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/8.2/sys/netinet6/frag6.c 207695 2010-05-06 06:44:19Z 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         IP6Q_LOCK();
  225 
  226         /*
  227          * Enforce upper bound on number of fragments.
  228          * If maxfrag is 0, never accept fragments.
  229          * If maxfrag is -1, accept all fragments without limitation.
  230          */
  231         if (V_ip6_maxfrags < 0)
  232                 ;
  233         else if (V_frag6_nfrags >= (u_int)V_ip6_maxfrags)
  234                 goto dropfrag;
  235 
  236         for (q6 = V_ip6q.ip6q_next; q6 != &V_ip6q; q6 = q6->ip6q_next)
  237                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  238                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  239                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst)
  240 #ifdef MAC
  241                     && mac_ip6q_match(m, q6)
  242 #endif
  243                     )
  244                         break;
  245 
  246         if (q6 == &V_ip6q) {
  247                 /*
  248                  * the first fragment to arrive, create a reassembly queue.
  249                  */
  250                 first_frag = 1;
  251 
  252                 /*
  253                  * Enforce upper bound on number of fragmented packets
  254                  * for which we attempt reassembly;
  255                  * If maxfragpackets is 0, never accept fragments.
  256                  * If maxfragpackets is -1, accept all fragments without
  257                  * limitation.
  258                  */
  259                 if (V_ip6_maxfragpackets < 0)
  260                         ;
  261                 else if (V_frag6_nfragpackets >= (u_int)V_ip6_maxfragpackets)
  262                         goto dropfrag;
  263                 V_frag6_nfragpackets++;
  264                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  265                     M_NOWAIT);
  266                 if (q6 == NULL)
  267                         goto dropfrag;
  268                 bzero(q6, sizeof(*q6));
  269 #ifdef MAC
  270                 if (mac_ip6q_init(q6, M_NOWAIT) != 0) {
  271                         free(q6, M_FTABLE);
  272                         goto dropfrag;
  273                 }
  274                 mac_ip6q_create(m, q6);
  275 #endif
  276                 frag6_insque(q6, &V_ip6q);
  277 
  278                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  279                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  280 #ifdef notyet
  281                 q6->ip6q_nxtp   = (u_char *)nxtp;
  282 #endif
  283                 q6->ip6q_ident  = ip6f->ip6f_ident;
  284                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  285                 q6->ip6q_src    = ip6->ip6_src;
  286                 q6->ip6q_dst    = ip6->ip6_dst;
  287                 q6->ip6q_ecn    =
  288                     (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  289                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  290 
  291                 q6->ip6q_nfrag = 0;
  292         }
  293 
  294         /*
  295          * If it's the 1st fragment, record the length of the
  296          * unfragmentable part and the next header of the fragment header.
  297          */
  298         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  299         if (fragoff == 0) {
  300                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  301                     sizeof(struct ip6_frag);
  302                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  303         }
  304 
  305         /*
  306          * Check that the reassembled packet would not exceed 65535 bytes
  307          * in size.
  308          * If it would exceed, discard the fragment and return an ICMP error.
  309          */
  310         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  311         if (q6->ip6q_unfrglen >= 0) {
  312                 /* The 1st fragment has already arrived. */
  313                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  314                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  315                             offset - sizeof(struct ip6_frag) +
  316                             offsetof(struct ip6_frag, ip6f_offlg));
  317                         IP6Q_UNLOCK();
  318                         return (IPPROTO_DONE);
  319                 }
  320         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  321                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  322                     offset - sizeof(struct ip6_frag) +
  323                     offsetof(struct ip6_frag, ip6f_offlg));
  324                 IP6Q_UNLOCK();
  325                 return (IPPROTO_DONE);
  326         }
  327         /*
  328          * If it's the first fragment, do the above check for each
  329          * fragment already stored in the reassembly queue.
  330          */
  331         if (fragoff == 0) {
  332                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  333                      af6 = af6dwn) {
  334                         af6dwn = af6->ip6af_down;
  335 
  336                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  337                             IPV6_MAXPACKET) {
  338                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  339                                 struct ip6_hdr *ip6err;
  340                                 int erroff = af6->ip6af_offset;
  341 
  342                                 /* dequeue the fragment. */
  343                                 frag6_deq(af6);
  344                                 free(af6, M_FTABLE);
  345 
  346                                 /* adjust pointer. */
  347                                 ip6err = mtod(merr, struct ip6_hdr *);
  348 
  349                                 /*
  350                                  * Restore source and destination addresses
  351                                  * in the erroneous IPv6 header.
  352                                  */
  353                                 ip6err->ip6_src = q6->ip6q_src;
  354                                 ip6err->ip6_dst = q6->ip6q_dst;
  355 
  356                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  357                                     ICMP6_PARAMPROB_HEADER,
  358                                     erroff - sizeof(struct ip6_frag) +
  359                                     offsetof(struct ip6_frag, ip6f_offlg));
  360                         }
  361                 }
  362         }
  363 
  364         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  365             M_NOWAIT);
  366         if (ip6af == NULL)
  367                 goto dropfrag;
  368         bzero(ip6af, sizeof(*ip6af));
  369         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  370         ip6af->ip6af_off = fragoff;
  371         ip6af->ip6af_frglen = frgpartlen;
  372         ip6af->ip6af_offset = offset;
  373         IP6_REASS_MBUF(ip6af) = m;
  374 
  375         if (first_frag) {
  376                 af6 = (struct ip6asfrag *)q6;
  377                 goto insert;
  378         }
  379 
  380         /*
  381          * Handle ECN by comparing this segment with the first one;
  382          * if CE is set, do not lose CE.
  383          * drop if CE and not-ECT are mixed for the same packet.
  384          */
  385         ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  386         ecn0 = q6->ip6q_ecn;
  387         if (ecn == IPTOS_ECN_CE) {
  388                 if (ecn0 == IPTOS_ECN_NOTECT) {
  389                         free(ip6af, M_FTABLE);
  390                         goto dropfrag;
  391                 }
  392                 if (ecn0 != IPTOS_ECN_CE)
  393                         q6->ip6q_ecn = IPTOS_ECN_CE;
  394         }
  395         if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
  396                 free(ip6af, M_FTABLE);
  397                 goto dropfrag;
  398         }
  399 
  400         /*
  401          * Find a segment which begins after this one does.
  402          */
  403         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  404              af6 = af6->ip6af_down)
  405                 if (af6->ip6af_off > ip6af->ip6af_off)
  406                         break;
  407 
  408 #if 0
  409         /*
  410          * If there is a preceding segment, it may provide some of
  411          * our data already.  If so, drop the data from the incoming
  412          * segment.  If it provides all of our data, drop us.
  413          */
  414         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  415                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  416                         - ip6af->ip6af_off;
  417                 if (i > 0) {
  418                         if (i >= ip6af->ip6af_frglen)
  419                                 goto dropfrag;
  420                         m_adj(IP6_REASS_MBUF(ip6af), i);
  421                         ip6af->ip6af_off += i;
  422                         ip6af->ip6af_frglen -= i;
  423                 }
  424         }
  425 
  426         /*
  427          * While we overlap succeeding segments trim them or,
  428          * if they are completely covered, dequeue them.
  429          */
  430         while (af6 != (struct ip6asfrag *)q6 &&
  431                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  432                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  433                 if (i < af6->ip6af_frglen) {
  434                         af6->ip6af_frglen -= i;
  435                         af6->ip6af_off += i;
  436                         m_adj(IP6_REASS_MBUF(af6), i);
  437                         break;
  438                 }
  439                 af6 = af6->ip6af_down;
  440                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  441                 frag6_deq(af6->ip6af_up);
  442         }
  443 #else
  444         /*
  445          * If the incoming framgent overlaps some existing fragments in
  446          * the reassembly queue, drop it, since it is dangerous to override
  447          * existing fragments from a security point of view.
  448          * We don't know which fragment is the bad guy - here we trust
  449          * fragment that came in earlier, with no real reason.
  450          *
  451          * Note: due to changes after disabling this part, mbuf passed to
  452          * m_adj() below now does not meet the requirement.
  453          */
  454         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  455                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  456                         - ip6af->ip6af_off;
  457                 if (i > 0) {
  458 #if 0                           /* suppress the noisy log */
  459                         log(LOG_ERR, "%d bytes of a fragment from %s "
  460                             "overlaps the previous fragment\n",
  461                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  462 #endif
  463                         free(ip6af, M_FTABLE);
  464                         goto dropfrag;
  465                 }
  466         }
  467         if (af6 != (struct ip6asfrag *)q6) {
  468                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  469                 if (i > 0) {
  470 #if 0                           /* suppress the noisy log */
  471                         log(LOG_ERR, "%d bytes of a fragment from %s "
  472                             "overlaps the succeeding fragment",
  473                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  474 #endif
  475                         free(ip6af, M_FTABLE);
  476                         goto dropfrag;
  477                 }
  478         }
  479 #endif
  480 
  481 insert:
  482 #ifdef MAC
  483         if (!first_frag)
  484                 mac_ip6q_update(m, q6);
  485 #endif
  486 
  487         /*
  488          * Stick new segment in its place;
  489          * check for complete reassembly.
  490          * Move to front of packet queue, as we are
  491          * the most recently active fragmented packet.
  492          */
  493         frag6_enq(ip6af, af6->ip6af_up);
  494         V_frag6_nfrags++;
  495         q6->ip6q_nfrag++;
  496 #if 0 /* xxx */
  497         if (q6 != V_ip6q.ip6q_next) {
  498                 frag6_remque(q6);
  499                 frag6_insque(q6, &V_ip6q);
  500         }
  501 #endif
  502         next = 0;
  503         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  504              af6 = af6->ip6af_down) {
  505                 if (af6->ip6af_off != next) {
  506                         IP6Q_UNLOCK();
  507                         return IPPROTO_DONE;
  508                 }
  509                 next += af6->ip6af_frglen;
  510         }
  511         if (af6->ip6af_up->ip6af_mff) {
  512                 IP6Q_UNLOCK();
  513                 return IPPROTO_DONE;
  514         }
  515 
  516         /*
  517          * Reassembly is complete; concatenate fragments.
  518          */
  519         ip6af = q6->ip6q_down;
  520         t = m = IP6_REASS_MBUF(ip6af);
  521         af6 = ip6af->ip6af_down;
  522         frag6_deq(ip6af);
  523         while (af6 != (struct ip6asfrag *)q6) {
  524                 af6dwn = af6->ip6af_down;
  525                 frag6_deq(af6);
  526                 while (t->m_next)
  527                         t = t->m_next;
  528                 t->m_next = IP6_REASS_MBUF(af6);
  529                 m_adj(t->m_next, af6->ip6af_offset);
  530                 free(af6, M_FTABLE);
  531                 af6 = af6dwn;
  532         }
  533 
  534         /* adjust offset to point where the original next header starts */
  535         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  536         free(ip6af, M_FTABLE);
  537         ip6 = mtod(m, struct ip6_hdr *);
  538         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  539         if (q6->ip6q_ecn == IPTOS_ECN_CE)
  540                 ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
  541         nxt = q6->ip6q_nxt;
  542 #ifdef notyet
  543         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  544 #endif
  545 
  546         /* Delete frag6 header */
  547         if (m->m_len >= offset + sizeof(struct ip6_frag)) {
  548                 /* This is the only possible case with !PULLDOWN_TEST */
  549                 ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
  550                     offset);
  551                 m->m_data += sizeof(struct ip6_frag);
  552                 m->m_len -= sizeof(struct ip6_frag);
  553         } else {
  554                 /* this comes with no copy if the boundary is on cluster */
  555                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  556                         frag6_remque(q6);
  557                         V_frag6_nfrags -= q6->ip6q_nfrag;
  558 #ifdef MAC
  559                         mac_ip6q_destroy(q6);
  560 #endif
  561                         free(q6, M_FTABLE);
  562                         V_frag6_nfragpackets--;
  563                         goto dropfrag;
  564                 }
  565                 m_adj(t, sizeof(struct ip6_frag));
  566                 m_cat(m, t);
  567         }
  568 
  569         /*
  570          * Store NXT to the original.
  571          */
  572         {
  573                 char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  574                 *prvnxtp = nxt;
  575         }
  576 
  577         frag6_remque(q6);
  578         V_frag6_nfrags -= q6->ip6q_nfrag;
  579 #ifdef MAC
  580         mac_ip6q_reassemble(q6, m);
  581         mac_ip6q_destroy(q6);
  582 #endif
  583         free(q6, M_FTABLE);
  584         V_frag6_nfragpackets--;
  585 
  586         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  587                 int plen = 0;
  588                 for (t = m; t; t = t->m_next)
  589                         plen += t->m_len;
  590                 m->m_pkthdr.len = plen;
  591         }
  592 
  593         V_ip6stat.ip6s_reassembled++;
  594         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  595 
  596         /*
  597          * Tell launch routine the next header
  598          */
  599 
  600         *mp = m;
  601         *offp = offset;
  602 
  603         IP6Q_UNLOCK();
  604         return nxt;
  605 
  606  dropfrag:
  607         IP6Q_UNLOCK();
  608         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  609         V_ip6stat.ip6s_fragdropped++;
  610         m_freem(m);
  611         return IPPROTO_DONE;
  612 }
  613 
  614 /*
  615  * Free a fragment reassembly header and all
  616  * associated datagrams.
  617  */
  618 void
  619 frag6_freef(struct ip6q *q6)
  620 {
  621         struct ip6asfrag *af6, *down6;
  622 
  623         IP6Q_LOCK_ASSERT();
  624 
  625         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  626              af6 = down6) {
  627                 struct mbuf *m = IP6_REASS_MBUF(af6);
  628 
  629                 down6 = af6->ip6af_down;
  630                 frag6_deq(af6);
  631 
  632                 /*
  633                  * Return ICMP time exceeded error for the 1st fragment.
  634                  * Just free other fragments.
  635                  */
  636                 if (af6->ip6af_off == 0) {
  637                         struct ip6_hdr *ip6;
  638 
  639                         /* adjust pointer */
  640                         ip6 = mtod(m, struct ip6_hdr *);
  641 
  642                         /* restore source and destination addresses */
  643                         ip6->ip6_src = q6->ip6q_src;
  644                         ip6->ip6_dst = q6->ip6q_dst;
  645 
  646                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  647                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  648                 } else
  649                         m_freem(m);
  650                 free(af6, M_FTABLE);
  651         }
  652         frag6_remque(q6);
  653         V_frag6_nfrags -= q6->ip6q_nfrag;
  654 #ifdef MAC
  655         mac_ip6q_destroy(q6);
  656 #endif
  657         free(q6, M_FTABLE);
  658         V_frag6_nfragpackets--;
  659 }
  660 
  661 /*
  662  * Put an ip fragment on a reassembly chain.
  663  * Like insque, but pointers in middle of structure.
  664  */
  665 void
  666 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6)
  667 {
  668 
  669         IP6Q_LOCK_ASSERT();
  670 
  671         af6->ip6af_up = up6;
  672         af6->ip6af_down = up6->ip6af_down;
  673         up6->ip6af_down->ip6af_up = af6;
  674         up6->ip6af_down = af6;
  675 }
  676 
  677 /*
  678  * To frag6_enq as remque is to insque.
  679  */
  680 void
  681 frag6_deq(struct ip6asfrag *af6)
  682 {
  683 
  684         IP6Q_LOCK_ASSERT();
  685 
  686         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  687         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  688 }
  689 
  690 void
  691 frag6_insque(struct ip6q *new, struct ip6q *old)
  692 {
  693 
  694         IP6Q_LOCK_ASSERT();
  695 
  696         new->ip6q_prev = old;
  697         new->ip6q_next = old->ip6q_next;
  698         old->ip6q_next->ip6q_prev= new;
  699         old->ip6q_next = new;
  700 }
  701 
  702 void
  703 frag6_remque(struct ip6q *p6)
  704 {
  705 
  706         IP6Q_LOCK_ASSERT();
  707 
  708         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  709         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  710 }
  711 
  712 /*
  713  * IPv6 reassembling timer processing;
  714  * if a timer expires on a reassembly
  715  * queue, discard it.
  716  */
  717 void
  718 frag6_slowtimo(void)
  719 {
  720         VNET_ITERATOR_DECL(vnet_iter);
  721         struct ip6q *q6;
  722 
  723         VNET_LIST_RLOCK_NOSLEEP();
  724         IP6Q_LOCK();
  725         VNET_FOREACH(vnet_iter) {
  726                 CURVNET_SET(vnet_iter);
  727                 q6 = V_ip6q.ip6q_next;
  728                 if (q6)
  729                         while (q6 != &V_ip6q) {
  730                                 --q6->ip6q_ttl;
  731                                 q6 = q6->ip6q_next;
  732                                 if (q6->ip6q_prev->ip6q_ttl == 0) {
  733                                         V_ip6stat.ip6s_fragtimeout++;
  734                                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  735                                         frag6_freef(q6->ip6q_prev);
  736                                 }
  737                         }
  738                 /*
  739                  * If we are over the maximum number of fragments
  740                  * (due to the limit being lowered), drain off
  741                  * enough to get down to the new limit.
  742                  */
  743                 while (V_frag6_nfragpackets > (u_int)V_ip6_maxfragpackets &&
  744                     V_ip6q.ip6q_prev) {
  745                         V_ip6stat.ip6s_fragoverflow++;
  746                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  747                         frag6_freef(V_ip6q.ip6q_prev);
  748                 }
  749                 CURVNET_RESTORE();
  750         }
  751         IP6Q_UNLOCK();
  752         VNET_LIST_RUNLOCK_NOSLEEP();
  753 }
  754 
  755 /*
  756  * Drain off all datagram fragments.
  757  */
  758 void
  759 frag6_drain(void)
  760 {
  761         VNET_ITERATOR_DECL(vnet_iter);
  762 
  763         VNET_LIST_RLOCK_NOSLEEP();
  764         if (IP6Q_TRYLOCK() == 0) {
  765                 VNET_LIST_RUNLOCK_NOSLEEP();
  766                 return;
  767         }
  768         VNET_FOREACH(vnet_iter) {
  769                 CURVNET_SET(vnet_iter);
  770                 while (V_ip6q.ip6q_next != &V_ip6q) {
  771                         V_ip6stat.ip6s_fragdropped++;
  772                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  773                         frag6_freef(V_ip6q.ip6q_next);
  774                 }
  775                 CURVNET_RESTORE();
  776         }
  777         IP6Q_UNLOCK();
  778         VNET_LIST_RUNLOCK_NOSLEEP();
  779 }

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