The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/netinet6/frag6.c

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    1 /*      $FreeBSD: releng/5.3/sys/netinet6/frag6.c 136588 2004-10-16 08:43:07Z cvs2svn $ */
    2 /*      $KAME: frag6.c,v 1.33 2002/01/07 11:34:48 kjc Exp $     */
    3 
    4 /*
    5  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    6  * 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 project 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 PROJECT 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 PROJECT 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 
   33 #include <sys/param.h>
   34 #include <sys/systm.h>
   35 #include <sys/malloc.h>
   36 #include <sys/mbuf.h>
   37 #include <sys/domain.h>
   38 #include <sys/protosw.h>
   39 #include <sys/socket.h>
   40 #include <sys/errno.h>
   41 #include <sys/time.h>
   42 #include <sys/kernel.h>
   43 #include <sys/syslog.h>
   44 
   45 #include <net/if.h>
   46 #include <net/route.h>
   47 
   48 #include <netinet/in.h>
   49 #include <netinet/in_var.h>
   50 #include <netinet/ip6.h>
   51 #include <netinet6/ip6_var.h>
   52 #include <netinet/icmp6.h>
   53 #include <netinet/in_systm.h>   /* for ECN definitions */
   54 #include <netinet/ip.h>         /* for ECN definitions */
   55 
   56 #include <net/net_osdep.h>
   57 
   58 /*
   59  * Define it to get a correct behavior on per-interface statistics.
   60  * You will need to perform an extra routing table lookup, per fragment,
   61  * to do it.  This may, or may not be, a performance hit.
   62  */
   63 #define IN6_IFSTAT_STRICT
   64 
   65 static void frag6_enq __P((struct ip6asfrag *, struct ip6asfrag *));
   66 static void frag6_deq __P((struct ip6asfrag *));
   67 static void frag6_insque __P((struct ip6q *, struct ip6q *));
   68 static void frag6_remque __P((struct ip6q *));
   69 static void frag6_freef __P((struct ip6q *));
   70 
   71 static struct mtx ip6qlock;
   72 /*
   73  * These fields all protected by ip6qlock.
   74  */
   75 static u_int frag6_nfragpackets;
   76 static u_int frag6_nfrags;
   77 static struct   ip6q ip6q;      /* ip6 reassemble queue */
   78 
   79 #define IP6Q_LOCK_INIT()        mtx_init(&ip6qlock, "ip6qlock", NULL, MTX_DEF);
   80 #define IP6Q_LOCK()             mtx_lock(&ip6qlock)
   81 #define IP6Q_TRYLOCK()          mtx_trylock(&ip6qlock)
   82 #define IP6Q_LOCK_ASSERT()      mtx_assert(&ip6qlock, MA_OWNED)
   83 #define IP6Q_UNLOCK()           mtx_unlock(&ip6qlock)
   84 
   85 static MALLOC_DEFINE(M_FTABLE, "fragment", "fragment reassembly header");
   86 
   87 /*
   88  * Initialise reassembly queue and fragment identifier.
   89  */
   90 void
   91 frag6_init()
   92 {
   93 
   94         ip6_maxfragpackets = nmbclusters / 4;
   95         ip6_maxfrags = nmbclusters / 4;
   96 
   97         IP6Q_LOCK_INIT();
   98 
   99         ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
  100 }
  101 
  102 /*
  103  * In RFC2460, fragment and reassembly rule do not agree with each other,
  104  * in terms of next header field handling in fragment header.
  105  * While the sender will use the same value for all of the fragmented packets,
  106  * receiver is suggested not to check the consistency.
  107  *
  108  * fragment rule (p20):
  109  *      (2) A Fragment header containing:
  110  *      The Next Header value that identifies the first header of
  111  *      the Fragmentable Part of the original packet.
  112  *              -> next header field is same for all fragments
  113  *
  114  * reassembly rule (p21):
  115  *      The Next Header field of the last header of the Unfragmentable
  116  *      Part is obtained from the Next Header field of the first
  117  *      fragment's Fragment header.
  118  *              -> should grab it from the first fragment only
  119  *
  120  * The following note also contradicts with fragment rule - noone is going to
  121  * send different fragment with different next header field.
  122  *
  123  * additional note (p22):
  124  *      The Next Header values in the Fragment headers of different
  125  *      fragments of the same original packet may differ.  Only the value
  126  *      from the Offset zero fragment packet is used for reassembly.
  127  *              -> should grab it from the first fragment only
  128  *
  129  * There is no explicit reason given in the RFC.  Historical reason maybe?
  130  */
  131 /*
  132  * Fragment input
  133  */
  134 int
  135 frag6_input(mp, offp, proto)
  136         struct mbuf **mp;
  137         int *offp, proto;
  138 {
  139         struct mbuf *m = *mp, *t;
  140         struct ip6_hdr *ip6;
  141         struct ip6_frag *ip6f;
  142         struct ip6q *q6;
  143         struct ip6asfrag *af6, *ip6af, *af6dwn;
  144 #ifdef IN6_IFSTAT_STRICT
  145         struct in6_ifaddr *ia;
  146 #endif
  147         int offset = *offp, nxt, i, next;
  148         int first_frag = 0;
  149         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  150         struct ifnet *dstifp;
  151         u_int8_t ecn, ecn0;
  152 
  153         ip6 = mtod(m, struct ip6_hdr *);
  154 #ifndef PULLDOWN_TEST
  155         IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
  156         ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
  157 #else
  158         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  159         if (ip6f == NULL)
  160                 return (IPPROTO_DONE);
  161 #endif
  162 
  163         dstifp = NULL;
  164 #ifdef IN6_IFSTAT_STRICT
  165         /* find the destination interface of the packet. */
  166         if ((ia = ip6_getdstifaddr(m)) != NULL)
  167                 dstifp = ia->ia_ifp;
  168 #else
  169         /* we are violating the spec, this is not the destination interface */
  170         if ((m->m_flags & M_PKTHDR) != 0)
  171                 dstifp = m->m_pkthdr.rcvif;
  172 #endif
  173 
  174         /* jumbo payload can't contain a fragment header */
  175         if (ip6->ip6_plen == 0) {
  176                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  177                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  178                 return IPPROTO_DONE;
  179         }
  180 
  181         /*
  182          * check whether fragment packet's fragment length is
  183          * multiple of 8 octets.
  184          * sizeof(struct ip6_frag) == 8
  185          * sizeof(struct ip6_hdr) = 40
  186          */
  187         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  188             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  189                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  190                     offsetof(struct ip6_hdr, ip6_plen));
  191                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  192                 return IPPROTO_DONE;
  193         }
  194 
  195         ip6stat.ip6s_fragments++;
  196         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  197 
  198         /* offset now points to data portion */
  199         offset += sizeof(struct ip6_frag);
  200 
  201         IP6Q_LOCK();
  202 
  203         /*
  204          * Enforce upper bound on number of fragments.
  205          * If maxfrag is 0, never accept fragments.
  206          * If maxfrag is -1, accept all fragments without limitation.
  207          */
  208         if (ip6_maxfrags < 0)
  209                 ;
  210         else if (frag6_nfrags >= (u_int)ip6_maxfrags)
  211                 goto dropfrag;
  212 
  213         for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next)
  214                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  215                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  216                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
  217                         break;
  218 
  219         if (q6 == &ip6q) {
  220                 /*
  221                  * the first fragment to arrive, create a reassembly queue.
  222                  */
  223                 first_frag = 1;
  224 
  225                 /*
  226                  * Enforce upper bound on number of fragmented packets
  227                  * for which we attempt reassembly;
  228                  * If maxfragpackets is 0, never accept fragments.
  229                  * If maxfragpackets is -1, accept all fragments without
  230                  * limitation.
  231                  */
  232                 if (ip6_maxfragpackets < 0)
  233                         ;
  234                 else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets)
  235                         goto dropfrag;
  236                 frag6_nfragpackets++;
  237                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  238                     M_NOWAIT);
  239                 if (q6 == NULL)
  240                         goto dropfrag;
  241                 bzero(q6, sizeof(*q6));
  242 
  243                 frag6_insque(q6, &ip6q);
  244 
  245                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  246                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  247 #ifdef notyet
  248                 q6->ip6q_nxtp   = (u_char *)nxtp;
  249 #endif
  250                 q6->ip6q_ident  = ip6f->ip6f_ident;
  251                 q6->ip6q_arrive = 0; /* Is it used anywhere? */
  252                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  253                 q6->ip6q_src    = ip6->ip6_src;
  254                 q6->ip6q_dst    = ip6->ip6_dst;
  255                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  256 
  257                 q6->ip6q_nfrag = 0;
  258         }
  259 
  260         /*
  261          * If it's the 1st fragment, record the length of the
  262          * unfragmentable part and the next header of the fragment header.
  263          */
  264         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  265         if (fragoff == 0) {
  266                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  267                     sizeof(struct ip6_frag);
  268                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  269         }
  270 
  271         /*
  272          * Check that the reassembled packet would not exceed 65535 bytes
  273          * in size.
  274          * If it would exceed, discard the fragment and return an ICMP error.
  275          */
  276         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  277         if (q6->ip6q_unfrglen >= 0) {
  278                 /* The 1st fragment has already arrived. */
  279                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  280                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  281                             offset - sizeof(struct ip6_frag) +
  282                             offsetof(struct ip6_frag, ip6f_offlg));
  283                         IP6Q_UNLOCK();
  284                         return (IPPROTO_DONE);
  285                 }
  286         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  287                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  288                     offset - sizeof(struct ip6_frag) +
  289                     offsetof(struct ip6_frag, ip6f_offlg));
  290                 IP6Q_UNLOCK();
  291                 return (IPPROTO_DONE);
  292         }
  293         /*
  294          * If it's the first fragment, do the above check for each
  295          * fragment already stored in the reassembly queue.
  296          */
  297         if (fragoff == 0) {
  298                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  299                      af6 = af6dwn) {
  300                         af6dwn = af6->ip6af_down;
  301 
  302                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  303                             IPV6_MAXPACKET) {
  304                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  305                                 struct ip6_hdr *ip6err;
  306                                 int erroff = af6->ip6af_offset;
  307 
  308                                 /* dequeue the fragment. */
  309                                 frag6_deq(af6);
  310                                 free(af6, M_FTABLE);
  311 
  312                                 /* adjust pointer. */
  313                                 ip6err = mtod(merr, struct ip6_hdr *);
  314 
  315                                 /*
  316                                  * Restore source and destination addresses
  317                                  * in the erroneous IPv6 header.
  318                                  */
  319                                 ip6err->ip6_src = q6->ip6q_src;
  320                                 ip6err->ip6_dst = q6->ip6q_dst;
  321 
  322                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  323                                     ICMP6_PARAMPROB_HEADER,
  324                                     erroff - sizeof(struct ip6_frag) +
  325                                     offsetof(struct ip6_frag, ip6f_offlg));
  326                         }
  327                 }
  328         }
  329 
  330         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  331             M_NOWAIT);
  332         if (ip6af == NULL)
  333                 goto dropfrag;
  334         bzero(ip6af, sizeof(*ip6af));
  335         ip6af->ip6af_head = ip6->ip6_flow;
  336         ip6af->ip6af_len = ip6->ip6_plen;
  337         ip6af->ip6af_nxt = ip6->ip6_nxt;
  338         ip6af->ip6af_hlim = ip6->ip6_hlim;
  339         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  340         ip6af->ip6af_off = fragoff;
  341         ip6af->ip6af_frglen = frgpartlen;
  342         ip6af->ip6af_offset = offset;
  343         IP6_REASS_MBUF(ip6af) = m;
  344 
  345         if (first_frag) {
  346                 af6 = (struct ip6asfrag *)q6;
  347                 goto insert;
  348         }
  349 
  350         /*
  351          * Handle ECN by comparing this segment with the first one;
  352          * if CE is set, do not lose CE.
  353          * drop if CE and not-ECT are mixed for the same packet.
  354          */
  355         ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  356         ecn0 = (ntohl(q6->ip6q_down->ip6af_head) >> 20) & IPTOS_ECN_MASK;
  357         if (ecn == IPTOS_ECN_CE) {
  358                 if (ecn0 == IPTOS_ECN_NOTECT) {
  359                         free(ip6af, M_FTABLE);
  360                         goto dropfrag;
  361                 }
  362                 if (ecn0 != IPTOS_ECN_CE)
  363                         q6->ip6q_down->ip6af_head |= htonl(IPTOS_ECN_CE << 20);
  364         }
  365         if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
  366                 free(ip6af, M_FTABLE);
  367                 goto dropfrag;
  368         }
  369 
  370         /*
  371          * Find a segment which begins after this one does.
  372          */
  373         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  374              af6 = af6->ip6af_down)
  375                 if (af6->ip6af_off > ip6af->ip6af_off)
  376                         break;
  377 
  378 #if 0
  379         /*
  380          * If there is a preceding segment, it may provide some of
  381          * our data already.  If so, drop the data from the incoming
  382          * segment.  If it provides all of our data, drop us.
  383          */
  384         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  385                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  386                         - ip6af->ip6af_off;
  387                 if (i > 0) {
  388                         if (i >= ip6af->ip6af_frglen)
  389                                 goto dropfrag;
  390                         m_adj(IP6_REASS_MBUF(ip6af), i);
  391                         ip6af->ip6af_off += i;
  392                         ip6af->ip6af_frglen -= i;
  393                 }
  394         }
  395 
  396         /*
  397          * While we overlap succeeding segments trim them or,
  398          * if they are completely covered, dequeue them.
  399          */
  400         while (af6 != (struct ip6asfrag *)q6 &&
  401                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  402                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  403                 if (i < af6->ip6af_frglen) {
  404                         af6->ip6af_frglen -= i;
  405                         af6->ip6af_off += i;
  406                         m_adj(IP6_REASS_MBUF(af6), i);
  407                         break;
  408                 }
  409                 af6 = af6->ip6af_down;
  410                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  411                 frag6_deq(af6->ip6af_up);
  412         }
  413 #else
  414         /*
  415          * If the incoming framgent overlaps some existing fragments in
  416          * the reassembly queue, drop it, since it is dangerous to override
  417          * existing fragments from a security point of view.
  418          * We don't know which fragment is the bad guy - here we trust
  419          * fragment that came in earlier, with no real reason.
  420          */
  421         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  422                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  423                         - ip6af->ip6af_off;
  424                 if (i > 0) {
  425 #if 0                           /* suppress the noisy log */
  426                         log(LOG_ERR, "%d bytes of a fragment from %s "
  427                             "overlaps the previous fragment\n",
  428                             i, ip6_sprintf(&q6->ip6q_src));
  429 #endif
  430                         free(ip6af, M_FTABLE);
  431                         goto dropfrag;
  432                 }
  433         }
  434         if (af6 != (struct ip6asfrag *)q6) {
  435                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  436                 if (i > 0) {
  437 #if 0                           /* suppress the noisy log */
  438                         log(LOG_ERR, "%d bytes of a fragment from %s "
  439                             "overlaps the succeeding fragment",
  440                             i, ip6_sprintf(&q6->ip6q_src));
  441 #endif
  442                         free(ip6af, M_FTABLE);
  443                         goto dropfrag;
  444                 }
  445         }
  446 #endif
  447 
  448 insert:
  449 
  450         /*
  451          * Stick new segment in its place;
  452          * check for complete reassembly.
  453          * Move to front of packet queue, as we are
  454          * the most recently active fragmented packet.
  455          */
  456         frag6_enq(ip6af, af6->ip6af_up);
  457         frag6_nfrags++;
  458         q6->ip6q_nfrag++;
  459 #if 0 /* xxx */
  460         if (q6 != ip6q.ip6q_next) {
  461                 frag6_remque(q6);
  462                 frag6_insque(q6, &ip6q);
  463         }
  464 #endif
  465         next = 0;
  466         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  467              af6 = af6->ip6af_down) {
  468                 if (af6->ip6af_off != next) {
  469                         IP6Q_UNLOCK();
  470                         return IPPROTO_DONE;
  471                 }
  472                 next += af6->ip6af_frglen;
  473         }
  474         if (af6->ip6af_up->ip6af_mff) {
  475                 IP6Q_UNLOCK();
  476                 return IPPROTO_DONE;
  477         }
  478 
  479         /*
  480          * Reassembly is complete; concatenate fragments.
  481          */
  482         ip6af = q6->ip6q_down;
  483         t = m = IP6_REASS_MBUF(ip6af);
  484         af6 = ip6af->ip6af_down;
  485         frag6_deq(ip6af);
  486         while (af6 != (struct ip6asfrag *)q6) {
  487                 af6dwn = af6->ip6af_down;
  488                 frag6_deq(af6);
  489                 while (t->m_next)
  490                         t = t->m_next;
  491                 t->m_next = IP6_REASS_MBUF(af6);
  492                 m_adj(t->m_next, af6->ip6af_offset);
  493                 free(af6, M_FTABLE);
  494                 af6 = af6dwn;
  495         }
  496 
  497         /* adjust offset to point where the original next header starts */
  498         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  499         free(ip6af, M_FTABLE);
  500         ip6 = mtod(m, struct ip6_hdr *);
  501         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  502         ip6->ip6_src = q6->ip6q_src;
  503         ip6->ip6_dst = q6->ip6q_dst;
  504         nxt = q6->ip6q_nxt;
  505 #ifdef notyet
  506         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  507 #endif
  508 
  509         /*
  510          * Delete frag6 header with as a few cost as possible.
  511          */
  512         if (offset < m->m_len) {
  513                 ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
  514                         offset);
  515                 m->m_data += sizeof(struct ip6_frag);
  516                 m->m_len -= sizeof(struct ip6_frag);
  517         } else {
  518                 /* this comes with no copy if the boundary is on cluster */
  519                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  520                         frag6_remque(q6);
  521                         frag6_nfrags -= q6->ip6q_nfrag;
  522                         free(q6, M_FTABLE);
  523                         frag6_nfragpackets--;
  524                         goto dropfrag;
  525                 }
  526                 m_adj(t, sizeof(struct ip6_frag));
  527                 m_cat(m, t);
  528         }
  529 
  530         /*
  531          * Store NXT to the original.
  532          */
  533         {
  534                 char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  535                 *prvnxtp = nxt;
  536         }
  537 
  538         frag6_remque(q6);
  539         frag6_nfrags -= q6->ip6q_nfrag;
  540         free(q6, M_FTABLE);
  541         frag6_nfragpackets--;
  542 
  543         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  544                 int plen = 0;
  545                 for (t = m; t; t = t->m_next)
  546                         plen += t->m_len;
  547                 m->m_pkthdr.len = plen;
  548         }
  549 
  550         ip6stat.ip6s_reassembled++;
  551         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  552 
  553         /*
  554          * Tell launch routine the next header
  555          */
  556 
  557         *mp = m;
  558         *offp = offset;
  559 
  560         IP6Q_UNLOCK();
  561         return nxt;
  562 
  563  dropfrag:
  564         IP6Q_UNLOCK();
  565         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  566         ip6stat.ip6s_fragdropped++;
  567         m_freem(m);
  568         return IPPROTO_DONE;
  569 }
  570 
  571 /*
  572  * Free a fragment reassembly header and all
  573  * associated datagrams.
  574  */
  575 void
  576 frag6_freef(q6)
  577         struct ip6q *q6;
  578 {
  579         struct ip6asfrag *af6, *down6;
  580 
  581         IP6Q_LOCK_ASSERT();
  582 
  583         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  584              af6 = down6) {
  585                 struct mbuf *m = IP6_REASS_MBUF(af6);
  586 
  587                 down6 = af6->ip6af_down;
  588                 frag6_deq(af6);
  589 
  590                 /*
  591                  * Return ICMP time exceeded error for the 1st fragment.
  592                  * Just free other fragments.
  593                  */
  594                 if (af6->ip6af_off == 0) {
  595                         struct ip6_hdr *ip6;
  596 
  597                         /* adjust pointer */
  598                         ip6 = mtod(m, struct ip6_hdr *);
  599 
  600                         /* restore source and destination addresses */
  601                         ip6->ip6_src = q6->ip6q_src;
  602                         ip6->ip6_dst = q6->ip6q_dst;
  603 
  604                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  605                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  606                 } else
  607                         m_freem(m);
  608                 free(af6, M_FTABLE);
  609         }
  610         frag6_remque(q6);
  611         frag6_nfrags -= q6->ip6q_nfrag;
  612         free(q6, M_FTABLE);
  613         frag6_nfragpackets--;
  614 }
  615 
  616 /*
  617  * Put an ip fragment on a reassembly chain.
  618  * Like insque, but pointers in middle of structure.
  619  */
  620 void
  621 frag6_enq(af6, up6)
  622         struct ip6asfrag *af6, *up6;
  623 {
  624 
  625         IP6Q_LOCK_ASSERT();
  626 
  627         af6->ip6af_up = up6;
  628         af6->ip6af_down = up6->ip6af_down;
  629         up6->ip6af_down->ip6af_up = af6;
  630         up6->ip6af_down = af6;
  631 }
  632 
  633 /*
  634  * To frag6_enq as remque is to insque.
  635  */
  636 void
  637 frag6_deq(af6)
  638         struct ip6asfrag *af6;
  639 {
  640 
  641         IP6Q_LOCK_ASSERT();
  642 
  643         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  644         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  645 }
  646 
  647 void
  648 frag6_insque(new, old)
  649         struct ip6q *new, *old;
  650 {
  651 
  652         IP6Q_LOCK_ASSERT();
  653 
  654         new->ip6q_prev = old;
  655         new->ip6q_next = old->ip6q_next;
  656         old->ip6q_next->ip6q_prev= new;
  657         old->ip6q_next = new;
  658 }
  659 
  660 void
  661 frag6_remque(p6)
  662         struct ip6q *p6;
  663 {
  664 
  665         IP6Q_LOCK_ASSERT();
  666 
  667         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  668         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  669 }
  670 
  671 /*
  672  * IPv6 reassembling timer processing;
  673  * if a timer expires on a reassembly
  674  * queue, discard it.
  675  */
  676 void
  677 frag6_slowtimo()
  678 {
  679         struct ip6q *q6;
  680         int s = splnet();
  681 
  682         IP6Q_LOCK();
  683         q6 = ip6q.ip6q_next;
  684         if (q6)
  685                 while (q6 != &ip6q) {
  686                         --q6->ip6q_ttl;
  687                         q6 = q6->ip6q_next;
  688                         if (q6->ip6q_prev->ip6q_ttl == 0) {
  689                                 ip6stat.ip6s_fragtimeout++;
  690                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  691                                 frag6_freef(q6->ip6q_prev);
  692                         }
  693                 }
  694         /*
  695          * If we are over the maximum number of fragments
  696          * (due to the limit being lowered), drain off
  697          * enough to get down to the new limit.
  698          */
  699         while (frag6_nfragpackets > (u_int)ip6_maxfragpackets &&
  700             ip6q.ip6q_prev) {
  701                 ip6stat.ip6s_fragoverflow++;
  702                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  703                 frag6_freef(ip6q.ip6q_prev);
  704         }
  705         IP6Q_UNLOCK();
  706 
  707 #if 0
  708         /*
  709          * Routing changes might produce a better route than we last used;
  710          * make sure we notice eventually, even if forwarding only for one
  711          * destination and the cache is never replaced.
  712          */
  713         if (ip6_forward_rt.ro_rt) {
  714                 RTFREE(ip6_forward_rt.ro_rt);
  715                 ip6_forward_rt.ro_rt = 0;
  716         }
  717         if (ipsrcchk_rt.ro_rt) {
  718                 RTFREE(ipsrcchk_rt.ro_rt);
  719                 ipsrcchk_rt.ro_rt = 0;
  720         }
  721 #endif
  722 
  723         splx(s);
  724 }
  725 
  726 /*
  727  * Drain off all datagram fragments.
  728  */
  729 void
  730 frag6_drain()
  731 {
  732 
  733         if (IP6Q_TRYLOCK() == 0)
  734                 return;
  735         while (ip6q.ip6q_next != &ip6q) {
  736                 ip6stat.ip6s_fragdropped++;
  737                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  738                 frag6_freef(ip6q.ip6q_next);
  739         }
  740         IP6Q_UNLOCK();
  741 }

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