The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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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: releng/9.1/sys/netinet6/frag6.c 238479 2012-07-15 11:27:15Z bz $");
   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 #include <net/vnet.h>
   50 
   51 #include <netinet/in.h>
   52 #include <netinet/in_var.h>
   53 #include <netinet/ip6.h>
   54 #include <netinet6/ip6_var.h>
   55 #include <netinet/icmp6.h>
   56 #include <netinet/in_systm.h>   /* for ECN definitions */
   57 #include <netinet/ip.h>         /* for ECN definitions */
   58 
   59 #include <security/mac/mac_framework.h>
   60 
   61 /*
   62  * Define it to get a correct behavior on per-interface statistics.
   63  * You will need to perform an extra routing table lookup, per fragment,
   64  * to do it.  This may, or may not be, a performance hit.
   65  */
   66 #define IN6_IFSTAT_STRICT
   67 
   68 static void frag6_enq(struct ip6asfrag *, struct ip6asfrag *);
   69 static void frag6_deq(struct ip6asfrag *);
   70 static void frag6_insque(struct ip6q *, struct ip6q *);
   71 static void frag6_remque(struct ip6q *);
   72 static void frag6_freef(struct ip6q *);
   73 
   74 static struct mtx ip6qlock;
   75 /*
   76  * These fields all protected by ip6qlock.
   77  */
   78 static VNET_DEFINE(u_int, frag6_nfragpackets);
   79 static VNET_DEFINE(u_int, frag6_nfrags);
   80 static VNET_DEFINE(struct ip6q, ip6q);  /* ip6 reassemble queue */
   81 
   82 #define V_frag6_nfragpackets            VNET(frag6_nfragpackets)
   83 #define V_frag6_nfrags                  VNET(frag6_nfrags)
   84 #define V_ip6q                          VNET(ip6q)
   85 
   86 #define IP6Q_LOCK_INIT()        mtx_init(&ip6qlock, "ip6qlock", NULL, MTX_DEF);
   87 #define IP6Q_LOCK()             mtx_lock(&ip6qlock)
   88 #define IP6Q_TRYLOCK()          mtx_trylock(&ip6qlock)
   89 #define IP6Q_LOCK_ASSERT()      mtx_assert(&ip6qlock, MA_OWNED)
   90 #define IP6Q_UNLOCK()           mtx_unlock(&ip6qlock)
   91 
   92 static MALLOC_DEFINE(M_FTABLE, "fragment", "fragment reassembly header");
   93 
   94 /*
   95  * Initialise reassembly queue and fragment identifier.
   96  */
   97 static void
   98 frag6_change(void *tag)
   99 {
  100 
  101         V_ip6_maxfragpackets = nmbclusters / 4;
  102         V_ip6_maxfrags = nmbclusters / 4;
  103 }
  104 
  105 void
  106 frag6_init(void)
  107 {
  108 
  109         V_ip6_maxfragpackets = nmbclusters / 4;
  110         V_ip6_maxfrags = nmbclusters / 4;
  111         V_ip6q.ip6q_next = V_ip6q.ip6q_prev = &V_ip6q;
  112 
  113         if (!IS_DEFAULT_VNET(curvnet))
  114                 return;
  115 
  116         EVENTHANDLER_REGISTER(nmbclusters_change,
  117             frag6_change, NULL, EVENTHANDLER_PRI_ANY);
  118 
  119         IP6Q_LOCK_INIT();
  120 }
  121 
  122 /*
  123  * In RFC2460, fragment and reassembly rule do not agree with each other,
  124  * in terms of next header field handling in fragment header.
  125  * While the sender will use the same value for all of the fragmented packets,
  126  * receiver is suggested not to check the consistency.
  127  *
  128  * fragment rule (p20):
  129  *      (2) A Fragment header containing:
  130  *      The Next Header value that identifies the first header of
  131  *      the Fragmentable Part of the original packet.
  132  *              -> next header field is same for all fragments
  133  *
  134  * reassembly rule (p21):
  135  *      The Next Header field of the last header of the Unfragmentable
  136  *      Part is obtained from the Next Header field of the first
  137  *      fragment's Fragment header.
  138  *              -> should grab it from the first fragment only
  139  *
  140  * The following note also contradicts with fragment rule - noone is going to
  141  * send different fragment with different next header field.
  142  *
  143  * additional note (p22):
  144  *      The Next Header values in the Fragment headers of different
  145  *      fragments of the same original packet may differ.  Only the value
  146  *      from the Offset zero fragment packet is used for reassembly.
  147  *              -> should grab it from the first fragment only
  148  *
  149  * There is no explicit reason given in the RFC.  Historical reason maybe?
  150  */
  151 /*
  152  * Fragment input
  153  */
  154 int
  155 frag6_input(struct mbuf **mp, int *offp, int proto)
  156 {
  157         struct mbuf *m = *mp, *t;
  158         struct ip6_hdr *ip6;
  159         struct ip6_frag *ip6f;
  160         struct ip6q *q6;
  161         struct ip6asfrag *af6, *ip6af, *af6dwn;
  162 #ifdef IN6_IFSTAT_STRICT
  163         struct in6_ifaddr *ia;
  164 #endif
  165         int offset = *offp, nxt, i, next;
  166         int first_frag = 0;
  167         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  168         struct ifnet *dstifp;
  169         u_int8_t ecn, ecn0;
  170 #if 0
  171         char ip6buf[INET6_ADDRSTRLEN];
  172 #endif
  173 
  174         ip6 = mtod(m, struct ip6_hdr *);
  175 #ifndef PULLDOWN_TEST
  176         IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
  177         ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
  178 #else
  179         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  180         if (ip6f == NULL)
  181                 return (IPPROTO_DONE);
  182 #endif
  183 
  184         dstifp = NULL;
  185 #ifdef IN6_IFSTAT_STRICT
  186         /* find the destination interface of the packet. */
  187         if ((ia = ip6_getdstifaddr(m)) != NULL) {
  188                 dstifp = ia->ia_ifp;
  189                 ifa_free(&ia->ia_ifa);
  190         }
  191 #else
  192         /* we are violating the spec, this is not the destination interface */
  193         if ((m->m_flags & M_PKTHDR) != 0)
  194                 dstifp = m->m_pkthdr.rcvif;
  195 #endif
  196 
  197         /* jumbo payload can't contain a fragment header */
  198         if (ip6->ip6_plen == 0) {
  199                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  200                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  201                 return IPPROTO_DONE;
  202         }
  203 
  204         /*
  205          * check whether fragment packet's fragment length is
  206          * multiple of 8 octets.
  207          * sizeof(struct ip6_frag) == 8
  208          * sizeof(struct ip6_hdr) = 40
  209          */
  210         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  211             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  212                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  213                     offsetof(struct ip6_hdr, ip6_plen));
  214                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  215                 return IPPROTO_DONE;
  216         }
  217 
  218         V_ip6stat.ip6s_fragments++;
  219         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  220 
  221         /* offset now points to data portion */
  222         offset += sizeof(struct ip6_frag);
  223 
  224         /*
  225          * XXX-BZ RFC XXXX (draft-gont-6man-ipv6-atomic-fragments)
  226          * Handle "atomic" fragments (offset and m bit set to 0) upfront,
  227          * unrelated to any reassembly.  Just skip the fragment header.
  228          */
  229         if ((ip6f->ip6f_offlg & ~IP6F_RESERVED_MASK) == 0) {
  230                 /* XXX-BZ we want dedicated counters for this. */
  231                 V_ip6stat.ip6s_reassembled++;
  232                 in6_ifstat_inc(dstifp, ifs6_reass_ok);
  233                 *offp = offset;
  234                 return (ip6f->ip6f_nxt);
  235         }
  236 
  237         IP6Q_LOCK();
  238 
  239         /*
  240          * Enforce upper bound on number of fragments.
  241          * If maxfrag is 0, never accept fragments.
  242          * If maxfrag is -1, accept all fragments without limitation.
  243          */
  244         if (V_ip6_maxfrags < 0)
  245                 ;
  246         else if (V_frag6_nfrags >= (u_int)V_ip6_maxfrags)
  247                 goto dropfrag;
  248 
  249         for (q6 = V_ip6q.ip6q_next; q6 != &V_ip6q; q6 = q6->ip6q_next)
  250                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  251                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  252                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst)
  253 #ifdef MAC
  254                     && mac_ip6q_match(m, q6)
  255 #endif
  256                     )
  257                         break;
  258 
  259         if (q6 == &V_ip6q) {
  260                 /*
  261                  * the first fragment to arrive, create a reassembly queue.
  262                  */
  263                 first_frag = 1;
  264 
  265                 /*
  266                  * Enforce upper bound on number of fragmented packets
  267                  * for which we attempt reassembly;
  268                  * If maxfragpackets is 0, never accept fragments.
  269                  * If maxfragpackets is -1, accept all fragments without
  270                  * limitation.
  271                  */
  272                 if (V_ip6_maxfragpackets < 0)
  273                         ;
  274                 else if (V_frag6_nfragpackets >= (u_int)V_ip6_maxfragpackets)
  275                         goto dropfrag;
  276                 V_frag6_nfragpackets++;
  277                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  278                     M_NOWAIT);
  279                 if (q6 == NULL)
  280                         goto dropfrag;
  281                 bzero(q6, sizeof(*q6));
  282 #ifdef MAC
  283                 if (mac_ip6q_init(q6, M_NOWAIT) != 0) {
  284                         free(q6, M_FTABLE);
  285                         goto dropfrag;
  286                 }
  287                 mac_ip6q_create(m, q6);
  288 #endif
  289                 frag6_insque(q6, &V_ip6q);
  290 
  291                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  292                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  293 #ifdef notyet
  294                 q6->ip6q_nxtp   = (u_char *)nxtp;
  295 #endif
  296                 q6->ip6q_ident  = ip6f->ip6f_ident;
  297                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  298                 q6->ip6q_src    = ip6->ip6_src;
  299                 q6->ip6q_dst    = ip6->ip6_dst;
  300                 q6->ip6q_ecn    =
  301                     (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  302                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  303 
  304                 q6->ip6q_nfrag = 0;
  305         }
  306 
  307         /*
  308          * If it's the 1st fragment, record the length of the
  309          * unfragmentable part and the next header of the fragment header.
  310          */
  311         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  312         if (fragoff == 0) {
  313                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  314                     sizeof(struct ip6_frag);
  315                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  316         }
  317 
  318         /*
  319          * Check that the reassembled packet would not exceed 65535 bytes
  320          * in size.
  321          * If it would exceed, discard the fragment and return an ICMP error.
  322          */
  323         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  324         if (q6->ip6q_unfrglen >= 0) {
  325                 /* The 1st fragment has already arrived. */
  326                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  327                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  328                             offset - sizeof(struct ip6_frag) +
  329                             offsetof(struct ip6_frag, ip6f_offlg));
  330                         IP6Q_UNLOCK();
  331                         return (IPPROTO_DONE);
  332                 }
  333         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  334                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  335                     offset - sizeof(struct ip6_frag) +
  336                     offsetof(struct ip6_frag, ip6f_offlg));
  337                 IP6Q_UNLOCK();
  338                 return (IPPROTO_DONE);
  339         }
  340         /*
  341          * If it's the first fragment, do the above check for each
  342          * fragment already stored in the reassembly queue.
  343          */
  344         if (fragoff == 0) {
  345                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  346                      af6 = af6dwn) {
  347                         af6dwn = af6->ip6af_down;
  348 
  349                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  350                             IPV6_MAXPACKET) {
  351                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  352                                 struct ip6_hdr *ip6err;
  353                                 int erroff = af6->ip6af_offset;
  354 
  355                                 /* dequeue the fragment. */
  356                                 frag6_deq(af6);
  357                                 free(af6, M_FTABLE);
  358 
  359                                 /* adjust pointer. */
  360                                 ip6err = mtod(merr, struct ip6_hdr *);
  361 
  362                                 /*
  363                                  * Restore source and destination addresses
  364                                  * in the erroneous IPv6 header.
  365                                  */
  366                                 ip6err->ip6_src = q6->ip6q_src;
  367                                 ip6err->ip6_dst = q6->ip6q_dst;
  368 
  369                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  370                                     ICMP6_PARAMPROB_HEADER,
  371                                     erroff - sizeof(struct ip6_frag) +
  372                                     offsetof(struct ip6_frag, ip6f_offlg));
  373                         }
  374                 }
  375         }
  376 
  377         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  378             M_NOWAIT);
  379         if (ip6af == NULL)
  380                 goto dropfrag;
  381         bzero(ip6af, sizeof(*ip6af));
  382         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  383         ip6af->ip6af_off = fragoff;
  384         ip6af->ip6af_frglen = frgpartlen;
  385         ip6af->ip6af_offset = offset;
  386         IP6_REASS_MBUF(ip6af) = m;
  387 
  388         if (first_frag) {
  389                 af6 = (struct ip6asfrag *)q6;
  390                 goto insert;
  391         }
  392 
  393         /*
  394          * Handle ECN by comparing this segment with the first one;
  395          * if CE is set, do not lose CE.
  396          * drop if CE and not-ECT are mixed for the same packet.
  397          */
  398         ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  399         ecn0 = q6->ip6q_ecn;
  400         if (ecn == IPTOS_ECN_CE) {
  401                 if (ecn0 == IPTOS_ECN_NOTECT) {
  402                         free(ip6af, M_FTABLE);
  403                         goto dropfrag;
  404                 }
  405                 if (ecn0 != IPTOS_ECN_CE)
  406                         q6->ip6q_ecn = IPTOS_ECN_CE;
  407         }
  408         if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
  409                 free(ip6af, M_FTABLE);
  410                 goto dropfrag;
  411         }
  412 
  413         /*
  414          * Find a segment which begins after this one does.
  415          */
  416         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  417              af6 = af6->ip6af_down)
  418                 if (af6->ip6af_off > ip6af->ip6af_off)
  419                         break;
  420 
  421 #if 0
  422         /*
  423          * If there is a preceding segment, it may provide some of
  424          * our data already.  If so, drop the data from the incoming
  425          * segment.  If it provides all of our data, drop us.
  426          */
  427         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  428                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  429                         - ip6af->ip6af_off;
  430                 if (i > 0) {
  431                         if (i >= ip6af->ip6af_frglen)
  432                                 goto dropfrag;
  433                         m_adj(IP6_REASS_MBUF(ip6af), i);
  434                         ip6af->ip6af_off += i;
  435                         ip6af->ip6af_frglen -= i;
  436                 }
  437         }
  438 
  439         /*
  440          * While we overlap succeeding segments trim them or,
  441          * if they are completely covered, dequeue them.
  442          */
  443         while (af6 != (struct ip6asfrag *)q6 &&
  444                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  445                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  446                 if (i < af6->ip6af_frglen) {
  447                         af6->ip6af_frglen -= i;
  448                         af6->ip6af_off += i;
  449                         m_adj(IP6_REASS_MBUF(af6), i);
  450                         break;
  451                 }
  452                 af6 = af6->ip6af_down;
  453                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  454                 frag6_deq(af6->ip6af_up);
  455         }
  456 #else
  457         /*
  458          * If the incoming framgent overlaps some existing fragments in
  459          * the reassembly queue, drop it, since it is dangerous to override
  460          * existing fragments from a security point of view.
  461          * We don't know which fragment is the bad guy - here we trust
  462          * fragment that came in earlier, with no real reason.
  463          *
  464          * Note: due to changes after disabling this part, mbuf passed to
  465          * m_adj() below now does not meet the requirement.
  466          */
  467         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  468                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  469                         - ip6af->ip6af_off;
  470                 if (i > 0) {
  471 #if 0                           /* suppress the noisy log */
  472                         log(LOG_ERR, "%d bytes of a fragment from %s "
  473                             "overlaps the previous fragment\n",
  474                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  475 #endif
  476                         free(ip6af, M_FTABLE);
  477                         goto dropfrag;
  478                 }
  479         }
  480         if (af6 != (struct ip6asfrag *)q6) {
  481                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  482                 if (i > 0) {
  483 #if 0                           /* suppress the noisy log */
  484                         log(LOG_ERR, "%d bytes of a fragment from %s "
  485                             "overlaps the succeeding fragment",
  486                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  487 #endif
  488                         free(ip6af, M_FTABLE);
  489                         goto dropfrag;
  490                 }
  491         }
  492 #endif
  493 
  494 insert:
  495 #ifdef MAC
  496         if (!first_frag)
  497                 mac_ip6q_update(m, q6);
  498 #endif
  499 
  500         /*
  501          * Stick new segment in its place;
  502          * check for complete reassembly.
  503          * Move to front of packet queue, as we are
  504          * the most recently active fragmented packet.
  505          */
  506         frag6_enq(ip6af, af6->ip6af_up);
  507         V_frag6_nfrags++;
  508         q6->ip6q_nfrag++;
  509 #if 0 /* xxx */
  510         if (q6 != V_ip6q.ip6q_next) {
  511                 frag6_remque(q6);
  512                 frag6_insque(q6, &V_ip6q);
  513         }
  514 #endif
  515         next = 0;
  516         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  517              af6 = af6->ip6af_down) {
  518                 if (af6->ip6af_off != next) {
  519                         IP6Q_UNLOCK();
  520                         return IPPROTO_DONE;
  521                 }
  522                 next += af6->ip6af_frglen;
  523         }
  524         if (af6->ip6af_up->ip6af_mff) {
  525                 IP6Q_UNLOCK();
  526                 return IPPROTO_DONE;
  527         }
  528 
  529         /*
  530          * Reassembly is complete; concatenate fragments.
  531          */
  532         ip6af = q6->ip6q_down;
  533         t = m = IP6_REASS_MBUF(ip6af);
  534         af6 = ip6af->ip6af_down;
  535         frag6_deq(ip6af);
  536         while (af6 != (struct ip6asfrag *)q6) {
  537                 af6dwn = af6->ip6af_down;
  538                 frag6_deq(af6);
  539                 while (t->m_next)
  540                         t = t->m_next;
  541                 t->m_next = IP6_REASS_MBUF(af6);
  542                 m_adj(t->m_next, af6->ip6af_offset);
  543                 free(af6, M_FTABLE);
  544                 af6 = af6dwn;
  545         }
  546 
  547         /* adjust offset to point where the original next header starts */
  548         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  549         free(ip6af, M_FTABLE);
  550         ip6 = mtod(m, struct ip6_hdr *);
  551         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  552         if (q6->ip6q_ecn == IPTOS_ECN_CE)
  553                 ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
  554         nxt = q6->ip6q_nxt;
  555 #ifdef notyet
  556         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  557 #endif
  558 
  559         /* Delete frag6 header */
  560         if (m->m_len >= offset + sizeof(struct ip6_frag)) {
  561                 /* This is the only possible case with !PULLDOWN_TEST */
  562                 ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
  563                     offset);
  564                 m->m_data += sizeof(struct ip6_frag);
  565                 m->m_len -= sizeof(struct ip6_frag);
  566         } else {
  567                 /* this comes with no copy if the boundary is on cluster */
  568                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  569                         frag6_remque(q6);
  570                         V_frag6_nfrags -= q6->ip6q_nfrag;
  571 #ifdef MAC
  572                         mac_ip6q_destroy(q6);
  573 #endif
  574                         free(q6, M_FTABLE);
  575                         V_frag6_nfragpackets--;
  576                         goto dropfrag;
  577                 }
  578                 m_adj(t, sizeof(struct ip6_frag));
  579                 m_cat(m, t);
  580         }
  581 
  582         /*
  583          * Store NXT to the original.
  584          */
  585         {
  586                 char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  587                 *prvnxtp = nxt;
  588         }
  589 
  590         frag6_remque(q6);
  591         V_frag6_nfrags -= q6->ip6q_nfrag;
  592 #ifdef MAC
  593         mac_ip6q_reassemble(q6, m);
  594         mac_ip6q_destroy(q6);
  595 #endif
  596         free(q6, M_FTABLE);
  597         V_frag6_nfragpackets--;
  598 
  599         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  600                 int plen = 0;
  601                 for (t = m; t; t = t->m_next)
  602                         plen += t->m_len;
  603                 m->m_pkthdr.len = plen;
  604         }
  605 
  606         V_ip6stat.ip6s_reassembled++;
  607         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  608 
  609         /*
  610          * Tell launch routine the next header
  611          */
  612 
  613         *mp = m;
  614         *offp = offset;
  615 
  616         IP6Q_UNLOCK();
  617         return nxt;
  618 
  619  dropfrag:
  620         IP6Q_UNLOCK();
  621         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  622         V_ip6stat.ip6s_fragdropped++;
  623         m_freem(m);
  624         return IPPROTO_DONE;
  625 }
  626 
  627 /*
  628  * Free a fragment reassembly header and all
  629  * associated datagrams.
  630  */
  631 void
  632 frag6_freef(struct ip6q *q6)
  633 {
  634         struct ip6asfrag *af6, *down6;
  635 
  636         IP6Q_LOCK_ASSERT();
  637 
  638         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  639              af6 = down6) {
  640                 struct mbuf *m = IP6_REASS_MBUF(af6);
  641 
  642                 down6 = af6->ip6af_down;
  643                 frag6_deq(af6);
  644 
  645                 /*
  646                  * Return ICMP time exceeded error for the 1st fragment.
  647                  * Just free other fragments.
  648                  */
  649                 if (af6->ip6af_off == 0) {
  650                         struct ip6_hdr *ip6;
  651 
  652                         /* adjust pointer */
  653                         ip6 = mtod(m, struct ip6_hdr *);
  654 
  655                         /* restore source and destination addresses */
  656                         ip6->ip6_src = q6->ip6q_src;
  657                         ip6->ip6_dst = q6->ip6q_dst;
  658 
  659                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  660                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  661                 } else
  662                         m_freem(m);
  663                 free(af6, M_FTABLE);
  664         }
  665         frag6_remque(q6);
  666         V_frag6_nfrags -= q6->ip6q_nfrag;
  667 #ifdef MAC
  668         mac_ip6q_destroy(q6);
  669 #endif
  670         free(q6, M_FTABLE);
  671         V_frag6_nfragpackets--;
  672 }
  673 
  674 /*
  675  * Put an ip fragment on a reassembly chain.
  676  * Like insque, but pointers in middle of structure.
  677  */
  678 void
  679 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6)
  680 {
  681 
  682         IP6Q_LOCK_ASSERT();
  683 
  684         af6->ip6af_up = up6;
  685         af6->ip6af_down = up6->ip6af_down;
  686         up6->ip6af_down->ip6af_up = af6;
  687         up6->ip6af_down = af6;
  688 }
  689 
  690 /*
  691  * To frag6_enq as remque is to insque.
  692  */
  693 void
  694 frag6_deq(struct ip6asfrag *af6)
  695 {
  696 
  697         IP6Q_LOCK_ASSERT();
  698 
  699         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  700         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  701 }
  702 
  703 void
  704 frag6_insque(struct ip6q *new, struct ip6q *old)
  705 {
  706 
  707         IP6Q_LOCK_ASSERT();
  708 
  709         new->ip6q_prev = old;
  710         new->ip6q_next = old->ip6q_next;
  711         old->ip6q_next->ip6q_prev= new;
  712         old->ip6q_next = new;
  713 }
  714 
  715 void
  716 frag6_remque(struct ip6q *p6)
  717 {
  718 
  719         IP6Q_LOCK_ASSERT();
  720 
  721         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  722         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  723 }
  724 
  725 /*
  726  * IPv6 reassembling timer processing;
  727  * if a timer expires on a reassembly
  728  * queue, discard it.
  729  */
  730 void
  731 frag6_slowtimo(void)
  732 {
  733         VNET_ITERATOR_DECL(vnet_iter);
  734         struct ip6q *q6;
  735 
  736         VNET_LIST_RLOCK_NOSLEEP();
  737         IP6Q_LOCK();
  738         VNET_FOREACH(vnet_iter) {
  739                 CURVNET_SET(vnet_iter);
  740                 q6 = V_ip6q.ip6q_next;
  741                 if (q6)
  742                         while (q6 != &V_ip6q) {
  743                                 --q6->ip6q_ttl;
  744                                 q6 = q6->ip6q_next;
  745                                 if (q6->ip6q_prev->ip6q_ttl == 0) {
  746                                         V_ip6stat.ip6s_fragtimeout++;
  747                                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  748                                         frag6_freef(q6->ip6q_prev);
  749                                 }
  750                         }
  751                 /*
  752                  * If we are over the maximum number of fragments
  753                  * (due to the limit being lowered), drain off
  754                  * enough to get down to the new limit.
  755                  */
  756                 while (V_frag6_nfragpackets > (u_int)V_ip6_maxfragpackets &&
  757                     V_ip6q.ip6q_prev) {
  758                         V_ip6stat.ip6s_fragoverflow++;
  759                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  760                         frag6_freef(V_ip6q.ip6q_prev);
  761                 }
  762                 CURVNET_RESTORE();
  763         }
  764         IP6Q_UNLOCK();
  765         VNET_LIST_RUNLOCK_NOSLEEP();
  766 }
  767 
  768 /*
  769  * Drain off all datagram fragments.
  770  */
  771 void
  772 frag6_drain(void)
  773 {
  774         VNET_ITERATOR_DECL(vnet_iter);
  775 
  776         VNET_LIST_RLOCK_NOSLEEP();
  777         if (IP6Q_TRYLOCK() == 0) {
  778                 VNET_LIST_RUNLOCK_NOSLEEP();
  779                 return;
  780         }
  781         VNET_FOREACH(vnet_iter) {
  782                 CURVNET_SET(vnet_iter);
  783                 while (V_ip6q.ip6q_next != &V_ip6q) {
  784                         V_ip6stat.ip6s_fragdropped++;
  785                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  786                         frag6_freef(V_ip6q.ip6q_next);
  787                 }
  788                 CURVNET_RESTORE();
  789         }
  790         IP6Q_UNLOCK();
  791         VNET_LIST_RUNLOCK_NOSLEEP();
  792 }

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