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

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    1 /*      $FreeBSD: releng/5.0/sys/netinet6/frag6.c 95023 2002-04-19 04:46:24Z suz $      */
    2 /*      $KAME: frag6.c,v 1.33 2002/01/07 11:34:48 kjc Exp $     */
    3 
    4 /*
    5  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. Neither the name of the project nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  */
   32 
   33 #include <sys/param.h>
   34 #include <sys/systm.h>
   35 #include <sys/malloc.h>
   36 #include <sys/mbuf.h>
   37 #include <sys/domain.h>
   38 #include <sys/protosw.h>
   39 #include <sys/socket.h>
   40 #include <sys/errno.h>
   41 #include <sys/time.h>
   42 #include <sys/kernel.h>
   43 #include <sys/syslog.h>
   44 
   45 #include <net/if.h>
   46 #include <net/route.h>
   47 
   48 #include <netinet/in.h>
   49 #include <netinet/in_var.h>
   50 #include <netinet/ip6.h>
   51 #include <netinet6/ip6_var.h>
   52 #include <netinet/icmp6.h>
   53 
   54 #include <net/net_osdep.h>
   55 
   56 /*
   57  * Define it to get a correct behavior on per-interface statistics.
   58  * You will need to perform an extra routing table lookup, per fragment,
   59  * to do it.  This may, or may not be, a performance hit.
   60  */
   61 #define IN6_IFSTAT_STRICT
   62 
   63 static void frag6_enq __P((struct ip6asfrag *, struct ip6asfrag *));
   64 static void frag6_deq __P((struct ip6asfrag *));
   65 static void frag6_insque __P((struct ip6q *, struct ip6q *));
   66 static void frag6_remque __P((struct ip6q *));
   67 static void frag6_freef __P((struct ip6q *));
   68 
   69 /* XXX we eventually need splreass6, or some real semaphore */
   70 int frag6_doing_reass;
   71 u_int frag6_nfragpackets;
   72 struct  ip6q ip6q;      /* ip6 reassemble queue */
   73 
   74 /* FreeBSD tweak */
   75 static MALLOC_DEFINE(M_FTABLE, "fragment", "fragment reassembly header");
   76 
   77 /*
   78  * Initialise reassembly queue and fragment identifier.
   79  */
   80 void
   81 frag6_init()
   82 {
   83         struct timeval tv;
   84 
   85         ip6_maxfragpackets = nmbclusters / 4;
   86 
   87         /*
   88          * in many cases, random() here does NOT return random number
   89          * as initialization during bootstrap time occur in fixed order.
   90          */
   91         microtime(&tv);
   92         ip6_id = random() ^ tv.tv_usec;
   93         ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
   94 }
   95 
   96 /*
   97  * In RFC2460, fragment and reassembly rule do not agree with each other,
   98  * in terms of next header field handling in fragment header.
   99  * While the sender will use the same value for all of the fragmented packets,
  100  * receiver is suggested not to check the consistency.
  101  *
  102  * fragment rule (p20):
  103  *      (2) A Fragment header containing:
  104  *      The Next Header value that identifies the first header of
  105  *      the Fragmentable Part of the original packet.
  106  *              -> next header field is same for all fragments
  107  *
  108  * reassembly rule (p21):
  109  *      The Next Header field of the last header of the Unfragmentable
  110  *      Part is obtained from the Next Header field of the first
  111  *      fragment's Fragment header.
  112  *              -> should grab it from the first fragment only
  113  *
  114  * The following note also contradicts with fragment rule - noone is going to
  115  * send different fragment with different next header field.
  116  *
  117  * additional note (p22):
  118  *      The Next Header values in the Fragment headers of different
  119  *      fragments of the same original packet may differ.  Only the value
  120  *      from the Offset zero fragment packet is used for reassembly.
  121  *              -> should grab it from the first fragment only
  122  *
  123  * There is no explicit reason given in the RFC.  Historical reason maybe?
  124  */
  125 /*
  126  * Fragment input
  127  */
  128 int
  129 frag6_input(mp, offp, proto)
  130         struct mbuf **mp;
  131         int *offp, proto;
  132 {
  133         struct mbuf *m = *mp, *t;
  134         struct ip6_hdr *ip6;
  135         struct ip6_frag *ip6f;
  136         struct ip6q *q6;
  137         struct ip6asfrag *af6, *ip6af, *af6dwn;
  138         int offset = *offp, nxt, i, next;
  139         int first_frag = 0;
  140         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  141         struct ifnet *dstifp;
  142 #ifdef IN6_IFSTAT_STRICT
  143         static struct route_in6 ro;
  144         struct sockaddr_in6 *dst;
  145 #endif
  146 
  147         ip6 = mtod(m, struct ip6_hdr *);
  148 #ifndef PULLDOWN_TEST
  149         IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
  150         ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
  151 #else
  152         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  153         if (ip6f == NULL)
  154                 return IPPROTO_DONE;
  155 #endif
  156 
  157         dstifp = NULL;
  158 #ifdef IN6_IFSTAT_STRICT
  159         /* find the destination interface of the packet. */
  160         dst = (struct sockaddr_in6 *)&ro.ro_dst;
  161         if (ro.ro_rt
  162          && ((ro.ro_rt->rt_flags & RTF_UP) == 0
  163           || !IN6_ARE_ADDR_EQUAL(&dst->sin6_addr, &ip6->ip6_dst))) {
  164                 RTFREE(ro.ro_rt);
  165                 ro.ro_rt = (struct rtentry *)0;
  166         }
  167         if (ro.ro_rt == NULL) {
  168                 bzero(dst, sizeof(*dst));
  169                 dst->sin6_family = AF_INET6;
  170                 dst->sin6_len = sizeof(struct sockaddr_in6);
  171                 dst->sin6_addr = ip6->ip6_dst;
  172         }
  173         rtalloc((struct route *)&ro);
  174         if (ro.ro_rt != NULL && ro.ro_rt->rt_ifa != NULL)
  175                 dstifp = ((struct in6_ifaddr *)ro.ro_rt->rt_ifa)->ia_ifp;
  176 #else
  177         /* we are violating the spec, this is not the destination interface */
  178         if ((m->m_flags & M_PKTHDR) != 0)
  179                 dstifp = m->m_pkthdr.rcvif;
  180 #endif
  181 
  182         /* jumbo payload can't contain a fragment header */
  183         if (ip6->ip6_plen == 0) {
  184                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  185                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  186                 return IPPROTO_DONE;
  187         }
  188 
  189         /*
  190          * check whether fragment packet's fragment length is
  191          * multiple of 8 octets.
  192          * sizeof(struct ip6_frag) == 8
  193          * sizeof(struct ip6_hdr) = 40
  194          */
  195         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  196             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  197                 icmp6_error(m, ICMP6_PARAM_PROB,
  198                             ICMP6_PARAMPROB_HEADER,
  199                             offsetof(struct ip6_hdr, ip6_plen));
  200                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  201                 return IPPROTO_DONE;
  202         }
  203 
  204         ip6stat.ip6s_fragments++;
  205         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  206         
  207         /* offset now points to data portion */
  208         offset += sizeof(struct ip6_frag);
  209 
  210         frag6_doing_reass = 1;
  211 
  212         for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next)
  213                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  214                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  215                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
  216                         break;
  217 
  218         if (q6 == &ip6q) {
  219                 /*
  220                  * the first fragment to arrive, create a reassembly queue.
  221                  */
  222                 first_frag = 1;
  223 
  224                 /*
  225                  * Enforce upper bound on number of fragmented packets
  226                  * for which we attempt reassembly;
  227                  * If maxfrag is 0, never accept fragments.
  228                  * If maxfrag is -1, accept all fragments without limitation.
  229                  */
  230                 if (ip6_maxfragpackets < 0)
  231                         ;
  232                 else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets)
  233                         goto dropfrag;
  234                 frag6_nfragpackets++;
  235                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  236                         M_DONTWAIT);
  237                 if (q6 == NULL)
  238                         goto dropfrag;
  239                 bzero(q6, sizeof(*q6));
  240 
  241                 frag6_insque(q6, &ip6q);
  242 
  243                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  244                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  245 #ifdef notyet
  246                 q6->ip6q_nxtp   = (u_char *)nxtp;
  247 #endif
  248                 q6->ip6q_ident  = ip6f->ip6f_ident;
  249                 q6->ip6q_arrive = 0; /* Is it used anywhere? */
  250                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  251                 q6->ip6q_src    = ip6->ip6_src;
  252                 q6->ip6q_dst    = ip6->ip6_dst;
  253                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  254         }
  255 
  256         /*
  257          * If it's the 1st fragment, record the length of the
  258          * unfragmentable part and the next header of the fragment header.
  259          */
  260         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  261         if (fragoff == 0) {
  262                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr)
  263                         - sizeof(struct ip6_frag);
  264                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  265         }
  266 
  267         /*
  268          * Check that the reassembled packet would not exceed 65535 bytes
  269          * in size.
  270          * If it would exceed, discard the fragment and return an ICMP error.
  271          */
  272         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  273         if (q6->ip6q_unfrglen >= 0) {
  274                 /* The 1st fragment has already arrived. */
  275                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  276                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  277                                     offset - sizeof(struct ip6_frag) +
  278                                         offsetof(struct ip6_frag, ip6f_offlg));
  279                         frag6_doing_reass = 0;
  280                         return(IPPROTO_DONE);
  281                 }
  282         }
  283         else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  284                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  285                             offset - sizeof(struct ip6_frag) +
  286                                 offsetof(struct ip6_frag, ip6f_offlg));
  287                 frag6_doing_reass = 0;
  288                 return(IPPROTO_DONE);
  289         }
  290         /*
  291          * If it's the first fragment, do the above check for each
  292          * fragment already stored in the reassembly queue.
  293          */
  294         if (fragoff == 0) {
  295                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  296                      af6 = af6dwn) {
  297                         af6dwn = af6->ip6af_down;
  298 
  299                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  300                             IPV6_MAXPACKET) {
  301                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  302                                 struct ip6_hdr *ip6err;
  303                                 int erroff = af6->ip6af_offset;
  304 
  305                                 /* dequeue the fragment. */
  306                                 frag6_deq(af6);
  307                                 free(af6, M_FTABLE);
  308 
  309                                 /* adjust pointer. */
  310                                 ip6err = mtod(merr, struct ip6_hdr *);
  311 
  312                                 /*
  313                                  * Restore source and destination addresses
  314                                  * in the erroneous IPv6 header.
  315                                  */
  316                                 ip6err->ip6_src = q6->ip6q_src;
  317                                 ip6err->ip6_dst = q6->ip6q_dst;
  318 
  319                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  320                                             ICMP6_PARAMPROB_HEADER,
  321                                             erroff - sizeof(struct ip6_frag) +
  322                                                 offsetof(struct ip6_frag, ip6f_offlg));
  323                         }
  324                 }
  325         }
  326 
  327         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  328             M_DONTWAIT);
  329         if (ip6af == NULL)
  330                 goto dropfrag;
  331         bzero(ip6af, sizeof(*ip6af));
  332         ip6af->ip6af_head = ip6->ip6_flow;
  333         ip6af->ip6af_len = ip6->ip6_plen;
  334         ip6af->ip6af_nxt = ip6->ip6_nxt;
  335         ip6af->ip6af_hlim = ip6->ip6_hlim;
  336         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  337         ip6af->ip6af_off = fragoff;
  338         ip6af->ip6af_frglen = frgpartlen;
  339         ip6af->ip6af_offset = offset;
  340         IP6_REASS_MBUF(ip6af) = m;
  341 
  342         if (first_frag) {
  343                 af6 = (struct ip6asfrag *)q6;
  344                 goto insert;
  345         }
  346 
  347         /*
  348          * Find a segment which begins after this one does.
  349          */
  350         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  351              af6 = af6->ip6af_down)
  352                 if (af6->ip6af_off > ip6af->ip6af_off)
  353                         break;
  354 
  355 #if 0
  356         /*
  357          * If there is a preceding segment, it may provide some of
  358          * our data already.  If so, drop the data from the incoming
  359          * segment.  If it provides all of our data, drop us.
  360          */
  361         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  362                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  363                         - ip6af->ip6af_off;
  364                 if (i > 0) {
  365                         if (i >= ip6af->ip6af_frglen)
  366                                 goto dropfrag;
  367                         m_adj(IP6_REASS_MBUF(ip6af), i);
  368                         ip6af->ip6af_off += i;
  369                         ip6af->ip6af_frglen -= i;
  370                 }
  371         }
  372 
  373         /*
  374          * While we overlap succeeding segments trim them or,
  375          * if they are completely covered, dequeue them.
  376          */
  377         while (af6 != (struct ip6asfrag *)q6 &&
  378                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  379                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  380                 if (i < af6->ip6af_frglen) {
  381                         af6->ip6af_frglen -= i;
  382                         af6->ip6af_off += i;
  383                         m_adj(IP6_REASS_MBUF(af6), i);
  384                         break;
  385                 }
  386                 af6 = af6->ip6af_down;
  387                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  388                 frag6_deq(af6->ip6af_up);
  389         }
  390 #else
  391         /*
  392          * If the incoming framgent overlaps some existing fragments in
  393          * the reassembly queue, drop it, since it is dangerous to override
  394          * existing fragments from a security point of view.
  395          */
  396         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  397                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  398                         - ip6af->ip6af_off;
  399                 if (i > 0) {
  400 #if 0                           /* suppress the noisy log */
  401                         log(LOG_ERR, "%d bytes of a fragment from %s "
  402                             "overlaps the previous fragment\n",
  403                             i, ip6_sprintf(&q6->ip6q_src));
  404 #endif
  405                         free(ip6af, M_FTABLE);
  406                         goto dropfrag;
  407                 }
  408         }
  409         if (af6 != (struct ip6asfrag *)q6) {
  410                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  411                 if (i > 0) {
  412 #if 0                           /* suppress the noisy log */
  413                         log(LOG_ERR, "%d bytes of a fragment from %s "
  414                             "overlaps the succeeding fragment",
  415                             i, ip6_sprintf(&q6->ip6q_src));
  416 #endif
  417                         free(ip6af, M_FTABLE);
  418                         goto dropfrag;
  419                 }
  420         }
  421 #endif
  422 
  423 insert:
  424 
  425         /*
  426          * Stick new segment in its place;
  427          * check for complete reassembly.
  428          * Move to front of packet queue, as we are
  429          * the most recently active fragmented packet.
  430          */
  431         frag6_enq(ip6af, af6->ip6af_up);
  432 #if 0 /* xxx */
  433         if (q6 != ip6q.ip6q_next) {
  434                 frag6_remque(q6);
  435                 frag6_insque(q6, &ip6q);
  436         }
  437 #endif
  438         next = 0;
  439         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  440              af6 = af6->ip6af_down) {
  441                 if (af6->ip6af_off != next) {
  442                         frag6_doing_reass = 0;
  443                         return IPPROTO_DONE;
  444                 }
  445                 next += af6->ip6af_frglen;
  446         }
  447         if (af6->ip6af_up->ip6af_mff) {
  448                 frag6_doing_reass = 0;
  449                 return IPPROTO_DONE;
  450         }
  451 
  452         /*
  453          * Reassembly is complete; concatenate fragments.
  454          */
  455         ip6af = q6->ip6q_down;
  456         t = m = IP6_REASS_MBUF(ip6af);
  457         af6 = ip6af->ip6af_down;
  458         frag6_deq(ip6af);
  459         while (af6 != (struct ip6asfrag *)q6) {
  460                 af6dwn = af6->ip6af_down;
  461                 frag6_deq(af6);
  462                 while (t->m_next)
  463                         t = t->m_next;
  464                 t->m_next = IP6_REASS_MBUF(af6);
  465                 m_adj(t->m_next, af6->ip6af_offset);
  466                 free(af6, M_FTABLE);
  467                 af6 = af6dwn;
  468         }
  469 
  470         /* adjust offset to point where the original next header starts */
  471         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  472         free(ip6af, M_FTABLE);
  473         ip6 = mtod(m, struct ip6_hdr *);
  474         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  475         ip6->ip6_src = q6->ip6q_src;
  476         ip6->ip6_dst = q6->ip6q_dst;
  477         nxt = q6->ip6q_nxt;
  478 #ifdef notyet
  479         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  480 #endif
  481 
  482         /*
  483          * Delete frag6 header with as a few cost as possible.
  484          */
  485         if (offset < m->m_len) {
  486                 ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
  487                         offset);
  488                 m->m_data += sizeof(struct ip6_frag);
  489                 m->m_len -= sizeof(struct ip6_frag);
  490         } else {
  491                 /* this comes with no copy if the boundary is on cluster */
  492                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  493                         frag6_remque(q6);
  494                         free(q6, M_FTABLE);
  495                         frag6_nfragpackets--;
  496                         goto dropfrag;
  497                 }
  498                 m_adj(t, sizeof(struct ip6_frag));
  499                 m_cat(m, t);
  500         }
  501 
  502         /*
  503          * Store NXT to the original.
  504          */
  505         {
  506                 char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  507                 *prvnxtp = nxt;
  508         }
  509 
  510         frag6_remque(q6);
  511         free(q6, M_FTABLE);
  512         frag6_nfragpackets--;
  513 
  514         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  515                 int plen = 0;
  516                 for (t = m; t; t = t->m_next)
  517                         plen += t->m_len;
  518                 m->m_pkthdr.len = plen;
  519         }
  520         
  521         ip6stat.ip6s_reassembled++;
  522         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  523 
  524         /*
  525          * Tell launch routine the next header
  526          */
  527 
  528         *mp = m;
  529         *offp = offset;
  530 
  531         frag6_doing_reass = 0;
  532         return nxt;
  533 
  534  dropfrag:
  535         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  536         ip6stat.ip6s_fragdropped++;
  537         m_freem(m);
  538         frag6_doing_reass = 0;
  539         return IPPROTO_DONE;
  540 }
  541 
  542 /*
  543  * Free a fragment reassembly header and all
  544  * associated datagrams.
  545  */
  546 void
  547 frag6_freef(q6)
  548         struct ip6q *q6;
  549 {
  550         struct ip6asfrag *af6, *down6;
  551 
  552         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  553              af6 = down6) {
  554                 struct mbuf *m = IP6_REASS_MBUF(af6);
  555 
  556                 down6 = af6->ip6af_down;
  557                 frag6_deq(af6);
  558 
  559                 /*
  560                  * Return ICMP time exceeded error for the 1st fragment.
  561                  * Just free other fragments.
  562                  */
  563                 if (af6->ip6af_off == 0) {
  564                         struct ip6_hdr *ip6;
  565 
  566                         /* adjust pointer */
  567                         ip6 = mtod(m, struct ip6_hdr *);
  568 
  569                         /* restoure source and destination addresses */
  570                         ip6->ip6_src = q6->ip6q_src;
  571                         ip6->ip6_dst = q6->ip6q_dst;
  572 
  573                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  574                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  575                 } else
  576                         m_freem(m);
  577                 free(af6, M_FTABLE);
  578         }
  579         frag6_remque(q6);
  580         free(q6, M_FTABLE);
  581         frag6_nfragpackets--;
  582 }
  583 
  584 /*
  585  * Put an ip fragment on a reassembly chain.
  586  * Like insque, but pointers in middle of structure.
  587  */
  588 void
  589 frag6_enq(af6, up6)
  590         struct ip6asfrag *af6, *up6;
  591 {
  592         af6->ip6af_up = up6;
  593         af6->ip6af_down = up6->ip6af_down;
  594         up6->ip6af_down->ip6af_up = af6;
  595         up6->ip6af_down = af6;
  596 }
  597 
  598 /*
  599  * To frag6_enq as remque is to insque.
  600  */
  601 void
  602 frag6_deq(af6)
  603         struct ip6asfrag *af6;
  604 {
  605         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  606         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  607 }
  608 
  609 void
  610 frag6_insque(new, old)
  611         struct ip6q *new, *old;
  612 {
  613         new->ip6q_prev = old;
  614         new->ip6q_next = old->ip6q_next;
  615         old->ip6q_next->ip6q_prev= new;
  616         old->ip6q_next = new;
  617 }
  618 
  619 void
  620 frag6_remque(p6)
  621         struct ip6q *p6;
  622 {
  623         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  624         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  625 }
  626 
  627 /*
  628  * IPv6 reassembling timer processing;
  629  * if a timer expires on a reassembly
  630  * queue, discard it.
  631  */
  632 void
  633 frag6_slowtimo()
  634 {
  635         struct ip6q *q6;
  636         int s = splnet();
  637 
  638         frag6_doing_reass = 1;
  639         q6 = ip6q.ip6q_next;
  640         if (q6)
  641                 while (q6 != &ip6q) {
  642                         --q6->ip6q_ttl;
  643                         q6 = q6->ip6q_next;
  644                         if (q6->ip6q_prev->ip6q_ttl == 0) {
  645                                 ip6stat.ip6s_fragtimeout++;
  646                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  647                                 frag6_freef(q6->ip6q_prev);
  648                         }
  649                 }
  650         /*
  651          * If we are over the maximum number of fragments
  652          * (due to the limit being lowered), drain off
  653          * enough to get down to the new limit.
  654          */
  655         while (frag6_nfragpackets > (u_int)ip6_maxfragpackets &&
  656             ip6q.ip6q_prev) {
  657                 ip6stat.ip6s_fragoverflow++;
  658                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  659                 frag6_freef(ip6q.ip6q_prev);
  660         }
  661         frag6_doing_reass = 0;
  662 
  663 #if 0
  664         /*
  665          * Routing changes might produce a better route than we last used;
  666          * make sure we notice eventually, even if forwarding only for one
  667          * destination and the cache is never replaced.
  668          */
  669         if (ip6_forward_rt.ro_rt) {
  670                 RTFREE(ip6_forward_rt.ro_rt);
  671                 ip6_forward_rt.ro_rt = 0;
  672         }
  673         if (ipsrcchk_rt.ro_rt) {
  674                 RTFREE(ipsrcchk_rt.ro_rt);
  675                 ipsrcchk_rt.ro_rt = 0;
  676         }
  677 #endif
  678 
  679         splx(s);
  680 }
  681 
  682 /*
  683  * Drain off all datagram fragments.
  684  */
  685 void
  686 frag6_drain()
  687 {
  688         if (frag6_doing_reass)
  689                 return;
  690         while (ip6q.ip6q_next != &ip6q) {
  691                 ip6stat.ip6s_fragdropped++;
  692                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  693                 frag6_freef(ip6q.ip6q_next);
  694         }
  695 }

Cache object: c49f942cb1df2a97df1b7ac0e0542be9


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