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_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN),
 136                         M_NOWAIT);
 137
 138         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 139         if (!srcrt) {
 140                 /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */
 141                 if (ip6_forward_rt.ro_rt == NULL ||
 142                     !(ip6_forward_rt.ro_rt->rt_flags & RTF_UP)) {
 143                         if (ip6_forward_rt.ro_rt) {
 144                                 RTFREE(ip6_forward_rt.ro_rt);
 145                                 ip6_forward_rt.ro_rt = 0;
 146                         }
 147
 148                         /* this probably fails but give it a try again */
 149                         rtalloc_ign((struct route *)&ip6_forward_rt,
 150                                     RTF_PRCLONING);
 151                 }
 152
 153                 if (ip6_forward_rt.ro_rt == NULL) {
 154                         ip6stat.ip6s_noroute++;
 155                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 156                         if (mcopy) {
 157                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 158                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 159                         }
 160                         m_freem(m);
 161                         return;
 162                 }
 163         } else if ((rt = ip6_forward_rt.ro_rt) == NULL ||
 164                    !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 165                 if (ip6_forward_rt.ro_rt) {
 166                         RTFREE(ip6_forward_rt.ro_rt);
 167                         ip6_forward_rt.ro_rt = 0;
 168                 }
 169                 bzero(dst, sizeof(*dst));
 170                 dst->sin6_len = sizeof(struct sockaddr_in6);
 171                 dst->sin6_family = AF_INET6;
 172                 dst->sin6_addr = ip6->ip6_dst;
 173
 174                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 175                 if (ip6_forward_rt.ro_rt == NULL) {
 176                         ip6stat.ip6s_noroute++;
 177                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 178                         if (mcopy) {
 179                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 180                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 181                         }
 182                         m_freem(m);
 183                         return;
 184                 }
 185         }
 186         rt = ip6_forward_rt.ro_rt;
 187
 188         /*
 189          * Scope check: if a packet can't be delivered to its destination
 190          * for the reason that the destination is beyond the scope of the
 191          * source address, discard the packet and return an icmp6 destination
 192          * unreachable error with Code 2 (beyond scope of source address).
 193          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 194          */
 195         if (in6_addr2zoneid(m->m_pkthdr.rcvif, &ip6->ip6_src, &srczone) ||
 196             in6_addr2zoneid(rt->rt_ifp, &ip6->ip6_src, &dstzone) ||
 197             srczone != dstzone) {
 198                 ip6stat.ip6s_cantforward++;
 199                 ip6stat.ip6s_badscope++;
 200                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 201
 202                 if (ip6_log_time + ip6_log_interval < time_uptime) {
 203                         ip6_log_time = time_uptime;
 204                         log(LOG_DEBUG,
 205                             "cannot forward "
 206                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 207                             ip6_sprintf(&ip6->ip6_src),
 208                             ip6_sprintf(&ip6->ip6_dst),
 209                             ip6->ip6_nxt,
 210                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 211                 }
 212                 if (mcopy)
 213                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 214                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 215                 m_freem(m);
 216                 return;
 217         }
 218
 219         if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
 220                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 221                 if (mcopy) {
 222                         u_long mtu;
 223
 224                         mtu = IN6_LINKMTU(rt->rt_ifp);
 225                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 226                 }
 227                 m_freem(m);
 228                 return;
 229         }
 230
 231         if (rt->rt_flags & RTF_GATEWAY)
 232                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 233
 234         /*
 235          * If we are to forward the packet using the same interface
 236          * as one we got the packet from, perhaps we should send a redirect
 237          * to sender to shortcut a hop.
 238          * Only send redirect if source is sending directly to us,
 239          * and if packet was not source routed (or has any options).
 240          * Also, don't send redirect if forwarding using a route
 241          * modified by a redirect.
 242          */
 243         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 244             (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) {
 245                 if (rt->rt_ifp->if_flags & IFF_POINTOPOINT) {
 246                         /*
 247                          * If the incoming interface is equal to the outgoing
 248                          * one, and the link attached to the interface is
 249                          * point-to-point, then it will be highly probable
 250                          * that a routing loop occurs. Thus, we immediately
 251                          * drop the packet and send an ICMPv6 error message.
 252                          *
 253                          * type/code is based on suggestion by Rich Draves.
 254                          * not sure if it is the best pick.
 255                          */
 256                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 257                                     ICMP6_DST_UNREACH_ADDR, 0);
 258                         m_freem(m);
 259                         return;
 260                 }
 261                 type = ND_REDIRECT;
 262         }
 263
 264         /*
 265          * Check with the firewall...
 266          */
 267         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 268                 u_short port = 0;
 269                 /* If ipfw says divert, we have to just drop packet */
 270                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 271                         m_freem(m);
 272                         goto freecopy;
 273                 }
 274                 if (!m)
 275                         goto freecopy;
 276         }
 277
 278         /*
 279          * Fake scoped addresses. Note that even link-local source or
 280          * destinaion can appear, if the originating node just sends the
 281          * packet to us (without address resolution for the destination).
 282          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 283          * link identifiers, we can do this stuff after making a copy for
 284          * returning an error.
 285          */
 286         if (rt->rt_ifp->if_flags & IFF_LOOPBACK) {
 287                 /*
 288                  * See corresponding comments in ip6_output.
 289                  * XXX: but is it possible that ip6_forward() sends a packet
 290                  *      to a loopback interface? I don't think so, and thus
 291                  *      I bark here. (jinmei@kame.net)
 292                  * XXX: it is common to route invalid packets to loopback.
 293                  *      also, the codepath will be visited on use of ::1 in
 294                  *      rthdr. (itojun)
 295                  */
 296 #if 1
 297                 if (0)
 298 #else
 299                 if ((rt->rt_flags & (RTF_BLACKHOLE | RTF_REJECT)) == 0)
 300 #endif
 301                 {
 302                         kprintf("ip6_forward: outgoing interface is loopback. "
 303                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 304                                 ip6_sprintf(&ip6->ip6_src),
 305                                 ip6_sprintf(&ip6->ip6_dst),
 306                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 307                                 if_name(rt->rt_ifp));
 308                 }
 309
 310                 /* we can just use rcvif in forwarding. */
 311                 origifp = m->m_pkthdr.rcvif;
 312         }
 313         else
 314                 origifp = rt->rt_ifp;
 315         /*
 316          * clear embedded scope identifiers if necessary.
 317          * in6_clearscope will touch the addresses only when necessary.
 318          */
 319         in6_clearscope(&ip6->ip6_src);
 320         in6_clearscope(&ip6->ip6_dst);
 321
 322         /*
 323          * Run through list of hooks for output packets.
 324          */
 325         if (pfil_has_hooks(&inet6_pfil_hook)) {
 326                 error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp,
 327                                        PFIL_OUT);
 328                 if (error != 0)
 329                         goto senderr;
 330                 if (m == NULL)
 331                         goto freecopy;
 332                 ip6 = mtod(m, struct ip6_hdr *);
 333         }
 334
 335         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 336         if (error) {
 337                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 338                 ip6stat.ip6s_cantforward++;
 339         } else {
 340                 ip6stat.ip6s_forward++;
 341                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 342                 if (type)
 343                         ip6stat.ip6s_redirectsent++;
 344                 else {
 345                         if (mcopy)
 346                                 goto freecopy;
 347                 }
 348         }
 349 senderr:
 350         if (mcopy == NULL)
 351                 return;
 352         switch (error) {
 353         case 0:
 354                 if (type == ND_REDIRECT) {
 355                         icmp6_redirect_output(mcopy, rt);
 356                         return;
 357                 }
 358                 goto freecopy;
 359
 360         case EMSGSIZE:
 361                 /* xxx MTU is constant in PPP? */
 362                 goto freecopy;
 363
 364         case ENOBUFS:
 365                 /* Tell source to slow down like source quench in IP? */
 366                 goto freecopy;
 367
 368         case ENETUNREACH:       /* shouldn't happen, checked above */
 369         case EHOSTUNREACH:
 370         case ENETDOWN:
 371         case EHOSTDOWN:
 372         default:
 373                 type = ICMP6_DST_UNREACH;
 374                 code = ICMP6_DST_UNREACH_ADDR;
 375                 break;
 376         }
 377         icmp6_error(mcopy, type, code, 0);
 378         return;
 379
 380 freecopy:
 381         m_freem(mcopy);
 382         return;
 383 }