FreeBSD/Linux Kernel Cross Reference
sys/netinet6/frag6.c

     /*-
      * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the project nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      $KAME: frag6.c,v 1.33 2002/01/07 11:34:48 kjc Exp $
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/domain.h>
    #include <sys/protosw.h>
    #include <sys/socket.h>
    #include <sys/errno.h>
    #include <sys/time.h>
    #include <sys/kernel.h>
    #include <sys/syslog.h>
    
    #include <net/if.h>
    #include <net/route.h>
    
    #include <netinet/in.h>
    #include <netinet/in_var.h>
    #include <netinet/ip6.h>
    #include <netinet6/ip6_var.h>
    #include <netinet/icmp6.h>
    #include <netinet/in_systm.h>   /* for ECN definitions */
    #include <netinet/ip.h>         /* for ECN definitions */
    
    #include <net/net_osdep.h>
    
    /*
     * Define it to get a correct behavior on per-interface statistics.
     * You will need to perform an extra routing table lookup, per fragment,
     * to do it.  This may, or may not be, a performance hit.
     */
    #define IN6_IFSTAT_STRICT
    
    static void frag6_enq(struct ip6asfrag *, struct ip6asfrag *);
    static void frag6_deq(struct ip6asfrag *);
    static void frag6_insque(struct ip6q *, struct ip6q *);
    static void frag6_remque(struct ip6q *);
    static void frag6_freef(struct ip6q *);
    
    static struct mtx ip6qlock;
    /*
     * These fields all protected by ip6qlock.
     */
    static u_int frag6_nfragpackets;
    static u_int frag6_nfrags;
    static struct   ip6q ip6q;      /* ip6 reassemble queue */
    
    #define IP6Q_LOCK_INIT()        mtx_init(&ip6qlock, "ip6qlock", NULL, MTX_DEF);
    #define IP6Q_LOCK()             mtx_lock(&ip6qlock)
    #define IP6Q_TRYLOCK()          mtx_trylock(&ip6qlock)
    #define IP6Q_LOCK_ASSERT()      mtx_assert(&ip6qlock, MA_OWNED)
    #define IP6Q_UNLOCK()           mtx_unlock(&ip6qlock)
    
    static MALLOC_DEFINE(M_FTABLE, "fragment", "fragment reassembly header");
    
    /*
     * Initialise reassembly queue and fragment identifier.
     */
    static void
    frag6_change(void *tag)
    {
    
            ip6_maxfragpackets = nmbclusters / 4;
            ip6_maxfrags = nmbclusters / 4;
    }
    
   void
   frag6_init()
   {
   
           ip6_maxfragpackets = nmbclusters / 4;
           ip6_maxfrags = nmbclusters / 4;
           EVENTHANDLER_REGISTER(nmbclusters_change,
               frag6_change, NULL, EVENTHANDLER_PRI_ANY);
   
           IP6Q_LOCK_INIT();
   
           ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
   }
   
   /*
    * In RFC2460, fragment and reassembly rule do not agree with each other,
    * in terms of next header field handling in fragment header.
    * While the sender will use the same value for all of the fragmented packets,
    * receiver is suggested not to check the consistency.
    *
    * fragment rule (p20):
    *      (2) A Fragment header containing:
    *      The Next Header value that identifies the first header of
    *      the Fragmentable Part of the original packet.
    *              -> next header field is same for all fragments
    *
    * reassembly rule (p21):
    *      The Next Header field of the last header of the Unfragmentable
    *      Part is obtained from the Next Header field of the first
    *      fragment's Fragment header.
    *              -> should grab it from the first fragment only
    *
    * The following note also contradicts with fragment rule - noone is going to
    * send different fragment with different next header field.
    *
    * additional note (p22):
    *      The Next Header values in the Fragment headers of different
    *      fragments of the same original packet may differ.  Only the value
    *      from the Offset zero fragment packet is used for reassembly.
    *              -> should grab it from the first fragment only
    *
    * There is no explicit reason given in the RFC.  Historical reason maybe?
    */
   /*
    * Fragment input
    */
   int
   frag6_input(mp, offp, proto)
           struct mbuf **mp;
           int *offp, proto;
   {
           struct mbuf *m = *mp, *t;
           struct ip6_hdr *ip6;
           struct ip6_frag *ip6f;
           struct ip6q *q6;
           struct ip6asfrag *af6, *ip6af, *af6dwn;
   #ifdef IN6_IFSTAT_STRICT
           struct in6_ifaddr *ia;
   #endif
           int offset = *offp, nxt, i, next;
           int first_frag = 0;
           int fragoff, frgpartlen;        /* must be larger than u_int16_t */
           struct ifnet *dstifp;
           u_int8_t ecn, ecn0;
   
           ip6 = mtod(m, struct ip6_hdr *);
   #ifndef PULLDOWN_TEST
           IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
           ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
   #else
           IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
           if (ip6f == NULL)
                   return (IPPROTO_DONE);
   #endif
   
           dstifp = NULL;
   #ifdef IN6_IFSTAT_STRICT
           /* find the destination interface of the packet. */
           if ((ia = ip6_getdstifaddr(m)) != NULL)
                   dstifp = ia->ia_ifp;
   #else
           /* we are violating the spec, this is not the destination interface */
           if ((m->m_flags & M_PKTHDR) != 0)
                   dstifp = m->m_pkthdr.rcvif;
   #endif
   
           /* jumbo payload can't contain a fragment header */
           if (ip6->ip6_plen == 0) {
                   icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
                   in6_ifstat_inc(dstifp, ifs6_reass_fail);
                   return IPPROTO_DONE;
           }
   
           /*
            * check whether fragment packet's fragment length is
            * multiple of 8 octets.
            * sizeof(struct ip6_frag) == 8
            * sizeof(struct ip6_hdr) = 40
            */
           if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
               (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
                   icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
                       offsetof(struct ip6_hdr, ip6_plen));
                   in6_ifstat_inc(dstifp, ifs6_reass_fail);
                   return IPPROTO_DONE;
           }
   
           ip6stat.ip6s_fragments++;
           in6_ifstat_inc(dstifp, ifs6_reass_reqd);
   
           /* offset now points to data portion */
           offset += sizeof(struct ip6_frag);
   
           IP6Q_LOCK();
   
           /*
            * Enforce upper bound on number of fragments.
            * If maxfrag is 0, never accept fragments.
            * If maxfrag is -1, accept all fragments without limitation.
            */
           if (ip6_maxfrags < 0)
                   ;
           else if (frag6_nfrags >= (u_int)ip6_maxfrags)
                   goto dropfrag;
   
           for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next)
                   if (ip6f->ip6f_ident == q6->ip6q_ident &&
                       IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
                       IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
                           break;
   
           if (q6 == &ip6q) {
                   /*
                    * the first fragment to arrive, create a reassembly queue.
                    */
                   first_frag = 1;
   
                   /*
                    * Enforce upper bound on number of fragmented packets
                    * for which we attempt reassembly;
                    * If maxfragpackets is 0, never accept fragments.
                    * If maxfragpackets is -1, accept all fragments without
                    * limitation.
                    */
                   if (ip6_maxfragpackets < 0)
                           ;
                   else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets)
                           goto dropfrag;
                   frag6_nfragpackets++;
                   q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
                       M_NOWAIT);
                   if (q6 == NULL)
                           goto dropfrag;
                   bzero(q6, sizeof(*q6));
   
                   frag6_insque(q6, &ip6q);
   
                   /* ip6q_nxt will be filled afterwards, from 1st fragment */
                   q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
   #ifdef notyet
                   q6->ip6q_nxtp   = (u_char *)nxtp;
   #endif
                   q6->ip6q_ident  = ip6f->ip6f_ident;
                   q6->ip6q_ttl    = IPV6_FRAGTTL;
                   q6->ip6q_src    = ip6->ip6_src;
                   q6->ip6q_dst    = ip6->ip6_dst;
                   q6->ip6q_ecn    =
                       (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
                   q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
   
                   q6->ip6q_nfrag = 0;
           }
   
           /*
            * If it's the 1st fragment, record the length of the
            * unfragmentable part and the next header of the fragment header.
            */
           fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
           if (fragoff == 0) {
                   q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
                       sizeof(struct ip6_frag);
                   q6->ip6q_nxt = ip6f->ip6f_nxt;
           }
   
           /*
            * Check that the reassembled packet would not exceed 65535 bytes
            * in size.
            * If it would exceed, discard the fragment and return an ICMP error.
            */
           frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
           if (q6->ip6q_unfrglen >= 0) {
                   /* The 1st fragment has already arrived. */
                   if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
                           icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
                               offset - sizeof(struct ip6_frag) +
                               offsetof(struct ip6_frag, ip6f_offlg));
                           IP6Q_UNLOCK();
                           return (IPPROTO_DONE);
                   }
           } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
                   icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
                       offset - sizeof(struct ip6_frag) +
                       offsetof(struct ip6_frag, ip6f_offlg));
                   IP6Q_UNLOCK();
                   return (IPPROTO_DONE);
           }
           /*
            * If it's the first fragment, do the above check for each
            * fragment already stored in the reassembly queue.
            */
           if (fragoff == 0) {
                   for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
                        af6 = af6dwn) {
                           af6dwn = af6->ip6af_down;
   
                           if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
                               IPV6_MAXPACKET) {
                                   struct mbuf *merr = IP6_REASS_MBUF(af6);
                                   struct ip6_hdr *ip6err;
                                   int erroff = af6->ip6af_offset;
   
                                   /* dequeue the fragment. */
                                   frag6_deq(af6);
                                   free(af6, M_FTABLE);
   
                                   /* adjust pointer. */
                                   ip6err = mtod(merr, struct ip6_hdr *);
   
                                   /*
                                    * Restore source and destination addresses
                                    * in the erroneous IPv6 header.
                                    */
                                   ip6err->ip6_src = q6->ip6q_src;
                                   ip6err->ip6_dst = q6->ip6q_dst;
   
                                   icmp6_error(merr, ICMP6_PARAM_PROB,
                                       ICMP6_PARAMPROB_HEADER,
                                       erroff - sizeof(struct ip6_frag) +
                                       offsetof(struct ip6_frag, ip6f_offlg));
                           }
                   }
           }
   
           ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
               M_NOWAIT);
           if (ip6af == NULL)
                   goto dropfrag;
           bzero(ip6af, sizeof(*ip6af));
           ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
           ip6af->ip6af_off = fragoff;
           ip6af->ip6af_frglen = frgpartlen;
           ip6af->ip6af_offset = offset;
           IP6_REASS_MBUF(ip6af) = m;
   
           if (first_frag) {
                   af6 = (struct ip6asfrag *)q6;
                   goto insert;
           }
   
           /*
            * Handle ECN by comparing this segment with the first one;
            * if CE is set, do not lose CE.
            * drop if CE and not-ECT are mixed for the same packet.
            */
           ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
           ecn0 = q6->ip6q_ecn;
           if (ecn == IPTOS_ECN_CE) {
                   if (ecn0 == IPTOS_ECN_NOTECT) {
                           free(ip6af, M_FTABLE);
                           goto dropfrag;
                   }
                   if (ecn0 != IPTOS_ECN_CE)
                           q6->ip6q_ecn = IPTOS_ECN_CE;
           }
           if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
                   free(ip6af, M_FTABLE);
                   goto dropfrag;
           }
   
           /*
            * Find a segment which begins after this one does.
            */
           for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
                af6 = af6->ip6af_down)
                   if (af6->ip6af_off > ip6af->ip6af_off)
                           break;
   
   #if 0
           /*
            * If there is a preceding segment, it may provide some of
            * our data already.  If so, drop the data from the incoming
            * segment.  If it provides all of our data, drop us.
            */
           if (af6->ip6af_up != (struct ip6asfrag *)q6) {
                   i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
                           - ip6af->ip6af_off;
                   if (i > 0) {
                           if (i >= ip6af->ip6af_frglen)
                                   goto dropfrag;
                           m_adj(IP6_REASS_MBUF(ip6af), i);
                           ip6af->ip6af_off += i;
                           ip6af->ip6af_frglen -= i;
                   }
           }
   
           /*
            * While we overlap succeeding segments trim them or,
            * if they are completely covered, dequeue them.
            */
           while (af6 != (struct ip6asfrag *)q6 &&
                  ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
                   i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
                   if (i < af6->ip6af_frglen) {
                           af6->ip6af_frglen -= i;
                           af6->ip6af_off += i;
                           m_adj(IP6_REASS_MBUF(af6), i);
                           break;
                   }
                   af6 = af6->ip6af_down;
                   m_freem(IP6_REASS_MBUF(af6->ip6af_up));
                   frag6_deq(af6->ip6af_up);
           }
   #else
           /*
            * If the incoming framgent overlaps some existing fragments in
            * the reassembly queue, drop it, since it is dangerous to override
            * existing fragments from a security point of view.
            * We don't know which fragment is the bad guy - here we trust
            * fragment that came in earlier, with no real reason.
            *
            * Note: due to changes after disabling this part, mbuf passed to
            * m_adj() below now does not meet the requirement.
            */
           if (af6->ip6af_up != (struct ip6asfrag *)q6) {
                   i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
                           - ip6af->ip6af_off;
                   if (i > 0) {
   #if 0                           /* suppress the noisy log */
                           log(LOG_ERR, "%d bytes of a fragment from %s "
                               "overlaps the previous fragment\n",
                               i, ip6_sprintf(&q6->ip6q_src));
   #endif
                           free(ip6af, M_FTABLE);
                           goto dropfrag;
                   }
           }
           if (af6 != (struct ip6asfrag *)q6) {
                   i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
                   if (i > 0) {
   #if 0                           /* suppress the noisy log */
                           log(LOG_ERR, "%d bytes of a fragment from %s "
                               "overlaps the succeeding fragment",
                               i, ip6_sprintf(&q6->ip6q_src));
   #endif
                           free(ip6af, M_FTABLE);
                           goto dropfrag;
                   }
           }
   #endif
   
   insert:
   
           /*
            * Stick new segment in its place;
            * check for complete reassembly.
            * Move to front of packet queue, as we are
            * the most recently active fragmented packet.
            */
           frag6_enq(ip6af, af6->ip6af_up);
           frag6_nfrags++;
           q6->ip6q_nfrag++;
   #if 0 /* xxx */
           if (q6 != ip6q.ip6q_next) {
                   frag6_remque(q6);
                   frag6_insque(q6, &ip6q);
           }
   #endif
           next = 0;
           for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
                af6 = af6->ip6af_down) {
                   if (af6->ip6af_off != next) {
                           IP6Q_UNLOCK();
                           return IPPROTO_DONE;
                   }
                   next += af6->ip6af_frglen;
           }
           if (af6->ip6af_up->ip6af_mff) {
                   IP6Q_UNLOCK();
                   return IPPROTO_DONE;
           }
   
           /*
            * Reassembly is complete; concatenate fragments.
            */
           ip6af = q6->ip6q_down;
           t = m = IP6_REASS_MBUF(ip6af);
           af6 = ip6af->ip6af_down;
           frag6_deq(ip6af);
           while (af6 != (struct ip6asfrag *)q6) {
                   af6dwn = af6->ip6af_down;
                   frag6_deq(af6);
                   while (t->m_next)
                           t = t->m_next;
                   t->m_next = IP6_REASS_MBUF(af6);
                   m_adj(t->m_next, af6->ip6af_offset);
                   free(af6, M_FTABLE);
                   af6 = af6dwn;
           }
   
           /* adjust offset to point where the original next header starts */
           offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
           free(ip6af, M_FTABLE);
           ip6 = mtod(m, struct ip6_hdr *);
           ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
           if (q6->ip6q_ecn == IPTOS_ECN_CE)
                   ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
           nxt = q6->ip6q_nxt;
   #ifdef notyet
           *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
   #endif
   
           /* Delete frag6 header */
           if (m->m_len >= offset + sizeof(struct ip6_frag)) {
                   /* This is the only possible case with !PULLDOWN_TEST */
                   ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
                       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) {
                           frag6_remque(q6);
                           frag6_nfrags -= q6->ip6q_nfrag;
                           free(q6, M_FTABLE);
                           frag6_nfragpackets--;
                           goto dropfrag;
                   }
                   m_adj(t, sizeof(struct ip6_frag));
                   m_cat(m, t);
           }
   
           /*
            * Store NXT to the original.
            */
           {
                   char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
                   *prvnxtp = nxt;
           }
   
           frag6_remque(q6);
           frag6_nfrags -= q6->ip6q_nfrag;
           free(q6, M_FTABLE);
           frag6_nfragpackets--;
   
           if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
                   int plen = 0;
                   for (t = m; t; t = t->m_next)
                           plen += t->m_len;
                   m->m_pkthdr.len = plen;
           }
   
           ip6stat.ip6s_reassembled++;
           in6_ifstat_inc(dstifp, ifs6_reass_ok);
   
           /*
            * Tell launch routine the next header
            */
   
           *mp = m;
           *offp = offset;
   
           IP6Q_UNLOCK();
           return nxt;
   
    dropfrag:
           IP6Q_UNLOCK();
           in6_ifstat_inc(dstifp, ifs6_reass_fail);
           ip6stat.ip6s_fragdropped++;
           m_freem(m);
           return IPPROTO_DONE;
   }
   
   /*
    * Free a fragment reassembly header and all
    * associated datagrams.
    */
   void
   frag6_freef(q6)
           struct ip6q *q6;
   {
           struct ip6asfrag *af6, *down6;
   
           IP6Q_LOCK_ASSERT();
   
           for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
                af6 = down6) {
                   struct mbuf *m = IP6_REASS_MBUF(af6);
   
                   down6 = af6->ip6af_down;
                   frag6_deq(af6);
   
                   /*
                    * 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;
   
                           icmp6_error(m, ICMP6_TIME_EXCEEDED,
                                       ICMP6_TIME_EXCEED_REASSEMBLY, 0);
                   } else
                           m_freem(m);
                   free(af6, M_FTABLE);
           }
           frag6_remque(q6);
           frag6_nfrags -= q6->ip6q_nfrag;
           free(q6, M_FTABLE);
           frag6_nfragpackets--;
   }
   
   /*
    * Put an ip fragment on a reassembly chain.
    * Like insque, but pointers in middle of structure.
    */
   void
   frag6_enq(af6, up6)
           struct ip6asfrag *af6, *up6;
   {
   
           IP6Q_LOCK_ASSERT();
   
           af6->ip6af_up = up6;
           af6->ip6af_down = up6->ip6af_down;
           up6->ip6af_down->ip6af_up = af6;
           up6->ip6af_down = af6;
   }
   
   /*
    * To frag6_enq as remque is to insque.
    */
   void
   frag6_deq(af6)
           struct ip6asfrag *af6;
   {
   
           IP6Q_LOCK_ASSERT();
   
           af6->ip6af_up->ip6af_down = af6->ip6af_down;
           af6->ip6af_down->ip6af_up = af6->ip6af_up;
   }
   
   void
   frag6_insque(new, old)
           struct ip6q *new, *old;
   {
   
           IP6Q_LOCK_ASSERT();
   
           new->ip6q_prev = old;
           new->ip6q_next = old->ip6q_next;
           old->ip6q_next->ip6q_prev= new;
           old->ip6q_next = new;
   }
   
   void
   frag6_remque(p6)
           struct ip6q *p6;
   {
   
           IP6Q_LOCK_ASSERT();
   
           p6->ip6q_prev->ip6q_next = p6->ip6q_next;
           p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
   }
   
   /*
    * IPv6 reassembling timer processing;
    * if a timer expires on a reassembly
    * queue, discard it.
    */
   void
   frag6_slowtimo()
   {
           struct ip6q *q6;
           int s = splnet();
   
           IP6Q_LOCK();
           q6 = ip6q.ip6q_next;
           if (q6)
                   while (q6 != &ip6q) {
                           --q6->ip6q_ttl;
                           q6 = q6->ip6q_next;
                           if (q6->ip6q_prev->ip6q_ttl == 0) {
                                   ip6stat.ip6s_fragtimeout++;
                                   /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
                                   frag6_freef(q6->ip6q_prev);
                           }
                   }
           /*
            * 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 &&
               ip6q.ip6q_prev) {
                   ip6stat.ip6s_fragoverflow++;
                   /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
                   frag6_freef(ip6q.ip6q_prev);
           }
           IP6Q_UNLOCK();
   
   #if 0
           /*
            * Routing changes might produce a better route than we last used;
            * make sure we notice eventually, even if forwarding only for one
            * destination and the cache is never replaced.
            */
           if (ip6_forward_rt.ro_rt) {
                   RTFREE(ip6_forward_rt.ro_rt);
                   ip6_forward_rt.ro_rt = 0;
           }
           if (ipsrcchk_rt.ro_rt) {
                   RTFREE(ipsrcchk_rt.ro_rt);
                   ipsrcchk_rt.ro_rt = 0;
           }
   #endif
   
           splx(s);
   }
   
   /*
    * Drain off all datagram fragments.
    */
   void
   frag6_drain()
   {
   
           if (IP6Q_TRYLOCK() == 0)
                   return;
           while (ip6q.ip6q_next != &ip6q) {
                   ip6stat.ip6s_fragdropped++;
                   /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
                   frag6_freef(ip6q.ip6q_next);
           }
           IP6Q_UNLOCK();
   }

Cache object: 5f9071fb699f650244924fb6b4202a14