ldpd/hello.c

   1 /*      $OpenBSD$ */
   2
   3 /*
   4  * Copyright (c) 2013, 2016 Renato Westphal <renato@openbsd.org>
   5  * Copyright (c) 2009 Michele Marchetto <michele@openbsd.org>
   6  *
   7  * Permission to use, copy, modify, and distribute this software for any
   8  * purpose with or without fee is hereby granted, provided that the above
   9  * copyright notice and this permission notice appear in all copies.
  10  *
  11  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  13  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  17  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  18  */
  19
  20 #include <zebra.h>
  21
  22 #include "ldpd.h"
  23 #include "ldpe.h"
  24 #include "log.h"
  25 #include "ldp_debug.h"
  26
  27 static int      gen_hello_prms_tlv(struct ibuf *buf, uint16_t, uint16_t);
  28 static int      gen_opt4_hello_prms_tlv(struct ibuf *, uint16_t, uint32_t);
  29 static int      gen_opt16_hello_prms_tlv(struct ibuf *, uint16_t, uint8_t *);
  30 static int      gen_ds_hello_prms_tlv(struct ibuf *, uint32_t);
  31 static int      tlv_decode_hello_prms(char *, uint16_t, uint16_t *, uint16_t *);
  32 static int      tlv_decode_opt_hello_prms(char *, uint16_t, int *, int,
  33                     union ldpd_addr *, uint32_t *, uint16_t *);
  34
  35 int
  36 send_hello(enum hello_type type, struct iface_af *ia, struct tnbr *tnbr)
  37 {
  38         int                      af;
  39         union ldpd_addr          dst;
  40         uint16_t                 size, holdtime = 0, flags = 0;
  41         int                      fd = 0;
  42         struct ibuf             *buf;
  43         int                      err = 0;
  44
  45         switch (type) {
  46         case HELLO_LINK:
  47                 af = ia->af;
  48                 holdtime = if_get_hello_holdtime(ia);
  49                 flags = 0;
  50                 fd = (ldp_af_global_get(&global, af))->ldp_disc_socket;
  51
  52                 /* multicast destination address */
  53                 switch (af) {
  54                 case AF_INET:
  55                         if (!(leconf->ipv4.flags & F_LDPD_AF_NO_GTSM))
  56                                 flags |= F_HELLO_GTSM;
  57                         dst.v4 = global.mcast_addr_v4;
  58                         break;
  59                 case AF_INET6:
  60                         dst.v6 = global.mcast_addr_v6;
  61                         break;
  62                 default:
  63                         fatalx("send_hello: unknown af");
  64                 }
  65                 break;
  66         case HELLO_TARGETED:
  67                 af = tnbr->af;
  68                 holdtime = tnbr_get_hello_holdtime(tnbr);
  69                 flags = F_HELLO_TARGETED;
  70                 if ((tnbr->flags & F_TNBR_CONFIGURED) || tnbr->pw_count)
  71                         flags |= F_HELLO_REQ_TARG;
  72                 fd = (ldp_af_global_get(&global, af))->ldp_edisc_socket;
  73
  74                 /* unicast destination address */
  75                 dst = tnbr->addr;
  76                 break;
  77         default:
  78                 fatalx("send_hello: unknown hello type");
  79         }
  80
  81         /* calculate message size */
  82         size = LDP_HDR_SIZE + LDP_MSG_SIZE + sizeof(struct hello_prms_tlv);
  83         switch (af) {
  84         case AF_INET:
  85                 size += sizeof(struct hello_prms_opt4_tlv);
  86                 break;
  87         case AF_INET6:
  88                 size += sizeof(struct hello_prms_opt16_tlv);
  89                 break;
  90         default:
  91                 fatalx("send_hello: unknown af");
  92         }
  93         size += sizeof(struct hello_prms_opt4_tlv);
  94         if (ldp_is_dual_stack(leconf))
  95                 size += sizeof(struct hello_prms_opt4_tlv);
  96
  97         /* generate message */
  98         if ((buf = ibuf_open(size)) == NULL)
  99                 fatal(__func__);
 100
 101         err |= gen_ldp_hdr(buf, size);
 102         size -= LDP_HDR_SIZE;
 103         err |= gen_msg_hdr(buf, MSG_TYPE_HELLO, size);
 104         err |= gen_hello_prms_tlv(buf, holdtime, flags);
 105
 106         /*
 107          * RFC 7552 - Section 6.1:
 108          * "An LSR MUST include only the transport address whose address
 109          * family is the same as that of the IP packet carrying the Hello
 110          * message".
 111          */
 112         switch (af) {
 113         case AF_INET:
 114                 err |= gen_opt4_hello_prms_tlv(buf, TLV_TYPE_IPV4TRANSADDR,
 115                     leconf->ipv4.trans_addr.v4.s_addr);
 116                 break;
 117         case AF_INET6:
 118                 err |= gen_opt16_hello_prms_tlv(buf, TLV_TYPE_IPV6TRANSADDR,
 119                     leconf->ipv6.trans_addr.v6.s6_addr);
 120                 break;
 121         default:
 122                 fatalx("send_hello: unknown af");
 123         }
 124
 125         err |= gen_opt4_hello_prms_tlv(buf, TLV_TYPE_CONFIG,
 126             htonl(global.conf_seqnum));
 127
 128         /*
 129          * RFC 7552 - Section 6.1.1:
 130          * "A Dual-stack LSR (i.e., an LSR supporting Dual-stack LDP for a peer)
 131          * MUST include the Dual-Stack capability TLV in all of its LDP Hellos".
 132          */
 133         if (ldp_is_dual_stack(leconf))
 134                 err |= gen_ds_hello_prms_tlv(buf, leconf->trans_pref);
 135
 136         if (err) {
 137                 ibuf_free(buf);
 138                 return (-1);
 139         }
 140
 141         switch (type) {
 142         case HELLO_LINK:
 143                 debug_hello_send("iface %s (%s) holdtime %u", ia->iface->name,
 144                     af_name(ia->af), holdtime);
 145                 break;
 146         case HELLO_TARGETED:
 147                 debug_hello_send("targeted-neighbor %s (%s) holdtime %u",
 148                     log_addr(tnbr->af, &tnbr->addr), af_name(tnbr->af),
 149                     holdtime);
 150                 break;
 151         default:
 152                 fatalx("send_hello: unknown hello type");
 153         }
 154
 155         send_packet(fd, af, &dst, ia, buf->buf, buf->wpos);
 156         ibuf_free(buf);
 157
 158         return (0);
 159 }
 160
 161 void
 162 recv_hello(struct in_addr lsr_id, struct ldp_msg *msg, int af,
 163     union ldpd_addr *src, struct iface *iface, int multicast, char *buf,
 164     uint16_t len)
 165 {
 166         struct adj              *adj = NULL;
 167         struct nbr              *nbr, *nbrt;
 168         uint16_t                 holdtime = 0, flags = 0;
 169         int                      tlvs_rcvd;
 170         int                      ds_tlv;
 171         union ldpd_addr          trans_addr;
 172         uint32_t                 scope_id = 0;
 173         uint32_t                 conf_seqnum;
 174         uint16_t                 trans_pref;
 175         int                      r;
 176         struct hello_source      source;
 177         struct iface_af         *ia = NULL;
 178         struct tnbr             *tnbr = NULL;
 179
 180         r = tlv_decode_hello_prms(buf, len, &holdtime, &flags);
 181         if (r == -1) {
 182                 log_debug("%s: lsr-id %s: failed to decode params", __func__,
 183                     inet_ntoa(lsr_id));
 184                 return;
 185         }
 186         /* safety checks */
 187         if (holdtime != 0 && holdtime < MIN_HOLDTIME) {
 188                 log_debug("%s: lsr-id %s: invalid hello holdtime (%u)",
 189                     __func__, inet_ntoa(lsr_id), holdtime);
 190                 return;
 191         }
 192         if (multicast && (flags & F_HELLO_TARGETED)) {
 193                 log_debug("%s: lsr-id %s: multicast targeted hello", __func__,
 194                     inet_ntoa(lsr_id));
 195                 return;
 196         }
 197         if (!multicast && !((flags & F_HELLO_TARGETED))) {
 198                 log_debug("%s: lsr-id %s: unicast link hello", __func__,
 199                     inet_ntoa(lsr_id));
 200                 return;
 201         }
 202         buf += r;
 203         len -= r;
 204
 205         r = tlv_decode_opt_hello_prms(buf, len, &tlvs_rcvd, af, &trans_addr,
 206             &conf_seqnum, &trans_pref);
 207         if (r == -1) {
 208                 log_debug("%s: lsr-id %s: failed to decode optional params",
 209                     __func__, inet_ntoa(lsr_id));
 210                 return;
 211         }
 212         if (r != len) {
 213                 log_debug("%s: lsr-id %s: unexpected data in message",
 214                     __func__, inet_ntoa(lsr_id));
 215                 return;
 216         }
 217
 218         /* implicit transport address */
 219         if (!(tlvs_rcvd & F_HELLO_TLV_RCVD_ADDR))
 220                 trans_addr = *src;
 221         if (bad_addr(af, &trans_addr)) {
 222                 log_debug("%s: lsr-id %s: invalid transport address %s",
 223                     __func__, inet_ntoa(lsr_id), log_addr(af, &trans_addr));
 224                 return;
 225         }
 226         if (af == AF_INET6 && IN6_IS_SCOPE_EMBED(&trans_addr.v6)) {
 227                 /*
 228                  * RFC 7552 - Section 6.1:
 229                  * "An LSR MUST use a global unicast IPv6 address in an IPv6
 230                  * Transport Address optional object of outgoing targeted
 231                  * Hellos and check for the same in incoming targeted Hellos
 232                  * (i.e., MUST discard the targeted Hello if it failed the
 233                  * check)".
 234                  */
 235                 if (flags & F_HELLO_TARGETED) {
 236                         log_debug("%s: lsr-id %s: invalid targeted hello "
 237                             "transport address %s", __func__, inet_ntoa(lsr_id),
 238                              log_addr(af, &trans_addr));
 239                         return;
 240                 }
 241                 scope_id = iface->ifindex;
 242         }
 243
 244         memset(&source, 0, sizeof(source));
 245         if (flags & F_HELLO_TARGETED) {
 246                 /*
 247                  * RFC 7552 - Section 5.2:
 248                 * "The link-local IPv6 addresses MUST NOT be used as the
 249                 * targeted LDP Hello packet's source or destination addresses".
 250                 */
 251                 if (af == AF_INET6 && IN6_IS_SCOPE_EMBED(&src->v6)) {
 252                         log_debug("%s: lsr-id %s: targeted hello with "
 253                             "link-local source address", __func__,
 254                             inet_ntoa(lsr_id));
 255                         return;
 256                 }
 257
 258                 tnbr = tnbr_find(leconf, af, src);
 259
 260                 /* remove the dynamic tnbr if the 'R' bit was cleared */
 261                 if (tnbr && (tnbr->flags & F_TNBR_DYNAMIC) &&
 262                     !((flags & F_HELLO_REQ_TARG))) {
 263                         tnbr->flags &= ~F_TNBR_DYNAMIC;
 264                         tnbr = tnbr_check(leconf, tnbr);
 265                 }
 266
 267                 if (!tnbr) {
 268                         struct ldpd_af_conf     *af_conf;
 269
 270                         if (!(flags & F_HELLO_REQ_TARG))
 271                                 return;
 272                         af_conf = ldp_af_conf_get(leconf, af);
 273                         if (!(af_conf->flags & F_LDPD_AF_THELLO_ACCEPT))
 274                                 return;
 275                         if (ldpe_acl_check(af_conf->acl_thello_accept_from, af,
 276                             src, (af == AF_INET) ? 32 : 128) != FILTER_PERMIT)
 277                                 return;
 278
 279                         tnbr = tnbr_new(af, src);
 280                         tnbr->flags |= F_TNBR_DYNAMIC;
 281                         tnbr_update(tnbr);
 282                         RB_INSERT(tnbr_head, &leconf->tnbr_tree, tnbr);
 283                 }
 284
 285                 source.type = HELLO_TARGETED;
 286                 source.target = tnbr;
 287         } else {
 288                 ia = iface_af_get(iface, af);
 289                 source.type = HELLO_LINK;
 290                 source.link.ia = ia;
 291                 source.link.src_addr = *src;
 292         }
 293
 294         adj = adj_find(&source);
 295         nbr = nbr_find_ldpid(lsr_id.s_addr);
 296
 297         /* check dual-stack tlv */
 298         ds_tlv = (tlvs_rcvd & F_HELLO_TLV_RCVD_DS) ? 1 : 0;
 299         if (ds_tlv && trans_pref != leconf->trans_pref) {
 300                 /*
 301                  * RFC 7552 - Section 6.1.1:
 302                  * "If the Dual-Stack capability TLV is present and the remote
 303                  * preference does not match the local preference (or does not
 304                  * get recognized), then the LSR MUST discard the Hello message
 305                  * and log an error.
 306                  * If an LDP session was already in place, then the LSR MUST
 307                  * send a fatal Notification message with status code of
 308                  * 'Transport Connection Mismatch' and reset the session".
 309                  */
 310                 log_debug("%s: lsr-id %s: remote transport preference does not "
 311                     "match the local preference", __func__, inet_ntoa(lsr_id));
 312                 if (nbr)
 313                         session_shutdown(nbr, S_TRANS_MISMTCH, msg->id,
 314                             msg->type);
 315                 if (adj)
 316                         adj_del(adj, S_SHUTDOWN);
 317                 return;
 318         }
 319
 320         /*
 321          * Check for noncompliant dual-stack neighbor according to
 322          * RFC 7552 section 6.1.1.
 323          */
 324         if (nbr && !ds_tlv) {
 325                 switch (af) {
 326                 case AF_INET:
 327                         if (nbr_adj_count(nbr, AF_INET6) > 0) {
 328                                 session_shutdown(nbr, S_DS_NONCMPLNCE,
 329                                     msg->id, msg->type);
 330                                 return;
 331                         }
 332                         break;
 333                 case AF_INET6:
 334                         if (nbr_adj_count(nbr, AF_INET) > 0) {
 335                                 session_shutdown(nbr, S_DS_NONCMPLNCE,
 336                                     msg->id, msg->type);
 337                                 return;
 338                         }
 339                         break;
 340                 default:
 341                         fatalx("recv_hello: unknown af");
 342                 }
 343         }
 344
 345         /*
 346          * Protections against misconfigured networks and buggy implementations.
 347          */
 348         if (nbr && nbr->af == af &&
 349             (ldp_addrcmp(af, &nbr->raddr, &trans_addr) ||
 350             nbr->raddr_scope != scope_id)) {
 351                 log_warnx("%s: lsr-id %s: hello packet advertising a different "
 352                     "transport address", __func__, inet_ntoa(lsr_id));
 353                 if (adj)
 354                         adj_del(adj, S_SHUTDOWN);
 355                 return;
 356         }
 357         if (nbr == NULL) {
 358                 nbrt = nbr_find_addr(af, &trans_addr);
 359                 if (nbrt) {
 360                         log_debug("%s: transport address %s is already being "
 361                             "used by lsr-id %s", __func__, log_addr(af,
 362                             &trans_addr), inet_ntoa(nbrt->id));
 363                         if (adj)
 364                                 adj_del(adj, S_SHUTDOWN);
 365                         return;
 366                 }
 367         }
 368
 369         if (adj == NULL) {
 370                 adj = adj_new(lsr_id, &source, &trans_addr);
 371                 if (nbr) {
 372                         adj->nbr = nbr;
 373                         RB_INSERT(nbr_adj_head, &nbr->adj_tree, adj);
 374                 }
 375         }
 376
 377         /*
 378          * If the hello adjacency's address-family doesn't match the local
 379          * preference, then an adjacency is still created but we don't attempt
 380          * to start an LDP session.
 381          */
 382         if (nbr == NULL && (!ds_tlv ||
 383             ((trans_pref == DUAL_STACK_LDPOV4 && af == AF_INET) ||
 384             (trans_pref == DUAL_STACK_LDPOV6 && af == AF_INET6))))
 385                 nbr = nbr_new(lsr_id, af, ds_tlv, &trans_addr, scope_id);
 386
 387         /* dynamic LDPv4 GTSM negotiation as per RFC 6720 */
 388         if (nbr) {
 389                 if (flags & F_HELLO_GTSM)
 390                         nbr->flags |= F_NBR_GTSM_NEGOTIATED;
 391                 else
 392                         nbr->flags &= ~F_NBR_GTSM_NEGOTIATED;
 393         }
 394
 395         /* update neighbor's configuration sequence number */
 396         if (nbr && (tlvs_rcvd & F_HELLO_TLV_RCVD_CONF)) {
 397                 if (conf_seqnum > nbr->conf_seqnum &&
 398                     nbr_pending_idtimer(nbr))
 399                         nbr_stop_idtimer(nbr);
 400                 nbr->conf_seqnum = conf_seqnum;
 401         }
 402
 403         /* always update the holdtime to properly handle runtime changes */
 404         switch (source.type) {
 405         case HELLO_LINK:
 406                 if (holdtime == 0)
 407                         holdtime = LINK_DFLT_HOLDTIME;
 408
 409                 adj->holdtime = min(if_get_hello_holdtime(ia), holdtime);
 410                 break;
 411         case HELLO_TARGETED:
 412                 if (holdtime == 0)
 413                         holdtime = TARGETED_DFLT_HOLDTIME;
 414
 415                 adj->holdtime = min(tnbr_get_hello_holdtime(tnbr), holdtime);
 416         }
 417         if (adj->holdtime != INFINITE_HOLDTIME)
 418                 adj_start_itimer(adj);
 419         else
 420                 adj_stop_itimer(adj);
 421
 422         debug_hello_recv("%s lsr-id %s transport-address %s holdtime %u%s",
 423             log_hello_src(&source), inet_ntoa(lsr_id), log_addr(af, &trans_addr),
 424              holdtime, (ds_tlv) ? " (dual stack TLV present)" : "");
 425
 426         if (nbr && nbr->state == NBR_STA_PRESENT && !nbr_pending_idtimer(nbr) &&
 427             nbr_session_active_role(nbr) && !nbr_pending_connect(nbr))
 428                 nbr_establish_connection(nbr);
 429 }
 430
 431 static int
 432 gen_hello_prms_tlv(struct ibuf *buf, uint16_t holdtime, uint16_t flags)
 433 {
 434         struct hello_prms_tlv   parms;
 435
 436         memset(&parms, 0, sizeof(parms));
 437         parms.type = htons(TLV_TYPE_COMMONHELLO);
 438         parms.length = htons(sizeof(parms.holdtime) + sizeof(parms.flags));
 439         parms.holdtime = htons(holdtime);
 440         parms.flags = htons(flags);
 441
 442         return (ibuf_add(buf, &parms, sizeof(parms)));
 443 }
 444
 445 static int
 446 gen_opt4_hello_prms_tlv(struct ibuf *buf, uint16_t type, uint32_t value)
 447 {
 448         struct hello_prms_opt4_tlv      parms;
 449
 450         memset(&parms, 0, sizeof(parms));
 451         parms.type = htons(type);
 452         parms.length = htons(sizeof(parms.value));
 453         parms.value = value;
 454
 455         return (ibuf_add(buf, &parms, sizeof(parms)));
 456 }
 457
 458 static int
 459 gen_opt16_hello_prms_tlv(struct ibuf *buf, uint16_t type, uint8_t *value)
 460 {
 461         struct hello_prms_opt16_tlv     parms;
 462
 463         memset(&parms, 0, sizeof(parms));
 464         parms.type = htons(type);
 465         parms.length = htons(sizeof(parms.value));
 466         memcpy(&parms.value, value, sizeof(parms.value));
 467
 468         return (ibuf_add(buf, &parms, sizeof(parms)));
 469 }
 470
 471 static int
 472 gen_ds_hello_prms_tlv(struct ibuf *buf, uint32_t value)
 473 {
 474         if (leconf->flags & F_LDPD_DS_CISCO_INTEROP)
 475                 value = htonl(value);
 476         else
 477                 value = htonl(value << 28);
 478
 479         return (gen_opt4_hello_prms_tlv(buf, TLV_TYPE_DUALSTACK, value));
 480 }
 481
 482 static int
 483 tlv_decode_hello_prms(char *buf, uint16_t len, uint16_t *holdtime,
 484     uint16_t *flags)
 485 {
 486         struct hello_prms_tlv   tlv;
 487
 488         if (len < sizeof(tlv))
 489                 return (-1);
 490         memcpy(&tlv, buf, sizeof(tlv));
 491
 492         if (tlv.type != htons(TLV_TYPE_COMMONHELLO))
 493                 return (-1);
 494         if (ntohs(tlv.length) != sizeof(tlv) - TLV_HDR_SIZE)
 495                 return (-1);
 496
 497         *holdtime = ntohs(tlv.holdtime);
 498         *flags = ntohs(tlv.flags);
 499
 500         return (sizeof(tlv));
 501 }
 502
 503 static int
 504 tlv_decode_opt_hello_prms(char *buf, uint16_t len, int *tlvs_rcvd, int af,
 505     union ldpd_addr *addr, uint32_t *conf_number, uint16_t *trans_pref)
 506 {
 507         struct tlv      tlv;
 508         uint16_t        tlv_len;
 509         int             total = 0;
 510
 511         *tlvs_rcvd = 0;
 512         memset(addr, 0, sizeof(*addr));
 513         *conf_number = 0;
 514         *trans_pref = 0;
 515
 516         /*
 517          * RFC 7552 - Section 6.1:
 518          * "An LSR SHOULD accept the Hello message that contains both IPv4 and
 519          * IPv6 Transport Address optional objects but MUST use only the
 520          * transport address whose address family is the same as that of the
 521          * IP packet carrying the Hello message.  An LSR SHOULD accept only
 522          * the first Transport Address optional object for a given address
 523          * family in the received Hello message and ignore the rest if the
 524          * LSR receives more than one Transport Address optional object for a
 525          * given address family".
 526          */
 527         while (len >= sizeof(tlv)) {
 528                 memcpy(&tlv, buf, TLV_HDR_SIZE);
 529                 tlv_len = ntohs(tlv.length);
 530                 if (tlv_len + TLV_HDR_SIZE > len)
 531                         return (-1);
 532                 buf += TLV_HDR_SIZE;
 533                 len -= TLV_HDR_SIZE;
 534                 total += TLV_HDR_SIZE;
 535
 536                 switch (ntohs(tlv.type)) {
 537                 case TLV_TYPE_IPV4TRANSADDR:
 538                         if (tlv_len != sizeof(addr->v4))
 539                                 return (-1);
 540                         if (af != AF_INET)
 541                                 return (-1);
 542                         if (*tlvs_rcvd & F_HELLO_TLV_RCVD_ADDR)
 543                                 break;
 544                         memcpy(&addr->v4, buf, sizeof(addr->v4));
 545                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_ADDR;
 546                         break;
 547                 case TLV_TYPE_IPV6TRANSADDR:
 548                         if (tlv_len != sizeof(addr->v6))
 549                                 return (-1);
 550                         if (af != AF_INET6)
 551                                 return (-1);
 552                         if (*tlvs_rcvd & F_HELLO_TLV_RCVD_ADDR)
 553                                 break;
 554                         memcpy(&addr->v6, buf, sizeof(addr->v6));
 555                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_ADDR;
 556                         break;
 557                 case TLV_TYPE_CONFIG:
 558                         if (tlv_len != sizeof(uint32_t))
 559                                 return (-1);
 560                         memcpy(conf_number, buf, sizeof(uint32_t));
 561                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_CONF;
 562                         break;
 563                 case TLV_TYPE_DUALSTACK:
 564                         if (tlv_len != sizeof(uint32_t))
 565                                 return (-1);
 566                         /*
 567                          * RFC 7552 - Section 6.1:
 568                          * "A Single-stack LSR does not need to use the
 569                          * Dual-Stack capability in Hello messages and SHOULD
 570                          * ignore this capability if received".
 571                          */
 572                         if (!ldp_is_dual_stack(leconf))
 573                                 break;
 574                         /* Shame on you, Cisco! */
 575                         if (leconf->flags & F_LDPD_DS_CISCO_INTEROP) {
 576                                 memcpy(trans_pref, buf + sizeof(uint16_t),
 577                                     sizeof(uint16_t));
 578                                 *trans_pref = ntohs(*trans_pref);
 579                         } else {
 580                                 memcpy(trans_pref, buf , sizeof(uint16_t));
 581                                 *trans_pref = ntohs(*trans_pref) >> 12;
 582                         }
 583                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_DS;
 584                         break;
 585                 default:
 586                         /* if unknown flag set, ignore TLV */
 587                         if (!(ntohs(tlv.type) & UNKNOWN_FLAG))
 588                                 return (-1);
 589                         break;
 590                 }
 591                 buf += tlv_len;
 592                 len -= tlv_len;
 593                 total += tlv_len;
 594         }
 595
 596         return (total);
 597 }