2 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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. Neither the name of the project nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * $KAME: frag6.c,v 1.33 2002/01/07 11:34:48 kjc Exp $
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/malloc.h>
41 #include <sys/domain.h>
42 #include <sys/eventhandler.h>
43 #include <sys/protosw.h>
44 #include <sys/socket.h>
45 #include <sys/errno.h>
47 #include <sys/kernel.h>
48 #include <sys/syslog.h>
51 #include <net/if_var.h>
52 #include <net/netisr.h>
53 #include <net/route.h>
56 #include <netinet/in.h>
57 #include <netinet/in_var.h>
58 #include <netinet/ip6.h>
59 #include <netinet6/ip6_var.h>
60 #include <netinet/icmp6.h>
61 #include <netinet/in_systm.h> /* for ECN definitions */
62 #include <netinet/ip.h> /* for ECN definitions */
64 #include <security/mac/mac_framework.h>
66 static void frag6_enq(struct ip6asfrag *, struct ip6asfrag *);
67 static void frag6_deq(struct ip6asfrag *);
68 static void frag6_insque(struct ip6q *, struct ip6q *);
69 static void frag6_remque(struct ip6q *);
70 static void frag6_freef(struct ip6q *);
72 static struct mtx ip6qlock;
74 * These fields all protected by ip6qlock.
76 static VNET_DEFINE(u_int, frag6_nfragpackets);
77 static VNET_DEFINE(u_int, frag6_nfrags);
78 static VNET_DEFINE(struct ip6q, ip6q); /* ip6 reassemble queue */
80 #define V_frag6_nfragpackets VNET(frag6_nfragpackets)
81 #define V_frag6_nfrags VNET(frag6_nfrags)
82 #define V_ip6q VNET(ip6q)
84 #define IP6Q_LOCK_INIT() mtx_init(&ip6qlock, "ip6qlock", NULL, MTX_DEF);
85 #define IP6Q_LOCK() mtx_lock(&ip6qlock)
86 #define IP6Q_TRYLOCK() mtx_trylock(&ip6qlock)
87 #define IP6Q_LOCK_ASSERT() mtx_assert(&ip6qlock, MA_OWNED)
88 #define IP6Q_UNLOCK() mtx_unlock(&ip6qlock)
90 static MALLOC_DEFINE(M_FTABLE, "fragment", "fragment reassembly header");
93 * Initialise reassembly queue and fragment identifier.
96 frag6_change(void *tag)
99 V_ip6_maxfragpackets = nmbclusters / 4;
100 V_ip6_maxfrags = nmbclusters / 4;
107 V_ip6_maxfragpackets = nmbclusters / 4;
108 V_ip6_maxfrags = nmbclusters / 4;
109 V_ip6q.ip6q_next = V_ip6q.ip6q_prev = &V_ip6q;
111 if (!IS_DEFAULT_VNET(curvnet))
114 EVENTHANDLER_REGISTER(nmbclusters_change,
115 frag6_change, NULL, EVENTHANDLER_PRI_ANY);
121 * In RFC2460, fragment and reassembly rule do not agree with each other,
122 * in terms of next header field handling in fragment header.
123 * While the sender will use the same value for all of the fragmented packets,
124 * receiver is suggested not to check the consistency.
126 * fragment rule (p20):
127 * (2) A Fragment header containing:
128 * The Next Header value that identifies the first header of
129 * the Fragmentable Part of the original packet.
130 * -> next header field is same for all fragments
132 * reassembly rule (p21):
133 * The Next Header field of the last header of the Unfragmentable
134 * Part is obtained from the Next Header field of the first
135 * fragment's Fragment header.
136 * -> should grab it from the first fragment only
138 * The following note also contradicts with fragment rule - no one is going to
139 * send different fragment with different next header field.
141 * additional note (p22):
142 * The Next Header values in the Fragment headers of different
143 * fragments of the same original packet may differ. Only the value
144 * from the Offset zero fragment packet is used for reassembly.
145 * -> should grab it from the first fragment only
147 * There is no explicit reason given in the RFC. Historical reason maybe?
153 frag6_input(struct mbuf **mp, int *offp, int proto)
155 struct mbuf *m = *mp, *t;
157 struct ip6_frag *ip6f;
159 struct ip6asfrag *af6, *ip6af, *af6dwn;
160 struct in6_ifaddr *ia;
161 int offset = *offp, nxt, i, next;
163 int fragoff, frgpartlen; /* must be larger than u_int16_t */
164 struct ifnet *dstifp;
168 struct ip6_direct_ctx *ip6dc;
172 char ip6buf[INET6_ADDRSTRLEN];
175 ip6 = mtod(m, struct ip6_hdr *);
176 #ifndef PULLDOWN_TEST
177 IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
178 ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
180 IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
182 return (IPPROTO_DONE);
186 /* find the destination interface of the packet. */
187 ia = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
190 ifa_free(&ia->ia_ifa);
192 /* jumbo payload can't contain a fragment header */
193 if (ip6->ip6_plen == 0) {
194 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
195 in6_ifstat_inc(dstifp, ifs6_reass_fail);
200 * check whether fragment packet's fragment length is
201 * multiple of 8 octets.
202 * sizeof(struct ip6_frag) == 8
203 * sizeof(struct ip6_hdr) = 40
205 if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
206 (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
207 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
208 offsetof(struct ip6_hdr, ip6_plen));
209 in6_ifstat_inc(dstifp, ifs6_reass_fail);
213 IP6STAT_INC(ip6s_fragments);
214 in6_ifstat_inc(dstifp, ifs6_reass_reqd);
216 /* offset now points to data portion */
217 offset += sizeof(struct ip6_frag);
220 * RFC 6946: Handle "atomic" fragments (offset and m bit set to 0)
221 * upfront, unrelated to any reassembly. Just skip the fragment header.
223 if ((ip6f->ip6f_offlg & ~IP6F_RESERVED_MASK) == 0) {
224 /* XXX-BZ we want dedicated counters for this. */
225 IP6STAT_INC(ip6s_reassembled);
226 in6_ifstat_inc(dstifp, ifs6_reass_ok);
228 return (ip6f->ip6f_nxt);
234 * Enforce upper bound on number of fragments.
235 * If maxfrag is 0, never accept fragments.
236 * If maxfrag is -1, accept all fragments without limitation.
238 if (V_ip6_maxfrags < 0)
240 else if (V_frag6_nfrags >= (u_int)V_ip6_maxfrags)
243 for (q6 = V_ip6q.ip6q_next; q6 != &V_ip6q; q6 = q6->ip6q_next)
244 if (ip6f->ip6f_ident == q6->ip6q_ident &&
245 IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
246 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst)
248 && mac_ip6q_match(m, q6)
255 * the first fragment to arrive, create a reassembly queue.
260 * Enforce upper bound on number of fragmented packets
261 * for which we attempt reassembly;
262 * If maxfragpackets is 0, never accept fragments.
263 * If maxfragpackets is -1, accept all fragments without
266 if (V_ip6_maxfragpackets < 0)
268 else if (V_frag6_nfragpackets >= (u_int)V_ip6_maxfragpackets)
270 V_frag6_nfragpackets++;
271 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
275 bzero(q6, sizeof(*q6));
277 if (mac_ip6q_init(q6, M_NOWAIT) != 0) {
281 mac_ip6q_create(m, q6);
283 frag6_insque(q6, &V_ip6q);
285 /* ip6q_nxt will be filled afterwards, from 1st fragment */
286 q6->ip6q_down = q6->ip6q_up = (struct ip6asfrag *)q6;
288 q6->ip6q_nxtp = (u_char *)nxtp;
290 q6->ip6q_ident = ip6f->ip6f_ident;
291 q6->ip6q_ttl = IPV6_FRAGTTL;
292 q6->ip6q_src = ip6->ip6_src;
293 q6->ip6q_dst = ip6->ip6_dst;
295 (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
296 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
302 * If it's the 1st fragment, record the length of the
303 * unfragmentable part and the next header of the fragment header.
305 fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
307 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
308 sizeof(struct ip6_frag);
309 q6->ip6q_nxt = ip6f->ip6f_nxt;
313 * Check that the reassembled packet would not exceed 65535 bytes
315 * If it would exceed, discard the fragment and return an ICMP error.
317 frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
318 if (q6->ip6q_unfrglen >= 0) {
319 /* The 1st fragment has already arrived. */
320 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
321 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
322 offset - sizeof(struct ip6_frag) +
323 offsetof(struct ip6_frag, ip6f_offlg));
325 return (IPPROTO_DONE);
327 } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
328 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
329 offset - sizeof(struct ip6_frag) +
330 offsetof(struct ip6_frag, ip6f_offlg));
332 return (IPPROTO_DONE);
335 * If it's the first fragment, do the above check for each
336 * fragment already stored in the reassembly queue.
339 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
341 af6dwn = af6->ip6af_down;
343 if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
345 struct mbuf *merr = IP6_REASS_MBUF(af6);
346 struct ip6_hdr *ip6err;
347 int erroff = af6->ip6af_offset;
349 /* dequeue the fragment. */
353 /* adjust pointer. */
354 ip6err = mtod(merr, struct ip6_hdr *);
357 * Restore source and destination addresses
358 * in the erroneous IPv6 header.
360 ip6err->ip6_src = q6->ip6q_src;
361 ip6err->ip6_dst = q6->ip6q_dst;
363 icmp6_error(merr, ICMP6_PARAM_PROB,
364 ICMP6_PARAMPROB_HEADER,
365 erroff - sizeof(struct ip6_frag) +
366 offsetof(struct ip6_frag, ip6f_offlg));
371 ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
375 bzero(ip6af, sizeof(*ip6af));
376 ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
377 ip6af->ip6af_off = fragoff;
378 ip6af->ip6af_frglen = frgpartlen;
379 ip6af->ip6af_offset = offset;
380 IP6_REASS_MBUF(ip6af) = m;
383 af6 = (struct ip6asfrag *)q6;
388 * Handle ECN by comparing this segment with the first one;
389 * if CE is set, do not lose CE.
390 * drop if CE and not-ECT are mixed for the same packet.
392 ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
394 if (ecn == IPTOS_ECN_CE) {
395 if (ecn0 == IPTOS_ECN_NOTECT) {
396 free(ip6af, M_FTABLE);
399 if (ecn0 != IPTOS_ECN_CE)
400 q6->ip6q_ecn = IPTOS_ECN_CE;
402 if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
403 free(ip6af, M_FTABLE);
408 * Find a segment which begins after this one does.
410 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
411 af6 = af6->ip6af_down)
412 if (af6->ip6af_off > ip6af->ip6af_off)
417 * If there is a preceding segment, it may provide some of
418 * our data already. If so, drop the data from the incoming
419 * segment. If it provides all of our data, drop us.
421 if (af6->ip6af_up != (struct ip6asfrag *)q6) {
422 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
425 if (i >= ip6af->ip6af_frglen)
427 m_adj(IP6_REASS_MBUF(ip6af), i);
428 ip6af->ip6af_off += i;
429 ip6af->ip6af_frglen -= i;
434 * While we overlap succeeding segments trim them or,
435 * if they are completely covered, dequeue them.
437 while (af6 != (struct ip6asfrag *)q6 &&
438 ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
439 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
440 if (i < af6->ip6af_frglen) {
441 af6->ip6af_frglen -= i;
443 m_adj(IP6_REASS_MBUF(af6), i);
446 af6 = af6->ip6af_down;
447 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
448 frag6_deq(af6->ip6af_up);
452 * If the incoming framgent overlaps some existing fragments in
453 * the reassembly queue, drop it, since it is dangerous to override
454 * existing fragments from a security point of view.
455 * We don't know which fragment is the bad guy - here we trust
456 * fragment that came in earlier, with no real reason.
458 * Note: due to changes after disabling this part, mbuf passed to
459 * m_adj() below now does not meet the requirement.
461 if (af6->ip6af_up != (struct ip6asfrag *)q6) {
462 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
465 #if 0 /* suppress the noisy log */
466 log(LOG_ERR, "%d bytes of a fragment from %s "
467 "overlaps the previous fragment\n",
468 i, ip6_sprintf(ip6buf, &q6->ip6q_src));
470 free(ip6af, M_FTABLE);
474 if (af6 != (struct ip6asfrag *)q6) {
475 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
477 #if 0 /* suppress the noisy log */
478 log(LOG_ERR, "%d bytes of a fragment from %s "
479 "overlaps the succeeding fragment",
480 i, ip6_sprintf(ip6buf, &q6->ip6q_src));
482 free(ip6af, M_FTABLE);
491 mac_ip6q_update(m, q6);
495 * Stick new segment in its place;
496 * check for complete reassembly.
497 * Move to front of packet queue, as we are
498 * the most recently active fragmented packet.
500 frag6_enq(ip6af, af6->ip6af_up);
504 if (q6 != V_ip6q.ip6q_next) {
506 frag6_insque(q6, &V_ip6q);
510 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
511 af6 = af6->ip6af_down) {
512 if (af6->ip6af_off != next) {
516 next += af6->ip6af_frglen;
518 if (af6->ip6af_up->ip6af_mff) {
524 * Reassembly is complete; concatenate fragments.
526 ip6af = q6->ip6q_down;
527 t = m = IP6_REASS_MBUF(ip6af);
528 af6 = ip6af->ip6af_down;
530 while (af6 != (struct ip6asfrag *)q6) {
531 af6dwn = af6->ip6af_down;
535 m_adj(IP6_REASS_MBUF(af6), af6->ip6af_offset);
536 m_cat(t, IP6_REASS_MBUF(af6));
541 /* adjust offset to point where the original next header starts */
542 offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
543 free(ip6af, M_FTABLE);
544 ip6 = mtod(m, struct ip6_hdr *);
545 ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
546 if (q6->ip6q_ecn == IPTOS_ECN_CE)
547 ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
550 *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
553 if (ip6_deletefraghdr(m, offset, M_NOWAIT) != 0) {
555 V_frag6_nfrags -= q6->ip6q_nfrag;
557 mac_ip6q_destroy(q6);
560 V_frag6_nfragpackets--;
566 * Store NXT to the original.
569 char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
574 V_frag6_nfrags -= q6->ip6q_nfrag;
576 mac_ip6q_reassemble(q6, m);
577 mac_ip6q_destroy(q6);
580 V_frag6_nfragpackets--;
582 if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
584 for (t = m; t; t = t->m_next)
586 m->m_pkthdr.len = plen;
590 mtag = m_tag_alloc(MTAG_ABI_IPV6, IPV6_TAG_DIRECT, sizeof(*ip6dc),
595 ip6dc = (struct ip6_direct_ctx *)(mtag + 1);
596 ip6dc->ip6dc_nxt = nxt;
597 ip6dc->ip6dc_off = offset;
599 m_tag_prepend(m, mtag);
603 IP6STAT_INC(ip6s_reassembled);
604 in6_ifstat_inc(dstifp, ifs6_reass_ok);
608 * Queue/dispatch for reprocessing.
610 netisr_dispatch(NETISR_IPV6_DIRECT, m);
615 * Tell launch routine the next header
625 in6_ifstat_inc(dstifp, ifs6_reass_fail);
626 IP6STAT_INC(ip6s_fragdropped);
632 * Free a fragment reassembly header and all
633 * associated datagrams.
636 frag6_freef(struct ip6q *q6)
638 struct ip6asfrag *af6, *down6;
642 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
644 struct mbuf *m = IP6_REASS_MBUF(af6);
646 down6 = af6->ip6af_down;
650 * Return ICMP time exceeded error for the 1st fragment.
651 * Just free other fragments.
653 if (af6->ip6af_off == 0) {
657 ip6 = mtod(m, struct ip6_hdr *);
659 /* restore source and destination addresses */
660 ip6->ip6_src = q6->ip6q_src;
661 ip6->ip6_dst = q6->ip6q_dst;
663 icmp6_error(m, ICMP6_TIME_EXCEEDED,
664 ICMP6_TIME_EXCEED_REASSEMBLY, 0);
670 V_frag6_nfrags -= q6->ip6q_nfrag;
672 mac_ip6q_destroy(q6);
675 V_frag6_nfragpackets--;
679 * Put an ip fragment on a reassembly chain.
680 * Like insque, but pointers in middle of structure.
683 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6)
689 af6->ip6af_down = up6->ip6af_down;
690 up6->ip6af_down->ip6af_up = af6;
691 up6->ip6af_down = af6;
695 * To frag6_enq as remque is to insque.
698 frag6_deq(struct ip6asfrag *af6)
703 af6->ip6af_up->ip6af_down = af6->ip6af_down;
704 af6->ip6af_down->ip6af_up = af6->ip6af_up;
708 frag6_insque(struct ip6q *new, struct ip6q *old)
713 new->ip6q_prev = old;
714 new->ip6q_next = old->ip6q_next;
715 old->ip6q_next->ip6q_prev= new;
716 old->ip6q_next = new;
720 frag6_remque(struct ip6q *p6)
725 p6->ip6q_prev->ip6q_next = p6->ip6q_next;
726 p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
730 * IPv6 reassembling timer processing;
731 * if a timer expires on a reassembly
737 VNET_ITERATOR_DECL(vnet_iter);
740 VNET_LIST_RLOCK_NOSLEEP();
742 VNET_FOREACH(vnet_iter) {
743 CURVNET_SET(vnet_iter);
744 q6 = V_ip6q.ip6q_next;
746 while (q6 != &V_ip6q) {
749 if (q6->ip6q_prev->ip6q_ttl == 0) {
750 IP6STAT_INC(ip6s_fragtimeout);
751 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
752 frag6_freef(q6->ip6q_prev);
756 * If we are over the maximum number of fragments
757 * (due to the limit being lowered), drain off
758 * enough to get down to the new limit.
760 while (V_frag6_nfragpackets > (u_int)V_ip6_maxfragpackets &&
762 IP6STAT_INC(ip6s_fragoverflow);
763 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
764 frag6_freef(V_ip6q.ip6q_prev);
769 VNET_LIST_RUNLOCK_NOSLEEP();
773 * Drain off all datagram fragments.
778 VNET_ITERATOR_DECL(vnet_iter);
780 VNET_LIST_RLOCK_NOSLEEP();
781 if (IP6Q_TRYLOCK() == 0) {
782 VNET_LIST_RUNLOCK_NOSLEEP();
785 VNET_FOREACH(vnet_iter) {
786 CURVNET_SET(vnet_iter);
787 while (V_ip6q.ip6q_next != &V_ip6q) {
788 IP6STAT_INC(ip6s_fragdropped);
789 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
790 frag6_freef(V_ip6q.ip6q_next);
795 VNET_LIST_RUNLOCK_NOSLEEP();
799 ip6_deletefraghdr(struct mbuf *m, int offset, int wait)
801 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
804 /* Delete frag6 header. */
805 if (m->m_len >= offset + sizeof(struct ip6_frag)) {
806 /* This is the only possible case with !PULLDOWN_TEST. */
807 bcopy(ip6, (char *)ip6 + sizeof(struct ip6_frag),
809 m->m_data += sizeof(struct ip6_frag);
810 m->m_len -= sizeof(struct ip6_frag);
812 /* This comes with no copy if the boundary is on cluster. */
813 if ((t = m_split(m, offset, wait)) == NULL)
815 m_adj(t, sizeof(struct ip6_frag));