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  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the project nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      $KAME: frag6.c,v 1.33 2002/01/07 11:34:48 kjc Exp $
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/12.0/sys/netinet6/frag6.c 338406 2018-08-31 08:37:15Z kp $");
   36 
   37 #include "opt_rss.h"
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/hash.h>
   42 #include <sys/malloc.h>
   43 #include <sys/mbuf.h>
   44 #include <sys/domain.h>
   45 #include <sys/eventhandler.h>
   46 #include <sys/protosw.h>
   47 #include <sys/socket.h>
   48 #include <sys/errno.h>
   49 #include <sys/time.h>
   50 #include <sys/kernel.h>
   51 #include <sys/syslog.h>
   52 
   53 #include <machine/atomic.h>
   54 
   55 #include <net/if.h>
   56 #include <net/if_var.h>
   57 #include <net/netisr.h>
   58 #include <net/route.h>
   59 #include <net/vnet.h>
   60 
   61 #include <netinet/in.h>
   62 #include <netinet/in_var.h>
   63 #include <netinet/ip6.h>
   64 #include <netinet6/ip6_var.h>
   65 #include <netinet/icmp6.h>
   66 #include <netinet/in_systm.h>   /* for ECN definitions */
   67 #include <netinet/ip.h>         /* for ECN definitions */
   68 
   69 #include <security/mac/mac_framework.h>
   70 
   71 /*
   72  * Reassembly headers are stored in hash buckets.
   73  */
   74 #define IP6REASS_NHASH_LOG2     10
   75 #define IP6REASS_NHASH          (1 << IP6REASS_NHASH_LOG2)
   76 #define IP6REASS_HMASK          (IP6REASS_NHASH - 1)
   77 
   78 static void frag6_enq(struct ip6asfrag *, struct ip6asfrag *,
   79     uint32_t bucket __unused);
   80 static void frag6_deq(struct ip6asfrag *, uint32_t bucket __unused);
   81 static void frag6_insque_head(struct ip6q *, struct ip6q *,
   82     uint32_t bucket);
   83 static void frag6_remque(struct ip6q *, uint32_t bucket);
   84 static void frag6_freef(struct ip6q *, uint32_t bucket);
   85 
   86 struct ip6qbucket {
   87         struct ip6q     ip6q;
   88         struct mtx      lock;
   89         int             count;
   90 };
   91 
   92 VNET_DEFINE_STATIC(volatile u_int, frag6_nfragpackets);
   93 volatile u_int frag6_nfrags = 0;
   94 VNET_DEFINE_STATIC(struct ip6qbucket, ip6q[IP6REASS_NHASH]);
   95 VNET_DEFINE_STATIC(uint32_t, ip6q_hashseed);
   96 
   97 #define V_frag6_nfragpackets            VNET(frag6_nfragpackets)
   98 #define V_ip6q                          VNET(ip6q)
   99 #define V_ip6q_hashseed                 VNET(ip6q_hashseed)
  100 
  101 #define IP6Q_LOCK(i)            mtx_lock(&V_ip6q[(i)].lock)
  102 #define IP6Q_TRYLOCK(i)         mtx_trylock(&V_ip6q[(i)].lock)
  103 #define IP6Q_LOCK_ASSERT(i)     mtx_assert(&V_ip6q[(i)].lock, MA_OWNED)
  104 #define IP6Q_UNLOCK(i)          mtx_unlock(&V_ip6q[(i)].lock)
  105 #define IP6Q_HEAD(i)            (&V_ip6q[(i)].ip6q)
  106 
  107 static MALLOC_DEFINE(M_FTABLE, "fragment", "fragment reassembly header");
  108 
  109 /*
  110  * By default, limit the number of IP6 fragments across all reassembly
  111  * queues to  1/32 of the total number of mbuf clusters.
  112  *
  113  * Limit the total number of reassembly queues per VNET to the
  114  * IP6 fragment limit, but ensure the limit will not allow any bucket
  115  * to grow above 100 items. (The bucket limit is
  116  * IP_MAXFRAGPACKETS / (IPREASS_NHASH / 2), so the 50 is the correct
  117  * multiplier to reach a 100-item limit.)
  118  * The 100-item limit was chosen as brief testing seems to show that
  119  * this produces "reasonable" performance on some subset of systems
  120  * under DoS attack.
  121  */
  122 #define IP6_MAXFRAGS            (nmbclusters / 32)
  123 #define IP6_MAXFRAGPACKETS      (imin(IP6_MAXFRAGS, IP6REASS_NHASH * 50))
  124 
  125 /*
  126  * Initialise reassembly queue and fragment identifier.
  127  */
  128 void
  129 frag6_set_bucketsize()
  130 {
  131         int i;
  132 
  133         if ((i = V_ip6_maxfragpackets) > 0)
  134                 V_ip6_maxfragbucketsize = imax(i / (IP6REASS_NHASH / 2), 1);
  135 }
  136 
  137 static void
  138 frag6_change(void *tag)
  139 {
  140         VNET_ITERATOR_DECL(vnet_iter);
  141 
  142         ip6_maxfrags = IP6_MAXFRAGS;
  143         VNET_LIST_RLOCK_NOSLEEP();
  144         VNET_FOREACH(vnet_iter) {
  145                 CURVNET_SET(vnet_iter);
  146                 V_ip6_maxfragpackets = IP6_MAXFRAGPACKETS;
  147                 frag6_set_bucketsize();
  148                 CURVNET_RESTORE();
  149         }
  150         VNET_LIST_RUNLOCK_NOSLEEP();
  151 }
  152 
  153 void
  154 frag6_init(void)
  155 {
  156         struct ip6q *q6;
  157         int i;
  158 
  159         V_ip6_maxfragpackets = IP6_MAXFRAGPACKETS;
  160         frag6_set_bucketsize();
  161         for (i = 0; i < IP6REASS_NHASH; i++) {
  162                 q6 = IP6Q_HEAD(i);
  163                 q6->ip6q_next = q6->ip6q_prev = q6;
  164                 mtx_init(&V_ip6q[i].lock, "ip6qlock", NULL, MTX_DEF);
  165                 V_ip6q[i].count = 0;
  166         }
  167         V_ip6q_hashseed = arc4random();
  168         V_ip6_maxfragsperpacket = 64;
  169         if (!IS_DEFAULT_VNET(curvnet))
  170                 return;
  171 
  172         ip6_maxfrags = IP6_MAXFRAGS;
  173         EVENTHANDLER_REGISTER(nmbclusters_change,
  174             frag6_change, NULL, EVENTHANDLER_PRI_ANY);
  175 }
  176 
  177 /*
  178  * In RFC2460, fragment and reassembly rule do not agree with each other,
  179  * in terms of next header field handling in fragment header.
  180  * While the sender will use the same value for all of the fragmented packets,
  181  * receiver is suggested not to check the consistency.
  182  *
  183  * fragment rule (p20):
  184  *      (2) A Fragment header containing:
  185  *      The Next Header value that identifies the first header of
  186  *      the Fragmentable Part of the original packet.
  187  *              -> next header field is same for all fragments
  188  *
  189  * reassembly rule (p21):
  190  *      The Next Header field of the last header of the Unfragmentable
  191  *      Part is obtained from the Next Header field of the first
  192  *      fragment's Fragment header.
  193  *              -> should grab it from the first fragment only
  194  *
  195  * The following note also contradicts with fragment rule - no one is going to
  196  * send different fragment with different next header field.
  197  *
  198  * additional note (p22):
  199  *      The Next Header values in the Fragment headers of different
  200  *      fragments of the same original packet may differ.  Only the value
  201  *      from the Offset zero fragment packet is used for reassembly.
  202  *              -> should grab it from the first fragment only
  203  *
  204  * There is no explicit reason given in the RFC.  Historical reason maybe?
  205  */
  206 /*
  207  * Fragment input
  208  */
  209 int
  210 frag6_input(struct mbuf **mp, int *offp, int proto)
  211 {
  212         struct mbuf *m = *mp, *t;
  213         struct ip6_hdr *ip6;
  214         struct ip6_frag *ip6f;
  215         struct ip6q *head, *q6;
  216         struct ip6asfrag *af6, *ip6af, *af6dwn;
  217         struct in6_ifaddr *ia;
  218         int offset = *offp, nxt, i, next;
  219         int first_frag = 0;
  220         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  221         uint32_t hashkey[(sizeof(struct in6_addr) * 2 +
  222                     sizeof(ip6f->ip6f_ident)) / sizeof(uint32_t)];
  223         uint32_t hash, *hashkeyp;
  224         struct ifnet *dstifp;
  225         u_int8_t ecn, ecn0;
  226 #ifdef RSS
  227         struct m_tag *mtag;
  228         struct ip6_direct_ctx *ip6dc;
  229 #endif
  230 
  231 #if 0
  232         char ip6buf[INET6_ADDRSTRLEN];
  233 #endif
  234 
  235         ip6 = mtod(m, struct ip6_hdr *);
  236 #ifndef PULLDOWN_TEST
  237         IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
  238         ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
  239 #else
  240         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  241         if (ip6f == NULL)
  242                 return (IPPROTO_DONE);
  243 #endif
  244 
  245         dstifp = NULL;
  246         /* find the destination interface of the packet. */
  247         ia = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
  248         if (ia != NULL) {
  249                 dstifp = ia->ia_ifp;
  250                 ifa_free(&ia->ia_ifa);
  251         }
  252         /* jumbo payload can't contain a fragment header */
  253         if (ip6->ip6_plen == 0) {
  254                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  255                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  256                 return IPPROTO_DONE;
  257         }
  258 
  259         /*
  260          * check whether fragment packet's fragment length is
  261          * multiple of 8 octets.
  262          * sizeof(struct ip6_frag) == 8
  263          * sizeof(struct ip6_hdr) = 40
  264          */
  265         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  266             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  267                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  268                     offsetof(struct ip6_hdr, ip6_plen));
  269                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  270                 return IPPROTO_DONE;
  271         }
  272 
  273         IP6STAT_INC(ip6s_fragments);
  274         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  275 
  276         /* offset now points to data portion */
  277         offset += sizeof(struct ip6_frag);
  278 
  279         /*
  280          * RFC 6946: Handle "atomic" fragments (offset and m bit set to 0)
  281          * upfront, unrelated to any reassembly.  Just skip the fragment header.
  282          */
  283         if ((ip6f->ip6f_offlg & ~IP6F_RESERVED_MASK) == 0) {
  284                 /* XXX-BZ we want dedicated counters for this. */
  285                 IP6STAT_INC(ip6s_reassembled);
  286                 in6_ifstat_inc(dstifp, ifs6_reass_ok);
  287                 *offp = offset;
  288                 m->m_flags |= M_FRAGMENTED;
  289                 return (ip6f->ip6f_nxt);
  290         }
  291 
  292         /* Get fragment length and discard 0-byte fragments. */
  293         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  294         if (frgpartlen == 0) {
  295                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  296                     offsetof(struct ip6_hdr, ip6_plen));
  297                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  298                 IP6STAT_INC(ip6s_fragdropped);
  299                 return IPPROTO_DONE;
  300         }
  301 
  302         hashkeyp = hashkey;
  303         memcpy(hashkeyp, &ip6->ip6_src, sizeof(struct in6_addr));
  304         hashkeyp += sizeof(struct in6_addr) / sizeof(*hashkeyp);
  305         memcpy(hashkeyp, &ip6->ip6_dst, sizeof(struct in6_addr));
  306         hashkeyp += sizeof(struct in6_addr) / sizeof(*hashkeyp);
  307         *hashkeyp = ip6f->ip6f_ident;
  308         hash = jenkins_hash32(hashkey, nitems(hashkey), V_ip6q_hashseed);
  309         hash &= IP6REASS_HMASK;
  310         head = IP6Q_HEAD(hash);
  311         IP6Q_LOCK(hash);
  312 
  313         /*
  314          * Enforce upper bound on number of fragments.
  315          * If maxfrag is 0, never accept fragments.
  316          * If maxfrag is -1, accept all fragments without limitation.
  317          */
  318         if (ip6_maxfrags < 0)
  319                 ;
  320         else if (atomic_load_int(&frag6_nfrags) >= (u_int)ip6_maxfrags)
  321                 goto dropfrag;
  322 
  323         for (q6 = head->ip6q_next; q6 != head; q6 = q6->ip6q_next)
  324                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  325                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  326                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst)
  327 #ifdef MAC
  328                     && mac_ip6q_match(m, q6)
  329 #endif
  330                     )
  331                         break;
  332 
  333         if (q6 == head) {
  334                 /*
  335                  * the first fragment to arrive, create a reassembly queue.
  336                  */
  337                 first_frag = 1;
  338 
  339                 /*
  340                  * Enforce upper bound on number of fragmented packets
  341                  * for which we attempt reassembly;
  342                  * If maxfragpackets is 0, never accept fragments.
  343                  * If maxfragpackets is -1, accept all fragments without
  344                  * limitation.
  345                  */
  346                 if (V_ip6_maxfragpackets < 0)
  347                         ;
  348                 else if (V_ip6q[hash].count >= V_ip6_maxfragbucketsize ||
  349                     atomic_load_int(&V_frag6_nfragpackets) >=
  350                     (u_int)V_ip6_maxfragpackets)
  351                         goto dropfrag;
  352                 atomic_add_int(&V_frag6_nfragpackets, 1);
  353                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  354                     M_NOWAIT);
  355                 if (q6 == NULL)
  356                         goto dropfrag;
  357                 bzero(q6, sizeof(*q6));
  358 #ifdef MAC
  359                 if (mac_ip6q_init(q6, M_NOWAIT) != 0) {
  360                         free(q6, M_FTABLE);
  361                         goto dropfrag;
  362                 }
  363                 mac_ip6q_create(m, q6);
  364 #endif
  365                 frag6_insque_head(q6, head, hash);
  366 
  367                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  368                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  369 #ifdef notyet
  370                 q6->ip6q_nxtp   = (u_char *)nxtp;
  371 #endif
  372                 q6->ip6q_ident  = ip6f->ip6f_ident;
  373                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  374                 q6->ip6q_src    = ip6->ip6_src;
  375                 q6->ip6q_dst    = ip6->ip6_dst;
  376                 q6->ip6q_ecn    =
  377                     (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  378                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  379 
  380                 q6->ip6q_nfrag = 0;
  381         }
  382 
  383         /*
  384          * If it's the 1st fragment, record the length of the
  385          * unfragmentable part and the next header of the fragment header.
  386          */
  387         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  388         if (fragoff == 0) {
  389                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  390                     sizeof(struct ip6_frag);
  391                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  392         }
  393 
  394         /*
  395          * Check that the reassembled packet would not exceed 65535 bytes
  396          * in size.
  397          * If it would exceed, discard the fragment and return an ICMP error.
  398          */
  399         if (q6->ip6q_unfrglen >= 0) {
  400                 /* The 1st fragment has already arrived. */
  401                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  402                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  403                             offset - sizeof(struct ip6_frag) +
  404                             offsetof(struct ip6_frag, ip6f_offlg));
  405                         IP6Q_UNLOCK(hash);
  406                         return (IPPROTO_DONE);
  407                 }
  408         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  409                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  410                     offset - sizeof(struct ip6_frag) +
  411                     offsetof(struct ip6_frag, ip6f_offlg));
  412                 IP6Q_UNLOCK(hash);
  413                 return (IPPROTO_DONE);
  414         }
  415         /*
  416          * If it's the first fragment, do the above check for each
  417          * fragment already stored in the reassembly queue.
  418          */
  419         if (fragoff == 0) {
  420                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  421                      af6 = af6dwn) {
  422                         af6dwn = af6->ip6af_down;
  423 
  424                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  425                             IPV6_MAXPACKET) {
  426                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  427                                 struct ip6_hdr *ip6err;
  428                                 int erroff = af6->ip6af_offset;
  429 
  430                                 /* dequeue the fragment. */
  431                                 frag6_deq(af6, hash);
  432                                 free(af6, M_FTABLE);
  433 
  434                                 /* adjust pointer. */
  435                                 ip6err = mtod(merr, struct ip6_hdr *);
  436 
  437                                 /*
  438                                  * Restore source and destination addresses
  439                                  * in the erroneous IPv6 header.
  440                                  */
  441                                 ip6err->ip6_src = q6->ip6q_src;
  442                                 ip6err->ip6_dst = q6->ip6q_dst;
  443 
  444                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  445                                     ICMP6_PARAMPROB_HEADER,
  446                                     erroff - sizeof(struct ip6_frag) +
  447                                     offsetof(struct ip6_frag, ip6f_offlg));
  448                         }
  449                 }
  450         }
  451 
  452         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  453             M_NOWAIT);
  454         if (ip6af == NULL)
  455                 goto dropfrag;
  456         bzero(ip6af, sizeof(*ip6af));
  457         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  458         ip6af->ip6af_off = fragoff;
  459         ip6af->ip6af_frglen = frgpartlen;
  460         ip6af->ip6af_offset = offset;
  461         IP6_REASS_MBUF(ip6af) = m;
  462 
  463         if (first_frag) {
  464                 af6 = (struct ip6asfrag *)q6;
  465                 goto insert;
  466         }
  467 
  468         /*
  469          * Handle ECN by comparing this segment with the first one;
  470          * if CE is set, do not lose CE.
  471          * drop if CE and not-ECT are mixed for the same packet.
  472          */
  473         ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  474         ecn0 = q6->ip6q_ecn;
  475         if (ecn == IPTOS_ECN_CE) {
  476                 if (ecn0 == IPTOS_ECN_NOTECT) {
  477                         free(ip6af, M_FTABLE);
  478                         goto dropfrag;
  479                 }
  480                 if (ecn0 != IPTOS_ECN_CE)
  481                         q6->ip6q_ecn = IPTOS_ECN_CE;
  482         }
  483         if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
  484                 free(ip6af, M_FTABLE);
  485                 goto dropfrag;
  486         }
  487 
  488         /*
  489          * Find a segment which begins after this one does.
  490          */
  491         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  492              af6 = af6->ip6af_down)
  493                 if (af6->ip6af_off > ip6af->ip6af_off)
  494                         break;
  495 
  496 #if 0
  497         /*
  498          * If there is a preceding segment, it may provide some of
  499          * our data already.  If so, drop the data from the incoming
  500          * segment.  If it provides all of our data, drop us.
  501          */
  502         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  503                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  504                         - ip6af->ip6af_off;
  505                 if (i > 0) {
  506                         if (i >= ip6af->ip6af_frglen)
  507                                 goto dropfrag;
  508                         m_adj(IP6_REASS_MBUF(ip6af), i);
  509                         ip6af->ip6af_off += i;
  510                         ip6af->ip6af_frglen -= i;
  511                 }
  512         }
  513 
  514         /*
  515          * While we overlap succeeding segments trim them or,
  516          * if they are completely covered, dequeue them.
  517          */
  518         while (af6 != (struct ip6asfrag *)q6 &&
  519                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  520                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  521                 if (i < af6->ip6af_frglen) {
  522                         af6->ip6af_frglen -= i;
  523                         af6->ip6af_off += i;
  524                         m_adj(IP6_REASS_MBUF(af6), i);
  525                         break;
  526                 }
  527                 af6 = af6->ip6af_down;
  528                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  529                 frag6_deq(af6->ip6af_up, hash);
  530         }
  531 #else
  532         /*
  533          * If the incoming framgent overlaps some existing fragments in
  534          * the reassembly queue, drop it, since it is dangerous to override
  535          * existing fragments from a security point of view.
  536          * We don't know which fragment is the bad guy - here we trust
  537          * fragment that came in earlier, with no real reason.
  538          *
  539          * Note: due to changes after disabling this part, mbuf passed to
  540          * m_adj() below now does not meet the requirement.
  541          */
  542         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  543                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  544                         - ip6af->ip6af_off;
  545                 if (i > 0) {
  546 #if 0                           /* suppress the noisy log */
  547                         log(LOG_ERR, "%d bytes of a fragment from %s "
  548                             "overlaps the previous fragment\n",
  549                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  550 #endif
  551                         free(ip6af, M_FTABLE);
  552                         goto dropfrag;
  553                 }
  554         }
  555         if (af6 != (struct ip6asfrag *)q6) {
  556                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  557                 if (i > 0) {
  558 #if 0                           /* suppress the noisy log */
  559                         log(LOG_ERR, "%d bytes of a fragment from %s "
  560                             "overlaps the succeeding fragment",
  561                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  562 #endif
  563                         free(ip6af, M_FTABLE);
  564                         goto dropfrag;
  565                 }
  566         }
  567 #endif
  568 
  569 insert:
  570 #ifdef MAC
  571         if (!first_frag)
  572                 mac_ip6q_update(m, q6);
  573 #endif
  574 
  575         /*
  576          * Stick new segment in its place;
  577          * check for complete reassembly.
  578          * If not complete, check fragment limit.
  579          * Move to front of packet queue, as we are
  580          * the most recently active fragmented packet.
  581          */
  582         frag6_enq(ip6af, af6->ip6af_up, hash);
  583         atomic_add_int(&frag6_nfrags, 1);
  584         q6->ip6q_nfrag++;
  585 #if 0 /* xxx */
  586         if (q6 != head->ip6q_next) {
  587                 frag6_remque(q6, hash);
  588                 frag6_insque_head(q6, head, hash);
  589         }
  590 #endif
  591         next = 0;
  592         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  593              af6 = af6->ip6af_down) {
  594                 if (af6->ip6af_off != next) {
  595                         if (q6->ip6q_nfrag > V_ip6_maxfragsperpacket) {
  596                                 IP6STAT_INC(ip6s_fragdropped);
  597                                 frag6_freef(q6, hash);
  598                         }
  599                         IP6Q_UNLOCK(hash);
  600                         return IPPROTO_DONE;
  601                 }
  602                 next += af6->ip6af_frglen;
  603         }
  604         if (af6->ip6af_up->ip6af_mff) {
  605                 if (q6->ip6q_nfrag > V_ip6_maxfragsperpacket) {
  606                         IP6STAT_INC(ip6s_fragdropped);
  607                         frag6_freef(q6, hash);
  608                 }
  609                 IP6Q_UNLOCK(hash);
  610                 return IPPROTO_DONE;
  611         }
  612 
  613         /*
  614          * Reassembly is complete; concatenate fragments.
  615          */
  616         ip6af = q6->ip6q_down;
  617         t = m = IP6_REASS_MBUF(ip6af);
  618         af6 = ip6af->ip6af_down;
  619         frag6_deq(ip6af, hash);
  620         while (af6 != (struct ip6asfrag *)q6) {
  621                 m->m_pkthdr.csum_flags &=
  622                     IP6_REASS_MBUF(af6)->m_pkthdr.csum_flags;
  623                 m->m_pkthdr.csum_data +=
  624                     IP6_REASS_MBUF(af6)->m_pkthdr.csum_data;
  625 
  626                 af6dwn = af6->ip6af_down;
  627                 frag6_deq(af6, hash);
  628                 while (t->m_next)
  629                         t = t->m_next;
  630                 m_adj(IP6_REASS_MBUF(af6), af6->ip6af_offset);
  631                 m_demote_pkthdr(IP6_REASS_MBUF(af6));
  632                 m_cat(t, IP6_REASS_MBUF(af6));
  633                 free(af6, M_FTABLE);
  634                 af6 = af6dwn;
  635         }
  636 
  637         while (m->m_pkthdr.csum_data & 0xffff0000)
  638                 m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
  639                     (m->m_pkthdr.csum_data >> 16);
  640 
  641         /* adjust offset to point where the original next header starts */
  642         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  643         free(ip6af, M_FTABLE);
  644         ip6 = mtod(m, struct ip6_hdr *);
  645         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  646         if (q6->ip6q_ecn == IPTOS_ECN_CE)
  647                 ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
  648         nxt = q6->ip6q_nxt;
  649 #ifdef notyet
  650         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  651 #endif
  652 
  653         if (ip6_deletefraghdr(m, offset, M_NOWAIT) != 0) {
  654                 frag6_remque(q6, hash);
  655                 atomic_subtract_int(&frag6_nfrags, q6->ip6q_nfrag);
  656 #ifdef MAC
  657                 mac_ip6q_destroy(q6);
  658 #endif
  659                 free(q6, M_FTABLE);
  660                 atomic_subtract_int(&V_frag6_nfragpackets, 1);
  661 
  662                 goto dropfrag;
  663         }
  664 
  665         /*
  666          * Store NXT to the original.
  667          */
  668         m_copyback(m, ip6_get_prevhdr(m, offset), sizeof(uint8_t),
  669             (caddr_t)&nxt);
  670 
  671         frag6_remque(q6, hash);
  672         atomic_subtract_int(&frag6_nfrags, q6->ip6q_nfrag);
  673 #ifdef MAC
  674         mac_ip6q_reassemble(q6, m);
  675         mac_ip6q_destroy(q6);
  676 #endif
  677         free(q6, M_FTABLE);
  678         atomic_subtract_int(&V_frag6_nfragpackets, 1);
  679 
  680         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  681                 int plen = 0;
  682                 for (t = m; t; t = t->m_next)
  683                         plen += t->m_len;
  684                 m->m_pkthdr.len = plen;
  685         }
  686 
  687 #ifdef RSS
  688         mtag = m_tag_alloc(MTAG_ABI_IPV6, IPV6_TAG_DIRECT, sizeof(*ip6dc),
  689             M_NOWAIT);
  690         if (mtag == NULL)
  691                 goto dropfrag;
  692 
  693         ip6dc = (struct ip6_direct_ctx *)(mtag + 1);
  694         ip6dc->ip6dc_nxt = nxt;
  695         ip6dc->ip6dc_off = offset;
  696 
  697         m_tag_prepend(m, mtag);
  698 #endif
  699 
  700         IP6Q_UNLOCK(hash);
  701         IP6STAT_INC(ip6s_reassembled);
  702         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  703 
  704 #ifdef RSS
  705         /*
  706          * Queue/dispatch for reprocessing.
  707          */
  708         netisr_dispatch(NETISR_IPV6_DIRECT, m);
  709         return IPPROTO_DONE;
  710 #endif
  711 
  712         /*
  713          * Tell launch routine the next header
  714          */
  715 
  716         *mp = m;
  717         *offp = offset;
  718 
  719         return nxt;
  720 
  721  dropfrag:
  722         IP6Q_UNLOCK(hash);
  723         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  724         IP6STAT_INC(ip6s_fragdropped);
  725         m_freem(m);
  726         return IPPROTO_DONE;
  727 }
  728 
  729 /*
  730  * Free a fragment reassembly header and all
  731  * associated datagrams.
  732  */
  733 static void
  734 frag6_freef(struct ip6q *q6, uint32_t bucket)
  735 {
  736         struct ip6asfrag *af6, *down6;
  737 
  738         IP6Q_LOCK_ASSERT(bucket);
  739 
  740         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  741              af6 = down6) {
  742                 struct mbuf *m = IP6_REASS_MBUF(af6);
  743 
  744                 down6 = af6->ip6af_down;
  745                 frag6_deq(af6, bucket);
  746 
  747                 /*
  748                  * Return ICMP time exceeded error for the 1st fragment.
  749                  * Just free other fragments.
  750                  */
  751                 if (af6->ip6af_off == 0) {
  752                         struct ip6_hdr *ip6;
  753 
  754                         /* adjust pointer */
  755                         ip6 = mtod(m, struct ip6_hdr *);
  756 
  757                         /* restore source and destination addresses */
  758                         ip6->ip6_src = q6->ip6q_src;
  759                         ip6->ip6_dst = q6->ip6q_dst;
  760 
  761                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  762                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  763                 } else
  764                         m_freem(m);
  765                 free(af6, M_FTABLE);
  766         }
  767         frag6_remque(q6, bucket);
  768         atomic_subtract_int(&frag6_nfrags, q6->ip6q_nfrag);
  769 #ifdef MAC
  770         mac_ip6q_destroy(q6);
  771 #endif
  772         free(q6, M_FTABLE);
  773         atomic_subtract_int(&V_frag6_nfragpackets, 1);
  774 }
  775 
  776 /*
  777  * Put an ip fragment on a reassembly chain.
  778  * Like insque, but pointers in middle of structure.
  779  */
  780 static void
  781 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6,
  782     uint32_t bucket __unused)
  783 {
  784 
  785         IP6Q_LOCK_ASSERT(bucket);
  786 
  787         af6->ip6af_up = up6;
  788         af6->ip6af_down = up6->ip6af_down;
  789         up6->ip6af_down->ip6af_up = af6;
  790         up6->ip6af_down = af6;
  791 }
  792 
  793 /*
  794  * To frag6_enq as remque is to insque.
  795  */
  796 static void
  797 frag6_deq(struct ip6asfrag *af6, uint32_t bucket __unused)
  798 {
  799 
  800         IP6Q_LOCK_ASSERT(bucket);
  801 
  802         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  803         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  804 }
  805 
  806 static void
  807 frag6_insque_head(struct ip6q *new, struct ip6q *old, uint32_t bucket)
  808 {
  809 
  810         IP6Q_LOCK_ASSERT(bucket);
  811         KASSERT(IP6Q_HEAD(bucket) == old,
  812             ("%s: attempt to insert at head of wrong bucket"
  813             " (bucket=%u, old=%p)", __func__, bucket, old));
  814 
  815         new->ip6q_prev = old;
  816         new->ip6q_next = old->ip6q_next;
  817         old->ip6q_next->ip6q_prev= new;
  818         old->ip6q_next = new;
  819         V_ip6q[bucket].count++;
  820 }
  821 
  822 static void
  823 frag6_remque(struct ip6q *p6, uint32_t bucket)
  824 {
  825 
  826         IP6Q_LOCK_ASSERT(bucket);
  827 
  828         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  829         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  830         V_ip6q[bucket].count--;
  831 }
  832 
  833 /*
  834  * IPv6 reassembling timer processing;
  835  * if a timer expires on a reassembly
  836  * queue, discard it.
  837  */
  838 void
  839 frag6_slowtimo(void)
  840 {
  841         VNET_ITERATOR_DECL(vnet_iter);
  842         struct ip6q *head, *q6;
  843         int i;
  844 
  845         VNET_LIST_RLOCK_NOSLEEP();
  846         VNET_FOREACH(vnet_iter) {
  847                 CURVNET_SET(vnet_iter);
  848                 for (i = 0; i < IP6REASS_NHASH; i++) {
  849                         IP6Q_LOCK(i);
  850                         head = IP6Q_HEAD(i);
  851                         q6 = head->ip6q_next;
  852                         if (q6 == NULL) {
  853                                 /*
  854                                  * XXXJTL: This should never happen. This
  855                                  * should turn into an assertion.
  856                                  */
  857                                 IP6Q_UNLOCK(i);
  858                                 continue;
  859                         }
  860                         while (q6 != head) {
  861                                 --q6->ip6q_ttl;
  862                                 q6 = q6->ip6q_next;
  863                                 if (q6->ip6q_prev->ip6q_ttl == 0) {
  864                                         IP6STAT_INC(ip6s_fragtimeout);
  865                                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  866                                         frag6_freef(q6->ip6q_prev, i);
  867                                 }
  868                         }
  869                         /*
  870                          * If we are over the maximum number of fragments
  871                          * (due to the limit being lowered), drain off
  872                          * enough to get down to the new limit.
  873                          * Note that we drain all reassembly queues if
  874                          * maxfragpackets is 0 (fragmentation is disabled),
  875                          * and don't enforce a limit when maxfragpackets
  876                          * is negative.
  877                          */
  878                         while ((V_ip6_maxfragpackets == 0 ||
  879                             (V_ip6_maxfragpackets > 0 &&
  880                             V_ip6q[i].count > V_ip6_maxfragbucketsize)) &&
  881                             head->ip6q_prev != head) {
  882                                 IP6STAT_INC(ip6s_fragoverflow);
  883                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  884                                 frag6_freef(head->ip6q_prev, i);
  885                         }
  886                         IP6Q_UNLOCK(i);
  887                 }
  888                 /*
  889                  * If we are still over the maximum number of fragmented
  890                  * packets, drain off enough to get down to the new limit.
  891                  */
  892                 i = 0;
  893                 while (V_ip6_maxfragpackets >= 0 &&
  894                     atomic_load_int(&V_frag6_nfragpackets) >
  895                     (u_int)V_ip6_maxfragpackets) {
  896                         IP6Q_LOCK(i);
  897                         head = IP6Q_HEAD(i);
  898                         if (head->ip6q_prev != head) {
  899                                 IP6STAT_INC(ip6s_fragoverflow);
  900                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  901                                 frag6_freef(head->ip6q_prev, i);
  902                         }
  903                         IP6Q_UNLOCK(i);
  904                         i = (i + 1) % IP6REASS_NHASH;
  905                 }
  906                 CURVNET_RESTORE();
  907         }
  908         VNET_LIST_RUNLOCK_NOSLEEP();
  909 }
  910 
  911 /*
  912  * Drain off all datagram fragments.
  913  */
  914 void
  915 frag6_drain(void)
  916 {
  917         VNET_ITERATOR_DECL(vnet_iter);
  918         struct ip6q *head;
  919         int i;
  920 
  921         VNET_LIST_RLOCK_NOSLEEP();
  922         VNET_FOREACH(vnet_iter) {
  923                 CURVNET_SET(vnet_iter);
  924                 for (i = 0; i < IP6REASS_NHASH; i++) {
  925                         if (IP6Q_TRYLOCK(i) == 0)
  926                                 continue;
  927                         head = IP6Q_HEAD(i);
  928                         while (head->ip6q_next != head) {
  929                                 IP6STAT_INC(ip6s_fragdropped);
  930                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  931                                 frag6_freef(head->ip6q_next, i);
  932                         }
  933                         IP6Q_UNLOCK(i);
  934                 }
  935                 CURVNET_RESTORE();
  936         }
  937         VNET_LIST_RUNLOCK_NOSLEEP();
  938 }
  939 
  940 int
  941 ip6_deletefraghdr(struct mbuf *m, int offset, int wait)
  942 {
  943         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  944         struct mbuf *t;
  945 
  946         /* Delete frag6 header. */
  947         if (m->m_len >= offset + sizeof(struct ip6_frag)) {
  948                 /* This is the only possible case with !PULLDOWN_TEST. */
  949                 bcopy(ip6, (char *)ip6 + sizeof(struct ip6_frag),
  950                     offset);
  951                 m->m_data += sizeof(struct ip6_frag);
  952                 m->m_len -= sizeof(struct ip6_frag);
  953         } else {
  954                 /* This comes with no copy if the boundary is on cluster. */
  955                 if ((t = m_split(m, offset, wait)) == NULL)
  956                         return (ENOMEM);
  957                 m_adj(t, sizeof(struct ip6_frag));
  958                 m_cat(m, t);
  959         }
  960 
  961         m->m_flags |= M_FRAGMENTED;
  962         return (0);
  963 }

Cache object: 037dc487880a8f43be55e2471b95cd6d


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