bsd/netinet6/ip6_forward.c

   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
  34 #include <sys/param.h>
  35 #include <sys/systm.h>
  36 #include <sys/malloc.h>
  37 #include <sys/mbuf.h>
  38 #include <sys/domain.h>
  39 #include <sys/protosw.h>
  40 #include <sys/socket.h>
  41 #include <sys/errno.h>
  42 #include <sys/time.h>
  43 #include <sys/kernel.h>
  44 #include <sys/syslog.h>
  45
  46 #include <net/if.h>
  47 #include <net/route.h>
  48
  49 #include <netinet/in.h>
  50 #include <netinet/in_var.h>
  51 #include <netinet/in_systm.h>
  52 #include <netinet/ip.h>
  53 #include <netinet/ip_var.h>
  54 #include <netinet6/in6_var.h>
  55 #include <netinet/ip6.h>
  56 #include <netinet6/ip6_var.h>
  57 #include <netinet/icmp6.h>
  58 #include <netinet6/nd6.h>
  59
  60 #include <netinet/in_pcb.h>
  61
  62 #if IPSEC
  63 #include <netinet6/ipsec.h>
  64 #if INET6
  65 #include <netinet6/ipsec6.h>
  66 #endif
  67 #include <netkey/key.h>
  68 extern int ipsec_bypass;
  69 extern lck_mtx_t *sadb_mutex;
  70 extern lck_mtx_t *ip6_mutex;
  71 #endif /* IPSEC */
  72
  73 #include <netinet6/ip6_fw.h>
  74
  75 #include <net/net_osdep.h>
  76
  77 struct  route_in6 ip6_forward_rt;
  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
  92 void
  93 ip6_forward(m, srcrt, locked)
  94         struct mbuf *m;
  95         int srcrt;
  96         int locked;
  97 {
  98         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  99         struct sockaddr_in6 *dst;
 100         struct rtentry *rt;
 101         int error, type = 0, code = 0;
 102         struct mbuf *mcopy = NULL;
 103         struct ifnet *origifp;  /* maybe unnecessary */
 104 #if IPSEC
 105         struct secpolicy *sp = NULL;
 106 #endif
 107         struct timeval timenow;
 108
 109         getmicrotime(&timenow);
 110
 111
 112 #if IPSEC
 113         /*
 114          * Check AH/ESP integrity.
 115          */
 116         /*
 117          * Don't increment ip6s_cantforward because this is the check
 118          * before forwarding packet actually.
 119          */
 120         if (ipsec_bypass == 0) {
 121                 lck_mtx_lock(sadb_mutex);
 122                 if (ipsec6_in_reject(m, NULL)) {
 123                         ipsec6stat.in_polvio++;
 124                         lck_mtx_unlock(sadb_mutex);
 125                         m_freem(m);
 126                         return;
 127                 }
 128                 lck_mtx_unlock(sadb_mutex);
 129         }
 130 #endif /*IPSEC*/
 131
 132         /*
 133          * Do not forward packets to multicast destination (should be handled
 134          * by ip6_mforward().
 135          * Do not forward packets with unspecified source.  It was discussed
 136          * in July 2000, on ipngwg mailing list.
 137          */
 138         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 139             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 140             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 141                 ip6stat.ip6s_cantforward++;
 142                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 143                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 144                         ip6_log_time = timenow.tv_sec;
 145                         log(LOG_DEBUG,
 146                             "cannot forward "
 147                             "from %s to %s nxt %d received on %s\n",
 148                             ip6_sprintf(&ip6->ip6_src),
 149                             ip6_sprintf(&ip6->ip6_dst),
 150                             ip6->ip6_nxt,
 151                             if_name(m->m_pkthdr.rcvif));
 152                 }
 153                 m_freem(m);
 154                 return;
 155         }
 156
 157         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 158                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 159                 if (locked)
 160                         lck_mtx_unlock(ip6_mutex);
 161                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 162                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 163                 if (locked)
 164                         lck_mtx_lock(ip6_mutex);
 165                 return;
 166         }
 167         ip6->ip6_hlim -= IPV6_HLIMDEC;
 168
 169         /*
 170          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 171          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 172          * we need to generate an ICMP6 message to the src.
 173          * Thanks to M_EXT, in most cases copy will not occur.
 174          *
 175          * It is important to save it before IPsec processing as IPsec
 176          * processing may modify the mbuf.
 177          */
 178         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 179
 180 #if IPSEC
 181         if (ipsec_bypass != 0)
 182                 goto skip_ipsec;
 183         lck_mtx_lock(sadb_mutex);
 184         /* get a security policy for this packet */
 185         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 186             &error);
 187         if (sp == NULL) {
 188                 ipsec6stat.out_inval++;
 189                 ip6stat.ip6s_cantforward++;
 190                 if (mcopy) {
 191 #if 0
 192                         /* XXX: what icmp ? */
 193 #else
 194                         m_freem(mcopy);
 195 #endif
 196                 }
 197                 lck_mtx_unlock(sadb_mutex);
 198                 m_freem(m);
 199                 return;
 200         }
 201
 202         error = 0;
 203
 204         /* check policy */
 205         switch (sp->policy) {
 206         case IPSEC_POLICY_DISCARD:
 207                 /*
 208                  * This packet is just discarded.
 209                  */
 210                 ipsec6stat.out_polvio++;
 211                 ip6stat.ip6s_cantforward++;
 212                 key_freesp(sp);
 213                 if (mcopy) {
 214 #if 0
 215                         /* XXX: what icmp ? */
 216 #else
 217                         m_freem(mcopy);
 218 #endif
 219                 }
 220                 lck_mtx_unlock(sadb_mutex);
 221                 m_freem(m);
 222                 return;
 223
 224         case IPSEC_POLICY_BYPASS:
 225         case IPSEC_POLICY_NONE:
 226                 /* no need to do IPsec. */
 227                 key_freesp(sp);
 228                 lck_mtx_unlock(sadb_mutex);
 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                         lck_mtx_unlock(sadb_mutex);
 245                         m_freem(m);
 246                         return;
 247                 }
 248                 /* do IPsec */
 249                 break;
 250
 251         case IPSEC_POLICY_ENTRUST:
 252         default:
 253                 /* should be panic ?? */
 254                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 255                 key_freesp(sp);
 256                 lck_mtx_unlock(sadb_mutex);
 257                 goto skip_ipsec;
 258         }
 259
 260     {
 261         struct ipsec_output_state state;
 262
 263         /*
 264          * All the extension headers will become inaccessible
 265          * (since they can be encrypted).
 266          * Don't panic, we need no more updates to extension headers
 267          * on inner IPv6 packet (since they are now encapsulated).
 268          *
 269          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 270          */
 271         bzero(&state, sizeof(state));
 272         state.m = m;
 273         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 274         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 275
 276         if (locked)
 277                         lck_mtx_unlock(ip6_mutex);
 278         error = ipsec6_output_tunnel(&state, sp, 0);
 279         if (locked) {
 280                         lck_mtx_unlock(sadb_mutex);
 281                         lck_mtx_lock(ip6_mutex);
 282                         lck_mtx_lock(sadb_mutex);
 283         }
 284
 285         m = state.m;
 286         key_freesp(sp);
 287
 288         if (error) {
 289                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 290                 switch (error) {
 291                 case EHOSTUNREACH:
 292                 case ENETUNREACH:
 293                 case EMSGSIZE:
 294                 case ENOBUFS:
 295                 case ENOMEM:
 296                         break;
 297                 default:
 298                         printf("ip6_output (ipsec): error code %d\n", error);
 299                         /* fall through */
 300                 case ENOENT:
 301                         /* don't show these error codes to the user */
 302                         break;
 303                 }
 304                 ip6stat.ip6s_cantforward++;
 305                 if (mcopy) {
 306 #if 0
 307                         /* XXX: what icmp ? */
 308 #else
 309                         m_freem(mcopy);
 310 #endif
 311                 }
 312                 lck_mtx_unlock(sadb_mutex);
 313                 m_freem(m);
 314                 return;
 315         }
 316     }
 317         lck_mtx_unlock(sadb_mutex);
 318     skip_ipsec:
 319 #endif /* IPSEC */
 320
 321         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 322         if (!srcrt) {
 323                 /*
 324                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 325                  */
 326                 if (ip6_forward_rt.ro_rt == 0 ||
 327                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 328                         if (ip6_forward_rt.ro_rt) {
 329                                 rtfree(ip6_forward_rt.ro_rt);
 330                                 ip6_forward_rt.ro_rt = 0;
 331                         }
 332                         /* this probably fails but give it a try again */
 333                         rtalloc_ign((struct route *)&ip6_forward_rt,
 334                                     RTF_PRCLONING);
 335                 }
 336
 337                 if (ip6_forward_rt.ro_rt == 0) {
 338                         ip6stat.ip6s_noroute++;
 339                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 340                         if (mcopy) {
 341                                 if (locked)
 342                                         lck_mtx_unlock(ip6_mutex);
 343                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 344                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 345                                 if (locked)
 346                                         lck_mtx_lock(ip6_mutex);
 347                         }
 348                         m_freem(m);
 349                         return;
 350                 }
 351         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 352                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 353                 if (ip6_forward_rt.ro_rt) {
 354                         rtfree(ip6_forward_rt.ro_rt);
 355                         ip6_forward_rt.ro_rt = 0;
 356                 }
 357                 bzero(dst, sizeof(*dst));
 358                 dst->sin6_len = sizeof(struct sockaddr_in6);
 359                 dst->sin6_family = AF_INET6;
 360                 dst->sin6_addr = ip6->ip6_dst;
 361
 362                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 363                 if (ip6_forward_rt.ro_rt == 0) {
 364                         ip6stat.ip6s_noroute++;
 365                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 366                         if (mcopy) {
 367                                 if (locked)
 368                                         lck_mtx_unlock(ip6_mutex);
 369                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 370                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 371                                 if (locked)
 372                                         lck_mtx_lock(ip6_mutex);
 373                         }
 374                         m_freem(m);
 375                         return;
 376                 }
 377         }
 378         rt = ip6_forward_rt.ro_rt;
 379
 380         /*
 381          * Scope check: if a packet can't be delivered to its destination
 382          * for the reason that the destination is beyond the scope of the
 383          * source address, discard the packet and return an icmp6 destination
 384          * unreachable error with Code 2 (beyond scope of source address).
 385          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 386          */
 387         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 388             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 389                 ip6stat.ip6s_cantforward++;
 390                 ip6stat.ip6s_badscope++;
 391                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 392
 393                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 394                         ip6_log_time = timenow.tv_sec;
 395                         log(LOG_DEBUG,
 396                             "cannot forward "
 397                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 398                             ip6_sprintf(&ip6->ip6_src),
 399                             ip6_sprintf(&ip6->ip6_dst),
 400                             ip6->ip6_nxt,
 401                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 402                 }
 403                 if (mcopy) {
 404                         if (locked)
 405                                 lck_mtx_unlock(ip6_mutex);
 406                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 407                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 408                         if (locked)
 409                                 lck_mtx_lock(ip6_mutex);
 410                 }
 411                 m_freem(m);
 412                 return;
 413         }
 414
 415         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 416                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 417                 if (mcopy) {
 418                         u_long mtu;
 419 #if IPSEC
 420                         struct secpolicy *sp;
 421                         int ipsecerror;
 422                         size_t ipsechdrsiz;
 423 #endif
 424
 425                         mtu = rt->rt_ifp->if_mtu;
 426 #if IPSEC
 427                         /*
 428                          * When we do IPsec tunnel ingress, we need to play
 429                          * with if_mtu value (decrement IPsec header size
 430                          * from mtu value).  The code is much simpler than v4
 431                          * case, as we have the outgoing interface for
 432                          * encapsulated packet as "rt->rt_ifp".
 433                          */
 434                         lck_mtx_lock(sadb_mutex);
 435                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 436                                 IP_FORWARDING, &ipsecerror);
 437                         if (sp) {
 438                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 439                                         IPSEC_DIR_OUTBOUND, NULL);
 440                                 if (ipsechdrsiz < mtu)
 441                                         mtu -= ipsechdrsiz;
 442                         }
 443                         lck_mtx_unlock(sadb_mutex);
 444                         /*
 445                          * if mtu becomes less than minimum MTU,
 446                          * tell minimum MTU (and I'll need to fragment it).
 447                          */
 448                         if (mtu < IPV6_MMTU)
 449                                 mtu = IPV6_MMTU;
 450 #endif
 451                         if (locked)
 452                                 lck_mtx_unlock(ip6_mutex);
 453                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 454                         if (locked)
 455                                 lck_mtx_lock(ip6_mutex);
 456                 }
 457                 m_freem(m);
 458                 return;
 459         }
 460
 461         if (rt->rt_flags & RTF_GATEWAY)
 462                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 463
 464         /*
 465          * If we are to forward the packet using the same interface
 466          * as one we got the packet from, perhaps we should send a redirect
 467          * to sender to shortcut a hop.
 468          * Only send redirect if source is sending directly to us,
 469          * and if packet was not source routed (or has any options).
 470          * Also, don't send redirect if forwarding using a route
 471          * modified by a redirect.
 472          */
 473         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 474             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 475                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 476                         /*
 477                          * If the incoming interface is equal to the outgoing
 478                          * one, and the link attached to the interface is
 479                          * point-to-point, then it will be highly probable
 480                          * that a routing loop occurs. Thus, we immediately
 481                          * drop the packet and send an ICMPv6 error message.
 482                          *
 483                          * type/code is based on suggestion by Rich Draves.
 484                          * not sure if it is the best pick.
 485                          */
 486                         if (locked)
 487                                 lck_mtx_unlock(ip6_mutex);
 488                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 489                                     ICMP6_DST_UNREACH_ADDR, 0);
 490                         if (locked)
 491                                 lck_mtx_lock(ip6_mutex);
 492                         m_freem(m);
 493                         return;
 494                 }
 495                 type = ND_REDIRECT;
 496         }
 497
 498         /*
 499          * Check with the firewall...
 500          */
 501         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 502                 u_short port = 0;
 503                 /* If ipfw says divert, we have to just drop packet */
 504                 if (ip6_fw_chk_ptr(&ip6, rt->rt_ifp, &port, &m)) {
 505                         m_freem(m);
 506                         goto freecopy;
 507                 }
 508                 if (!m)
 509                         goto freecopy;
 510         }
 511
 512         /*
 513          * Fake scoped addresses. Note that even link-local source or
 514          * destinaion can appear, if the originating node just sends the
 515          * packet to us (without address resolution for the destination).
 516          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 517          * link identifiers, we can do this stuff after making a copy for
 518          * returning an error.
 519          */
 520         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 521                 /*
 522                  * See corresponding comments in ip6_output.
 523                  * XXX: but is it possible that ip6_forward() sends a packet
 524                  *      to a loopback interface? I don't think so, and thus
 525                  *      I bark here. (jinmei@kame.net)
 526                  * XXX: it is common to route invalid packets to loopback.
 527                  *      also, the codepath will be visited on use of ::1 in
 528                  *      rthdr. (itojun)
 529                  */
 530 #if 1
 531                 if (0)
 532 #else
 533                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 534 #endif
 535                 {
 536                         printf("ip6_forward: outgoing interface is loopback. "
 537                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 538                                 ip6_sprintf(&ip6->ip6_src),
 539                                 ip6_sprintf(&ip6->ip6_dst),
 540                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 541                                 if_name(rt->rt_ifp));
 542                 }
 543
 544                 /* we can just use rcvif in forwarding. */
 545                 origifp = m->m_pkthdr.rcvif;
 546         }
 547         else
 548                 origifp = rt->rt_ifp;
 549 #ifndef SCOPEDROUTING
 550         /*
 551          * clear embedded scope identifiers if necessary.
 552          * in6_clearscope will touch the addresses only when necessary.
 553          */
 554         in6_clearscope(&ip6->ip6_src);
 555         in6_clearscope(&ip6->ip6_dst);
 556 #endif
 557
 558         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt, locked);
 559         if (error) {
 560                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 561                 ip6stat.ip6s_cantforward++;
 562         } else {
 563                 ip6stat.ip6s_forward++;
 564                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 565                 if (type)
 566                         ip6stat.ip6s_redirectsent++;
 567                 else {
 568                         if (mcopy)
 569                                 goto freecopy;
 570                 }
 571         }
 572         if (mcopy == NULL)
 573                 return;
 574
 575         switch (error) {
 576         case 0:
 577 #if 1
 578                 if (type == ND_REDIRECT) {
 579                         icmp6_redirect_output(mcopy, rt);
 580                         return;
 581                 }
 582 #endif
 583                 goto freecopy;
 584
 585         case EMSGSIZE:
 586                 /* xxx MTU is constant in PPP? */
 587                 goto freecopy;
 588
 589         case ENOBUFS:
 590                 /* Tell source to slow down like source quench in IP? */
 591                 goto freecopy;
 592
 593         case ENETUNREACH:       /* shouldn't happen, checked above */
 594         case EHOSTUNREACH:
 595         case ENETDOWN:
 596         case EHOSTDOWN:
 597         default:
 598                 type = ICMP6_DST_UNREACH;
 599                 code = ICMP6_DST_UNREACH_ADDR;
 600                 break;
 601         }
 602         if (locked)
 603                 lck_mtx_unlock(ip6_mutex);
 604         icmp6_error(mcopy, type, code, 0);
 605         if (locked)
 606                 lck_mtx_lock(ip6_mutex);
 607         return;
 608
 609  freecopy:
 610         m_freem(mcopy);
 611         return;
 612 }