The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/netinet6/frag6.c

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    1 /*-
    2  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. Neither the name of the project nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      $KAME: frag6.c,v 1.33 2002/01/07 11:34:48 kjc Exp $
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/11.2/sys/netinet6/frag6.c 338978 2018-09-27 18:29:55Z gordon $");
   34 
   35 #include "opt_rss.h"
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/hash.h>
   40 #include <sys/malloc.h>
   41 #include <sys/mbuf.h>
   42 #include <sys/domain.h>
   43 #include <sys/eventhandler.h>
   44 #include <sys/protosw.h>
   45 #include <sys/socket.h>
   46 #include <sys/errno.h>
   47 #include <sys/time.h>
   48 #include <sys/kernel.h>
   49 #include <sys/syslog.h>
   50 
   51 #include <machine/atomic.h>
   52 
   53 #include <net/if.h>
   54 #include <net/if_var.h>
   55 #include <net/netisr.h>
   56 #include <net/route.h>
   57 #include <net/vnet.h>
   58 
   59 #include <netinet/in.h>
   60 #include <netinet/in_var.h>
   61 #include <netinet/ip6.h>
   62 #include <netinet6/ip6_var.h>
   63 #include <netinet/icmp6.h>
   64 #include <netinet/in_systm.h>   /* for ECN definitions */
   65 #include <netinet/ip.h>         /* for ECN definitions */
   66 
   67 #include <security/mac/mac_framework.h>
   68 
   69 /*
   70  * Reassembly headers are stored in hash buckets.
   71  */
   72 #define IP6REASS_NHASH_LOG2     10
   73 #define IP6REASS_NHASH          (1 << IP6REASS_NHASH_LOG2)
   74 #define IP6REASS_HMASK          (IP6REASS_NHASH - 1)
   75 
   76 static void frag6_enq(struct ip6asfrag *, struct ip6asfrag *,
   77     uint32_t bucket __unused);
   78 static void frag6_deq(struct ip6asfrag *, uint32_t bucket __unused);
   79 static void frag6_insque_head(struct ip6q *, struct ip6q *,
   80     uint32_t bucket);
   81 static void frag6_remque(struct ip6q *, uint32_t bucket);
   82 static void frag6_freef(struct ip6q *, uint32_t bucket);
   83 
   84 struct ip6qbucket {
   85         struct ip6q     ip6q;
   86         struct mtx      lock;
   87         int             count;
   88 };
   89 
   90 static VNET_DEFINE(volatile u_int, frag6_nfragpackets);
   91 volatile u_int frag6_nfrags = 0;
   92 static VNET_DEFINE(struct ip6qbucket, ip6q[IP6REASS_NHASH]);
   93 static VNET_DEFINE(uint32_t, ip6q_hashseed);
   94 
   95 #define V_frag6_nfragpackets            VNET(frag6_nfragpackets)
   96 #define V_ip6q                          VNET(ip6q)
   97 #define V_ip6q_hashseed                 VNET(ip6q_hashseed)
   98 
   99 #define IP6Q_LOCK(i)            mtx_lock(&V_ip6q[(i)].lock)
  100 #define IP6Q_TRYLOCK(i)         mtx_trylock(&V_ip6q[(i)].lock)
  101 #define IP6Q_LOCK_ASSERT(i)     mtx_assert(&V_ip6q[(i)].lock, MA_OWNED)
  102 #define IP6Q_UNLOCK(i)          mtx_unlock(&V_ip6q[(i)].lock)
  103 #define IP6Q_HEAD(i)            (&V_ip6q[(i)].ip6q)
  104 
  105 static MALLOC_DEFINE(M_FTABLE, "fragment", "fragment reassembly header");
  106 
  107 /*
  108  * By default, limit the number of IP6 fragments across all reassembly
  109  * queues to  1/32 of the total number of mbuf clusters.
  110  *
  111  * Limit the total number of reassembly queues per VNET to the
  112  * IP6 fragment limit, but ensure the limit will not allow any bucket
  113  * to grow above 100 items. (The bucket limit is
  114  * IP_MAXFRAGPACKETS / (IPREASS_NHASH / 2), so the 50 is the correct
  115  * multiplier to reach a 100-item limit.)
  116  * The 100-item limit was chosen as brief testing seems to show that
  117  * this produces "reasonable" performance on some subset of systems
  118  * under DoS attack.
  119  */
  120 #define IP6_MAXFRAGS            (nmbclusters / 32)
  121 #define IP6_MAXFRAGPACKETS      (imin(IP6_MAXFRAGS, IP6REASS_NHASH * 50))
  122 
  123 /*
  124  * Initialise reassembly queue and fragment identifier.
  125  */
  126 void
  127 frag6_set_bucketsize()
  128 {
  129         int i;
  130 
  131         if ((i = V_ip6_maxfragpackets) > 0)
  132                 V_ip6_maxfragbucketsize = imax(i / (IP6REASS_NHASH / 2), 1);
  133 }
  134 
  135 static void
  136 frag6_change(void *tag)
  137 {
  138         VNET_ITERATOR_DECL(vnet_iter);
  139 
  140         ip6_maxfrags = IP6_MAXFRAGS;
  141         VNET_LIST_RLOCK_NOSLEEP();
  142         VNET_FOREACH(vnet_iter) {
  143                 CURVNET_SET(vnet_iter);
  144                 V_ip6_maxfragpackets = IP6_MAXFRAGPACKETS;
  145                 frag6_set_bucketsize();
  146                 CURVNET_RESTORE();
  147         }
  148         VNET_LIST_RUNLOCK_NOSLEEP();
  149 }
  150 
  151 void
  152 frag6_init(void)
  153 {
  154         struct ip6q *q6;
  155         int i;
  156 
  157         V_ip6_maxfragpackets = IP6_MAXFRAGPACKETS;
  158         frag6_set_bucketsize();
  159         for (i = 0; i < IP6REASS_NHASH; i++) {
  160                 q6 = IP6Q_HEAD(i);
  161                 q6->ip6q_next = q6->ip6q_prev = q6;
  162                 mtx_init(&V_ip6q[i].lock, "ip6qlock", NULL, MTX_DEF);
  163                 V_ip6q[i].count = 0;
  164         }
  165         V_ip6q_hashseed = arc4random();
  166         V_ip6_maxfragsperpacket = 64;
  167         if (!IS_DEFAULT_VNET(curvnet))
  168                 return;
  169 
  170         ip6_maxfrags = IP6_MAXFRAGS;
  171         EVENTHANDLER_REGISTER(nmbclusters_change,
  172             frag6_change, NULL, EVENTHANDLER_PRI_ANY);
  173 }
  174 
  175 /*
  176  * In RFC2460, fragment and reassembly rule do not agree with each other,
  177  * in terms of next header field handling in fragment header.
  178  * While the sender will use the same value for all of the fragmented packets,
  179  * receiver is suggested not to check the consistency.
  180  *
  181  * fragment rule (p20):
  182  *      (2) A Fragment header containing:
  183  *      The Next Header value that identifies the first header of
  184  *      the Fragmentable Part of the original packet.
  185  *              -> next header field is same for all fragments
  186  *
  187  * reassembly rule (p21):
  188  *      The Next Header field of the last header of the Unfragmentable
  189  *      Part is obtained from the Next Header field of the first
  190  *      fragment's Fragment header.
  191  *              -> should grab it from the first fragment only
  192  *
  193  * The following note also contradicts with fragment rule - no one is going to
  194  * send different fragment with different next header field.
  195  *
  196  * additional note (p22):
  197  *      The Next Header values in the Fragment headers of different
  198  *      fragments of the same original packet may differ.  Only the value
  199  *      from the Offset zero fragment packet is used for reassembly.
  200  *              -> should grab it from the first fragment only
  201  *
  202  * There is no explicit reason given in the RFC.  Historical reason maybe?
  203  */
  204 /*
  205  * Fragment input
  206  */
  207 int
  208 frag6_input(struct mbuf **mp, int *offp, int proto)
  209 {
  210         struct mbuf *m = *mp, *t;
  211         struct ip6_hdr *ip6;
  212         struct ip6_frag *ip6f;
  213         struct ip6q *head, *q6;
  214         struct ip6asfrag *af6, *ip6af, *af6dwn;
  215         struct in6_ifaddr *ia;
  216         int offset = *offp, nxt, i, next;
  217         int first_frag = 0;
  218         int fragoff, frgpartlen;        /* must be larger than u_int16_t */
  219         uint32_t hashkey[(sizeof(struct in6_addr) * 2 +
  220                     sizeof(ip6f->ip6f_ident)) / sizeof(uint32_t)];
  221         uint32_t hash, *hashkeyp;
  222         struct ifnet *dstifp;
  223         u_int8_t ecn, ecn0;
  224 #ifdef RSS
  225         struct m_tag *mtag;
  226         struct ip6_direct_ctx *ip6dc;
  227 #endif
  228 
  229 #if 0
  230         char ip6buf[INET6_ADDRSTRLEN];
  231 #endif
  232 
  233         ip6 = mtod(m, struct ip6_hdr *);
  234 #ifndef PULLDOWN_TEST
  235         IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
  236         ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
  237 #else
  238         IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
  239         if (ip6f == NULL)
  240                 return (IPPROTO_DONE);
  241 #endif
  242 
  243         dstifp = NULL;
  244         /* find the destination interface of the packet. */
  245         ia = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
  246         if (ia != NULL) {
  247                 dstifp = ia->ia_ifp;
  248                 ifa_free(&ia->ia_ifa);
  249         }
  250         /* jumbo payload can't contain a fragment header */
  251         if (ip6->ip6_plen == 0) {
  252                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
  253                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  254                 return IPPROTO_DONE;
  255         }
  256 
  257         /*
  258          * check whether fragment packet's fragment length is
  259          * multiple of 8 octets.
  260          * sizeof(struct ip6_frag) == 8
  261          * sizeof(struct ip6_hdr) = 40
  262          */
  263         if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
  264             (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
  265                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  266                     offsetof(struct ip6_hdr, ip6_plen));
  267                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  268                 return IPPROTO_DONE;
  269         }
  270 
  271         IP6STAT_INC(ip6s_fragments);
  272         in6_ifstat_inc(dstifp, ifs6_reass_reqd);
  273 
  274         /* offset now points to data portion */
  275         offset += sizeof(struct ip6_frag);
  276 
  277         /*
  278          * RFC 6946: Handle "atomic" fragments (offset and m bit set to 0)
  279          * upfront, unrelated to any reassembly.  Just skip the fragment header.
  280          */
  281         if ((ip6f->ip6f_offlg & ~IP6F_RESERVED_MASK) == 0) {
  282                 /* XXX-BZ we want dedicated counters for this. */
  283                 IP6STAT_INC(ip6s_reassembled);
  284                 in6_ifstat_inc(dstifp, ifs6_reass_ok);
  285                 *offp = offset;
  286                 m->m_flags |= M_FRAGMENTED;
  287                 return (ip6f->ip6f_nxt);
  288         }
  289 
  290         /* Get fragment length and discard 0-byte fragments. */
  291         frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
  292         if (frgpartlen == 0) {
  293                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  294                     offsetof(struct ip6_hdr, ip6_plen));
  295                 in6_ifstat_inc(dstifp, ifs6_reass_fail);
  296                 IP6STAT_INC(ip6s_fragdropped);
  297                 return IPPROTO_DONE;
  298         }
  299 
  300         hashkeyp = hashkey;
  301         memcpy(hashkeyp, &ip6->ip6_src, sizeof(struct in6_addr));
  302         hashkeyp += sizeof(struct in6_addr) / sizeof(*hashkeyp);
  303         memcpy(hashkeyp, &ip6->ip6_dst, sizeof(struct in6_addr));
  304         hashkeyp += sizeof(struct in6_addr) / sizeof(*hashkeyp);
  305         *hashkeyp = ip6f->ip6f_ident;
  306         hash = jenkins_hash32(hashkey, nitems(hashkey), V_ip6q_hashseed);
  307         hash &= IP6REASS_HMASK;
  308         head = IP6Q_HEAD(hash);
  309         IP6Q_LOCK(hash);
  310 
  311         /*
  312          * Enforce upper bound on number of fragments.
  313          * If maxfrag is 0, never accept fragments.
  314          * If maxfrag is -1, accept all fragments without limitation.
  315          */
  316         if (ip6_maxfrags < 0)
  317                 ;
  318         else if (frag6_nfrags >= (u_int)ip6_maxfrags)
  319                 goto dropfrag;
  320 
  321         for (q6 = head->ip6q_next; q6 != head; q6 = q6->ip6q_next)
  322                 if (ip6f->ip6f_ident == q6->ip6q_ident &&
  323                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
  324                     IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst)
  325 #ifdef MAC
  326                     && mac_ip6q_match(m, q6)
  327 #endif
  328                     )
  329                         break;
  330 
  331         if (q6 == head) {
  332                 /*
  333                  * the first fragment to arrive, create a reassembly queue.
  334                  */
  335                 first_frag = 1;
  336 
  337                 /*
  338                  * Enforce upper bound on number of fragmented packets
  339                  * for which we attempt reassembly;
  340                  * If maxfragpackets is 0, never accept fragments.
  341                  * If maxfragpackets is -1, accept all fragments without
  342                  * limitation.
  343                  */
  344                 if (V_ip6_maxfragpackets < 0)
  345                         ;
  346                 else if (V_ip6q[hash].count >= V_ip6_maxfragbucketsize ||
  347                     V_frag6_nfragpackets >= (u_int)V_ip6_maxfragpackets)
  348                         goto dropfrag;
  349                 atomic_add_int(&V_frag6_nfragpackets, 1);
  350                 q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
  351                     M_NOWAIT);
  352                 if (q6 == NULL)
  353                         goto dropfrag;
  354                 bzero(q6, sizeof(*q6));
  355 #ifdef MAC
  356                 if (mac_ip6q_init(q6, M_NOWAIT) != 0) {
  357                         free(q6, M_FTABLE);
  358                         goto dropfrag;
  359                 }
  360                 mac_ip6q_create(m, q6);
  361 #endif
  362                 frag6_insque_head(q6, head, hash);
  363 
  364                 /* ip6q_nxt will be filled afterwards, from 1st fragment */
  365                 q6->ip6q_down   = q6->ip6q_up = (struct ip6asfrag *)q6;
  366 #ifdef notyet
  367                 q6->ip6q_nxtp   = (u_char *)nxtp;
  368 #endif
  369                 q6->ip6q_ident  = ip6f->ip6f_ident;
  370                 q6->ip6q_ttl    = IPV6_FRAGTTL;
  371                 q6->ip6q_src    = ip6->ip6_src;
  372                 q6->ip6q_dst    = ip6->ip6_dst;
  373                 q6->ip6q_ecn    =
  374                     (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  375                 q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */
  376 
  377                 q6->ip6q_nfrag = 0;
  378         }
  379 
  380         /*
  381          * If it's the 1st fragment, record the length of the
  382          * unfragmentable part and the next header of the fragment header.
  383          */
  384         fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
  385         if (fragoff == 0) {
  386                 q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) -
  387                     sizeof(struct ip6_frag);
  388                 q6->ip6q_nxt = ip6f->ip6f_nxt;
  389         }
  390 
  391         /*
  392          * Check that the reassembled packet would not exceed 65535 bytes
  393          * in size.
  394          * If it would exceed, discard the fragment and return an ICMP error.
  395          */
  396         if (q6->ip6q_unfrglen >= 0) {
  397                 /* The 1st fragment has already arrived. */
  398                 if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
  399                         icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  400                             offset - sizeof(struct ip6_frag) +
  401                             offsetof(struct ip6_frag, ip6f_offlg));
  402                         IP6Q_UNLOCK(hash);
  403                         return (IPPROTO_DONE);
  404                 }
  405         } else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
  406                 icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
  407                     offset - sizeof(struct ip6_frag) +
  408                     offsetof(struct ip6_frag, ip6f_offlg));
  409                 IP6Q_UNLOCK(hash);
  410                 return (IPPROTO_DONE);
  411         }
  412         /*
  413          * If it's the first fragment, do the above check for each
  414          * fragment already stored in the reassembly queue.
  415          */
  416         if (fragoff == 0) {
  417                 for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  418                      af6 = af6dwn) {
  419                         af6dwn = af6->ip6af_down;
  420 
  421                         if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
  422                             IPV6_MAXPACKET) {
  423                                 struct mbuf *merr = IP6_REASS_MBUF(af6);
  424                                 struct ip6_hdr *ip6err;
  425                                 int erroff = af6->ip6af_offset;
  426 
  427                                 /* dequeue the fragment. */
  428                                 frag6_deq(af6, hash);
  429                                 free(af6, M_FTABLE);
  430 
  431                                 /* adjust pointer. */
  432                                 ip6err = mtod(merr, struct ip6_hdr *);
  433 
  434                                 /*
  435                                  * Restore source and destination addresses
  436                                  * in the erroneous IPv6 header.
  437                                  */
  438                                 ip6err->ip6_src = q6->ip6q_src;
  439                                 ip6err->ip6_dst = q6->ip6q_dst;
  440 
  441                                 icmp6_error(merr, ICMP6_PARAM_PROB,
  442                                     ICMP6_PARAMPROB_HEADER,
  443                                     erroff - sizeof(struct ip6_frag) +
  444                                     offsetof(struct ip6_frag, ip6f_offlg));
  445                         }
  446                 }
  447         }
  448 
  449         ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
  450             M_NOWAIT);
  451         if (ip6af == NULL)
  452                 goto dropfrag;
  453         bzero(ip6af, sizeof(*ip6af));
  454         ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
  455         ip6af->ip6af_off = fragoff;
  456         ip6af->ip6af_frglen = frgpartlen;
  457         ip6af->ip6af_offset = offset;
  458         IP6_REASS_MBUF(ip6af) = m;
  459 
  460         if (first_frag) {
  461                 af6 = (struct ip6asfrag *)q6;
  462                 goto insert;
  463         }
  464 
  465         /*
  466          * Handle ECN by comparing this segment with the first one;
  467          * if CE is set, do not lose CE.
  468          * drop if CE and not-ECT are mixed for the same packet.
  469          */
  470         ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK;
  471         ecn0 = q6->ip6q_ecn;
  472         if (ecn == IPTOS_ECN_CE) {
  473                 if (ecn0 == IPTOS_ECN_NOTECT) {
  474                         free(ip6af, M_FTABLE);
  475                         goto dropfrag;
  476                 }
  477                 if (ecn0 != IPTOS_ECN_CE)
  478                         q6->ip6q_ecn = IPTOS_ECN_CE;
  479         }
  480         if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) {
  481                 free(ip6af, M_FTABLE);
  482                 goto dropfrag;
  483         }
  484 
  485         /*
  486          * Find a segment which begins after this one does.
  487          */
  488         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  489              af6 = af6->ip6af_down)
  490                 if (af6->ip6af_off > ip6af->ip6af_off)
  491                         break;
  492 
  493 #if 0
  494         /*
  495          * If there is a preceding segment, it may provide some of
  496          * our data already.  If so, drop the data from the incoming
  497          * segment.  If it provides all of our data, drop us.
  498          */
  499         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  500                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  501                         - ip6af->ip6af_off;
  502                 if (i > 0) {
  503                         if (i >= ip6af->ip6af_frglen)
  504                                 goto dropfrag;
  505                         m_adj(IP6_REASS_MBUF(ip6af), i);
  506                         ip6af->ip6af_off += i;
  507                         ip6af->ip6af_frglen -= i;
  508                 }
  509         }
  510 
  511         /*
  512          * While we overlap succeeding segments trim them or,
  513          * if they are completely covered, dequeue them.
  514          */
  515         while (af6 != (struct ip6asfrag *)q6 &&
  516                ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
  517                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  518                 if (i < af6->ip6af_frglen) {
  519                         af6->ip6af_frglen -= i;
  520                         af6->ip6af_off += i;
  521                         m_adj(IP6_REASS_MBUF(af6), i);
  522                         break;
  523                 }
  524                 af6 = af6->ip6af_down;
  525                 m_freem(IP6_REASS_MBUF(af6->ip6af_up));
  526                 frag6_deq(af6->ip6af_up, hash);
  527         }
  528 #else
  529         /*
  530          * If the incoming framgent overlaps some existing fragments in
  531          * the reassembly queue, drop it, since it is dangerous to override
  532          * existing fragments from a security point of view.
  533          * We don't know which fragment is the bad guy - here we trust
  534          * fragment that came in earlier, with no real reason.
  535          *
  536          * Note: due to changes after disabling this part, mbuf passed to
  537          * m_adj() below now does not meet the requirement.
  538          */
  539         if (af6->ip6af_up != (struct ip6asfrag *)q6) {
  540                 i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
  541                         - ip6af->ip6af_off;
  542                 if (i > 0) {
  543 #if 0                           /* suppress the noisy log */
  544                         log(LOG_ERR, "%d bytes of a fragment from %s "
  545                             "overlaps the previous fragment\n",
  546                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  547 #endif
  548                         free(ip6af, M_FTABLE);
  549                         goto dropfrag;
  550                 }
  551         }
  552         if (af6 != (struct ip6asfrag *)q6) {
  553                 i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
  554                 if (i > 0) {
  555 #if 0                           /* suppress the noisy log */
  556                         log(LOG_ERR, "%d bytes of a fragment from %s "
  557                             "overlaps the succeeding fragment",
  558                             i, ip6_sprintf(ip6buf, &q6->ip6q_src));
  559 #endif
  560                         free(ip6af, M_FTABLE);
  561                         goto dropfrag;
  562                 }
  563         }
  564 #endif
  565 
  566 insert:
  567 #ifdef MAC
  568         if (!first_frag)
  569                 mac_ip6q_update(m, q6);
  570 #endif
  571 
  572         /*
  573          * Stick new segment in its place;
  574          * check for complete reassembly.
  575          * If not complete, check fragment limit.
  576          * Move to front of packet queue, as we are
  577          * the most recently active fragmented packet.
  578          */
  579         frag6_enq(ip6af, af6->ip6af_up, hash);
  580         atomic_add_int(&frag6_nfrags, 1);
  581         q6->ip6q_nfrag++;
  582 #if 0 /* xxx */
  583         if (q6 != head->ip6q_next) {
  584                 frag6_remque(q6, hash);
  585                 frag6_insque_head(q6, head, hash);
  586         }
  587 #endif
  588         next = 0;
  589         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  590              af6 = af6->ip6af_down) {
  591                 if (af6->ip6af_off != next) {
  592                         if (q6->ip6q_nfrag > V_ip6_maxfragsperpacket) {
  593                                 IP6STAT_INC(ip6s_fragdropped);
  594                                 frag6_freef(q6, hash);
  595                         }
  596                         IP6Q_UNLOCK(hash);
  597                         return IPPROTO_DONE;
  598                 }
  599                 next += af6->ip6af_frglen;
  600         }
  601         if (af6->ip6af_up->ip6af_mff) {
  602                 if (q6->ip6q_nfrag > V_ip6_maxfragsperpacket) {
  603                         IP6STAT_INC(ip6s_fragdropped);
  604                         frag6_freef(q6, hash);
  605                 }
  606                 IP6Q_UNLOCK(hash);
  607                 return IPPROTO_DONE;
  608         }
  609 
  610         /*
  611          * Reassembly is complete; concatenate fragments.
  612          */
  613         ip6af = q6->ip6q_down;
  614         t = m = IP6_REASS_MBUF(ip6af);
  615         af6 = ip6af->ip6af_down;
  616         frag6_deq(ip6af, hash);
  617         while (af6 != (struct ip6asfrag *)q6) {
  618                 m->m_pkthdr.csum_flags &=
  619                     IP6_REASS_MBUF(af6)->m_pkthdr.csum_flags;
  620                 m->m_pkthdr.csum_data +=
  621                     IP6_REASS_MBUF(af6)->m_pkthdr.csum_data;
  622 
  623                 af6dwn = af6->ip6af_down;
  624                 frag6_deq(af6, hash);
  625                 while (t->m_next)
  626                         t = t->m_next;
  627                 m_adj(IP6_REASS_MBUF(af6), af6->ip6af_offset);
  628                 m_demote_pkthdr(IP6_REASS_MBUF(af6));
  629                 m_cat(t, IP6_REASS_MBUF(af6));
  630                 free(af6, M_FTABLE);
  631                 af6 = af6dwn;
  632         }
  633 
  634         while (m->m_pkthdr.csum_data & 0xffff0000)
  635                 m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
  636                     (m->m_pkthdr.csum_data >> 16);
  637 
  638         /* adjust offset to point where the original next header starts */
  639         offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
  640         free(ip6af, M_FTABLE);
  641         ip6 = mtod(m, struct ip6_hdr *);
  642         ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
  643         if (q6->ip6q_ecn == IPTOS_ECN_CE)
  644                 ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20);
  645         nxt = q6->ip6q_nxt;
  646 #ifdef notyet
  647         *q6->ip6q_nxtp = (u_char)(nxt & 0xff);
  648 #endif
  649 
  650         if (ip6_deletefraghdr(m, offset, M_NOWAIT) != 0) {
  651                 frag6_remque(q6, hash);
  652                 atomic_subtract_int(&frag6_nfrags, q6->ip6q_nfrag);
  653 #ifdef MAC
  654                 mac_ip6q_destroy(q6);
  655 #endif
  656                 free(q6, M_FTABLE);
  657                 atomic_subtract_int(&V_frag6_nfragpackets, 1);
  658 
  659                 goto dropfrag;
  660         }
  661 
  662         /*
  663          * Store NXT to the original.
  664          */
  665         m_copyback(m, ip6_get_prevhdr(m, offset), sizeof(uint8_t),
  666             (caddr_t)&nxt);
  667 
  668         frag6_remque(q6, hash);
  669         atomic_subtract_int(&frag6_nfrags, q6->ip6q_nfrag);
  670 #ifdef MAC
  671         mac_ip6q_reassemble(q6, m);
  672         mac_ip6q_destroy(q6);
  673 #endif
  674         free(q6, M_FTABLE);
  675         atomic_subtract_int(&V_frag6_nfragpackets, 1);
  676 
  677         if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
  678                 int plen = 0;
  679                 for (t = m; t; t = t->m_next)
  680                         plen += t->m_len;
  681                 m->m_pkthdr.len = plen;
  682         }
  683 
  684 #ifdef RSS
  685         mtag = m_tag_alloc(MTAG_ABI_IPV6, IPV6_TAG_DIRECT, sizeof(*ip6dc),
  686             M_NOWAIT);
  687         if (mtag == NULL)
  688                 goto dropfrag;
  689 
  690         ip6dc = (struct ip6_direct_ctx *)(mtag + 1);
  691         ip6dc->ip6dc_nxt = nxt;
  692         ip6dc->ip6dc_off = offset;
  693 
  694         m_tag_prepend(m, mtag);
  695 #endif
  696 
  697         IP6Q_UNLOCK(hash);
  698         IP6STAT_INC(ip6s_reassembled);
  699         in6_ifstat_inc(dstifp, ifs6_reass_ok);
  700 
  701 #ifdef RSS
  702         /*
  703          * Queue/dispatch for reprocessing.
  704          */
  705         netisr_dispatch(NETISR_IPV6_DIRECT, m);
  706         return IPPROTO_DONE;
  707 #endif
  708 
  709         /*
  710          * Tell launch routine the next header
  711          */
  712 
  713         *mp = m;
  714         *offp = offset;
  715 
  716         return nxt;
  717 
  718  dropfrag:
  719         IP6Q_UNLOCK(hash);
  720         in6_ifstat_inc(dstifp, ifs6_reass_fail);
  721         IP6STAT_INC(ip6s_fragdropped);
  722         m_freem(m);
  723         return IPPROTO_DONE;
  724 }
  725 
  726 /*
  727  * Free a fragment reassembly header and all
  728  * associated datagrams.
  729  */
  730 static void
  731 frag6_freef(struct ip6q *q6, uint32_t bucket)
  732 {
  733         struct ip6asfrag *af6, *down6;
  734 
  735         IP6Q_LOCK_ASSERT(bucket);
  736 
  737         for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
  738              af6 = down6) {
  739                 struct mbuf *m = IP6_REASS_MBUF(af6);
  740 
  741                 down6 = af6->ip6af_down;
  742                 frag6_deq(af6, bucket);
  743 
  744                 /*
  745                  * Return ICMP time exceeded error for the 1st fragment.
  746                  * Just free other fragments.
  747                  */
  748                 if (af6->ip6af_off == 0) {
  749                         struct ip6_hdr *ip6;
  750 
  751                         /* adjust pointer */
  752                         ip6 = mtod(m, struct ip6_hdr *);
  753 
  754                         /* restore source and destination addresses */
  755                         ip6->ip6_src = q6->ip6q_src;
  756                         ip6->ip6_dst = q6->ip6q_dst;
  757 
  758                         icmp6_error(m, ICMP6_TIME_EXCEEDED,
  759                                     ICMP6_TIME_EXCEED_REASSEMBLY, 0);
  760                 } else
  761                         m_freem(m);
  762                 free(af6, M_FTABLE);
  763         }
  764         frag6_remque(q6, bucket);
  765         atomic_subtract_int(&frag6_nfrags, q6->ip6q_nfrag);
  766 #ifdef MAC
  767         mac_ip6q_destroy(q6);
  768 #endif
  769         free(q6, M_FTABLE);
  770         atomic_subtract_int(&V_frag6_nfragpackets, 1);
  771 }
  772 
  773 /*
  774  * Put an ip fragment on a reassembly chain.
  775  * Like insque, but pointers in middle of structure.
  776  */
  777 static void
  778 frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6,
  779     uint32_t bucket __unused)
  780 {
  781 
  782         IP6Q_LOCK_ASSERT(bucket);
  783 
  784         af6->ip6af_up = up6;
  785         af6->ip6af_down = up6->ip6af_down;
  786         up6->ip6af_down->ip6af_up = af6;
  787         up6->ip6af_down = af6;
  788 }
  789 
  790 /*
  791  * To frag6_enq as remque is to insque.
  792  */
  793 static void
  794 frag6_deq(struct ip6asfrag *af6, uint32_t bucket __unused)
  795 {
  796 
  797         IP6Q_LOCK_ASSERT(bucket);
  798 
  799         af6->ip6af_up->ip6af_down = af6->ip6af_down;
  800         af6->ip6af_down->ip6af_up = af6->ip6af_up;
  801 }
  802 
  803 static void
  804 frag6_insque_head(struct ip6q *new, struct ip6q *old, uint32_t bucket)
  805 {
  806 
  807         IP6Q_LOCK_ASSERT(bucket);
  808         KASSERT(IP6Q_HEAD(bucket) == old,
  809             ("%s: attempt to insert at head of wrong bucket"
  810             " (bucket=%u, old=%p)", __func__, bucket, old));
  811 
  812         new->ip6q_prev = old;
  813         new->ip6q_next = old->ip6q_next;
  814         old->ip6q_next->ip6q_prev= new;
  815         old->ip6q_next = new;
  816         V_ip6q[bucket].count++;
  817 }
  818 
  819 static void
  820 frag6_remque(struct ip6q *p6, uint32_t bucket)
  821 {
  822 
  823         IP6Q_LOCK_ASSERT(bucket);
  824 
  825         p6->ip6q_prev->ip6q_next = p6->ip6q_next;
  826         p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
  827         V_ip6q[bucket].count--;
  828 }
  829 
  830 /*
  831  * IPv6 reassembling timer processing;
  832  * if a timer expires on a reassembly
  833  * queue, discard it.
  834  */
  835 void
  836 frag6_slowtimo(void)
  837 {
  838         VNET_ITERATOR_DECL(vnet_iter);
  839         struct ip6q *head, *q6;
  840         int i;
  841 
  842         VNET_LIST_RLOCK_NOSLEEP();
  843         VNET_FOREACH(vnet_iter) {
  844                 CURVNET_SET(vnet_iter);
  845                 for (i = 0; i < IP6REASS_NHASH; i++) {
  846                         IP6Q_LOCK(i);
  847                         head = IP6Q_HEAD(i);
  848                         q6 = head->ip6q_next;
  849                         if (q6 == NULL) {
  850                                 /*
  851                                  * XXXJTL: This should never happen. This
  852                                  * should turn into an assertion.
  853                                  */
  854                                 IP6Q_UNLOCK(i);
  855                                 continue;
  856                         }
  857                         while (q6 != head) {
  858                                 --q6->ip6q_ttl;
  859                                 q6 = q6->ip6q_next;
  860                                 if (q6->ip6q_prev->ip6q_ttl == 0) {
  861                                         IP6STAT_INC(ip6s_fragtimeout);
  862                                         /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  863                                         frag6_freef(q6->ip6q_prev, i);
  864                                 }
  865                         }
  866                         /*
  867                          * If we are over the maximum number of fragments
  868                          * (due to the limit being lowered), drain off
  869                          * enough to get down to the new limit.
  870                          * Note that we drain all reassembly queues if
  871                          * maxfragpackets is 0 (fragmentation is disabled),
  872                          * and don't enforce a limit when maxfragpackets
  873                          * is negative.
  874                          */
  875                         while ((V_ip6_maxfragpackets == 0 ||
  876                             (V_ip6_maxfragpackets > 0 &&
  877                             V_ip6q[i].count > V_ip6_maxfragbucketsize)) &&
  878                             head->ip6q_prev != head) {
  879                                 IP6STAT_INC(ip6s_fragoverflow);
  880                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  881                                 frag6_freef(head->ip6q_prev, i);
  882                         }
  883                         IP6Q_UNLOCK(i);
  884                 }
  885                 /*
  886                  * If we are still over the maximum number of fragmented
  887                  * packets, drain off enough to get down to the new limit.
  888                  */
  889                 i = 0;
  890                 while (V_ip6_maxfragpackets >= 0 &&
  891                     V_frag6_nfragpackets > (u_int)V_ip6_maxfragpackets) {
  892                         IP6Q_LOCK(i);
  893                         head = IP6Q_HEAD(i);
  894                         if (head->ip6q_prev != head) {
  895                                 IP6STAT_INC(ip6s_fragoverflow);
  896                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  897                                 frag6_freef(head->ip6q_prev, i);
  898                         }
  899                         IP6Q_UNLOCK(i);
  900                         i = (i + 1) % IP6REASS_NHASH;
  901                 }
  902                 CURVNET_RESTORE();
  903         }
  904         VNET_LIST_RUNLOCK_NOSLEEP();
  905 }
  906 
  907 /*
  908  * Drain off all datagram fragments.
  909  */
  910 void
  911 frag6_drain(void)
  912 {
  913         VNET_ITERATOR_DECL(vnet_iter);
  914         struct ip6q *head;
  915         int i;
  916 
  917         VNET_LIST_RLOCK_NOSLEEP();
  918         VNET_FOREACH(vnet_iter) {
  919                 CURVNET_SET(vnet_iter);
  920                 for (i = 0; i < IP6REASS_NHASH; i++) {
  921                         if (IP6Q_TRYLOCK(i) == 0)
  922                                 continue;
  923                         head = IP6Q_HEAD(i);
  924                         while (head->ip6q_next != head) {
  925                                 IP6STAT_INC(ip6s_fragdropped);
  926                                 /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
  927                                 frag6_freef(head->ip6q_next, i);
  928                         }
  929                         IP6Q_UNLOCK(i);
  930                 }
  931                 CURVNET_RESTORE();
  932         }
  933         VNET_LIST_RUNLOCK_NOSLEEP();
  934 }
  935 
  936 int
  937 ip6_deletefraghdr(struct mbuf *m, int offset, int wait)
  938 {
  939         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  940         struct mbuf *t;
  941 
  942         /* Delete frag6 header. */
  943         if (m->m_len >= offset + sizeof(struct ip6_frag)) {
  944                 /* This is the only possible case with !PULLDOWN_TEST. */
  945                 bcopy(ip6, (char *)ip6 + sizeof(struct ip6_frag),
  946                     offset);
  947                 m->m_data += sizeof(struct ip6_frag);
  948                 m->m_len -= sizeof(struct ip6_frag);
  949         } else {
  950                 /* This comes with no copy if the boundary is on cluster. */
  951                 if ((t = m_split(m, offset, wait)) == NULL)
  952                         return (ENOMEM);
  953                 m_adj(t, sizeof(struct ip6_frag));
  954                 m_cat(m, t);
  955         }
  956 
  957         m->m_flags |= M_FRAGMENTED;
  958         return (0);
  959 }

Cache object: c15eeaecaf1c919da9f8b2226c75ef96


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