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sys/netinet6/ip6_forward.c

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    1 /*      $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.16 2002/10/16 02:25:05 sam Exp $   */
    2 /*      $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 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 "opt_ip6fw.h"
   34 #include "opt_inet.h"
   35 #include "opt_inet6.h"
   36 #include "opt_ipsec.h"
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h>
   40 #include <sys/malloc.h>
   41 #include <sys/mbuf.h>
   42 #include <sys/domain.h>
   43 #include <sys/protosw.h>
   44 #include <sys/socket.h>
   45 #include <sys/errno.h>
   46 #include <sys/time.h>
   47 #include <sys/kernel.h>
   48 #include <sys/syslog.h>
   49 
   50 #include <net/if.h>
   51 #include <net/route.h>
   52 #ifdef PFIL_HOOKS
   53 #include <net/pfil.h>
   54 #endif
   55 
   56 #include <netinet/in.h>
   57 #include <netinet/in_var.h>
   58 #include <netinet/in_systm.h>
   59 #include <netinet/ip.h>
   60 #include <netinet/ip_var.h>
   61 #include <netinet6/in6_var.h>
   62 #include <netinet/ip6.h>
   63 #include <netinet6/ip6_var.h>
   64 #include <netinet/icmp6.h>
   65 #include <netinet6/nd6.h>
   66 
   67 #include <netinet/in_pcb.h>
   68 
   69 #ifdef IPSEC
   70 #include <netinet6/ipsec.h>
   71 #ifdef INET6
   72 #include <netinet6/ipsec6.h>
   73 #endif
   74 #include <netkey/key.h>
   75 #endif /* IPSEC */
   76 
   77 #ifdef FAST_IPSEC
   78 #include <netipsec/ipsec.h>
   79 #include <netipsec/ipsec6.h>
   80 #include <netipsec/key.h>
   81 #define IPSEC
   82 #endif /* FAST_IPSEC */
   83 
   84 #include <netinet6/ip6_fw.h>
   85 
   86 #include <net/net_osdep.h>
   87 
   88 #include <netinet6/ip6protosw.h>
   89 
   90 struct  route_in6 ip6_forward_rt;
   91 
   92 /*
   93  * Forward a packet.  If some error occurs return the sender
   94  * an icmp packet.  Note we can't always generate a meaningful
   95  * icmp message because icmp doesn't have a large enough repertoire
   96  * of codes and types.
   97  *
   98  * If not forwarding, just drop the packet.  This could be confusing
   99  * if ipforwarding was zero but some routing protocol was advancing
  100  * us as a gateway to somewhere.  However, we must let the routing
  101  * protocol deal with that.
  102  *
  103  */
  104 
  105 void
  106 ip6_forward(m, srcrt)
  107         struct mbuf *m;
  108         int srcrt;
  109 {
  110         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  111         struct sockaddr_in6 *dst;
  112         struct rtentry *rt;
  113         int error, type = 0, code = 0;
  114         struct mbuf *mcopy = NULL;
  115         struct ifnet *origifp;  /* maybe unnecessary */
  116 #ifdef PFIL_HOOKS
  117         struct packet_filter_hook *pfh;
  118         struct mbuf *m1;
  119         int rv;
  120 #endif /* PFIL_HOOKS */
  121 #ifdef IPSEC
  122         struct secpolicy *sp = NULL;
  123 #endif
  124 
  125 #ifdef IPSEC
  126         /*
  127          * Check AH/ESP integrity.
  128          */
  129         /*
  130          * Don't increment ip6s_cantforward because this is the check
  131          * before forwarding packet actually.
  132          */
  133         if (ipsec6_in_reject(m, NULL)) {
  134 #if !defined(FAST_IPSEC)
  135                 ipsec6stat.in_polvio++;
  136 #endif
  137                 m_freem(m);
  138                 return;
  139         }
  140 #endif /* IPSEC */
  141 
  142         /*
  143          * Do not forward packets to multicast destination (should be handled
  144          * by ip6_mforward().
  145          * Do not forward packets with unspecified source.  It was discussed
  146          * in July 2000, on ipngwg mailing list.
  147          */
  148         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
  149             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
  150             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
  151                 ip6stat.ip6s_cantforward++;
  152                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
  153                 if (ip6_log_time + ip6_log_interval < time_second) {
  154                         ip6_log_time = time_second;
  155                         log(LOG_DEBUG,
  156                             "cannot forward "
  157                             "from %s to %s nxt %d received on %s\n",
  158                             ip6_sprintf(&ip6->ip6_src),
  159                             ip6_sprintf(&ip6->ip6_dst),
  160                             ip6->ip6_nxt,
  161                             if_name(m->m_pkthdr.rcvif));
  162                 }
  163                 m_freem(m);
  164                 return;
  165         }
  166 
  167         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
  168                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
  169                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
  170                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
  171                 return;
  172         }
  173         ip6->ip6_hlim -= IPV6_HLIMDEC;
  174 
  175         /*
  176          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
  177          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
  178          * we need to generate an ICMP6 message to the src.
  179          * Thanks to M_EXT, in most cases copy will not occur.
  180          *
  181          * It is important to save it before IPsec processing as IPsec
  182          * processing may modify the mbuf.
  183          */
  184         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
  185 
  186 #ifdef IPSEC
  187         /* get a security policy for this packet */
  188         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
  189             &error);
  190         if (sp == NULL) {
  191                 ipsec6stat.out_inval++;
  192                 ip6stat.ip6s_cantforward++;
  193                 if (mcopy) {
  194 #if 0
  195                         /* XXX: what icmp ? */
  196 #else
  197                         m_freem(mcopy);
  198 #endif
  199                 }
  200                 m_freem(m);
  201                 return;
  202         }
  203 
  204         error = 0;
  205 
  206         /* check policy */
  207         switch (sp->policy) {
  208         case IPSEC_POLICY_DISCARD:
  209                 /*
  210                  * This packet is just discarded.
  211                  */
  212                 ipsec6stat.out_polvio++;
  213                 ip6stat.ip6s_cantforward++;
  214                 key_freesp(sp);
  215                 if (mcopy) {
  216 #if 0
  217                         /* XXX: what icmp ? */
  218 #else
  219                         m_freem(mcopy);
  220 #endif
  221                 }
  222                 m_freem(m);
  223                 return;
  224 
  225         case IPSEC_POLICY_BYPASS:
  226         case IPSEC_POLICY_NONE:
  227                 /* no need to do IPsec. */
  228                 key_freesp(sp);
  229                 goto skip_ipsec;
  230 
  231         case IPSEC_POLICY_IPSEC:
  232                 if (sp->req == NULL) {
  233                         /* XXX should be panic ? */
  234                         printf("ip6_forward: No IPsec request specified.\n");
  235                         ip6stat.ip6s_cantforward++;
  236                         key_freesp(sp);
  237                         if (mcopy) {
  238 #if 0
  239                                 /* XXX: what icmp ? */
  240 #else
  241                                 m_freem(mcopy);
  242 #endif
  243                         }
  244                         m_freem(m);
  245                         return;
  246                 }
  247                 /* do IPsec */
  248                 break;
  249 
  250         case IPSEC_POLICY_ENTRUST:
  251         default:
  252                 /* should be panic ?? */
  253                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
  254                 key_freesp(sp);
  255                 goto skip_ipsec;
  256         }
  257 
  258     {
  259         struct ipsec_output_state state;
  260 
  261         /*
  262          * All the extension headers will become inaccessible
  263          * (since they can be encrypted).
  264          * Don't panic, we need no more updates to extension headers
  265          * on inner IPv6 packet (since they are now encapsulated).
  266          *
  267          * IPv6 [ESP|AH] IPv6 [extension headers] payload
  268          */
  269         bzero(&state, sizeof(state));
  270         state.m = m;
  271         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
  272         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
  273 
  274         error = ipsec6_output_tunnel(&state, sp, 0);
  275 
  276         m = state.m;
  277         key_freesp(sp);
  278 
  279         if (error) {
  280                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
  281                 switch (error) {
  282                 case EHOSTUNREACH:
  283                 case ENETUNREACH:
  284                 case EMSGSIZE:
  285                 case ENOBUFS:
  286                 case ENOMEM:
  287                         break;
  288                 default:
  289                         printf("ip6_output (ipsec): error code %d\n", error);
  290                         /* fall through */
  291                 case ENOENT:
  292                         /* don't show these error codes to the user */
  293                         break;
  294                 }
  295                 ip6stat.ip6s_cantforward++;
  296                 if (mcopy) {
  297 #if 0
  298                         /* XXX: what icmp ? */
  299 #else
  300                         m_freem(mcopy);
  301 #endif
  302                 }
  303                 m_freem(m);
  304                 return;
  305         }
  306     }
  307     skip_ipsec:
  308 #endif /* IPSEC */
  309 
  310         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
  311         if (!srcrt) {
  312                 /*
  313                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
  314                  */
  315                 if (ip6_forward_rt.ro_rt == 0 ||
  316                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
  317                         if (ip6_forward_rt.ro_rt) {
  318                                 RTFREE(ip6_forward_rt.ro_rt);
  319                                 ip6_forward_rt.ro_rt = 0;
  320                         }
  321                         /* this probably fails but give it a try again */
  322                         rtalloc_ign((struct route *)&ip6_forward_rt,
  323                                     RTF_PRCLONING);
  324                 }
  325 
  326                 if (ip6_forward_rt.ro_rt == 0) {
  327                         ip6stat.ip6s_noroute++;
  328                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
  329                         if (mcopy) {
  330                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
  331                                             ICMP6_DST_UNREACH_NOROUTE, 0);
  332                         }
  333                         m_freem(m);
  334                         return;
  335                 }
  336         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
  337                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
  338                 if (ip6_forward_rt.ro_rt) {
  339                         RTFREE(ip6_forward_rt.ro_rt);
  340                         ip6_forward_rt.ro_rt = 0;
  341                 }
  342                 bzero(dst, sizeof(*dst));
  343                 dst->sin6_len = sizeof(struct sockaddr_in6);
  344                 dst->sin6_family = AF_INET6;
  345                 dst->sin6_addr = ip6->ip6_dst;
  346 
  347                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
  348                 if (ip6_forward_rt.ro_rt == 0) {
  349                         ip6stat.ip6s_noroute++;
  350                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
  351                         if (mcopy) {
  352                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
  353                                             ICMP6_DST_UNREACH_NOROUTE, 0);
  354                         }
  355                         m_freem(m);
  356                         return;
  357                 }
  358         }
  359         rt = ip6_forward_rt.ro_rt;
  360 
  361         /*
  362          * Scope check: if a packet can't be delivered to its destination
  363          * for the reason that the destination is beyond the scope of the
  364          * source address, discard the packet and return an icmp6 destination
  365          * unreachable error with Code 2 (beyond scope of source address).
  366          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
  367          */
  368         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
  369             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
  370                 ip6stat.ip6s_cantforward++;
  371                 ip6stat.ip6s_badscope++;
  372                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
  373 
  374                 if (ip6_log_time + ip6_log_interval < time_second) {
  375                         ip6_log_time = time_second;
  376                         log(LOG_DEBUG,
  377                             "cannot forward "
  378                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
  379                             ip6_sprintf(&ip6->ip6_src),
  380                             ip6_sprintf(&ip6->ip6_dst),
  381                             ip6->ip6_nxt,
  382                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
  383                 }
  384                 if (mcopy)
  385                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
  386                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
  387                 m_freem(m);
  388                 return;
  389         }
  390 
  391         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
  392                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
  393                 if (mcopy) {
  394                         u_long mtu;
  395 #ifdef IPSEC
  396                         struct secpolicy *sp;
  397                         int ipsecerror;
  398                         size_t ipsechdrsiz;
  399 #endif
  400 
  401                         mtu = rt->rt_ifp->if_mtu;
  402 #ifdef IPSEC
  403                         /*
  404                          * When we do IPsec tunnel ingress, we need to play
  405                          * with if_mtu value (decrement IPsec header size
  406                          * from mtu value).  The code is much simpler than v4
  407                          * case, as we have the outgoing interface for
  408                          * encapsulated packet as "rt->rt_ifp".
  409                          */
  410                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
  411                                 IP_FORWARDING, &ipsecerror);
  412                         if (sp) {
  413                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
  414                                         IPSEC_DIR_OUTBOUND, NULL);
  415                                 if (ipsechdrsiz < mtu)
  416                                         mtu -= ipsechdrsiz;
  417                         }
  418 
  419                         /*
  420                          * if mtu becomes less than minimum MTU,
  421                          * tell minimum MTU (and I'll need to fragment it).
  422                          */
  423                         if (mtu < IPV6_MMTU)
  424                                 mtu = IPV6_MMTU;
  425 #endif
  426                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
  427                 }
  428                 m_freem(m);
  429                 return;
  430         }
  431 
  432         if (rt->rt_flags & RTF_GATEWAY)
  433                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
  434 
  435         /*
  436          * If we are to forward the packet using the same interface
  437          * as one we got the packet from, perhaps we should send a redirect
  438          * to sender to shortcut a hop.
  439          * Only send redirect if source is sending directly to us,
  440          * and if packet was not source routed (or has any options).
  441          * Also, don't send redirect if forwarding using a route
  442          * modified by a redirect.
  443          */
  444         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
  445             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
  446                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
  447                         /*
  448                          * If the incoming interface is equal to the outgoing
  449                          * one, and the link attached to the interface is
  450                          * point-to-point, then it will be highly probable
  451                          * that a routing loop occurs. Thus, we immediately
  452                          * drop the packet and send an ICMPv6 error message.
  453                          *
  454                          * type/code is based on suggestion by Rich Draves.
  455                          * not sure if it is the best pick.
  456                          */
  457                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
  458                                     ICMP6_DST_UNREACH_ADDR, 0);
  459                         m_freem(m);
  460                         return;
  461                 }
  462                 type = ND_REDIRECT;
  463         }
  464 
  465         /*
  466          * Check with the firewall...
  467          */
  468         if (ip6_fw_enable && ip6_fw_chk_ptr) {
  469                 u_short port = 0;
  470                 /* If ipfw says divert, we have to just drop packet */
  471                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
  472                         m_freem(m);
  473                         goto freecopy;
  474                 }
  475                 if (!m)
  476                         goto freecopy;
  477         }
  478 
  479         /*
  480          * Fake scoped addresses. Note that even link-local source or
  481          * destinaion can appear, if the originating node just sends the
  482          * packet to us (without address resolution for the destination).
  483          * Since both icmp6_error and icmp6_redirect_output fill the embedded
  484          * link identifiers, we can do this stuff after making a copy for
  485          * returning an error.
  486          */
  487         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
  488                 /*
  489                  * See corresponding comments in ip6_output.
  490                  * XXX: but is it possible that ip6_forward() sends a packet
  491                  *      to a loopback interface? I don't think so, and thus
  492                  *      I bark here. (jinmei@kame.net)
  493                  * XXX: it is common to route invalid packets to loopback.
  494                  *      also, the codepath will be visited on use of ::1 in
  495                  *      rthdr. (itojun)
  496                  */
  497 #if 1
  498                 if (0)
  499 #else
  500                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
  501 #endif
  502                 {
  503                         printf("ip6_forward: outgoing interface is loopback. "
  504                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
  505                                 ip6_sprintf(&ip6->ip6_src),
  506                                 ip6_sprintf(&ip6->ip6_dst),
  507                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
  508                                 if_name(rt->rt_ifp));
  509                 }
  510 
  511                 /* we can just use rcvif in forwarding. */
  512                 origifp = m->m_pkthdr.rcvif;
  513         }
  514         else
  515                 origifp = rt->rt_ifp;
  516 #ifndef SCOPEDROUTING
  517         /*
  518          * clear embedded scope identifiers if necessary.
  519          * in6_clearscope will touch the addresses only when necessary.
  520          */
  521         in6_clearscope(&ip6->ip6_src);
  522         in6_clearscope(&ip6->ip6_dst);
  523 #endif
  524 
  525 #ifdef PFIL_HOOKS
  526         /*
  527          * Run through list of hooks for output packets.
  528          */
  529         m1 = m;
  530         pfh = pfil_hook_get(PFIL_OUT, &inet6sw[ip6_protox[IPPROTO_IPV6]].pr_pfh);
  531         for (; pfh; pfh = pfh->pfil_link.tqe_next)
  532                 if (pfh->pfil_func) {
  533                         rv = pfh->pfil_func(ip6, sizeof(*ip6),
  534                                             rt->rt_ifp, 1, &m1);
  535                         if (rv) {
  536                                 error = EHOSTUNREACH;
  537                                 goto freecopy;
  538                         }
  539                         m = m1;
  540                         if (m == NULL)
  541                                 goto freecopy;
  542                         ip6 = mtod(m, struct ip6_hdr *);
  543                 }
  544 #endif /* PFIL_HOOKS */
  545 
  546         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
  547         if (error) {
  548                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
  549                 ip6stat.ip6s_cantforward++;
  550         } else {
  551                 ip6stat.ip6s_forward++;
  552                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
  553                 if (type)
  554                         ip6stat.ip6s_redirectsent++;
  555                 else {
  556                         if (mcopy)
  557                                 goto freecopy;
  558                 }
  559         }
  560         if (mcopy == NULL)
  561                 return;
  562         switch (error) {
  563         case 0:
  564 #if 1
  565                 if (type == ND_REDIRECT) {
  566                         icmp6_redirect_output(mcopy, rt);
  567                         return;
  568                 }
  569 #endif
  570                 goto freecopy;
  571 
  572         case EMSGSIZE:
  573                 /* xxx MTU is constant in PPP? */
  574                 goto freecopy;
  575 
  576         case ENOBUFS:
  577                 /* Tell source to slow down like source quench in IP? */
  578                 goto freecopy;
  579 
  580         case ENETUNREACH:       /* shouldn't happen, checked above */
  581         case EHOSTUNREACH:
  582         case ENETDOWN:
  583         case EHOSTDOWN:
  584         default:
  585                 type = ICMP6_DST_UNREACH;
  586                 code = ICMP6_DST_UNREACH_ADDR;
  587                 break;
  588         }
  589         icmp6_error(mcopy, type, code, 0);
  590         return;
  591 
  592  freecopy:
  593         m_freem(mcopy);
  594         return;
  595 }

Cache object: f2dc8d0b772cdc1405c95e443ae353f4


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