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/8.0/sys/netinet6/frag6.c 196019 2009-08-01 19:26:27Z rwatson $");
   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_ip6q.ip6q_next = V_ip6q.ip6q_prev = &V_ip6q;
  110         V_ip6_maxfragpackets = nmbclusters / 4;
  111         V_ip6_maxfrags = nmbclusters / 4;
  112 
  113         if (!IS_DEFAULT_VNET(curvnet))
  114                 return;
  115 
  116         IP6Q_LOCK_INIT();
  117         EVENTHANDLER_REGISTER(nmbclusters_change,
  118             frag6_change, NULL, EVENTHANDLER_PRI_ANY);
  119 }
  120 
  121 /*
  122  * In RFC2460, fragment and reassembly rule do not agree with each other,
  123  * in terms of next header field handling in fragment header.
  124  * While the sender will use the same value for all of the fragmented packets,
  125  * receiver is suggested not to check the consistency.
  126  *
  127  * fragment rule (p20):
  128  *      (2) A Fragment header containing:
  129  *      The Next Header value that identifies the first header of
  130  *      the Fragmentable Part of the original packet.
  131  *              -> next header field is same for all fragments
  132  *
  133  * reassembly rule (p21):
  134  *      The Next Header field of the last header of the Unfragmentable
  135  *      Part is obtained from the Next Header field of the first
  136  *      fragment's Fragment header.
  137  *              -> should grab it from the first fragment only
  138  *
  139  * The following note also contradicts with fragment rule - noone is going to
  140  * send different fragment with different next header field.
  141  *
  142  * additional note (p22):
  143  *      The Next Header values in the Fragment headers of different
  144  *      fragments of the same original packet may differ.  Only the value
  145  *      from the Offset zero fragment packet is used for reassembly.
  146  *              -> should grab it from the first fragment only
  147  *
  148  * There is no explicit reason given in the RFC.  Historical reason maybe?
  149  */
  150 /*
  151  * Fragment input
  152  */
  153 int
  154 frag6_input(struct mbuf **mp, int *offp, int proto)
  155 {
  156         struct mbuf *m = *mp, *t;
  157         struct ip6_hdr *ip6;
  158         struct ip6_frag *ip6f;
  159         struct ip6q *q6;
  160         struct ip6asfrag *af6, *ip6af, *af6dwn;
  161 #ifdef IN6_IFSTAT_STRICT
  162         struct in6_ifaddr *ia;
  163 #endif
  164         int offset = *offp, nxt, i, next;
  165         int first_frag = 0;
  166         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  167         struct ifnet *dstifp;
  168         u_int8_t ecn, ecn0;
  169 #if 0
  170         char ip6buf[INET6_ADDRSTRLEN];
  171 #endif
  172 
  173         ip6 = mtod(m, struct ip6_hdr *);
  174 #ifndef PULLDOWN_TEST
  175         IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
  176         ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
  177 #else
  178         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  179         if (ip6f == NULL)
  180                 return (IPPROTO_DONE);
  181 #endif
  182 
  183         dstifp = NULL;
  184 #ifdef IN6_IFSTAT_STRICT
  185         /* find the destination interface of the packet. */
  186         if ((ia = ip6_getdstifaddr(m)) != NULL) {
  187                 dstifp = ia->ia_ifp;
  188                 ifa_free(&ia->ia_ifa);
  189         }
  190 #else
  191         /* we are violating the spec, this is not the destination interface */
  192         if ((m->m_flags & M_PKTHDR) != 0)
  193                 dstifp = m->m_pkthdr.rcvif;
  194 #endif
  195 
  196         /* jumbo payload can't contain a fragment header */
  197         if (ip6->ip6_plen == 0) {
  198                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  199                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  200                 return IPPROTO_DONE;
  201         }
  202 
  203         /*
  204          * check whether fragment packet's fragment length is
  205          * multiple of 8 octets.
  206          * sizeof(struct ip6_frag) == 8
  207          * sizeof(struct ip6_hdr) = 40
  208          */
  209         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  210             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  211                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  212                     offsetof(struct ip6_hdr, ip6_plen));
  213                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  214                 return IPPROTO_DONE;
  215         }
  216 
  217         V_ip6stat.ip6s_fragments++;
  218         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  219 
  220         /* offset now points to data portion */
  221         offset += sizeof(struct ip6_frag);
  222 
  223         IP6Q_LOCK();
  224 
  225         /*
  226          * Enforce upper bound on number of fragments.
  227          * If maxfrag is 0, never accept fragments.
  228          * If maxfrag is -1, accept all fragments without limitation.
  229          */
  230         if (V_ip6_maxfrags < 0)
  231                 ;
  232         else if (V_frag6_nfrags >= (u_int)V_ip6_maxfrags)
  233                 goto dropfrag;
  234 
  235         for (q6 = V_ip6q.ip6q_next; q6 != &V_ip6q; q6 = q6->ip6q_next)
  236                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  237                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  238                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst)
  239 #ifdef MAC
  240                     && mac_ip6q_match(m, q6)
  241 #endif
  242                     )
  243                         break;
  244 
  245         if (q6 == &V_ip6q) {
  246                 /*
  247                  * the first fragment to arrive, create a reassembly queue.
  248                  */
  249                 first_frag = 1;
  250 
  251                 /*
  252                  * Enforce upper bound on number of fragmented packets
  253                  * for which we attempt reassembly;
  254                  * If maxfragpackets is 0, never accept fragments.
  255                  * If maxfragpackets is -1, accept all fragments without
  256                  * limitation.
  257                  */
  258                 if (V_ip6_maxfragpackets < 0)
  259                         ;
  260                 else if (V_frag6_nfragpackets >= (u_int)V_ip6_maxfragpackets)
  261                         goto dropfrag;
  262                 V_frag6_nfragpackets++;
  263                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  264                     M_NOWAIT);
  265                 if (q6 == NULL)
  266                         goto dropfrag;
  267                 bzero(q6, sizeof(*q6));
  268 #ifdef MAC
  269                 if (mac_ip6q_init(q6, M_NOWAIT) != 0) {
  270                         free(q6, M_FTABLE);
  271                         goto dropfrag;
  272                 }
  273                 mac_ip6q_create(m, q6);
  274 #endif
  275                 frag6_insque(q6, &V_ip6q);
  276 
  277                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  278                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  279 #ifdef notyet
  280                 q6->ip6q_nxtp   = (u_char *)nxtp;
  281 #endif
  282                 q6->ip6q_ident  = ip6f->ip6f_ident;
  283                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  284                 q6->ip6q_src    = ip6->ip6_src;
  285                 q6->ip6q_dst    = ip6->ip6_dst;
  286                 q6->ip6q_ecn    =
  287                     (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  288                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  289 
  290                 q6->ip6q_nfrag = 0;
  291         }
  292 
  293         /*
  294          * If it's the 1st fragment, record the length of the
  295          * unfragmentable part and the next header of the fragment header.
  296          */
  297         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  298         if (fragoff == 0) {
  299                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  300                     sizeof(struct ip6_frag);
  301                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  302         }
  303 
  304         /*
  305          * Check that the reassembled packet would not exceed 65535 bytes
  306          * in size.
  307          * If it would exceed, discard the fragment and return an ICMP error.
  308          */
  309         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  310         if (q6->ip6q_unfrglen >= 0) {
  311                 /* The 1st fragment has already arrived. */
  312                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  313                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  314                             offset - sizeof(struct ip6_frag) +
  315                             offsetof(struct ip6_frag, ip6f_offlg));
  316                         IP6Q_UNLOCK();
  317                         return (IPPROTO_DONE);
  318                 }
  319         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  320                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  321                     offset - sizeof(struct ip6_frag) +
  322                     offsetof(struct ip6_frag, ip6f_offlg));
  323                 IP6Q_UNLOCK();
  324                 return (IPPROTO_DONE);
  325         }
  326         /*
  327          * If it's the first fragment, do the above check for each
  328          * fragment already stored in the reassembly queue.
  329          */
  330         if (fragoff == 0) {
  331                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  332                      af6 = af6dwn) {
  333                         af6dwn = af6->ip6af_down;
  334 
  335                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  336                             IPV6_MAXPACKET) {
  337                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  338                                 struct ip6_hdr *ip6err;
  339                                 int erroff = af6->ip6af_offset;
  340 
  341                                 /* dequeue the fragment. */
  342                                 frag6_deq(af6);
  343                                 free(af6, M_FTABLE);
  344 
  345                                 /* adjust pointer. */
  346                                 ip6err = mtod(merr, struct ip6_hdr *);
  347 
  348                                 /*
  349                                  * Restore source and destination addresses
  350                                  * in the erroneous IPv6 header.
  351                                  */
  352                                 ip6err->ip6_src = q6->ip6q_src;
  353                                 ip6err->ip6_dst = q6->ip6q_dst;
  354 
  355                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  356                                     ICMP6_PARAMPROB_HEADER,
  357                                     erroff - sizeof(struct ip6_frag) +
  358                                     offsetof(struct ip6_frag, ip6f_offlg));
  359                         }
  360                 }
  361         }
  362 
  363         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  364             M_NOWAIT);
  365         if (ip6af == NULL)
  366                 goto dropfrag;
  367         bzero(ip6af, sizeof(*ip6af));
  368         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  369         ip6af->ip6af_off = fragoff;
  370         ip6af->ip6af_frglen = frgpartlen;
  371         ip6af->ip6af_offset = offset;
  372         IP6_REASS_MBUF(ip6af) = m;
  373 
  374         if (first_frag) {
  375                 af6 = (struct ip6asfrag *)q6;
  376                 goto insert;
  377         }
  378 
  379         /*
  380          * Handle ECN by comparing this segment with the first one;
  381          * if CE is set, do not lose CE.
  382          * drop if CE and not-ECT are mixed for the same packet.
  383          */
  384         ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  385         ecn0 = q6->ip6q_ecn;
  386         if (ecn == IPTOS_ECN_CE) {
  387                 if (ecn0 == IPTOS_ECN_NOTECT) {
  388                         free(ip6af, M_FTABLE);
  389                         goto dropfrag;
  390                 }
  391                 if (ecn0 != IPTOS_ECN_CE)
  392                         q6->ip6q_ecn = IPTOS_ECN_CE;
  393         }
  394         if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
  395                 free(ip6af, M_FTABLE);
  396                 goto dropfrag;
  397         }
  398 
  399         /*
  400          * Find a segment which begins after this one does.
  401          */
  402         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  403              af6 = af6->ip6af_down)
  404                 if (af6->ip6af_off > ip6af->ip6af_off)
  405                         break;
  406 
  407 #if 0
  408         /*
  409          * If there is a preceding segment, it may provide some of
  410          * our data already.  If so, drop the data from the incoming
  411          * segment.  If it provides all of our data, drop us.
  412          */
  413         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  414                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  415                         - ip6af->ip6af_off;
  416                 if (i > 0) {
  417                         if (i >= ip6af->ip6af_frglen)
  418                                 goto dropfrag;
  419                         m_adj(IP6_REASS_MBUF(ip6af), i);
  420                         ip6af->ip6af_off += i;
  421                         ip6af->ip6af_frglen -= i;
  422                 }
  423         }
  424 
  425         /*
  426          * While we overlap succeeding segments trim them or,
  427          * if they are completely covered, dequeue them.
  428          */
  429         while (af6 != (struct ip6asfrag *)q6 &&
  430                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  431                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  432                 if (i < af6->ip6af_frglen) {
  433                         af6->ip6af_frglen -= i;
  434                         af6->ip6af_off += i;
  435                         m_adj(IP6_REASS_MBUF(af6), i);
  436                         break;
  437                 }
  438                 af6 = af6->ip6af_down;
  439                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  440                 frag6_deq(af6->ip6af_up);
  441         }
  442 #else
  443         /*
  444          * If the incoming framgent overlaps some existing fragments in
  445          * the reassembly queue, drop it, since it is dangerous to override
  446          * existing fragments from a security point of view.
  447          * We don't know which fragment is the bad guy - here we trust
  448          * fragment that came in earlier, with no real reason.
  449          *
  450          * Note: due to changes after disabling this part, mbuf passed to
  451          * m_adj() below now does not meet the requirement.
  452          */
  453         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  454                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  455                         - ip6af->ip6af_off;
  456                 if (i > 0) {
  457 #if 0                           /* suppress the noisy log */
  458                         log(LOG_ERR, "%d bytes of a fragment from %s "
  459                             "overlaps the previous fragment\n",
  460                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  461 #endif
  462                         free(ip6af, M_FTABLE);
  463                         goto dropfrag;
  464                 }
  465         }
  466         if (af6 != (struct ip6asfrag *)q6) {
  467                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  468                 if (i > 0) {
  469 #if 0                           /* suppress the noisy log */
  470                         log(LOG_ERR, "%d bytes of a fragment from %s "
  471                             "overlaps the succeeding fragment",
  472                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  473 #endif
  474                         free(ip6af, M_FTABLE);
  475                         goto dropfrag;
  476                 }
  477         }
  478 #endif
  479 
  480 insert:
  481 #ifdef MAC
  482         if (!first_frag)
  483                 mac_ip6q_update(m, q6);
  484 #endif
  485 
  486         /*
  487          * Stick new segment in its place;
  488          * check for complete reassembly.
  489          * Move to front of packet queue, as we are
  490          * the most recently active fragmented packet.
  491          */
  492         frag6_enq(ip6af, af6->ip6af_up);
  493         V_frag6_nfrags++;
  494         q6->ip6q_nfrag++;
  495 #if 0 /* xxx */
  496         if (q6 != V_ip6q.ip6q_next) {
  497                 frag6_remque(q6);
  498                 frag6_insque(q6, &V_ip6q);
  499         }
  500 #endif
  501         next = 0;
  502         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  503              af6 = af6->ip6af_down) {
  504                 if (af6->ip6af_off != next) {
  505                         IP6Q_UNLOCK();
  506                         return IPPROTO_DONE;
  507                 }
  508                 next += af6->ip6af_frglen;
  509         }
  510         if (af6->ip6af_up->ip6af_mff) {
  511                 IP6Q_UNLOCK();
  512                 return IPPROTO_DONE;
  513         }
  514 
  515         /*
  516          * Reassembly is complete; concatenate fragments.
  517          */
  518         ip6af = q6->ip6q_down;
  519         t = m = IP6_REASS_MBUF(ip6af);
  520         af6 = ip6af->ip6af_down;
  521         frag6_deq(ip6af);
  522         while (af6 != (struct ip6asfrag *)q6) {
  523                 af6dwn = af6->ip6af_down;
  524                 frag6_deq(af6);
  525                 while (t->m_next)
  526                         t = t->m_next;
  527                 t->m_next = IP6_REASS_MBUF(af6);
  528                 m_adj(t->m_next, af6->ip6af_offset);
  529                 free(af6, M_FTABLE);
  530                 af6 = af6dwn;
  531         }
  532 
  533         /* adjust offset to point where the original next header starts */
  534         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  535         free(ip6af, M_FTABLE);
  536         ip6 = mtod(m, struct ip6_hdr *);
  537         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  538         if (q6->ip6q_ecn == IPTOS_ECN_CE)
  539                 ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
  540         nxt = q6->ip6q_nxt;
  541 #ifdef notyet
  542         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  543 #endif
  544 
  545         /* Delete frag6 header */
  546         if (m->m_len >= offset + sizeof(struct ip6_frag)) {
  547                 /* This is the only possible case with !PULLDOWN_TEST */
  548                 ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
  549                     offset);
  550                 m->m_data += sizeof(struct ip6_frag);
  551                 m->m_len -= sizeof(struct ip6_frag);
  552         } else {
  553                 /* this comes with no copy if the boundary is on cluster */
  554                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  555                         frag6_remque(q6);
  556                         V_frag6_nfrags -= q6->ip6q_nfrag;
  557 #ifdef MAC
  558                         mac_ip6q_destroy(q6);
  559 #endif
  560                         free(q6, M_FTABLE);
  561                         V_frag6_nfragpackets--;
  562                         goto dropfrag;
  563                 }
  564                 m_adj(t, sizeof(struct ip6_frag));
  565                 m_cat(m, t);
  566         }
  567 
  568         /*
  569          * Store NXT to the original.
  570          */
  571         {
  572                 char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  573                 *prvnxtp = nxt;
  574         }
  575 
  576         frag6_remque(q6);
  577         V_frag6_nfrags -= q6->ip6q_nfrag;
  578 #ifdef MAC
  579         mac_ip6q_reassemble(q6, m);
  580         mac_ip6q_destroy(q6);
  581 #endif
  582         free(q6, M_FTABLE);
  583         V_frag6_nfragpackets--;
  584 
  585         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  586                 int plen = 0;
  587                 for (t = m; t; t = t->m_next)
  588                         plen += t->m_len;
  589                 m->m_pkthdr.len = plen;
  590         }
  591 
  592         V_ip6stat.ip6s_reassembled++;
  593         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  594 
  595         /*
  596          * Tell launch routine the next header
  597          */
  598 
  599         *mp = m;
  600         *offp = offset;
  601 
  602         IP6Q_UNLOCK();
  603         return nxt;
  604 
  605  dropfrag:
  606         IP6Q_UNLOCK();
  607         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  608         V_ip6stat.ip6s_fragdropped++;
  609         m_freem(m);
  610         return IPPROTO_DONE;
  611 }
  612 
  613 /*
  614  * Free a fragment reassembly header and all
  615  * associated datagrams.
  616  */
  617 void
  618 frag6_freef(struct ip6q *q6)
  619 {
  620         struct ip6asfrag *af6, *down6;
  621 
  622         IP6Q_LOCK_ASSERT();
  623 
  624         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  625              af6 = down6) {
  626                 struct mbuf *m = IP6_REASS_MBUF(af6);
  627 
  628                 down6 = af6->ip6af_down;
  629                 frag6_deq(af6);
  630 
  631                 /*
  632                  * Return ICMP time exceeded error for the 1st fragment.
  633                  * Just free other fragments.
  634                  */
  635                 if (af6->ip6af_off == 0) {
  636                         struct ip6_hdr *ip6;
  637 
  638                         /* adjust pointer */
  639                         ip6 = mtod(m, struct ip6_hdr *);
  640 
  641                         /* restore source and destination addresses */
  642                         ip6->ip6_src = q6->ip6q_src;
  643                         ip6->ip6_dst = q6->ip6q_dst;
  644 
  645                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  646                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  647                 } else
  648                         m_freem(m);
  649                 free(af6, M_FTABLE);
  650         }
  651         frag6_remque(q6);
  652         V_frag6_nfrags -= q6->ip6q_nfrag;
  653 #ifdef MAC
  654         mac_ip6q_destroy(q6);
  655 #endif
  656         free(q6, M_FTABLE);
  657         V_frag6_nfragpackets--;
  658 }
  659 
  660 /*
  661  * Put an ip fragment on a reassembly chain.
  662  * Like insque, but pointers in middle of structure.
  663  */
  664 void
  665 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6)
  666 {
  667 
  668         IP6Q_LOCK_ASSERT();
  669 
  670         af6->ip6af_up = up6;
  671         af6->ip6af_down = up6->ip6af_down;
  672         up6->ip6af_down->ip6af_up = af6;
  673         up6->ip6af_down = af6;
  674 }
  675 
  676 /*
  677  * To frag6_enq as remque is to insque.
  678  */
  679 void
  680 frag6_deq(struct ip6asfrag *af6)
  681 {
  682 
  683         IP6Q_LOCK_ASSERT();
  684 
  685         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  686         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  687 }
  688 
  689 void
  690 frag6_insque(struct ip6q *new, struct ip6q *old)
  691 {
  692 
  693         IP6Q_LOCK_ASSERT();
  694 
  695         new->ip6q_prev = old;
  696         new->ip6q_next = old->ip6q_next;
  697         old->ip6q_next->ip6q_prev= new;
  698         old->ip6q_next = new;
  699 }
  700 
  701 void
  702 frag6_remque(struct ip6q *p6)
  703 {
  704 
  705         IP6Q_LOCK_ASSERT();
  706 
  707         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  708         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  709 }
  710 
  711 /*
  712  * IPv6 reassembling timer processing;
  713  * if a timer expires on a reassembly
  714  * queue, discard it.
  715  */
  716 void
  717 frag6_slowtimo(void)
  718 {
  719         VNET_ITERATOR_DECL(vnet_iter);
  720         struct ip6q *q6;
  721 
  722         VNET_LIST_RLOCK_NOSLEEP();
  723         IP6Q_LOCK();
  724         VNET_FOREACH(vnet_iter) {
  725                 CURVNET_SET(vnet_iter);
  726                 q6 = V_ip6q.ip6q_next;
  727                 if (q6)
  728                         while (q6 != &V_ip6q) {
  729                                 --q6->ip6q_ttl;
  730                                 q6 = q6->ip6q_next;
  731                                 if (q6->ip6q_prev->ip6q_ttl == 0) {
  732                                         V_ip6stat.ip6s_fragtimeout++;
  733                                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  734                                         frag6_freef(q6->ip6q_prev);
  735                                 }
  736                         }
  737                 /*
  738                  * If we are over the maximum number of fragments
  739                  * (due to the limit being lowered), drain off
  740                  * enough to get down to the new limit.
  741                  */
  742                 while (V_frag6_nfragpackets > (u_int)V_ip6_maxfragpackets &&
  743                     V_ip6q.ip6q_prev) {
  744                         V_ip6stat.ip6s_fragoverflow++;
  745                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  746                         frag6_freef(V_ip6q.ip6q_prev);
  747                 }
  748                 CURVNET_RESTORE();
  749         }
  750         IP6Q_UNLOCK();
  751         VNET_LIST_RUNLOCK_NOSLEEP();
  752 }
  753 
  754 /*
  755  * Drain off all datagram fragments.
  756  */
  757 void
  758 frag6_drain(void)
  759 {
  760         VNET_ITERATOR_DECL(vnet_iter);
  761 
  762         VNET_LIST_RLOCK_NOSLEEP();
  763         if (IP6Q_TRYLOCK() == 0) {
  764                 VNET_LIST_RUNLOCK_NOSLEEP();
  765                 return;
  766         }
  767         VNET_FOREACH(vnet_iter) {
  768                 CURVNET_SET(vnet_iter);
  769                 while (V_ip6q.ip6q_next != &V_ip6q) {
  770                         V_ip6stat.ip6s_fragdropped++;
  771                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  772                         frag6_freef(V_ip6q.ip6q_next);
  773                 }
  774                 CURVNET_RESTORE();
  775         }
  776         IP6Q_UNLOCK();
  777         VNET_LIST_RUNLOCK_NOSLEEP();
  778 }

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