sys/netinet6/ip6_forward.c

   1 /*      $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.4.2.7 2003/01/24 05:11:35 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
  37 #include <sys/param.h>
  38 #include <sys/systm.h>
  39 #include <sys/malloc.h>
  40 #include <sys/mbuf.h>
  41 #include <sys/domain.h>
  42 #include <sys/protosw.h>
  43 #include <sys/socket.h>
  44 #include <sys/errno.h>
  45 #include <sys/time.h>
  46 #include <sys/kernel.h>
  47 #include <sys/syslog.h>
  48
  49 #include <net/if.h>
  50 #include <net/route.h>
  51 #include <net/pfil.h>
  52
  53 #include <netinet/in.h>
  54 #include <netinet/in_var.h>
  55 #include <netinet/in_systm.h>
  56 #include <netinet/ip.h>
  57 #include <netinet/ip_var.h>
  58 #include <netinet6/in6_var.h>
  59 #include <netinet/ip6.h>
  60 #include <netinet6/ip6_var.h>
  61 #include <netinet/icmp6.h>
  62 #include <netinet6/nd6.h>
  63
  64 #include <netinet/in_pcb.h>
  65
  66 #include <net/ip6fw/ip6_fw.h>
  67
  68 #include <net/net_osdep.h>
  69
  70 struct  route_in6 ip6_forward_rt;
  71
  72 /*
  73  * Forward a packet.  If some error occurs return the sender
  74  * an icmp packet.  Note we can't always generate a meaningful
  75  * icmp message because icmp doesn't have a large enough repertoire
  76  * of codes and types.
  77  *
  78  * If not forwarding, just drop the packet.  This could be confusing
  79  * if ipforwarding was zero but some routing protocol was advancing
  80  * us as a gateway to somewhere.  However, we must let the routing
  81  * protocol deal with that.
  82  *
  83  */
  84
  85 void
  86 ip6_forward(struct mbuf *m, int srcrt)
  87 {
  88         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  89         struct sockaddr_in6 *dst;
  90         struct rtentry *rt;
  91         int error, type = 0, code = 0;
  92         struct mbuf *mcopy = NULL;
  93         struct ifnet *origifp;  /* maybe unnecessary */
  94         u_int32_t srczone, dstzone;
  95
  96         /*
  97          * Do not forward packets to multicast destination (should be handled
  98          * by ip6_mforward().
  99          * Do not forward packets with unspecified source.  It was discussed
 100          * in July 2000, on the ipngwg mailing list.
 101          */
 102         if ((m->m_flags & (M_BCAST | M_MCAST)) != 0 ||
 103             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 104             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 105                 ip6stat.ip6s_cantforward++;
 106                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 107                 if (ip6_log_time + ip6_log_interval < time_uptime) {
 108                         ip6_log_time = time_uptime;
 109                         log(LOG_DEBUG,
 110                             "cannot forward "
 111                             "from %s to %s nxt %d received on %s\n",
 112                             ip6_sprintf(&ip6->ip6_src),
 113                             ip6_sprintf(&ip6->ip6_dst),
 114                             ip6->ip6_nxt,
 115                             if_name(m->m_pkthdr.rcvif));
 116                 }
 117                 m_freem(m);
 118                 return;
 119         }
 120
 121         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 122                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 123                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 124                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 125                 return;
 126         }
 127         ip6->ip6_hlim -= IPV6_HLIMDEC;
 128
 129         /*
 130          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 131          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 132          * we need to generate an ICMP6 message to the src.
 133          * Thanks to M_EXT, in most cases copy will not occur.
 134          */
 135         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 136
 137         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 138         if (!srcrt) {
 139                 /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */
 140                 if (ip6_forward_rt.ro_rt == NULL ||
 141                     !(ip6_forward_rt.ro_rt->rt_flags & RTF_UP)) {
 142                         if (ip6_forward_rt.ro_rt) {
 143                                 RTFREE(ip6_forward_rt.ro_rt);
 144                                 ip6_forward_rt.ro_rt = 0;
 145                         }
 146
 147                         /* this probably fails but give it a try again */
 148                         rtalloc_ign((struct route *)&ip6_forward_rt,
 149                                     RTF_PRCLONING);
 150                 }
 151
 152                 if (ip6_forward_rt.ro_rt == NULL) {
 153                         ip6stat.ip6s_noroute++;
 154                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 155                         if (mcopy) {
 156                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 157                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 158                         }
 159                         m_freem(m);
 160                         return;
 161                 }
 162         } else if ((rt = ip6_forward_rt.ro_rt) == NULL ||
 163                    !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 164                 if (ip6_forward_rt.ro_rt) {
 165                         RTFREE(ip6_forward_rt.ro_rt);
 166                         ip6_forward_rt.ro_rt = 0;
 167                 }
 168                 bzero(dst, sizeof(*dst));
 169                 dst->sin6_len = sizeof(struct sockaddr_in6);
 170                 dst->sin6_family = AF_INET6;
 171                 dst->sin6_addr = ip6->ip6_dst;
 172
 173                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 174                 if (ip6_forward_rt.ro_rt == NULL) {
 175                         ip6stat.ip6s_noroute++;
 176                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 177                         if (mcopy) {
 178                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 179                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 180                         }
 181                         m_freem(m);
 182                         return;
 183                 }
 184         }
 185         rt = ip6_forward_rt.ro_rt;
 186
 187         /*
 188          * Scope check: if a packet can't be delivered to its destination
 189          * for the reason that the destination is beyond the scope of the
 190          * source address, discard the packet and return an icmp6 destination
 191          * unreachable error with Code 2 (beyond scope of source address).
 192          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 193          */
 194         if (in6_addr2zoneid(m->m_pkthdr.rcvif, &ip6->ip6_src, &srczone) ||
 195             in6_addr2zoneid(rt->rt_ifp, &ip6->ip6_src, &dstzone) ||
 196             srczone != dstzone) {
 197                 ip6stat.ip6s_cantforward++;
 198                 ip6stat.ip6s_badscope++;
 199                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 200
 201                 if (ip6_log_time + ip6_log_interval < time_uptime) {
 202                         ip6_log_time = time_uptime;
 203                         log(LOG_DEBUG,
 204                             "cannot forward "
 205                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 206                             ip6_sprintf(&ip6->ip6_src),
 207                             ip6_sprintf(&ip6->ip6_dst),
 208                             ip6->ip6_nxt,
 209                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 210                 }
 211                 if (mcopy)
 212                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 213                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 214                 m_freem(m);
 215                 return;
 216         }
 217
 218         if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
 219                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 220                 if (mcopy) {
 221                         u_long mtu;
 222
 223                         mtu = IN6_LINKMTU(rt->rt_ifp);
 224                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 225                 }
 226                 m_freem(m);
 227                 return;
 228         }
 229
 230         if (rt->rt_flags & RTF_GATEWAY)
 231                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 232
 233         /*
 234          * If we are to forward the packet using the same interface
 235          * as one we got the packet from, perhaps we should send a redirect
 236          * to sender to shortcut a hop.
 237          * Only send redirect if source is sending directly to us,
 238          * and if packet was not source routed (or has any options).
 239          * Also, don't send redirect if forwarding using a route
 240          * modified by a redirect.
 241          */
 242         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 243             (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) {
 244                 if (rt->rt_ifp->if_flags & IFF_POINTOPOINT) {
 245                         /*
 246                          * If the incoming interface is equal to the outgoing
 247                          * one, and the link attached to the interface is
 248                          * point-to-point, then it will be highly probable
 249                          * that a routing loop occurs. Thus, we immediately
 250                          * drop the packet and send an ICMPv6 error message.
 251                          *
 252                          * type/code is based on suggestion by Rich Draves.
 253                          * not sure if it is the best pick.
 254                          */
 255                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 256                                     ICMP6_DST_UNREACH_ADDR, 0);
 257                         m_freem(m);
 258                         return;
 259                 }
 260                 type = ND_REDIRECT;
 261         }
 262
 263         /*
 264          * Check with the firewall...
 265          */
 266         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 267                 u_short port = 0;
 268                 /* If ipfw says divert, we have to just drop packet */
 269                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 270                         m_freem(m);
 271                         goto freecopy;
 272                 }
 273                 if (!m)
 274                         goto freecopy;
 275         }
 276
 277         /*
 278          * Fake scoped addresses. Note that even link-local source or
 279          * destinaion can appear, if the originating node just sends the
 280          * packet to us (without address resolution for the destination).
 281          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 282          * link identifiers, we can do this stuff after making a copy for
 283          * returning an error.
 284          */
 285         if (rt->rt_ifp->if_flags & IFF_LOOPBACK) {
 286                 /*
 287                  * See corresponding comments in ip6_output.
 288                  * XXX: but is it possible that ip6_forward() sends a packet
 289                  *      to a loopback interface? I don't think so, and thus
 290                  *      I bark here. (jinmei@kame.net)
 291                  * XXX: it is common to route invalid packets to loopback.
 292                  *      also, the codepath will be visited on use of ::1 in
 293                  *      rthdr. (itojun)
 294                  */
 295 #if 1
 296                 if (0)
 297 #else
 298                 if ((rt->rt_flags & (RTF_BLACKHOLE | RTF_REJECT)) == 0)
 299 #endif
 300                 {
 301                         kprintf("ip6_forward: outgoing interface is loopback. "
 302                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 303                                 ip6_sprintf(&ip6->ip6_src),
 304                                 ip6_sprintf(&ip6->ip6_dst),
 305                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 306                                 if_name(rt->rt_ifp));
 307                 }
 308
 309                 /* we can just use rcvif in forwarding. */
 310                 origifp = m->m_pkthdr.rcvif;
 311         }
 312         else
 313                 origifp = rt->rt_ifp;
 314         /*
 315          * clear embedded scope identifiers if necessary.
 316          * in6_clearscope will touch the addresses only when necessary.
 317          */
 318         in6_clearscope(&ip6->ip6_src);
 319         in6_clearscope(&ip6->ip6_dst);
 320
 321         /*
 322          * Run through list of hooks for output packets.
 323          */
 324         if (pfil_has_hooks(&inet6_pfil_hook)) {
 325                 error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp,
 326                                        PFIL_OUT);
 327                 if (error != 0)
 328                         goto senderr;
 329                 if (m == NULL)
 330                         goto freecopy;
 331                 ip6 = mtod(m, struct ip6_hdr *);
 332         }
 333
 334         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 335         if (error) {
 336                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 337                 ip6stat.ip6s_cantforward++;
 338         } else {
 339                 ip6stat.ip6s_forward++;
 340                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 341                 if (type)
 342                         ip6stat.ip6s_redirectsent++;
 343                 else {
 344                         if (mcopy)
 345                                 goto freecopy;
 346                 }
 347         }
 348 senderr:
 349         if (mcopy == NULL)
 350                 return;
 351         switch (error) {
 352         case 0:
 353                 if (type == ND_REDIRECT) {
 354                         icmp6_redirect_output(mcopy, rt);
 355                         return;
 356                 }
 357                 goto freecopy;
 358
 359         case EMSGSIZE:
 360                 /* xxx MTU is constant in PPP? */
 361                 goto freecopy;
 362
 363         case ENOBUFS:
 364                 /* Tell source to slow down like source quench in IP? */
 365                 goto freecopy;
 366
 367         case ENETUNREACH:       /* shouldn't happen, checked above */
 368         case EHOSTUNREACH:
 369         case ENETDOWN:
 370         case EHOSTDOWN:
 371         default:
 372                 type = ICMP6_DST_UNREACH;
 373                 code = ICMP6_DST_UNREACH_ADDR;
 374                 break;
 375         }
 376         icmp6_error(mcopy, type, code, 0);
 377         return;
 378
 379 freecopy:
 380         m_freem(mcopy);
 381         return;
 382 }