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

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    1 /*      $NetBSD: frag6.c,v 1.46 2008/05/21 17:08:07 drochner Exp $      */
    2 /*      $KAME: frag6.c,v 1.40 2002/05/27 21:40:31 itojun 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/cdefs.h>
   34 __KERNEL_RCSID(0, "$NetBSD: frag6.c,v 1.46 2008/05/21 17:08:07 drochner Exp $");
   35 
   36 #include <sys/param.h>
   37 #include <sys/systm.h>
   38 #include <sys/malloc.h>
   39 #include <sys/mbuf.h>
   40 #include <sys/domain.h>
   41 #include <sys/protosw.h>
   42 #include <sys/socket.h>
   43 #include <sys/socketvar.h>
   44 #include <sys/errno.h>
   45 #include <sys/time.h>
   46 #include <sys/kernel.h>
   47 #include <sys/syslog.h>
   48 
   49 #include <net/if.h>
   50 #include <net/route.h>
   51 
   52 #include <netinet/in.h>
   53 #include <netinet/in_var.h>
   54 #include <netinet/ip6.h>
   55 #include <netinet6/ip6_var.h>
   56 #include <netinet6/ip6_private.h>
   57 #include <netinet/icmp6.h>
   58 
   59 #include <net/net_osdep.h>
   60 
   61 static void frag6_enq(struct ip6asfrag *, struct ip6asfrag *);
   62 static void frag6_deq(struct ip6asfrag *);
   63 static void frag6_insque(struct ip6q *, struct ip6q *);
   64 static void frag6_remque(struct ip6q *);
   65 static void frag6_freef(struct ip6q *);
   66 
   67 static int ip6q_locked;
   68 u_int frag6_nfragpackets;
   69 u_int frag6_nfrags;
   70 struct  ip6q ip6q;      /* ip6 reassemble queue */
   71 
   72 static inline int ip6q_lock_try(void);
   73 static inline void ip6q_unlock(void);
   74 
   75 static inline int
   76 ip6q_lock_try(void)
   77 {
   78         int s;
   79 
   80         /*
   81          * Use splvm() -- we're bloking things that would cause
   82          * mbuf allocation.
   83          */
   84         s = splvm();
   85         if (ip6q_locked) {
   86                 splx(s);
   87                 return (0);
   88         }
   89         ip6q_locked = 1;
   90         splx(s);
   91         return (1);
   92 }
   93 
   94 static inline void
   95 ip6q_unlock(void)
   96 {
   97         int s;
   98 
   99         s = splvm();
  100         ip6q_locked = 0;
  101         splx(s);
  102 }
  103 
  104 #ifdef DIAGNOSTIC
  105 #define IP6Q_LOCK()                                                     \
  106 do {                                                                    \
  107         if (ip6q_lock_try() == 0) {                                     \
  108                 printf("%s:%d: ip6q already locked\n", __FILE__, __LINE__); \
  109                 panic("ip6q_lock");                                     \
  110         }                                                               \
  111 } while (/*CONSTCOND*/ 0)
  112 #define IP6Q_LOCK_CHECK()                                               \
  113 do {                                                                    \
  114         if (ip6q_locked == 0) {                                         \
  115                 printf("%s:%d: ip6q lock not held\n", __FILE__, __LINE__); \
  116                 panic("ip6q lock check");                               \
  117         }                                                               \
  118 } while (/*CONSTCOND*/ 0)
  119 #else
  120 #define IP6Q_LOCK()             (void) ip6q_lock_try()
  121 #define IP6Q_LOCK_CHECK()       /* nothing */
  122 #endif
  123 
  124 #define IP6Q_UNLOCK()           ip6q_unlock()
  125 
  126 #ifndef offsetof                /* XXX */
  127 #define offsetof(type, member)  ((size_t)(&((type *)0)->member))
  128 #endif
  129 
  130 /*
  131  * Initialise reassembly queue and fragment identifier.
  132  */
  133 void
  134 frag6_init(void)
  135 {
  136 
  137         ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
  138 }
  139 
  140 /*
  141  * In RFC2460, fragment and reassembly rule do not agree with each other,
  142  * in terms of next header field handling in fragment header.
  143  * While the sender will use the same value for all of the fragmented packets,
  144  * receiver is suggested not to check the consistency.
  145  *
  146  * fragment rule (p20):
  147  *      (2) A Fragment header containing:
  148  *      The Next Header value that identifies the first header of
  149  *      the Fragmentable Part of the original packet.
  150  *              -> next header field is same for all fragments
  151  *
  152  * reassembly rule (p21):
  153  *      The Next Header field of the last header of the Unfragmentable
  154  *      Part is obtained from the Next Header field of the first
  155  *      fragment's Fragment header.
  156  *              -> should grab it from the first fragment only
  157  *
  158  * The following note also contradicts with fragment rule - noone is going to
  159  * send different fragment with different next header field.
  160  *
  161  * additional note (p22):
  162  *      The Next Header values in the Fragment headers of different
  163  *      fragments of the same original packet may differ.  Only the value
  164  *      from the Offset zero fragment packet is used for reassembly.
  165  *              -> should grab it from the first fragment only
  166  *
  167  * There is no explicit reason given in the RFC.  Historical reason maybe?
  168  */
  169 /*
  170  * Fragment input
  171  */
  172 int
  173 frag6_input(struct mbuf **mp, int *offp, int proto)
  174 {
  175         struct rtentry *rt;
  176         struct mbuf *m = *mp, *t;
  177         struct ip6_hdr *ip6;
  178         struct ip6_frag *ip6f;
  179         struct ip6q *q6;
  180         struct ip6asfrag *af6, *ip6af, *af6dwn;
  181         int offset = *offp, nxt, i, next;
  182         int first_frag = 0;
  183         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  184         struct ifnet *dstifp;
  185         static struct route ro;
  186         union {
  187                 struct sockaddr         dst;
  188                 struct sockaddr_in6     dst6;
  189         } u;
  190 
  191         ip6 = mtod(m, struct ip6_hdr *);
  192         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  193         if (ip6f == NULL)
  194                 return IPPROTO_DONE;
  195 
  196         dstifp = NULL;
  197         /* find the destination interface of the packet. */
  198         sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0);
  199         if ((rt = rtcache_lookup(&ro, &u.dst)) != NULL && rt->rt_ifa != NULL)
  200                 dstifp = ((struct in6_ifaddr *)rt->rt_ifa)->ia_ifp;
  201 
  202         /* jumbo payload can't contain a fragment header */
  203         if (ip6->ip6_plen == 0) {
  204                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  205                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  206                 return IPPROTO_DONE;
  207         }
  208 
  209         /*
  210          * check whether fragment packet's fragment length is
  211          * multiple of 8 octets.
  212          * sizeof(struct ip6_frag) == 8
  213          * sizeof(struct ip6_hdr) = 40
  214          */
  215         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  216             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  217                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  218                     offsetof(struct ip6_hdr, ip6_plen));
  219                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  220                 return IPPROTO_DONE;
  221         }
  222 
  223         IP6_STATINC(IP6_STAT_FRAGMENTS);
  224         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  225 
  226         /* offset now points to data portion */
  227         offset += sizeof(struct ip6_frag);
  228 
  229         IP6Q_LOCK();
  230 
  231         /*
  232          * Enforce upper bound on number of fragments.
  233          * If maxfrag is 0, never accept fragments.
  234          * If maxfrag is -1, accept all fragments without limitation.
  235          */
  236         if (ip6_maxfrags < 0)
  237                 ;
  238         else if (frag6_nfrags >= (u_int)ip6_maxfrags)
  239                 goto dropfrag;
  240 
  241         for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next)
  242                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  243                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  244                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
  245                         break;
  246 
  247         if (q6 == &ip6q) {
  248                 /*
  249                  * the first fragment to arrive, create a reassembly queue.
  250                  */
  251                 first_frag = 1;
  252 
  253                 /*
  254                  * Enforce upper bound on number of fragmented packets
  255                  * for which we attempt reassembly;
  256                  * If maxfragpackets is 0, never accept fragments.
  257                  * If maxfragpackets is -1, accept all fragments without
  258                  * limitation.
  259                  */
  260                 if (ip6_maxfragpackets < 0)
  261                         ;
  262                 else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets)
  263                         goto dropfrag;
  264                 frag6_nfragpackets++;
  265                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  266                     M_DONTWAIT);
  267                 if (q6 == NULL)
  268                         goto dropfrag;
  269                 bzero(q6, sizeof(*q6));
  270 
  271                 frag6_insque(q6, &ip6q);
  272 
  273                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  274                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  275 #ifdef notyet
  276                 q6->ip6q_nxtp   = (u_char *)nxtp;
  277 #endif
  278                 q6->ip6q_ident  = ip6f->ip6f_ident;
  279                 q6->ip6q_arrive = 0; /* Is it used anywhere? */
  280                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  281                 q6->ip6q_src    = ip6->ip6_src;
  282                 q6->ip6q_dst    = ip6->ip6_dst;
  283                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  284 
  285                 q6->ip6q_nfrag = 0;
  286         }
  287 
  288         /*
  289          * If it's the 1st fragment, record the length of the
  290          * unfragmentable part and the next header of the fragment header.
  291          */
  292         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  293         if (fragoff == 0) {
  294                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  295                     sizeof(struct ip6_frag);
  296                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  297         }
  298 
  299         /*
  300          * Check that the reassembled packet would not exceed 65535 bytes
  301          * in size.
  302          * If it would exceed, discard the fragment and return an ICMP error.
  303          */
  304         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  305         if (q6->ip6q_unfrglen >= 0) {
  306                 /* The 1st fragment has already arrived. */
  307                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  308                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  309                             offset - sizeof(struct ip6_frag) +
  310                             offsetof(struct ip6_frag, ip6f_offlg));
  311                         IP6Q_UNLOCK();
  312                         return (IPPROTO_DONE);
  313                 }
  314         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  315                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  316                             offset - sizeof(struct ip6_frag) +
  317                                 offsetof(struct ip6_frag, ip6f_offlg));
  318                 IP6Q_UNLOCK();
  319                 return (IPPROTO_DONE);
  320         }
  321         /*
  322          * If it's the first fragment, do the above check for each
  323          * fragment already stored in the reassembly queue.
  324          */
  325         if (fragoff == 0) {
  326                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  327                      af6 = af6dwn) {
  328                         af6dwn = af6->ip6af_down;
  329 
  330                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  331                             IPV6_MAXPACKET) {
  332                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  333                                 struct ip6_hdr *ip6err;
  334                                 int erroff = af6->ip6af_offset;
  335 
  336                                 /* dequeue the fragment. */
  337                                 frag6_deq(af6);
  338                                 free(af6, M_FTABLE);
  339 
  340                                 /* adjust pointer. */
  341                                 ip6err = mtod(merr, struct ip6_hdr *);
  342 
  343                                 /*
  344                                  * Restore source and destination addresses
  345                                  * in the erroneous IPv6 header.
  346                                  */
  347                                 ip6err->ip6_src = q6->ip6q_src;
  348                                 ip6err->ip6_dst = q6->ip6q_dst;
  349 
  350                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  351                                     ICMP6_PARAMPROB_HEADER,
  352                                     erroff - sizeof(struct ip6_frag) +
  353                                     offsetof(struct ip6_frag, ip6f_offlg));
  354                         }
  355                 }
  356         }
  357 
  358         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  359             M_DONTWAIT);
  360         if (ip6af == NULL)
  361                 goto dropfrag;
  362         bzero(ip6af, sizeof(*ip6af));
  363         ip6af->ip6af_head = ip6->ip6_flow;
  364         ip6af->ip6af_len = ip6->ip6_plen;
  365         ip6af->ip6af_nxt = ip6->ip6_nxt;
  366         ip6af->ip6af_hlim = ip6->ip6_hlim;
  367         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  368         ip6af->ip6af_off = fragoff;
  369         ip6af->ip6af_frglen = frgpartlen;
  370         ip6af->ip6af_offset = offset;
  371         IP6_REASS_MBUF(ip6af) = m;
  372 
  373         if (first_frag) {
  374                 af6 = (struct ip6asfrag *)q6;
  375                 goto insert;
  376         }
  377 
  378         /*
  379          * Find a segment which begins after this one does.
  380          */
  381         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  382              af6 = af6->ip6af_down)
  383                 if (af6->ip6af_off > ip6af->ip6af_off)
  384                         break;
  385 
  386 #if 0
  387         /*
  388          * If there is a preceding segment, it may provide some of
  389          * our data already.  If so, drop the data from the incoming
  390          * segment.  If it provides all of our data, drop us.
  391          */
  392         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  393                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  394                         - ip6af->ip6af_off;
  395                 if (i > 0) {
  396                         if (i >= ip6af->ip6af_frglen)
  397                                 goto dropfrag;
  398                         m_adj(IP6_REASS_MBUF(ip6af), i);
  399                         ip6af->ip6af_off += i;
  400                         ip6af->ip6af_frglen -= i;
  401                 }
  402         }
  403 
  404         /*
  405          * While we overlap succeeding segments trim them or,
  406          * if they are completely covered, dequeue them.
  407          */
  408         while (af6 != (struct ip6asfrag *)q6 &&
  409                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  410                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  411                 if (i < af6->ip6af_frglen) {
  412                         af6->ip6af_frglen -= i;
  413                         af6->ip6af_off += i;
  414                         m_adj(IP6_REASS_MBUF(af6), i);
  415                         break;
  416                 }
  417                 af6 = af6->ip6af_down;
  418                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  419                 frag6_deq(af6->ip6af_up);
  420         }
  421 #else
  422         /*
  423          * If the incoming framgent overlaps some existing fragments in
  424          * the reassembly queue, drop it, since it is dangerous to override
  425          * existing fragments from a security point of view.
  426          * We don't know which fragment is the bad guy - here we trust
  427          * fragment that came in earlier, with no real reason.
  428          */
  429         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  430                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  431                         - ip6af->ip6af_off;
  432                 if (i > 0) {
  433 #if 0                           /* suppress the noisy log */
  434                         log(LOG_ERR, "%d bytes of a fragment from %s "
  435                             "overlaps the previous fragment\n",
  436                             i, ip6_sprintf(&q6->ip6q_src));
  437 #endif
  438                         free(ip6af, M_FTABLE);
  439                         goto dropfrag;
  440                 }
  441         }
  442         if (af6 != (struct ip6asfrag *)q6) {
  443                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  444                 if (i > 0) {
  445 #if 0                           /* suppress the noisy log */
  446                         log(LOG_ERR, "%d bytes of a fragment from %s "
  447                             "overlaps the succeeding fragment",
  448                             i, ip6_sprintf(&q6->ip6q_src));
  449 #endif
  450                         free(ip6af, M_FTABLE);
  451                         goto dropfrag;
  452                 }
  453         }
  454 #endif
  455 
  456 insert:
  457 
  458         /*
  459          * Stick new segment in its place;
  460          * check for complete reassembly.
  461          * Move to front of packet queue, as we are
  462          * the most recently active fragmented packet.
  463          */
  464         frag6_enq(ip6af, af6->ip6af_up);
  465         frag6_nfrags++;
  466         q6->ip6q_nfrag++;
  467 #if 0 /* xxx */
  468         if (q6 != ip6q.ip6q_next) {
  469                 frag6_remque(q6);
  470                 frag6_insque(q6, &ip6q);
  471         }
  472 #endif
  473         next = 0;
  474         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  475              af6 = af6->ip6af_down) {
  476                 if (af6->ip6af_off != next) {
  477                         IP6Q_UNLOCK();
  478                         return IPPROTO_DONE;
  479                 }
  480                 next += af6->ip6af_frglen;
  481         }
  482         if (af6->ip6af_up->ip6af_mff) {
  483                 IP6Q_UNLOCK();
  484                 return IPPROTO_DONE;
  485         }
  486 
  487         /*
  488          * Reassembly is complete; concatenate fragments.
  489          */
  490         ip6af = q6->ip6q_down;
  491         t = m = IP6_REASS_MBUF(ip6af);
  492         af6 = ip6af->ip6af_down;
  493         frag6_deq(ip6af);
  494         while (af6 != (struct ip6asfrag *)q6) {
  495                 af6dwn = af6->ip6af_down;
  496                 frag6_deq(af6);
  497                 while (t->m_next)
  498                         t = t->m_next;
  499                 t->m_next = IP6_REASS_MBUF(af6);
  500                 m_adj(t->m_next, af6->ip6af_offset);
  501                 free(af6, M_FTABLE);
  502                 af6 = af6dwn;
  503         }
  504 
  505         /* adjust offset to point where the original next header starts */
  506         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  507         free(ip6af, M_FTABLE);
  508         ip6 = mtod(m, struct ip6_hdr *);
  509         ip6->ip6_plen = htons(next + offset - sizeof(struct ip6_hdr));
  510         ip6->ip6_src = q6->ip6q_src;
  511         ip6->ip6_dst = q6->ip6q_dst;
  512         nxt = q6->ip6q_nxt;
  513 #ifdef notyet
  514         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  515 #endif
  516 
  517         /*
  518          * Delete frag6 header with as a few cost as possible.
  519          */
  520         if (offset < m->m_len) {
  521                 memmove((char *)ip6 + sizeof(struct ip6_frag), ip6, offset);
  522                 m->m_data += sizeof(struct ip6_frag);
  523                 m->m_len -= sizeof(struct ip6_frag);
  524         } else {
  525                 /* this comes with no copy if the boundary is on cluster */
  526                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  527                         frag6_remque(q6);
  528                         frag6_nfrags -= q6->ip6q_nfrag;
  529                         free(q6, M_FTABLE);
  530                         frag6_nfragpackets--;
  531                         goto dropfrag;
  532                 }
  533                 m_adj(t, sizeof(struct ip6_frag));
  534                 m_cat(m, t);
  535         }
  536 
  537         /*
  538          * Store NXT to the original.
  539          */
  540         {
  541                 u_int8_t *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  542                 *prvnxtp = nxt;
  543         }
  544 
  545         frag6_remque(q6);
  546         frag6_nfrags -= q6->ip6q_nfrag;
  547         free(q6, M_FTABLE);
  548         frag6_nfragpackets--;
  549 
  550         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  551                 int plen = 0;
  552                 for (t = m; t; t = t->m_next)
  553                         plen += t->m_len;
  554                 m->m_pkthdr.len = plen;
  555         }
  556 
  557         IP6_STATINC(IP6_STAT_REASSEMBLED);
  558         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  559 
  560         /*
  561          * Tell launch routine the next header
  562          */
  563 
  564         *mp = m;
  565         *offp = offset;
  566 
  567         IP6Q_UNLOCK();
  568         return nxt;
  569 
  570  dropfrag:
  571         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  572         IP6_STATINC(IP6_STAT_FRAGDROPPED);
  573         m_freem(m);
  574         IP6Q_UNLOCK();
  575         return IPPROTO_DONE;
  576 }
  577 
  578 /*
  579  * Free a fragment reassembly header and all
  580  * associated datagrams.
  581  */
  582 void
  583 frag6_freef(struct ip6q *q6)
  584 {
  585         struct ip6asfrag *af6, *down6;
  586 
  587         IP6Q_LOCK_CHECK();
  588 
  589         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  590              af6 = down6) {
  591                 struct mbuf *m = IP6_REASS_MBUF(af6);
  592 
  593                 down6 = af6->ip6af_down;
  594                 frag6_deq(af6);
  595 
  596                 /*
  597                  * Return ICMP time exceeded error for the 1st fragment.
  598                  * Just free other fragments.
  599                  */
  600                 if (af6->ip6af_off == 0) {
  601                         struct ip6_hdr *ip6;
  602 
  603                         /* adjust pointer */
  604                         ip6 = mtod(m, struct ip6_hdr *);
  605 
  606                         /* restoure source and destination addresses */
  607                         ip6->ip6_src = q6->ip6q_src;
  608                         ip6->ip6_dst = q6->ip6q_dst;
  609 
  610                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  611                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  612                 } else
  613                         m_freem(m);
  614                 free(af6, M_FTABLE);
  615         }
  616         frag6_remque(q6);
  617         frag6_nfrags -= q6->ip6q_nfrag;
  618         free(q6, M_FTABLE);
  619         frag6_nfragpackets--;
  620 }
  621 
  622 /*
  623  * Put an ip fragment on a reassembly chain.
  624  * Like insque, but pointers in middle of structure.
  625  */
  626 void
  627 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6)
  628 {
  629 
  630         IP6Q_LOCK_CHECK();
  631 
  632         af6->ip6af_up = up6;
  633         af6->ip6af_down = up6->ip6af_down;
  634         up6->ip6af_down->ip6af_up = af6;
  635         up6->ip6af_down = af6;
  636 }
  637 
  638 /*
  639  * To frag6_enq as remque is to insque.
  640  */
  641 void
  642 frag6_deq(struct ip6asfrag *af6)
  643 {
  644 
  645         IP6Q_LOCK_CHECK();
  646 
  647         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  648         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  649 }
  650 
  651 void
  652 frag6_insque(struct ip6q *new, struct ip6q *old)
  653 {
  654 
  655         IP6Q_LOCK_CHECK();
  656 
  657         new->ip6q_prev = old;
  658         new->ip6q_next = old->ip6q_next;
  659         old->ip6q_next->ip6q_prev= new;
  660         old->ip6q_next = new;
  661 }
  662 
  663 void
  664 frag6_remque(struct ip6q *p6)
  665 {
  666 
  667         IP6Q_LOCK_CHECK();
  668 
  669         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  670         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  671 }
  672 
  673 /*
  674  * IPv6 reassembling timer processing;
  675  * if a timer expires on a reassembly
  676  * queue, discard it.
  677  */
  678 void
  679 frag6_slowtimo(void)
  680 {
  681         struct ip6q *q6;
  682 
  683         mutex_enter(softnet_lock);
  684         KERNEL_LOCK(1, NULL);
  685 
  686         IP6Q_LOCK();
  687         q6 = ip6q.ip6q_next;
  688         if (q6)
  689                 while (q6 != &ip6q) {
  690                         --q6->ip6q_ttl;
  691                         q6 = q6->ip6q_next;
  692                         if (q6->ip6q_prev->ip6q_ttl == 0) {
  693                                 IP6_STATINC(IP6_STAT_FRAGTIMEOUT);
  694                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  695                                 frag6_freef(q6->ip6q_prev);
  696                         }
  697                 }
  698         /*
  699          * If we are over the maximum number of fragments
  700          * (due to the limit being lowered), drain off
  701          * enough to get down to the new limit.
  702          */
  703         while (frag6_nfragpackets > (u_int)ip6_maxfragpackets &&
  704             ip6q.ip6q_prev) {
  705                 IP6_STATINC(IP6_STAT_FRAGOVERFLOW);
  706                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  707                 frag6_freef(ip6q.ip6q_prev);
  708         }
  709         IP6Q_UNLOCK();
  710 
  711 #if 0
  712         /*
  713          * Routing changes might produce a better route than we last used;
  714          * make sure we notice eventually, even if forwarding only for one
  715          * destination and the cache is never replaced.
  716          */
  717         rtcache_free(&ip6_forward_rt);
  718         rtcache_free(&ipsrcchk_rt);
  719 #endif
  720 
  721         KERNEL_UNLOCK_ONE(NULL);
  722         mutex_exit(softnet_lock);
  723 }
  724 
  725 /*
  726  * Drain off all datagram fragments.
  727  */
  728 void
  729 frag6_drain(void)
  730 {
  731 
  732         KERNEL_LOCK(1, NULL);
  733         if (ip6q_lock_try() != 0) {
  734                 while (ip6q.ip6q_next != &ip6q) {
  735                         IP6_STATINC(IP6_STAT_FRAGDROPPED);
  736                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  737                         frag6_freef(ip6q.ip6q_next);
  738                 }
  739                 IP6Q_UNLOCK();
  740         }
  741         KERNEL_UNLOCK_ONE(NULL);
  742 }

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