    196 			adst = arcbroadcastaddr;
    197 		else {
    198 			uint8_t *tha = ar_tha(arph);
    199 			if (tha == NULL)
    200 				return 0;
    201 			adst = *tha;
    202 		}
    203 
    204 		arph->ar_hrd = htons(ARPHRD_ARCNET);
    205 
    206 		switch (ntohs(arph->ar_op)) {
    207 		case ARPOP_REVREQUEST:
    208 		case ARPOP_REVREPLY:
    209 			if (!(ifp->if_flags & IFF_LINK0)) {
    210 				printf("%s: can't handle af%d\n",
    211 				    ifp->if_xname, dst->sa_family);
    212 				senderr(EAFNOSUPPORT);
    213 			}
    214 
    215 			atype = htons(ARCTYPE_REVARP);
    216 			newencoding = 1;
    217 			break;
    218 
    219 		case ARPOP_REQUEST:
    220 		case ARPOP_REPLY:
    221 		default:
    222 			if (ifp->if_flags & IFF_LINK0) {
    223 				atype = htons(ARCTYPE_ARP);
    224 				newencoding = 1;
    225 			} else {
    226 				atype = htons(ARCTYPE_ARP_OLD);
    227 				newencoding = 0;
    228 			}
    229 		}
    230 #ifdef ARCNET_ALLOW_BROKEN_ARP
    231 		/*
    232 		 * XXX It's not clear per RFC826 if this is needed, but
    233 		 * "assigned numbers" say this is wrong.
    234 		 * However, e.g., AmiTCP 3.0Beta used it... we make this
    235 		 * switchable for emergency cases. Not perfect, but...
    236 		 */
    237 		if (ifp->if_flags & IFF_LINK2)
    238 			arph->ar_pro = atype - 1;
    239 #endif
    240 		break;
    241 #endif
    242 #ifdef INET6
    243 	case AF_INET6:
    244 		if (!nd6_storelladdr(ifp, rt, m, dst, &adst, sizeof(adst)))
    245 			return (0); /* it must be impossible, but... */
    246 		atype = htons(ARCTYPE_INET6);
    247 		newencoding = 1;
    248 		break;
    249 #endif
    250 
    251 	case AF_UNSPEC:
    252 		cah = (const struct arc_header *)dst->sa_data;
    253  		adst = cah->arc_dhost;
    254 		atype = cah->arc_type;
    255 		break;
    256 
    257 	default:
    258 		printf("%s: can't handle af%d\n", ifp->if_xname,
    259 		    dst->sa_family);
    260 		senderr(EAFNOSUPPORT);
    261 	}
    262 
    263 	if (mcopy)
    264 		(void) looutput(ifp, mcopy, dst, rt);
    265 
    266 	/*
    267 	 * Add local net header.  If no space in first mbuf,
    268 	 * allocate another.
    269 	 *
    270 	 * For ARCnet, this is just symbolic. The header changes
    271 	 * form and position on its way into the hardware and out of
    272 	 * the wire.  At this point, it contains source, destination and
    273 	 * packet type.
    274 	 */
    275 	if (newencoding) {
    276 		++ac->ac_seqid; /* make the seqid unique */
    277 
    278 		tfrags = (m->m_pkthdr.len + 503) / 504;
    279 		fsflag = 2 * tfrags - 3;
    280 		sflag = 0;
    281 		rsflag = fsflag;
    282 
    283 		while (sflag < fsflag) {
    284 			/* we CAN'T have short packets here */
    285 			m1 = m_split(m, 504, M_DONTWAIT);
    286 			if (m1 == 0)
    287 				senderr(ENOBUFS);
    288 
    289 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
    290 			if (m == 0)
    291 				senderr(ENOBUFS);
    292 			ah = mtod(m, struct arc_header *);
    293 			ah->arc_type = atype;
    294 			ah->arc_dhost = adst;
    295 			ah->arc_shost = myself;
    296 			ah->arc_flag = rsflag;
    297 			ah->arc_seqid = ac->ac_seqid;
    298 
    299 			if ((error = ifq_enqueue(ifp, m ALTQ_COMMA
    300 			    ALTQ_DECL(&pktattr))) != 0)
    301 				return (error);
    302 
    303 			m = m1;
    304 			sflag += 2;
    305 			rsflag = sflag;
    306 		}
    307 		m1 = NULL;
    308 
    309 
    310 		/* here we can have small, especially forbidden packets */
    311 
    312 		if ((m->m_pkthdr.len >=
    313 		    ARC_MIN_FORBID_LEN - ARC_HDRNEWLEN + 2) &&
    314 		    (m->m_pkthdr.len <=
    315 		    ARC_MAX_FORBID_LEN - ARC_HDRNEWLEN + 2)) {
    316 
    317 			M_PREPEND(m, ARC_HDRNEWLEN_EXC, M_DONTWAIT);
    318 			if (m == 0)
    319 				senderr(ENOBUFS);
    320 			ah = mtod(m, struct arc_header *);
    321 			ah->arc_flag = 0xFF;
    322 			ah->arc_seqid = 0xFFFF;
    323 			ah->arc_type2 = atype;
    324 			ah->arc_flag2 = sflag;
    325 			ah->arc_seqid2 = ac->ac_seqid;
    326 		} else {
    327 			M_PREPEND(m, ARC_HDRNEWLEN, M_DONTWAIT);
    328 			if (m == 0)
    329 				senderr(ENOBUFS);
    330 			ah = mtod(m, struct arc_header *);
    331 			ah->arc_flag = sflag;
    332 			ah->arc_seqid = ac->ac_seqid;
    333 		}
    334 
    335 		ah->arc_dhost = adst;
    336 		ah->arc_shost = myself;
    337 		ah->arc_type = atype;
    338 	} else {
    339 		M_PREPEND(m, ARC_HDRLEN, M_DONTWAIT);
    340 		if (m == 0)
    341 			senderr(ENOBUFS);
    342 		ah = mtod(m, struct arc_header *);
    343 		ah->arc_type = atype;
    344 		ah->arc_dhost = adst;
    345 		ah->arc_shost = myself;
    346 	}
    347 
    348 	return ifq_enqueue(ifp, m ALTQ_COMMA ALTQ_DECL(&pktattr));
    349 
    350 bad:
    351 	if (m1)
    352 		m_freem(m1);
    353 	if (m)
    354 		m_freem(m);
    355 	return (error);
    356 }
    357 
    358 /*
    359  * Defragmenter. Returns mbuf if last packet found, else
    360  * NULL. frees imcoming mbuf as necessary.
    361  */
    362 
    363 static struct mbuf *
    364 arc_defrag(struct ifnet *ifp, struct mbuf *m)
    365 {
    366 	struct arc_header *ah, *ah1;
    367 	struct arccom *ac;
    368 	struct ac_frag *af;
    369 	struct mbuf *m1;
    370 	const char *s;
    371 	int newflen;
    372 	u_char src, dst, typ;
    373 
    374 	ac = (struct arccom *)ifp;
    375 
    376 	if (m->m_len < ARC_HDRNEWLEN) {
    377 		m = m_pullup(m, ARC_HDRNEWLEN);
    378 		if (m == NULL) {
    379 			++ifp->if_ierrors;
    380 			return NULL;
    381 		}
    382 	}
    383 
    384 	ah = mtod(m, struct arc_header *);
    385 	typ = ah->arc_type;
    386 
    387 	if (!arc_isphds(typ))
    388 		return m;
    389 
    390 	src = ah->arc_shost;
    391 	dst = ah->arc_dhost;
    392 
    393 	if (ah->arc_flag == 0xff) {
    394 		m_adj(m, 4);
    395 
    396 		if (m->m_len < ARC_HDRNEWLEN) {
    397 			m = m_pullup(m, ARC_HDRNEWLEN);
    398 			if (m == NULL) {
    399 				++ifp->if_ierrors;
    400 				return NULL;
    401 			}
    402 		}
    403 
    404 		ah = mtod(m, struct arc_header *);
    405 	}
    406 
    407 	af = &ac->ac_fragtab[src];
    408 	m1 = af->af_packet;
    409 	s = "debug code error";
    410 
    411 	if (ah->arc_flag & 1) {
    412 		/*
    413 		 * first fragment. We always initialize, which is
    414 		 * about the right thing to do, as we only want to
    415 		 * accept one fragmented packet per src at a time.
    416 		 */
    417 		if (m1 != NULL)
    418 			m_freem(m1);
    419 
    420 		af->af_packet = m;
    421 		m1 = m;
    422 		af->af_maxflag = ah->arc_flag;
    423 		af->af_lastseen = 0;
    424 		af->af_seqid = ah->arc_seqid;
    425 
    426 		return NULL;
    427 		/* notreached */
    428 	} else {
    429 		/* check for unfragmented packet */
    430 		if (ah->arc_flag == 0)
    431 			return m;
    432 
    433 		/* do we have a first packet from that src? */
    434 		if (m1 == NULL) {
    435 			s = "no first frag";
    436 			goto outofseq;
    437 		}
    438 
    439 		ah1 = mtod(m1, struct arc_header *);
    440 
    441 		if (ah->arc_seqid != ah1->arc_seqid) {
    442 			s = "seqid differs";
    443 			goto outofseq;
    444 		}
    445 
    446 		if (typ != ah1->arc_type) {
    447 			s = "type differs";
    448 			goto outofseq;
    449 		}
    450 
    451 		if (dst != ah1->arc_dhost) {
    452 			s = "dest host differs";
    453 			goto outofseq;
    454 		}
    455 
    456 		/* typ, seqid and dst are ok here. */
    457 
    458 		if (ah->arc_flag == af->af_lastseen) {
    459 			m_freem(m);
    460 			return NULL;
    461 		}
    462 
    463 		if (ah->arc_flag == af->af_lastseen + 2) {
    464 			/* ok, this is next fragment */
    465 			af->af_lastseen = ah->arc_flag;
    466 			m_adj(m, ARC_HDRNEWLEN);
    467 
    468 			/*
    469 			 * m_cat might free the first mbuf (with pkthdr)
    470 			 * in 2nd chain; therefore:
    471 			 */
    472 
    473 			newflen = m->m_pkthdr.len;
    474 
    475 			m_cat(m1, m);
    476 
    477 			m1->m_pkthdr.len += newflen;
    478 
    479 			/* is it the last one? */
    480 			if (af->af_lastseen > af->af_maxflag) {
    481 				af->af_packet = NULL;
    482 				return (m1);
    483 			} else
    484 				return NULL;
    485 		}
    486 		s = "other reason";
    487 		/* if all else fails, it is out of sequence, too */
    488 	}
    489 outofseq:
    490 	if (m1) {
    491 		m_freem(m1);
    492 		af->af_packet = NULL;
    493 	}
    494 
    495 	if (m)
    496 		m_freem(m);
    497 
    498 	log(LOG_INFO,"%s: got out of seq. packet: %s\n",
    499 	    ifp->if_xname, s);
    500 
    501 	return NULL;
    502 }
    503 
    504 /*
    505  * return 1 if Packet Header Definition Standard, else 0.
    506  * For now: old IP, old ARP aren't obviously. Lacking correct information,
    507  * we guess that besides new IP and new ARP also IPX and APPLETALK are PHDS.
    508  * (Apple and Novell corporations were involved, among others, in PHDS work).
    509  * Easiest is to assume that everybody else uses that, too.
    510  */
    511 int
    512 arc_isphds(uint8_t type)
    513 {
    514 	return (type != ARCTYPE_IP_OLD &&
    515 		type != ARCTYPE_ARP_OLD &&
    516 		type != ARCTYPE_DIAGNOSE);
    517 }
    518 
    519 /*
    520  * Process a received Arcnet packet;
    521  * the packet is in the mbuf chain m with
    522  * the ARCnet header.
    523  */
    524 static void
    525 arc_input(struct ifnet *ifp, struct mbuf *m)
    526 {
    527 	struct arc_header *ah;
    528 	struct ifqueue *inq;
    529 	uint8_t atype;
    530 	int s;
    531 
    532 	if ((ifp->if_flags & IFF_UP) == 0) {
    533 		m_freem(m);
    534 		return;
    535 	}
    536 
    537 	/* possibly defragment: */
    538 	m = arc_defrag(ifp, m);
    539 	if (m == NULL)
    540 		return;
    541 
    542 	ah = mtod(m, struct arc_header *);
    543 
    544 	ifp->if_ibytes += m->m_pkthdr.len;
    545 
    546 	if (arcbroadcastaddr == ah->arc_dhost) {
    547 		m->m_flags |= M_BCAST|M_MCAST;
    548 		ifp->if_imcasts++;
    549 	}
    550 
    551 	atype = ah->arc_type;
    552 	switch (atype) {
    553 #ifdef INET
    554 	case ARCTYPE_IP:
    555 		m_adj(m, ARC_HDRNEWLEN);
    556 		schednetisr(NETISR_IP);
    557 		inq = &ipintrq;
    558 		break;
    559 
    560 	case ARCTYPE_IP_OLD:
    561 		m_adj(m, ARC_HDRLEN);
    562 		schednetisr(NETISR_IP);
    563 		inq = &ipintrq;
    564 		break;
    565 
    566 	case ARCTYPE_ARP:
    567 		m_adj(m, ARC_HDRNEWLEN);
    568 		schednetisr(NETISR_ARP);
    569 		inq = &arpintrq;
    570 #ifdef ARCNET_ALLOW_BROKEN_ARP
    571 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
    572 #endif
    573 		break;
    574 
    575 	case ARCTYPE_ARP_OLD:
    576 		m_adj(m, ARC_HDRLEN);
    577 		schednetisr(NETISR_ARP);
    578 		inq = &arpintrq;
    579 #ifdef ARCNET_ALLOW_BROKEN_ARP
    580 		mtod(m, struct arphdr *)->ar_pro = htons(ETHERTYPE_IP);
    581 #endif
    582 		break;
    583 #endif
    584 #ifdef INET6
    585 	case ARCTYPE_INET6:
    586 		m_adj(m, ARC_HDRNEWLEN);
    587 		schednetisr(NETISR_IPV6);
    588 		inq = &ip6intrq;
    589 		break;
    590 #endif
    591 	default:
    592 		m_freem(m);
    593 		return;
    594 	}
    595 
    596 	s = splnet();
    597 	if (IF_QFULL(inq)) {
    598 		IF_DROP(inq);
    599 		m_freem(m);
    600 	} else
    601 		IF_ENQUEUE(inq, m);
    602 	splx(s);
    603 }
    604 
    605 /*
    606  * Convert Arcnet address to printable (loggable) representation.
    607  */
    608 char *
    609 arc_sprintf(uint8_t *ap)
    610 {
    611 	static char arcbuf[3];
    612 	char *cp = arcbuf;
    613 
    614 	*cp++ = hexdigits[*ap >> 4];
    615 	*cp++ = hexdigits[*ap++ & 0xf];
    616 	*cp   = 0;
    617 	return (arcbuf);
    618 }
    619 
    620 /*
    621  * Perform common duties while attaching to interface list
    622  */
    623 void
    624 arc_ifattach(struct ifnet *ifp, uint8_t lla)
    625 {
    626 	struct arccom *ac;
    627 
    628 	ifp->if_type = IFT_ARCNET;
    629 	ifp->if_addrlen = 1;
    630 	ifp->if_hdrlen = ARC_HDRLEN;
    631 	ifp->if_dlt = DLT_ARCNET;
    632 	if (ifp->if_flags & IFF_BROADCAST)
    633 		ifp->if_flags |= IFF_MULTICAST|IFF_ALLMULTI;
    634 	if (ifp->if_flags & IFF_LINK0 && arc_ipmtu > ARC_PHDS_MAXMTU)
    635 		log(LOG_ERR,
    636 		    "%s: arc_ipmtu is %d, but must not exceed %d",
    637 		    ifp->if_xname, arc_ipmtu, ARC_PHDS_MAXMTU);
    638 
    639 	ifp->if_output = arc_output;
    640 	ifp->if_input = arc_input;
    641 	ac = (struct arccom *)ifp;
    642 	ac->ac_seqid = (time_second) & 0xFFFF; /* try to make seqid unique */
    643 	if (lla == 0) {
    644 		/* XXX this message isn't entirely clear, to me -- cgd */
    645 		log(LOG_ERR,"%s: link address 0 reserved for broadcasts.  Please change it and ifconfig %s down up\n",
    646 		   ifp->if_xname, ifp->if_xname);
    647 	}
    648 	if_attach(ifp);
    649 	if_set_sadl(ifp, &lla, sizeof(lla), true);
    650 
    651 	ifp->if_broadcastaddr = &arcbroadcastaddr;
    652 
    653 	bpf_attach(ifp, DLT_ARCNET, ARC_HDRLEN);
    654 }
    655