613 lines
16 KiB
C
613 lines
16 KiB
C
/* $OpenBSD: frag6.c,v 1.88 2024/03/26 23:48:49 bluhm Exp $ */
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/* $KAME: frag6.c,v 1.40 2002/05/27 21:40:31 itojun Exp $ */
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/*
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* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the project nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/mbuf.h>
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#include <sys/socket.h>
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#include <sys/errno.h>
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#include <sys/time.h>
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#include <sys/kernel.h>
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#include <sys/pool.h>
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#include <sys/mutex.h>
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#include <net/if.h>
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#include <net/if_var.h>
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#include <net/route.h>
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#include <netinet/in.h>
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#include <netinet6/in6_var.h>
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#include <netinet/ip6.h>
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#include <netinet6/ip6_var.h>
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#include <netinet/icmp6.h>
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#include <netinet/ip.h> /* for ECN definitions */
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/* Protects `frag6_queue', `frag6_nfragpackets' and `frag6_nfrags'. */
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struct mutex frag6_mutex = MUTEX_INITIALIZER(IPL_SOFTNET);
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u_int frag6_nfragpackets;
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u_int frag6_nfrags;
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TAILQ_HEAD(ip6q_head, ip6q) frag6_queue; /* ip6 reassemble queue */
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void frag6_freef(struct ip6q *);
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void frag6_unlink(struct ip6q *, struct ip6q_head *);
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struct pool ip6af_pool;
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struct pool ip6q_pool;
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/*
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* Initialise reassembly queue and pools.
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*/
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void
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frag6_init(void)
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{
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pool_init(&ip6af_pool, sizeof(struct ip6asfrag),
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0, IPL_SOFTNET, 0, "ip6af", NULL);
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pool_init(&ip6q_pool, sizeof(struct ip6q),
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0, IPL_SOFTNET, 0, "ip6q", NULL);
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TAILQ_INIT(&frag6_queue);
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}
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/*
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* In RFC2460, fragment and reassembly rule do not agree with each other,
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* in terms of next header field handling in fragment header.
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* While the sender will use the same value for all of the fragmented packets,
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* receiver is suggested not to check the consistency.
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*
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* fragment rule (p20):
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* (2) A Fragment header containing:
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* The Next Header value that identifies the first header of
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* the Fragmentable Part of the original packet.
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* -> next header field is same for all fragments
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*
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* reassembly rule (p21):
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* The Next Header field of the last header of the Unfragmentable
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* Part is obtained from the Next Header field of the first
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* fragment's Fragment header.
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* -> should grab it from the first fragment only
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*
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* The following note also contradicts with fragment rule - noone is going to
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* send different fragment with different next header field.
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*
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* additional note (p22):
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* The Next Header values in the Fragment headers of different
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* fragments of the same original packet may differ. Only the value
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* from the Offset zero fragment packet is used for reassembly.
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* -> should grab it from the first fragment only
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*
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* There is no explicit reason given in the RFC. Historical reason maybe?
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*/
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/*
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* Fragment input
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*/
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int
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frag6_input(struct mbuf **mp, int *offp, int proto, int af)
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{
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struct mbuf *m = *mp, *t;
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struct ip6_hdr *ip6;
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struct ip6_frag *ip6f;
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struct ip6q *q6;
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struct ip6asfrag *af6, *ip6af, *naf6, *paf6;
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int offset = *offp, nxt, i, next;
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int first_frag = 0;
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int fragoff, frgpartlen; /* must be larger than u_int16_t */
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u_int8_t ecn, ecn0;
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ip6 = mtod(m, struct ip6_hdr *);
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IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
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if (ip6f == NULL)
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return IPPROTO_DONE;
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/* jumbo payload can't contain a fragment header */
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if (ip6->ip6_plen == 0) {
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icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
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return IPPROTO_DONE;
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}
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/*
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* check whether fragment packet's fragment length is
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* multiple of 8 octets.
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* sizeof(struct ip6_frag) == 8
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* sizeof(struct ip6_hdr) = 40
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*/
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if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
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(((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
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icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
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offsetof(struct ip6_hdr, ip6_plen));
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return IPPROTO_DONE;
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}
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ip6stat_inc(ip6s_fragments);
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/* offset now points to data portion */
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offset += sizeof(struct ip6_frag);
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/*
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* RFC6946: A host that receives an IPv6 packet which includes
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* a Fragment Header with the "Fragment Offset" equal to 0 and
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* the "M" bit equal to 0 MUST process such packet in isolation
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* from any other packets/fragments.
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*/
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fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
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if (fragoff == 0 && !(ip6f->ip6f_offlg & IP6F_MORE_FRAG)) {
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ip6stat_inc(ip6s_reassembled);
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*offp = offset;
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return ip6f->ip6f_nxt;
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}
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/* Ignore empty non atomic fragment, do not classify as overlapping. */
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if (sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) <= offset) {
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m_freem(m);
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return IPPROTO_DONE;
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}
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mtx_enter(&frag6_mutex);
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/*
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* Enforce upper bound on number of fragments.
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* If maxfrag is 0, never accept fragments.
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* If maxfrag is -1, accept all fragments without limitation.
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*/
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if (ip6_maxfrags >= 0 && frag6_nfrags >= (u_int)ip6_maxfrags) {
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mtx_leave(&frag6_mutex);
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goto dropfrag;
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}
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TAILQ_FOREACH(q6, &frag6_queue, ip6q_queue)
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if (ip6f->ip6f_ident == q6->ip6q_ident &&
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IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
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IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
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break;
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if (q6 == NULL) {
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/*
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* the first fragment to arrive, create a reassembly queue.
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*/
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first_frag = 1;
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/*
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* Enforce upper bound on number of fragmented packets
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* for which we attempt reassembly;
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* If maxfragpackets is 0, never accept fragments.
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* If maxfragpackets is -1, accept all fragments without
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* limitation.
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*/
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if (ip6_maxfragpackets >= 0 &&
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frag6_nfragpackets >= (u_int)ip6_maxfragpackets) {
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mtx_leave(&frag6_mutex);
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goto dropfrag;
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}
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frag6_nfragpackets++;
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q6 = pool_get(&ip6q_pool, PR_NOWAIT | PR_ZERO);
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if (q6 == NULL) {
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mtx_leave(&frag6_mutex);
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goto dropfrag;
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}
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TAILQ_INSERT_HEAD(&frag6_queue, q6, ip6q_queue);
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/* ip6q_nxt will be filled afterwards, from 1st fragment */
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LIST_INIT(&q6->ip6q_asfrag);
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q6->ip6q_ident = ip6f->ip6f_ident;
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q6->ip6q_ttl = IPV6_FRAGTTL;
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q6->ip6q_src = ip6->ip6_src;
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q6->ip6q_dst = ip6->ip6_dst;
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q6->ip6q_ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
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q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
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q6->ip6q_nfrag = 0;
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}
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/*
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* If it's the 1st fragment, record the length of the
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* unfragmentable part and the next header of the fragment header.
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*/
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if (fragoff == 0) {
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q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
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sizeof(struct ip6_frag);
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q6->ip6q_nxt = ip6f->ip6f_nxt;
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}
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/*
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* Check that the reassembled packet would not exceed 65535 bytes
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* in size.
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* If it would exceed, discard the fragment and return an ICMP error.
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*/
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frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
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if (q6->ip6q_unfrglen >= 0) {
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/* The 1st fragment has already arrived. */
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if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
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mtx_leave(&frag6_mutex);
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icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
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offset - sizeof(struct ip6_frag) +
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offsetof(struct ip6_frag, ip6f_offlg));
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return (IPPROTO_DONE);
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}
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} else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
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mtx_leave(&frag6_mutex);
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icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
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offset - sizeof(struct ip6_frag) +
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offsetof(struct ip6_frag, ip6f_offlg));
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return (IPPROTO_DONE);
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}
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/*
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* If it's the first fragment, do the above check for each
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* fragment already stored in the reassembly queue.
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*/
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if (fragoff == 0) {
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LIST_FOREACH_SAFE(af6, &q6->ip6q_asfrag, ip6af_list, naf6) {
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if (q6->ip6q_unfrglen + af6->ip6af_off +
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af6->ip6af_frglen > IPV6_MAXPACKET) {
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struct mbuf *merr = af6->ip6af_m;
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struct ip6_hdr *ip6err;
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int erroff = af6->ip6af_offset;
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/* dequeue the fragment. */
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LIST_REMOVE(af6, ip6af_list);
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pool_put(&ip6af_pool, af6);
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/* adjust pointer. */
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ip6err = mtod(merr, struct ip6_hdr *);
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/*
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* Restore source and destination addresses
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* in the erroneous IPv6 header.
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*/
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ip6err->ip6_src = q6->ip6q_src;
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ip6err->ip6_dst = q6->ip6q_dst;
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icmp6_error(merr, ICMP6_PARAM_PROB,
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ICMP6_PARAMPROB_HEADER,
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erroff - sizeof(struct ip6_frag) +
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offsetof(struct ip6_frag, ip6f_offlg));
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}
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}
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}
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ip6af = pool_get(&ip6af_pool, PR_NOWAIT | PR_ZERO);
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if (ip6af == NULL) {
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mtx_leave(&frag6_mutex);
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goto dropfrag;
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}
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ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
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ip6af->ip6af_off = fragoff;
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ip6af->ip6af_frglen = frgpartlen;
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ip6af->ip6af_offset = offset;
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ip6af->ip6af_m = m;
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if (first_frag) {
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paf6 = NULL;
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goto insert;
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}
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/*
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* Handle ECN by comparing this segment with the first one;
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* if CE is set, do not lose CE.
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* drop if CE and not-ECT are mixed for the same packet.
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*/
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ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
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ecn0 = q6->ip6q_ecn;
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if (ecn == IPTOS_ECN_CE) {
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if (ecn0 == IPTOS_ECN_NOTECT) {
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mtx_leave(&frag6_mutex);
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pool_put(&ip6af_pool, ip6af);
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goto dropfrag;
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}
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if (ecn0 != IPTOS_ECN_CE)
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q6->ip6q_ecn = IPTOS_ECN_CE;
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}
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if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
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mtx_leave(&frag6_mutex);
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pool_put(&ip6af_pool, ip6af);
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goto dropfrag;
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}
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/*
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* Find a segment which begins after this one does.
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*/
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for (paf6 = NULL, af6 = LIST_FIRST(&q6->ip6q_asfrag);
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af6 != NULL;
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paf6 = af6, af6 = LIST_NEXT(af6, ip6af_list))
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if (af6->ip6af_off > ip6af->ip6af_off)
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break;
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/*
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* RFC 5722, Errata 3089: When reassembling an IPv6 datagram, if one
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* or more its constituent fragments is determined to be an overlapping
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* fragment, the entire datagram (and any constituent fragments) MUST
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* be silently discarded.
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*/
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if (paf6 != NULL) {
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i = (paf6->ip6af_off + paf6->ip6af_frglen) - ip6af->ip6af_off;
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if (i > 0)
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goto flushfrags;
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}
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if (af6 != NULL) {
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i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
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if (i > 0)
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goto flushfrags;
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}
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insert:
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/*
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* Stick new segment in its place;
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* check for complete reassembly.
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* Move to front of packet queue, as we are
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* the most recently active fragmented packet.
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*/
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if (paf6 != NULL)
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LIST_INSERT_AFTER(paf6, ip6af, ip6af_list);
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else
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LIST_INSERT_HEAD(&q6->ip6q_asfrag, ip6af, ip6af_list);
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frag6_nfrags++;
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q6->ip6q_nfrag++;
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next = 0;
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for (paf6 = NULL, af6 = LIST_FIRST(&q6->ip6q_asfrag);
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af6 != NULL;
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paf6 = af6, af6 = LIST_NEXT(af6, ip6af_list)) {
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if (af6->ip6af_off != next) {
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mtx_leave(&frag6_mutex);
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return IPPROTO_DONE;
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}
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next += af6->ip6af_frglen;
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}
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if (paf6->ip6af_mff) {
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mtx_leave(&frag6_mutex);
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return IPPROTO_DONE;
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}
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/*
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* Reassembly is complete; concatenate fragments.
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*/
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ip6af = LIST_FIRST(&q6->ip6q_asfrag);
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LIST_REMOVE(ip6af, ip6af_list);
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t = m = ip6af->ip6af_m;
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while ((af6 = LIST_FIRST(&q6->ip6q_asfrag)) != NULL) {
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LIST_REMOVE(af6, ip6af_list);
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while (t->m_next)
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t = t->m_next;
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t->m_next = af6->ip6af_m;
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m_adj(t->m_next, af6->ip6af_offset);
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m_removehdr(t->m_next);
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pool_put(&ip6af_pool, af6);
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}
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/* adjust offset to point where the original next header starts */
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offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
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pool_put(&ip6af_pool, ip6af);
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next += offset - sizeof(struct ip6_hdr);
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if ((u_int)next > IPV6_MAXPACKET) {
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TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue);
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frag6_nfrags -= q6->ip6q_nfrag;
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frag6_nfragpackets--;
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mtx_leave(&frag6_mutex);
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pool_put(&ip6q_pool, q6);
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goto dropfrag;
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}
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ip6 = mtod(m, struct ip6_hdr *);
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ip6->ip6_plen = htons(next);
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ip6->ip6_src = q6->ip6q_src;
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ip6->ip6_dst = q6->ip6q_dst;
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if (q6->ip6q_ecn == IPTOS_ECN_CE)
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ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
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nxt = q6->ip6q_nxt;
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/* Delete frag6 header */
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if (frag6_deletefraghdr(m, offset) != 0) {
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TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue);
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frag6_nfrags -= q6->ip6q_nfrag;
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frag6_nfragpackets--;
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mtx_leave(&frag6_mutex);
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pool_put(&ip6q_pool, q6);
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goto dropfrag;
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}
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TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue);
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frag6_nfrags -= q6->ip6q_nfrag;
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frag6_nfragpackets--;
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mtx_leave(&frag6_mutex);
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pool_put(&ip6q_pool, q6);
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m_calchdrlen(m);
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/*
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* Restore NXT to the original.
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*/
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{
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int prvnxt = ip6_get_prevhdr(m, offset);
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uint8_t *prvnxtp;
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IP6_EXTHDR_GET(prvnxtp, uint8_t *, m, prvnxt,
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sizeof(*prvnxtp));
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if (prvnxtp == NULL)
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goto dropfrag;
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*prvnxtp = nxt;
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}
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ip6stat_inc(ip6s_reassembled);
|
|
|
|
/*
|
|
* Tell launch routine the next header
|
|
*/
|
|
|
|
*mp = m;
|
|
*offp = offset;
|
|
|
|
return nxt;
|
|
|
|
flushfrags:
|
|
TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue);
|
|
frag6_nfrags -= q6->ip6q_nfrag;
|
|
frag6_nfragpackets--;
|
|
|
|
mtx_leave(&frag6_mutex);
|
|
|
|
pool_put(&ip6af_pool, ip6af);
|
|
|
|
while ((af6 = LIST_FIRST(&q6->ip6q_asfrag)) != NULL) {
|
|
LIST_REMOVE(af6, ip6af_list);
|
|
m_freem(af6->ip6af_m);
|
|
pool_put(&ip6af_pool, af6);
|
|
}
|
|
ip6stat_add(ip6s_fragdropped, q6->ip6q_nfrag + 1);
|
|
pool_put(&ip6q_pool, q6);
|
|
m_freem(m);
|
|
return IPPROTO_DONE;
|
|
|
|
dropfrag:
|
|
ip6stat_inc(ip6s_fragdropped);
|
|
m_freem(m);
|
|
return IPPROTO_DONE;
|
|
}
|
|
|
|
/*
|
|
* Delete fragment header after the unfragmentable header portions.
|
|
*/
|
|
int
|
|
frag6_deletefraghdr(struct mbuf *m, int offset)
|
|
{
|
|
struct mbuf *t;
|
|
|
|
if (m->m_len >= offset + sizeof(struct ip6_frag)) {
|
|
memmove(mtod(m, caddr_t) + sizeof(struct ip6_frag),
|
|
mtod(m, caddr_t), offset);
|
|
m->m_data += sizeof(struct ip6_frag);
|
|
m->m_len -= sizeof(struct ip6_frag);
|
|
} else {
|
|
/* this comes with no copy if the boundary is on cluster */
|
|
if ((t = m_split(m, offset, M_DONTWAIT)) == NULL)
|
|
return (ENOBUFS);
|
|
m_adj(t, sizeof(struct ip6_frag));
|
|
m_cat(m, t);
|
|
}
|
|
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Free a fragment reassembly header and all
|
|
* associated datagrams.
|
|
* The header must not be in any queue.
|
|
*/
|
|
void
|
|
frag6_freef(struct ip6q *q6)
|
|
{
|
|
struct ip6asfrag *af6;
|
|
|
|
while ((af6 = LIST_FIRST(&q6->ip6q_asfrag)) != NULL) {
|
|
struct mbuf *m = af6->ip6af_m;
|
|
|
|
LIST_REMOVE(af6, ip6af_list);
|
|
|
|
/*
|
|
* Return ICMP time exceeded error for the 1st fragment.
|
|
* Just free other fragments.
|
|
*/
|
|
if (af6->ip6af_off == 0) {
|
|
struct ip6_hdr *ip6;
|
|
|
|
/* adjust pointer */
|
|
ip6 = mtod(m, struct ip6_hdr *);
|
|
|
|
/* restore source and destination addresses */
|
|
ip6->ip6_src = q6->ip6q_src;
|
|
ip6->ip6_dst = q6->ip6q_dst;
|
|
|
|
NET_LOCK();
|
|
icmp6_error(m, ICMP6_TIME_EXCEEDED,
|
|
ICMP6_TIME_EXCEED_REASSEMBLY, 0);
|
|
NET_UNLOCK();
|
|
} else
|
|
m_freem(m);
|
|
pool_put(&ip6af_pool, af6);
|
|
}
|
|
pool_put(&ip6q_pool, q6);
|
|
}
|
|
|
|
/*
|
|
* Unlinks a fragment reassembly header from the reassembly queue
|
|
* and inserts it into a given remove queue.
|
|
*/
|
|
void
|
|
frag6_unlink(struct ip6q *q6, struct ip6q_head *rmq6)
|
|
{
|
|
MUTEX_ASSERT_LOCKED(&frag6_mutex);
|
|
|
|
TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue);
|
|
TAILQ_INSERT_HEAD(rmq6, q6, ip6q_queue);
|
|
frag6_nfrags -= q6->ip6q_nfrag;
|
|
frag6_nfragpackets--;
|
|
}
|
|
|
|
/*
|
|
* IPv6 reassembling timer processing;
|
|
* if a timer expires on a reassembly
|
|
* queue, discard it.
|
|
*/
|
|
void
|
|
frag6_slowtimo(void)
|
|
{
|
|
struct ip6q_head rmq6;
|
|
struct ip6q *q6, *nq6;
|
|
|
|
TAILQ_INIT(&rmq6);
|
|
|
|
mtx_enter(&frag6_mutex);
|
|
|
|
TAILQ_FOREACH_SAFE(q6, &frag6_queue, ip6q_queue, nq6) {
|
|
if (--q6->ip6q_ttl == 0) {
|
|
ip6stat_inc(ip6s_fragtimeout);
|
|
frag6_unlink(q6, &rmq6);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If we are over the maximum number of fragments
|
|
* (due to the limit being lowered), drain off
|
|
* enough to get down to the new limit.
|
|
*/
|
|
while (frag6_nfragpackets > (u_int)ip6_maxfragpackets &&
|
|
!TAILQ_EMPTY(&frag6_queue)) {
|
|
ip6stat_inc(ip6s_fragoverflow);
|
|
frag6_unlink(TAILQ_LAST(&frag6_queue, ip6q_head), &rmq6);
|
|
}
|
|
|
|
mtx_leave(&frag6_mutex);
|
|
|
|
while ((q6 = TAILQ_FIRST(&rmq6)) != NULL) {
|
|
TAILQ_REMOVE(&rmq6, q6, ip6q_queue);
|
|
frag6_freef(q6);
|
|
}
|
|
}
|