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

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    1 /*-
    2  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. Neither the name of the project nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      $KAME: frag6.c,v 1.33 2002/01/07 11:34:48 kjc Exp $
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD$");
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/malloc.h>
   38 #include <sys/mbuf.h>
   39 #include <sys/domain.h>
   40 #include <sys/protosw.h>
   41 #include <sys/socket.h>
   42 #include <sys/errno.h>
   43 #include <sys/time.h>
   44 #include <sys/kernel.h>
   45 #include <sys/syslog.h>
   46 
   47 #include <net/if.h>
   48 #include <net/route.h>
   49 
   50 #include <netinet/in.h>
   51 #include <netinet/in_var.h>
   52 #include <netinet/ip6.h>
   53 #include <netinet6/ip6_var.h>
   54 #include <netinet/icmp6.h>
   55 #include <netinet/in_systm.h>   /* for ECN definitions */
   56 #include <netinet/ip.h>         /* for ECN definitions */
   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(struct ip6asfrag *, struct ip6asfrag *);
   66 static void frag6_deq(struct ip6asfrag *);
   67 static void frag6_insque(struct ip6q *, struct ip6q *);
   68 static void frag6_remque(struct ip6q *);
   69 static void frag6_freef(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 static void
   91 frag6_change(void *tag)
   92 {
   93 
   94         ip6_maxfragpackets = nmbclusters / 4;
   95         ip6_maxfrags = nmbclusters / 4;
   96 }
   97 
   98 void
   99 frag6_init(void)
  100 {
  101 
  102         ip6_maxfragpackets = nmbclusters / 4;
  103         ip6_maxfrags = nmbclusters / 4;
  104         EVENTHANDLER_REGISTER(nmbclusters_change,
  105             frag6_change, NULL, EVENTHANDLER_PRI_ANY);
  106 
  107         IP6Q_LOCK_INIT();
  108 
  109         ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
  110 }
  111 
  112 /*
  113  * In RFC2460, fragment and reassembly rule do not agree with each other,
  114  * in terms of next header field handling in fragment header.
  115  * While the sender will use the same value for all of the fragmented packets,
  116  * receiver is suggested not to check the consistency.
  117  *
  118  * fragment rule (p20):
  119  *      (2) A Fragment header containing:
  120  *      The Next Header value that identifies the first header of
  121  *      the Fragmentable Part of the original packet.
  122  *              -> next header field is same for all fragments
  123  *
  124  * reassembly rule (p21):
  125  *      The Next Header field of the last header of the Unfragmentable
  126  *      Part is obtained from the Next Header field of the first
  127  *      fragment's Fragment header.
  128  *              -> should grab it from the first fragment only
  129  *
  130  * The following note also contradicts with fragment rule - noone is going to
  131  * send different fragment with different next header field.
  132  *
  133  * additional note (p22):
  134  *      The Next Header values in the Fragment headers of different
  135  *      fragments of the same original packet may differ.  Only the value
  136  *      from the Offset zero fragment packet is used for reassembly.
  137  *              -> should grab it from the first fragment only
  138  *
  139  * There is no explicit reason given in the RFC.  Historical reason maybe?
  140  */
  141 /*
  142  * Fragment input
  143  */
  144 int
  145 frag6_input(struct mbuf **mp, int *offp, int proto)
  146 {
  147         struct mbuf *m = *mp, *t;
  148         struct ip6_hdr *ip6;
  149         struct ip6_frag *ip6f;
  150         struct ip6q *q6;
  151         struct ip6asfrag *af6, *ip6af, *af6dwn;
  152 #ifdef IN6_IFSTAT_STRICT
  153         struct in6_ifaddr *ia;
  154 #endif
  155         int offset = *offp, nxt, i, next;
  156         int first_frag = 0;
  157         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  158         struct ifnet *dstifp;
  159         u_int8_t ecn, ecn0;
  160 #if 0
  161         char ip6buf[INET6_ADDRSTRLEN];
  162 #endif
  163 
  164         ip6 = mtod(m, struct ip6_hdr *);
  165 #ifndef PULLDOWN_TEST
  166         IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
  167         ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
  168 #else
  169         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  170         if (ip6f == NULL)
  171                 return (IPPROTO_DONE);
  172 #endif
  173 
  174         dstifp = NULL;
  175 #ifdef IN6_IFSTAT_STRICT
  176         /* find the destination interface of the packet. */
  177         if ((ia = ip6_getdstifaddr(m)) != NULL)
  178                 dstifp = ia->ia_ifp;
  179 #else
  180         /* we are violating the spec, this is not the destination interface */
  181         if ((m->m_flags & M_PKTHDR) != 0)
  182                 dstifp = m->m_pkthdr.rcvif;
  183 #endif
  184 
  185         /* jumbo payload can't contain a fragment header */
  186         if (ip6->ip6_plen == 0) {
  187                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  188                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  189                 return IPPROTO_DONE;
  190         }
  191 
  192         /*
  193          * check whether fragment packet's fragment length is
  194          * multiple of 8 octets.
  195          * sizeof(struct ip6_frag) == 8
  196          * sizeof(struct ip6_hdr) = 40
  197          */
  198         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  199             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  200                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  201                     offsetof(struct ip6_hdr, ip6_plen));
  202                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  203                 return IPPROTO_DONE;
  204         }
  205 
  206         ip6stat.ip6s_fragments++;
  207         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  208 
  209         /* offset now points to data portion */
  210         offset += sizeof(struct ip6_frag);
  211 
  212         IP6Q_LOCK();
  213 
  214         /*
  215          * Enforce upper bound on number of fragments.
  216          * If maxfrag is 0, never accept fragments.
  217          * If maxfrag is -1, accept all fragments without limitation.
  218          */
  219         if (ip6_maxfrags < 0)
  220                 ;
  221         else if (frag6_nfrags >= (u_int)ip6_maxfrags)
  222                 goto dropfrag;
  223 
  224         for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next)
  225                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  226                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  227                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
  228                         break;
  229 
  230         if (q6 == &ip6q) {
  231                 /*
  232                  * the first fragment to arrive, create a reassembly queue.
  233                  */
  234                 first_frag = 1;
  235 
  236                 /*
  237                  * Enforce upper bound on number of fragmented packets
  238                  * for which we attempt reassembly;
  239                  * If maxfragpackets is 0, never accept fragments.
  240                  * If maxfragpackets is -1, accept all fragments without
  241                  * limitation.
  242                  */
  243                 if (ip6_maxfragpackets < 0)
  244                         ;
  245                 else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets)
  246                         goto dropfrag;
  247                 frag6_nfragpackets++;
  248                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  249                     M_NOWAIT);
  250                 if (q6 == NULL)
  251                         goto dropfrag;
  252                 bzero(q6, sizeof(*q6));
  253 
  254                 frag6_insque(q6, &ip6q);
  255 
  256                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  257                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  258 #ifdef notyet
  259                 q6->ip6q_nxtp   = (u_char *)nxtp;
  260 #endif
  261                 q6->ip6q_ident  = ip6f->ip6f_ident;
  262                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  263                 q6->ip6q_src    = ip6->ip6_src;
  264                 q6->ip6q_dst    = ip6->ip6_dst;
  265                 q6->ip6q_ecn    =
  266                     (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  267                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  268 
  269                 q6->ip6q_nfrag = 0;
  270         }
  271 
  272         /*
  273          * If it's the 1st fragment, record the length of the
  274          * unfragmentable part and the next header of the fragment header.
  275          */
  276         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  277         if (fragoff == 0) {
  278                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  279                     sizeof(struct ip6_frag);
  280                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  281         }
  282 
  283         /*
  284          * Check that the reassembled packet would not exceed 65535 bytes
  285          * in size.
  286          * If it would exceed, discard the fragment and return an ICMP error.
  287          */
  288         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  289         if (q6->ip6q_unfrglen >= 0) {
  290                 /* The 1st fragment has already arrived. */
  291                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  292                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  293                             offset - sizeof(struct ip6_frag) +
  294                             offsetof(struct ip6_frag, ip6f_offlg));
  295                         IP6Q_UNLOCK();
  296                         return (IPPROTO_DONE);
  297                 }
  298         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  299                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  300                     offset - sizeof(struct ip6_frag) +
  301                     offsetof(struct ip6_frag, ip6f_offlg));
  302                 IP6Q_UNLOCK();
  303                 return (IPPROTO_DONE);
  304         }
  305         /*
  306          * If it's the first fragment, do the above check for each
  307          * fragment already stored in the reassembly queue.
  308          */
  309         if (fragoff == 0) {
  310                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  311                      af6 = af6dwn) {
  312                         af6dwn = af6->ip6af_down;
  313 
  314                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  315                             IPV6_MAXPACKET) {
  316                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  317                                 struct ip6_hdr *ip6err;
  318                                 int erroff = af6->ip6af_offset;
  319 
  320                                 /* dequeue the fragment. */
  321                                 frag6_deq(af6);
  322                                 free(af6, M_FTABLE);
  323 
  324                                 /* adjust pointer. */
  325                                 ip6err = mtod(merr, struct ip6_hdr *);
  326 
  327                                 /*
  328                                  * Restore source and destination addresses
  329                                  * in the erroneous IPv6 header.
  330                                  */
  331                                 ip6err->ip6_src = q6->ip6q_src;
  332                                 ip6err->ip6_dst = q6->ip6q_dst;
  333 
  334                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  335                                     ICMP6_PARAMPROB_HEADER,
  336                                     erroff - sizeof(struct ip6_frag) +
  337                                     offsetof(struct ip6_frag, ip6f_offlg));
  338                         }
  339                 }
  340         }
  341 
  342         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  343             M_NOWAIT);
  344         if (ip6af == NULL)
  345                 goto dropfrag;
  346         bzero(ip6af, sizeof(*ip6af));
  347         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  348         ip6af->ip6af_off = fragoff;
  349         ip6af->ip6af_frglen = frgpartlen;
  350         ip6af->ip6af_offset = offset;
  351         IP6_REASS_MBUF(ip6af) = m;
  352 
  353         if (first_frag) {
  354                 af6 = (struct ip6asfrag *)q6;
  355                 goto insert;
  356         }
  357 
  358         /*
  359          * Handle ECN by comparing this segment with the first one;
  360          * if CE is set, do not lose CE.
  361          * drop if CE and not-ECT are mixed for the same packet.
  362          */
  363         ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  364         ecn0 = q6->ip6q_ecn;
  365         if (ecn == IPTOS_ECN_CE) {
  366                 if (ecn0 == IPTOS_ECN_NOTECT) {
  367                         free(ip6af, M_FTABLE);
  368                         goto dropfrag;
  369                 }
  370                 if (ecn0 != IPTOS_ECN_CE)
  371                         q6->ip6q_ecn = IPTOS_ECN_CE;
  372         }
  373         if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
  374                 free(ip6af, M_FTABLE);
  375                 goto dropfrag;
  376         }
  377 
  378         /*
  379          * Find a segment which begins after this one does.
  380          */
  381         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  382              af6 = af6->ip6af_down)
  383                 if (af6->ip6af_off > ip6af->ip6af_off)
  384                         break;
  385 
  386 #if 0
  387         /*
  388          * If there is a preceding segment, it may provide some of
  389          * our data already.  If so, drop the data from the incoming
  390          * segment.  If it provides all of our data, drop us.
  391          */
  392         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  393                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  394                         - ip6af->ip6af_off;
  395                 if (i > 0) {
  396                         if (i >= ip6af->ip6af_frglen)
  397                                 goto dropfrag;
  398                         m_adj(IP6_REASS_MBUF(ip6af), i);
  399                         ip6af->ip6af_off += i;
  400                         ip6af->ip6af_frglen -= i;
  401                 }
  402         }
  403 
  404         /*
  405          * While we overlap succeeding segments trim them or,
  406          * if they are completely covered, dequeue them.
  407          */
  408         while (af6 != (struct ip6asfrag *)q6 &&
  409                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  410                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  411                 if (i < af6->ip6af_frglen) {
  412                         af6->ip6af_frglen -= i;
  413                         af6->ip6af_off += i;
  414                         m_adj(IP6_REASS_MBUF(af6), i);
  415                         break;
  416                 }
  417                 af6 = af6->ip6af_down;
  418                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  419                 frag6_deq(af6->ip6af_up);
  420         }
  421 #else
  422         /*
  423          * If the incoming framgent overlaps some existing fragments in
  424          * the reassembly queue, drop it, since it is dangerous to override
  425          * existing fragments from a security point of view.
  426          * We don't know which fragment is the bad guy - here we trust
  427          * fragment that came in earlier, with no real reason.
  428          *
  429          * Note: due to changes after disabling this part, mbuf passed to
  430          * m_adj() below now does not meet the requirement.
  431          */
  432         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  433                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  434                         - ip6af->ip6af_off;
  435                 if (i > 0) {
  436 #if 0                           /* suppress the noisy log */
  437                         log(LOG_ERR, "%d bytes of a fragment from %s "
  438                             "overlaps the previous fragment\n",
  439                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  440 #endif
  441                         free(ip6af, M_FTABLE);
  442                         goto dropfrag;
  443                 }
  444         }
  445         if (af6 != (struct ip6asfrag *)q6) {
  446                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  447                 if (i > 0) {
  448 #if 0                           /* suppress the noisy log */
  449                         log(LOG_ERR, "%d bytes of a fragment from %s "
  450                             "overlaps the succeeding fragment",
  451                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  452 #endif
  453                         free(ip6af, M_FTABLE);
  454                         goto dropfrag;
  455                 }
  456         }
  457 #endif
  458 
  459 insert:
  460 
  461         /*
  462          * Stick new segment in its place;
  463          * check for complete reassembly.
  464          * Move to front of packet queue, as we are
  465          * the most recently active fragmented packet.
  466          */
  467         frag6_enq(ip6af, af6->ip6af_up);
  468         frag6_nfrags++;
  469         q6->ip6q_nfrag++;
  470 #if 0 /* xxx */
  471         if (q6 != ip6q.ip6q_next) {
  472                 frag6_remque(q6);
  473                 frag6_insque(q6, &ip6q);
  474         }
  475 #endif
  476         next = 0;
  477         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  478              af6 = af6->ip6af_down) {
  479                 if (af6->ip6af_off != next) {
  480                         IP6Q_UNLOCK();
  481                         return IPPROTO_DONE;
  482                 }
  483                 next += af6->ip6af_frglen;
  484         }
  485         if (af6->ip6af_up->ip6af_mff) {
  486                 IP6Q_UNLOCK();
  487                 return IPPROTO_DONE;
  488         }
  489 
  490         /*
  491          * Reassembly is complete; concatenate fragments.
  492          */
  493         ip6af = q6->ip6q_down;
  494         t = m = IP6_REASS_MBUF(ip6af);
  495         af6 = ip6af->ip6af_down;
  496         frag6_deq(ip6af);
  497         while (af6 != (struct ip6asfrag *)q6) {
  498                 af6dwn = af6->ip6af_down;
  499                 frag6_deq(af6);
  500                 while (t->m_next)
  501                         t = t->m_next;
  502                 t->m_next = IP6_REASS_MBUF(af6);
  503                 m_adj(t->m_next, af6->ip6af_offset);
  504                 free(af6, M_FTABLE);
  505                 af6 = af6dwn;
  506         }
  507 
  508         /* adjust offset to point where the original next header starts */
  509         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  510         free(ip6af, M_FTABLE);
  511         ip6 = mtod(m, struct ip6_hdr *);
  512         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  513         if (q6->ip6q_ecn == IPTOS_ECN_CE)
  514                 ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
  515         nxt = q6->ip6q_nxt;
  516 #ifdef notyet
  517         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  518 #endif
  519 
  520         /* Delete frag6 header */
  521         if (m->m_len >= offset + sizeof(struct ip6_frag)) {
  522                 /* This is the only possible case with !PULLDOWN_TEST */
  523                 ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
  524                     offset);
  525                 m->m_data += sizeof(struct ip6_frag);
  526                 m->m_len -= sizeof(struct ip6_frag);
  527         } else {
  528                 /* this comes with no copy if the boundary is on cluster */
  529                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  530                         frag6_remque(q6);
  531                         frag6_nfrags -= q6->ip6q_nfrag;
  532                         free(q6, M_FTABLE);
  533                         frag6_nfragpackets--;
  534                         goto dropfrag;
  535                 }
  536                 m_adj(t, sizeof(struct ip6_frag));
  537                 m_cat(m, t);
  538         }
  539 
  540         /*
  541          * Store NXT to the original.
  542          */
  543         {
  544                 char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  545                 *prvnxtp = nxt;
  546         }
  547 
  548         frag6_remque(q6);
  549         frag6_nfrags -= q6->ip6q_nfrag;
  550         free(q6, M_FTABLE);
  551         frag6_nfragpackets--;
  552 
  553         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  554                 int plen = 0;
  555                 for (t = m; t; t = t->m_next)
  556                         plen += t->m_len;
  557                 m->m_pkthdr.len = plen;
  558         }
  559 
  560         ip6stat.ip6s_reassembled++;
  561         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  562 
  563         /*
  564          * Tell launch routine the next header
  565          */
  566 
  567         *mp = m;
  568         *offp = offset;
  569 
  570         IP6Q_UNLOCK();
  571         return nxt;
  572 
  573  dropfrag:
  574         IP6Q_UNLOCK();
  575         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  576         ip6stat.ip6s_fragdropped++;
  577         m_freem(m);
  578         return IPPROTO_DONE;
  579 }
  580 
  581 /*
  582  * Free a fragment reassembly header and all
  583  * associated datagrams.
  584  */
  585 void
  586 frag6_freef(struct ip6q *q6)
  587 {
  588         struct ip6asfrag *af6, *down6;
  589 
  590         IP6Q_LOCK_ASSERT();
  591 
  592         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  593              af6 = down6) {
  594                 struct mbuf *m = IP6_REASS_MBUF(af6);
  595 
  596                 down6 = af6->ip6af_down;
  597                 frag6_deq(af6);
  598 
  599                 /*
  600                  * Return ICMP time exceeded error for the 1st fragment.
  601                  * Just free other fragments.
  602                  */
  603                 if (af6->ip6af_off == 0) {
  604                         struct ip6_hdr *ip6;
  605 
  606                         /* adjust pointer */
  607                         ip6 = mtod(m, struct ip6_hdr *);
  608 
  609                         /* restore source and destination addresses */
  610                         ip6->ip6_src = q6->ip6q_src;
  611                         ip6->ip6_dst = q6->ip6q_dst;
  612 
  613                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  614                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  615                 } else
  616                         m_freem(m);
  617                 free(af6, M_FTABLE);
  618         }
  619         frag6_remque(q6);
  620         frag6_nfrags -= q6->ip6q_nfrag;
  621         free(q6, M_FTABLE);
  622         frag6_nfragpackets--;
  623 }
  624 
  625 /*
  626  * Put an ip fragment on a reassembly chain.
  627  * Like insque, but pointers in middle of structure.
  628  */
  629 void
  630 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6)
  631 {
  632 
  633         IP6Q_LOCK_ASSERT();
  634 
  635         af6->ip6af_up = up6;
  636         af6->ip6af_down = up6->ip6af_down;
  637         up6->ip6af_down->ip6af_up = af6;
  638         up6->ip6af_down = af6;
  639 }
  640 
  641 /*
  642  * To frag6_enq as remque is to insque.
  643  */
  644 void
  645 frag6_deq(struct ip6asfrag *af6)
  646 {
  647 
  648         IP6Q_LOCK_ASSERT();
  649 
  650         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  651         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  652 }
  653 
  654 void
  655 frag6_insque(struct ip6q *new, struct ip6q *old)
  656 {
  657 
  658         IP6Q_LOCK_ASSERT();
  659 
  660         new->ip6q_prev = old;
  661         new->ip6q_next = old->ip6q_next;
  662         old->ip6q_next->ip6q_prev= new;
  663         old->ip6q_next = new;
  664 }
  665 
  666 void
  667 frag6_remque(struct ip6q *p6)
  668 {
  669 
  670         IP6Q_LOCK_ASSERT();
  671 
  672         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  673         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  674 }
  675 
  676 /*
  677  * IPv6 reassembling timer processing;
  678  * if a timer expires on a reassembly
  679  * queue, discard it.
  680  */
  681 void
  682 frag6_slowtimo(void)
  683 {
  684         struct ip6q *q6;
  685 
  686 #if 0
  687         GIANT_REQUIRED; /* XXX bz: ip6_forward_rt */
  688 #endif
  689 
  690         IP6Q_LOCK();
  691         q6 = ip6q.ip6q_next;
  692         if (q6)
  693                 while (q6 != &ip6q) {
  694                         --q6->ip6q_ttl;
  695                         q6 = q6->ip6q_next;
  696                         if (q6->ip6q_prev->ip6q_ttl == 0) {
  697                                 ip6stat.ip6s_fragtimeout++;
  698                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  699                                 frag6_freef(q6->ip6q_prev);
  700                         }
  701                 }
  702         /*
  703          * If we are over the maximum number of fragments
  704          * (due to the limit being lowered), drain off
  705          * enough to get down to the new limit.
  706          */
  707         while (frag6_nfragpackets > (u_int)ip6_maxfragpackets &&
  708             ip6q.ip6q_prev) {
  709                 ip6stat.ip6s_fragoverflow++;
  710                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  711                 frag6_freef(ip6q.ip6q_prev);
  712         }
  713         IP6Q_UNLOCK();
  714 
  715 #if 0
  716         /*
  717          * Routing changes might produce a better route than we last used;
  718          * make sure we notice eventually, even if forwarding only for one
  719          * destination and the cache is never replaced.
  720          */
  721         if (ip6_forward_rt.ro_rt) {
  722                 RTFREE(ip6_forward_rt.ro_rt);
  723                 ip6_forward_rt.ro_rt = 0;
  724         }
  725         if (ipsrcchk_rt.ro_rt) {
  726                 RTFREE(ipsrcchk_rt.ro_rt);
  727                 ipsrcchk_rt.ro_rt = 0;
  728         }
  729 #endif
  730 }
  731 
  732 /*
  733  * Drain off all datagram fragments.
  734  */
  735 void
  736 frag6_drain(void)
  737 {
  738 
  739         if (IP6Q_TRYLOCK() == 0)
  740                 return;
  741         while (ip6q.ip6q_next != &ip6q) {
  742                 ip6stat.ip6s_fragdropped++;
  743                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  744                 frag6_freef(ip6q.ip6q_next);
  745         }
  746         IP6Q_UNLOCK();
  747 }

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