The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/netinet6/ip6_forward.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: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD$");
   36 
   37 #include "opt_inet.h"
   38 #include "opt_inet6.h"
   39 #include "opt_ipsec.h"
   40 #include "opt_ipstealth.h"
   41 #include "opt_sctp.h"
   42 
   43 #include <sys/param.h>
   44 #include <sys/systm.h>
   45 #include <sys/malloc.h>
   46 #include <sys/mbuf.h>
   47 #include <sys/domain.h>
   48 #include <sys/protosw.h>
   49 #include <sys/socket.h>
   50 #include <sys/errno.h>
   51 #include <sys/time.h>
   52 #include <sys/kernel.h>
   53 #include <sys/syslog.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/route/nhop.h>
   60 #include <net/pfil.h>
   61 
   62 #include <netinet/in.h>
   63 #include <netinet/in_var.h>
   64 #include <netinet/in_systm.h>
   65 #include <netinet/ip.h>
   66 #include <netinet/ip_var.h>
   67 #include <netinet6/in6_var.h>
   68 #include <netinet/ip6.h>
   69 #include <netinet6/in6_fib.h>
   70 #include <netinet6/ip6_var.h>
   71 #include <netinet6/scope6_var.h>
   72 #include <netinet/icmp6.h>
   73 #include <netinet6/nd6.h>
   74 
   75 #include <netinet/in_pcb.h>
   76 
   77 #include <netipsec/ipsec_support.h>
   78 
   79 /*
   80  * Forward a packet.  If some error occurs return the sender
   81  * an icmp packet.  Note we can't always generate a meaningful
   82  * icmp message because icmp doesn't have a large enough repertoire
   83  * of codes and types.
   84  *
   85  * If not forwarding, just drop the packet.  This could be confusing
   86  * if ipforwarding was zero but some routing protocol was advancing
   87  * us as a gateway to somewhere.  However, we must let the routing
   88  * protocol deal with that.
   89  *
   90  */
   91 void
   92 ip6_forward(struct mbuf *m, int srcrt)
   93 {
   94         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
   95         struct sockaddr_in6 dst;
   96         struct nhop_object *nh = NULL;
   97         int error, type = 0, code = 0;
   98         struct mbuf *mcopy = NULL;
   99         struct ifnet *origifp;  /* maybe unnecessary */
  100         u_int32_t inzone, outzone;
  101         struct in6_addr odst;
  102         struct m_tag *fwd_tag;
  103         char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
  104 
  105         /*
  106          * Do not forward packets to multicast destination (should be handled
  107          * by ip6_mforward().
  108          * Do not forward packets with unspecified source.  It was discussed
  109          * in July 2000, on the ipngwg mailing list.
  110          */
  111         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
  112             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
  113             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
  114                 IP6STAT_INC(ip6s_cantforward);
  115                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
  116                 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
  117                         V_ip6_log_time = time_uptime;
  118                         log(LOG_DEBUG,
  119                             "cannot forward "
  120                             "from %s to %s nxt %d received on %s\n",
  121                             ip6_sprintf(ip6bufs, &ip6->ip6_src),
  122                             ip6_sprintf(ip6bufd, &ip6->ip6_dst),
  123                             ip6->ip6_nxt,
  124                             if_name(m->m_pkthdr.rcvif));
  125                 }
  126                 m_freem(m);
  127                 return;
  128         }
  129 
  130         if (
  131 #ifdef IPSTEALTH
  132             V_ip6stealth == 0 &&
  133 #endif
  134             ip6->ip6_hlim <= IPV6_HLIMDEC) {
  135                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
  136                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
  137                     ICMP6_TIME_EXCEED_TRANSIT, 0);
  138                 return;
  139         }
  140 
  141         /*
  142          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
  143          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
  144          * we need to generate an ICMP6 message to the src.
  145          * Thanks to M_EXT, in most cases copy will not occur.
  146          *
  147          * It is important to save it before IPsec processing as IPsec
  148          * processing may modify the mbuf.
  149          */
  150         mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
  151             M_NOWAIT);
  152 #ifdef IPSTEALTH
  153         if (V_ip6stealth == 0)
  154 #endif
  155                 ip6->ip6_hlim -= IPV6_HLIMDEC;
  156 
  157 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
  158         if (IPSEC_ENABLED(ipv6)) {
  159                 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) {
  160                         /* mbuf consumed by IPsec */
  161                         m_freem(mcopy);
  162                         if (error != EINPROGRESS)
  163                                 IP6STAT_INC(ip6s_cantforward);
  164                         return;
  165                 }
  166                 /* No IPsec processing required */
  167         }
  168 #endif
  169         /*
  170          * ip6_forward() operates with IPv6 addresses with deembedded scope.
  171          *
  172          * There are 3 sources of IPv6 destination address:
  173          *
  174          * 1) ip6_input(), where ip6_dst contains deembedded address.
  175          *   In order to deal with forwarding of link-local packets,
  176          *   calculate the scope based on input interface (RFC 4007, clause 9).
  177          * 2) packet filters changing ip6_dst directly. It would embed scope
  178          *   for LL addresses, so in6_localip() performs properly.
  179          * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed
  180          *   scope for the nexthop.
  181          */
  182         bzero(&dst, sizeof(struct sockaddr_in6));
  183         dst.sin6_family = AF_INET6;
  184         dst.sin6_addr = ip6->ip6_dst;
  185         dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
  186 again:
  187         nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id,
  188             NHR_REF, m->m_pkthdr.flowid);
  189         if (nh == NULL) {
  190                 IP6STAT_INC(ip6s_noroute);
  191                 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
  192                 if (mcopy) {
  193                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
  194                         ICMP6_DST_UNREACH_NOROUTE, 0);
  195                 }
  196                 goto bad;
  197         }
  198 
  199         /*
  200          * Source scope check: if a packet can't be delivered to its
  201          * destination for the reason that the destination is beyond the scope
  202          * of the source address, discard the packet and return an icmp6
  203          * destination unreachable error with Code 2 (beyond scope of source
  204          * address).
  205          * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
  206          */
  207         outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp);
  208         inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif);
  209         if (inzone != outzone) {
  210                 IP6STAT_INC(ip6s_cantforward);
  211                 IP6STAT_INC(ip6s_badscope);
  212                 in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard);
  213 
  214                 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
  215                         V_ip6_log_time = time_uptime;
  216                         log(LOG_DEBUG,
  217                             "cannot forward "
  218                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
  219                             ip6_sprintf(ip6bufs, &ip6->ip6_src),
  220                             ip6_sprintf(ip6bufd, &ip6->ip6_dst),
  221                             ip6->ip6_nxt,
  222                             if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp));
  223                 }
  224                 if (mcopy)
  225                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
  226                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
  227                 goto bad;
  228         }
  229 
  230         /*
  231          * Destination scope check: if a packet is going to break the scope
  232          * zone of packet's destination address, discard it.  This case should
  233          * usually be prevented by appropriately-configured routing table, but
  234          * we need an explicit check because we may mistakenly forward the
  235          * packet to a different zone by (e.g.) a default route.
  236          */
  237         inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif);
  238         outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp);
  239 
  240         if (inzone != outzone) {
  241                 IP6STAT_INC(ip6s_cantforward);
  242                 IP6STAT_INC(ip6s_badscope);
  243                 goto bad;
  244         }
  245 
  246         if (nh->nh_flags & NHF_GATEWAY) {
  247                 /* Store gateway address in deembedded form */
  248                 dst.sin6_addr = nh->gw6_sa.sin6_addr;
  249                 dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr));
  250                 in6_clearscope(&dst.sin6_addr);
  251         }
  252 
  253         /*
  254          * If we are to forward the packet using the same interface
  255          * as one we got the packet from, perhaps we should send a redirect
  256          * to sender to shortcut a hop.
  257          * Only send redirect if source is sending directly to us,
  258          * and if packet was not source routed (or has any options).
  259          * Also, don't send redirect if forwarding using a route
  260          * modified by a redirect.
  261          */
  262         if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt &&
  263             (nh->nh_flags & NHF_REDIRECT) == 0)
  264                 type = ND_REDIRECT;
  265 
  266         /*
  267          * Fake scoped addresses. Note that even link-local source or
  268          * destinaion can appear, if the originating node just sends the
  269          * packet to us (without address resolution for the destination).
  270          * Since both icmp6_error and icmp6_redirect_output fill the embedded
  271          * link identifiers, we can do this stuff after making a copy for
  272          * returning an error.
  273          */
  274         if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) {
  275                 /*
  276                  * See corresponding comments in ip6_output.
  277                  * XXX: but is it possible that ip6_forward() sends a packet
  278                  *      to a loopback interface? I don't think so, and thus
  279                  *      I bark here. (jinmei@kame.net)
  280                  * XXX: it is common to route invalid packets to loopback.
  281                  *      also, the codepath will be visited on use of ::1 in
  282                  *      rthdr. (itojun)
  283                  */
  284 #if 1
  285                 if (0)
  286 #else
  287                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
  288 #endif
  289                 {
  290                         printf("ip6_forward: outgoing interface is loopback. "
  291                                "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
  292                                ip6_sprintf(ip6bufs, &ip6->ip6_src),
  293                                ip6_sprintf(ip6bufd, &ip6->ip6_dst),
  294                                ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
  295                                if_name(nh->nh_ifp));
  296                 }
  297 
  298                 /* we can just use rcvif in forwarding. */
  299                 origifp = m->m_pkthdr.rcvif;
  300         }
  301         else
  302                 origifp = nh->nh_ifp;
  303         /*
  304          * clear embedded scope identifiers if necessary.
  305          * in6_clearscope will touch the addresses only when necessary.
  306          */
  307         in6_clearscope(&ip6->ip6_src);
  308         in6_clearscope(&ip6->ip6_dst);
  309 
  310         /* Jump over all PFIL processing if hooks are not active. */
  311         if (!PFIL_HOOKED_OUT(V_inet6_pfil_head))
  312                 goto pass;
  313 
  314         odst = ip6->ip6_dst;
  315         /* Run through list of hooks for forwarded packets. */
  316         if (pfil_run_hooks(V_inet6_pfil_head, &m, nh->nh_ifp, PFIL_OUT |
  317             PFIL_FWD, NULL) != PFIL_PASS)
  318                 goto freecopy;
  319         ip6 = mtod(m, struct ip6_hdr *);
  320 
  321         /* See if destination IP address was changed by packet filter. */
  322         if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) {
  323                 m->m_flags |= M_SKIP_FIREWALL;
  324                 /* If destination is now ourself drop to ip6_input(). */
  325                 if (in6_localip(&ip6->ip6_dst))
  326                         m->m_flags |= M_FASTFWD_OURS;
  327                 else {
  328                         NH_FREE(nh);
  329 
  330                         /* Update address and scopeid. Assume scope is embedded */
  331                         dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst));
  332                         dst.sin6_addr = ip6->ip6_dst;
  333                         in6_clearscope(&dst.sin6_addr);
  334                         goto again;     /* Redo the routing table lookup. */
  335                 }
  336         }
  337 
  338         /* See if local, if yes, send it to netisr. */
  339         if (m->m_flags & M_FASTFWD_OURS) {
  340                 if (m->m_pkthdr.rcvif == NULL)
  341                         m->m_pkthdr.rcvif = V_loif;
  342                 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
  343                         m->m_pkthdr.csum_flags |=
  344                             CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
  345                         m->m_pkthdr.csum_data = 0xffff;
  346                 }
  347 #if defined(SCTP) || defined(SCTP_SUPPORT)
  348                 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
  349                         m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
  350 #endif
  351                 error = netisr_queue(NETISR_IPV6, m);
  352                 goto out;
  353         }
  354         /* Or forward to some other address? */
  355         if ((m->m_flags & M_IP6_NEXTHOP) &&
  356             (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
  357                 struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1);
  358 
  359                 /* Update address and scopeid. Assume scope is embedded */
  360                 dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr));
  361                 dst.sin6_addr = gw6->sin6_addr;
  362                 in6_clearscope(&dst.sin6_addr);
  363 
  364                 m->m_flags |= M_SKIP_FIREWALL;
  365                 m->m_flags &= ~M_IP6_NEXTHOP;
  366                 m_tag_delete(m, fwd_tag);
  367                 NH_FREE(nh);
  368                 goto again;
  369         }
  370 
  371 pass:
  372         /* See if the size was changed by the packet filter. */
  373         /* TODO: change to nh->nh_mtu */
  374         if (m->m_pkthdr.len > IN6_LINKMTU(nh->nh_ifp)) {
  375                 in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig);
  376                 if (mcopy)
  377                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0,
  378                             IN6_LINKMTU(nh->nh_ifp));
  379                 goto bad;
  380         }
  381 
  382         /* Currently LLE layer stores embedded IPv6 addresses */
  383         if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) {
  384                 in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id);
  385                 dst.sin6_scope_id = 0;
  386         }
  387         error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL);
  388         if (error) {
  389                 in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard);
  390                 IP6STAT_INC(ip6s_cantforward);
  391         } else {
  392                 IP6STAT_INC(ip6s_forward);
  393                 in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward);
  394                 if (type)
  395                         IP6STAT_INC(ip6s_redirectsent);
  396                 else {
  397                         if (mcopy)
  398                                 goto freecopy;
  399                 }
  400         }
  401 
  402         if (mcopy == NULL)
  403                 goto out;
  404         switch (error) {
  405         case 0:
  406                 if (type == ND_REDIRECT) {
  407                         icmp6_redirect_output(mcopy, nh);
  408                         goto out;
  409                 }
  410                 goto freecopy;
  411 
  412         case EMSGSIZE:
  413                 /* xxx MTU is constant in PPP? */
  414                 goto freecopy;
  415 
  416         case ENOBUFS:
  417                 /* Tell source to slow down like source quench in IP? */
  418                 goto freecopy;
  419 
  420         case ENETUNREACH:       /* shouldn't happen, checked above */
  421         case EHOSTUNREACH:
  422         case ENETDOWN:
  423         case EHOSTDOWN:
  424         default:
  425                 type = ICMP6_DST_UNREACH;
  426                 code = ICMP6_DST_UNREACH_ADDR;
  427                 break;
  428         }
  429         icmp6_error(mcopy, type, code, 0);
  430         goto out;
  431 
  432  freecopy:
  433         m_freem(mcopy);
  434         goto out;
  435 bad:
  436         m_freem(m);
  437 out:
  438         if (nh != NULL)
  439                 NH_FREE(nh);
  440 }

Cache object: 8243777f7ed043e88c61a43925c23d21


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