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 1.49 2011/05/03 17:44:30 dyoung 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 1.49 2011/05/03 17:44:30 dyoung 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 static int frag6_drainwanted;
   69 
   70 u_int frag6_nfragpackets;
   71 u_int frag6_nfrags;
   72 struct  ip6q ip6q;      /* ip6 reassemble queue */
   73 
   74 static inline int ip6q_lock_try(void);
   75 static inline void ip6q_unlock(void);
   76 
   77 static inline int
   78 ip6q_lock_try(void)
   79 {
   80         int s;
   81 
   82         /*
   83          * Use splvm() -- we're bloking things that would cause
   84          * mbuf allocation.
   85          */
   86         s = splvm();
   87         if (ip6q_locked) {
   88                 splx(s);
   89                 return (0);
   90         }
   91         ip6q_locked = 1;
   92         splx(s);
   93         return (1);
   94 }
   95 
   96 static inline void
   97 ip6q_unlock(void)
   98 {
   99         int s;
  100 
  101         s = splvm();
  102         ip6q_locked = 0;
  103         splx(s);
  104 }
  105 
  106 #ifdef DIAGNOSTIC
  107 #define IP6Q_LOCK()                                                     \
  108 do {                                                                    \
  109         if (ip6q_lock_try() == 0) {                                     \
  110                 printf("%s:%d: ip6q already locked\n", __FILE__, __LINE__); \
  111                 panic("ip6q_lock");                                     \
  112         }                                                               \
  113 } while (/*CONSTCOND*/ 0)
  114 #define IP6Q_LOCK_CHECK()                                               \
  115 do {                                                                    \
  116         if (ip6q_locked == 0) {                                         \
  117                 printf("%s:%d: ip6q lock not held\n", __FILE__, __LINE__); \
  118                 panic("ip6q lock check");                               \
  119         }                                                               \
  120 } while (/*CONSTCOND*/ 0)
  121 #else
  122 #define IP6Q_LOCK()             (void) ip6q_lock_try()
  123 #define IP6Q_LOCK_CHECK()       /* nothing */
  124 #endif
  125 
  126 #define IP6Q_UNLOCK()           ip6q_unlock()
  127 
  128 #ifndef offsetof                /* XXX */
  129 #define offsetof(type, member)  ((size_t)(&((type *)0)->member))
  130 #endif
  131 
  132 /*
  133  * Initialise reassembly queue and fragment identifier.
  134  */
  135 void
  136 frag6_init(void)
  137 {
  138 
  139         ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
  140 }
  141 
  142 /*
  143  * In RFC2460, fragment and reassembly rule do not agree with each other,
  144  * in terms of next header field handling in fragment header.
  145  * While the sender will use the same value for all of the fragmented packets,
  146  * receiver is suggested not to check the consistency.
  147  *
  148  * fragment rule (p20):
  149  *      (2) A Fragment header containing:
  150  *      The Next Header value that identifies the first header of
  151  *      the Fragmentable Part of the original packet.
  152  *              -> next header field is same for all fragments
  153  *
  154  * reassembly rule (p21):
  155  *      The Next Header field of the last header of the Unfragmentable
  156  *      Part is obtained from the Next Header field of the first
  157  *      fragment's Fragment header.
  158  *              -> should grab it from the first fragment only
  159  *
  160  * The following note also contradicts with fragment rule - noone is going to
  161  * send different fragment with different next header field.
  162  *
  163  * additional note (p22):
  164  *      The Next Header values in the Fragment headers of different
  165  *      fragments of the same original packet may differ.  Only the value
  166  *      from the Offset zero fragment packet is used for reassembly.
  167  *              -> should grab it from the first fragment only
  168  *
  169  * There is no explicit reason given in the RFC.  Historical reason maybe?
  170  */
  171 /*
  172  * Fragment input
  173  */
  174 int
  175 frag6_input(struct mbuf **mp, int *offp, int proto)
  176 {
  177         struct rtentry *rt;
  178         struct mbuf *m = *mp, *t;
  179         struct ip6_hdr *ip6;
  180         struct ip6_frag *ip6f;
  181         struct ip6q *q6;
  182         struct ip6asfrag *af6, *ip6af, *af6dwn;
  183         int offset = *offp, nxt, i, next;
  184         int first_frag = 0;
  185         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  186         struct ifnet *dstifp;
  187         static struct route ro;
  188         union {
  189                 struct sockaddr         dst;
  190                 struct sockaddr_in6     dst6;
  191         } u;
  192 
  193         ip6 = mtod(m, struct ip6_hdr *);
  194         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  195         if (ip6f == NULL)
  196                 return IPPROTO_DONE;
  197 
  198         dstifp = NULL;
  199         /* find the destination interface of the packet. */
  200         sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0);
  201         if ((rt = rtcache_lookup(&ro, &u.dst)) != NULL && rt->rt_ifa != NULL)
  202                 dstifp = ((struct in6_ifaddr *)rt->rt_ifa)->ia_ifp;
  203 
  204         /* jumbo payload can't contain a fragment header */
  205         if (ip6->ip6_plen == 0) {
  206                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  207                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  208                 return IPPROTO_DONE;
  209         }
  210 
  211         /*
  212          * check whether fragment packet's fragment length is
  213          * multiple of 8 octets.
  214          * sizeof(struct ip6_frag) == 8
  215          * sizeof(struct ip6_hdr) = 40
  216          */
  217         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  218             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  219                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  220                     offsetof(struct ip6_hdr, ip6_plen));
  221                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  222                 return IPPROTO_DONE;
  223         }
  224 
  225         IP6_STATINC(IP6_STAT_FRAGMENTS);
  226         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  227 
  228         /* offset now points to data portion */
  229         offset += sizeof(struct ip6_frag);
  230 
  231         IP6Q_LOCK();
  232 
  233         /*
  234          * Enforce upper bound on number of fragments.
  235          * If maxfrag is 0, never accept fragments.
  236          * If maxfrag is -1, accept all fragments without limitation.
  237          */
  238         if (ip6_maxfrags < 0)
  239                 ;
  240         else if (frag6_nfrags >= (u_int)ip6_maxfrags)
  241                 goto dropfrag;
  242 
  243         for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next)
  244                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  245                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  246                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
  247                         break;
  248 
  249         if (q6 == &ip6q) {
  250                 /*
  251                  * the first fragment to arrive, create a reassembly queue.
  252                  */
  253                 first_frag = 1;
  254 
  255                 /*
  256                  * Enforce upper bound on number of fragmented packets
  257                  * for which we attempt reassembly;
  258                  * If maxfragpackets is 0, never accept fragments.
  259                  * If maxfragpackets is -1, accept all fragments without
  260                  * limitation.
  261                  */
  262                 if (ip6_maxfragpackets < 0)
  263                         ;
  264                 else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets)
  265                         goto dropfrag;
  266                 frag6_nfragpackets++;
  267                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  268                     M_DONTWAIT);
  269                 if (q6 == NULL)
  270                         goto dropfrag;
  271                 memset(q6, 0, sizeof(*q6));
  272 
  273                 frag6_insque(q6, &ip6q);
  274 
  275                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  276                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  277 #ifdef notyet
  278                 q6->ip6q_nxtp   = (u_char *)nxtp;
  279 #endif
  280                 q6->ip6q_ident  = ip6f->ip6f_ident;
  281                 q6->ip6q_arrive = 0; /* Is it used anywhere? */
  282                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  283                 q6->ip6q_src    = ip6->ip6_src;
  284                 q6->ip6q_dst    = ip6->ip6_dst;
  285                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  286 
  287                 q6->ip6q_nfrag = 0;
  288         }
  289 
  290         /*
  291          * If it's the 1st fragment, record the length of the
  292          * unfragmentable part and the next header of the fragment header.
  293          */
  294         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  295         if (fragoff == 0) {
  296                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  297                     sizeof(struct ip6_frag);
  298                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  299         }
  300 
  301         /*
  302          * Check that the reassembled packet would not exceed 65535 bytes
  303          * in size.
  304          * If it would exceed, discard the fragment and return an ICMP error.
  305          */
  306         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  307         if (q6->ip6q_unfrglen >= 0) {
  308                 /* The 1st fragment has already arrived. */
  309                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  310                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  311                             offset - sizeof(struct ip6_frag) +
  312                             offsetof(struct ip6_frag, ip6f_offlg));
  313                         IP6Q_UNLOCK();
  314                         return (IPPROTO_DONE);
  315                 }
  316         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  317                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  318                             offset - sizeof(struct ip6_frag) +
  319                                 offsetof(struct ip6_frag, ip6f_offlg));
  320                 IP6Q_UNLOCK();
  321                 return (IPPROTO_DONE);
  322         }
  323         /*
  324          * If it's the first fragment, do the above check for each
  325          * fragment already stored in the reassembly queue.
  326          */
  327         if (fragoff == 0) {
  328                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  329                      af6 = af6dwn) {
  330                         af6dwn = af6->ip6af_down;
  331 
  332                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  333                             IPV6_MAXPACKET) {
  334                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  335                                 struct ip6_hdr *ip6err;
  336                                 int erroff = af6->ip6af_offset;
  337 
  338                                 /* dequeue the fragment. */
  339                                 frag6_deq(af6);
  340                                 free(af6, M_FTABLE);
  341 
  342                                 /* adjust pointer. */
  343                                 ip6err = mtod(merr, struct ip6_hdr *);
  344 
  345                                 /*
  346                                  * Restore source and destination addresses
  347                                  * in the erroneous IPv6 header.
  348                                  */
  349                                 ip6err->ip6_src = q6->ip6q_src;
  350                                 ip6err->ip6_dst = q6->ip6q_dst;
  351 
  352                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  353                                     ICMP6_PARAMPROB_HEADER,
  354                                     erroff - sizeof(struct ip6_frag) +
  355                                     offsetof(struct ip6_frag, ip6f_offlg));
  356                         }
  357                 }
  358         }
  359 
  360         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  361             M_DONTWAIT);
  362         if (ip6af == NULL)
  363                 goto dropfrag;
  364         memset(ip6af, 0, sizeof(*ip6af));
  365         ip6af->ip6af_head = ip6->ip6_flow;
  366         ip6af->ip6af_len = ip6->ip6_plen;
  367         ip6af->ip6af_nxt = ip6->ip6_nxt;
  368         ip6af->ip6af_hlim = ip6->ip6_hlim;
  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          * Find a segment which begins after this one does.
  382          */
  383         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  384              af6 = af6->ip6af_down)
  385                 if (af6->ip6af_off > ip6af->ip6af_off)
  386                         break;
  387 
  388 #if 0
  389         /*
  390          * If there is a preceding segment, it may provide some of
  391          * our data already.  If so, drop the data from the incoming
  392          * segment.  If it provides all of our data, drop us.
  393          */
  394         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  395                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  396                         - ip6af->ip6af_off;
  397                 if (i > 0) {
  398                         if (i >= ip6af->ip6af_frglen)
  399                                 goto dropfrag;
  400                         m_adj(IP6_REASS_MBUF(ip6af), i);
  401                         ip6af->ip6af_off += i;
  402                         ip6af->ip6af_frglen -= i;
  403                 }
  404         }
  405 
  406         /*
  407          * While we overlap succeeding segments trim them or,
  408          * if they are completely covered, dequeue them.
  409          */
  410         while (af6 != (struct ip6asfrag *)q6 &&
  411                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  412                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  413                 if (i < af6->ip6af_frglen) {
  414                         af6->ip6af_frglen -= i;
  415                         af6->ip6af_off += i;
  416                         m_adj(IP6_REASS_MBUF(af6), i);
  417                         break;
  418                 }
  419                 af6 = af6->ip6af_down;
  420                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  421                 frag6_deq(af6->ip6af_up);
  422         }
  423 #else
  424         /*
  425          * If the incoming framgent overlaps some existing fragments in
  426          * the reassembly queue, drop it, since it is dangerous to override
  427          * existing fragments from a security point of view.
  428          * We don't know which fragment is the bad guy - here we trust
  429          * fragment that came in earlier, with no real reason.
  430          */
  431         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  432                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  433                         - ip6af->ip6af_off;
  434                 if (i > 0) {
  435 #if 0                           /* suppress the noisy log */
  436                         log(LOG_ERR, "%d bytes of a fragment from %s "
  437                             "overlaps the previous fragment\n",
  438                             i, ip6_sprintf(&q6->ip6q_src));
  439 #endif
  440                         free(ip6af, M_FTABLE);
  441                         goto dropfrag;
  442                 }
  443         }
  444         if (af6 != (struct ip6asfrag *)q6) {
  445                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  446                 if (i > 0) {
  447 #if 0                           /* suppress the noisy log */
  448                         log(LOG_ERR, "%d bytes of a fragment from %s "
  449                             "overlaps the succeeding fragment",
  450                             i, ip6_sprintf(&q6->ip6q_src));
  451 #endif
  452                         free(ip6af, M_FTABLE);
  453                         goto dropfrag;
  454                 }
  455         }
  456 #endif
  457 
  458 insert:
  459 
  460         /*
  461          * Stick new segment in its place;
  462          * check for complete reassembly.
  463          * Move to front of packet queue, as we are
  464          * the most recently active fragmented packet.
  465          */
  466         frag6_enq(ip6af, af6->ip6af_up);
  467         frag6_nfrags++;
  468         q6->ip6q_nfrag++;
  469 #if 0 /* xxx */
  470         if (q6 != ip6q.ip6q_next) {
  471                 frag6_remque(q6);
  472                 frag6_insque(q6, &ip6q);
  473         }
  474 #endif
  475         next = 0;
  476         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  477              af6 = af6->ip6af_down) {
  478                 if (af6->ip6af_off != next) {
  479                         IP6Q_UNLOCK();
  480                         return IPPROTO_DONE;
  481                 }
  482                 next += af6->ip6af_frglen;
  483         }
  484         if (af6->ip6af_up->ip6af_mff) {
  485                 IP6Q_UNLOCK();
  486                 return IPPROTO_DONE;
  487         }
  488 
  489         /*
  490          * Reassembly is complete; concatenate fragments.
  491          */
  492         ip6af = q6->ip6q_down;
  493         t = m = IP6_REASS_MBUF(ip6af);
  494         af6 = ip6af->ip6af_down;
  495         frag6_deq(ip6af);
  496         while (af6 != (struct ip6asfrag *)q6) {
  497                 af6dwn = af6->ip6af_down;
  498                 frag6_deq(af6);
  499                 while (t->m_next)
  500                         t = t->m_next;
  501                 t->m_next = IP6_REASS_MBUF(af6);
  502                 m_adj(t->m_next, af6->ip6af_offset);
  503                 free(af6, M_FTABLE);
  504                 af6 = af6dwn;
  505         }
  506 
  507         /* adjust offset to point where the original next header starts */
  508         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  509         free(ip6af, M_FTABLE);
  510         ip6 = mtod(m, struct ip6_hdr *);
  511         ip6->ip6_plen = htons(next + offset - sizeof(struct ip6_hdr));
  512         ip6->ip6_src = q6->ip6q_src;
  513         ip6->ip6_dst = q6->ip6q_dst;
  514         nxt = q6->ip6q_nxt;
  515 #ifdef notyet
  516         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  517 #endif
  518 
  519         /*
  520          * Delete frag6 header with as a few cost as possible.
  521          */
  522         if (m->m_len >= offset + sizeof(struct ip6_frag)) {
  523                 memmove((char *)ip6 + sizeof(struct ip6_frag), ip6, offset);
  524                 m->m_data += sizeof(struct ip6_frag);
  525                 m->m_len -= sizeof(struct ip6_frag);
  526         } else {
  527                 /* this comes with no copy if the boundary is on cluster */
  528                 if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
  529                         frag6_remque(q6);
  530                         frag6_nfrags -= q6->ip6q_nfrag;
  531                         free(q6, M_FTABLE);
  532                         frag6_nfragpackets--;
  533                         goto dropfrag;
  534                 }
  535                 m_adj(t, sizeof(struct ip6_frag));
  536                 m_cat(m, t);
  537         }
  538 
  539         /*
  540          * Store NXT to the original.
  541          */
  542         {
  543                 u_int8_t *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
  544                 *prvnxtp = nxt;
  545         }
  546 
  547         frag6_remque(q6);
  548         frag6_nfrags -= q6->ip6q_nfrag;
  549         free(q6, M_FTABLE);
  550         frag6_nfragpackets--;
  551 
  552         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  553                 int plen = 0;
  554                 for (t = m; t; t = t->m_next)
  555                         plen += t->m_len;
  556                 m->m_pkthdr.len = plen;
  557         }
  558 
  559         IP6_STATINC(IP6_STAT_REASSEMBLED);
  560         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  561 
  562         /*
  563          * Tell launch routine the next header
  564          */
  565 
  566         *mp = m;
  567         *offp = offset;
  568 
  569         IP6Q_UNLOCK();
  570         return nxt;
  571 
  572  dropfrag:
  573         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  574         IP6_STATINC(IP6_STAT_FRAGDROPPED);
  575         m_freem(m);
  576         IP6Q_UNLOCK();
  577         return IPPROTO_DONE;
  578 }
  579 
  580 /*
  581  * Free a fragment reassembly header and all
  582  * associated datagrams.
  583  */
  584 void
  585 frag6_freef(struct ip6q *q6)
  586 {
  587         struct ip6asfrag *af6, *down6;
  588 
  589         IP6Q_LOCK_CHECK();
  590 
  591         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  592              af6 = down6) {
  593                 struct mbuf *m = IP6_REASS_MBUF(af6);
  594 
  595                 down6 = af6->ip6af_down;
  596                 frag6_deq(af6);
  597 
  598                 /*
  599                  * Return ICMP time exceeded error for the 1st fragment.
  600                  * Just free other fragments.
  601                  */
  602                 if (af6->ip6af_off == 0) {
  603                         struct ip6_hdr *ip6;
  604 
  605                         /* adjust pointer */
  606                         ip6 = mtod(m, struct ip6_hdr *);
  607 
  608                         /* restoure source and destination addresses */
  609                         ip6->ip6_src = q6->ip6q_src;
  610                         ip6->ip6_dst = q6->ip6q_dst;
  611 
  612                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  613                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  614                 } else
  615                         m_freem(m);
  616                 free(af6, M_FTABLE);
  617         }
  618         frag6_remque(q6);
  619         frag6_nfrags -= q6->ip6q_nfrag;
  620         free(q6, M_FTABLE);
  621         frag6_nfragpackets--;
  622 }
  623 
  624 /*
  625  * Put an ip fragment on a reassembly chain.
  626  * Like insque, but pointers in middle of structure.
  627  */
  628 void
  629 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6)
  630 {
  631 
  632         IP6Q_LOCK_CHECK();
  633 
  634         af6->ip6af_up = up6;
  635         af6->ip6af_down = up6->ip6af_down;
  636         up6->ip6af_down->ip6af_up = af6;
  637         up6->ip6af_down = af6;
  638 }
  639 
  640 /*
  641  * To frag6_enq as remque is to insque.
  642  */
  643 void
  644 frag6_deq(struct ip6asfrag *af6)
  645 {
  646 
  647         IP6Q_LOCK_CHECK();
  648 
  649         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  650         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  651 }
  652 
  653 void
  654 frag6_insque(struct ip6q *new, struct ip6q *old)
  655 {
  656 
  657         IP6Q_LOCK_CHECK();
  658 
  659         new->ip6q_prev = old;
  660         new->ip6q_next = old->ip6q_next;
  661         old->ip6q_next->ip6q_prev= new;
  662         old->ip6q_next = new;
  663 }
  664 
  665 void
  666 frag6_remque(struct ip6q *p6)
  667 {
  668 
  669         IP6Q_LOCK_CHECK();
  670 
  671         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  672         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  673 }
  674 
  675 void
  676 frag6_fasttimo(void)
  677 {
  678         if (frag6_drainwanted) {
  679                 frag6_drain();
  680                 frag6_drainwanted = 0;
  681         }
  682 }
  683 
  684 /*
  685  * IPv6 reassembling timer processing;
  686  * if a timer expires on a reassembly
  687  * queue, discard it.
  688  */
  689 void
  690 frag6_slowtimo(void)
  691 {
  692         struct ip6q *q6;
  693 
  694         mutex_enter(softnet_lock);
  695         KERNEL_LOCK(1, NULL);
  696 
  697         IP6Q_LOCK();
  698         q6 = ip6q.ip6q_next;
  699         if (q6)
  700                 while (q6 != &ip6q) {
  701                         --q6->ip6q_ttl;
  702                         q6 = q6->ip6q_next;
  703                         if (q6->ip6q_prev->ip6q_ttl == 0) {
  704                                 IP6_STATINC(IP6_STAT_FRAGTIMEOUT);
  705                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  706                                 frag6_freef(q6->ip6q_prev);
  707                         }
  708                 }
  709         /*
  710          * If we are over the maximum number of fragments
  711          * (due to the limit being lowered), drain off
  712          * enough to get down to the new limit.
  713          */
  714         while (frag6_nfragpackets > (u_int)ip6_maxfragpackets &&
  715             ip6q.ip6q_prev) {
  716                 IP6_STATINC(IP6_STAT_FRAGOVERFLOW);
  717                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  718                 frag6_freef(ip6q.ip6q_prev);
  719         }
  720         IP6Q_UNLOCK();
  721 
  722 #if 0
  723         /*
  724          * Routing changes might produce a better route than we last used;
  725          * make sure we notice eventually, even if forwarding only for one
  726          * destination and the cache is never replaced.
  727          */
  728         rtcache_free(&ip6_forward_rt);
  729         rtcache_free(&ipsrcchk_rt);
  730 #endif
  731 
  732         KERNEL_UNLOCK_ONE(NULL);
  733         mutex_exit(softnet_lock);
  734 }
  735 
  736 void
  737 frag6_drainstub(void)
  738 {
  739         frag6_drainwanted = 1;
  740 }
  741 
  742 /*
  743  * Drain off all datagram fragments.
  744  */
  745 void
  746 frag6_drain(void)
  747 {
  748 
  749         KERNEL_LOCK(1, NULL);
  750         if (ip6q_lock_try() != 0) {
  751                 while (ip6q.ip6q_next != &ip6q) {
  752                         IP6_STATINC(IP6_STAT_FRAGDROPPED);
  753                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  754                         frag6_freef(ip6q.ip6q_next);
  755                 }
  756                 IP6Q_UNLOCK();
  757         }
  758         KERNEL_UNLOCK_ONE(NULL);
  759 }

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