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                     || tnbr->rlfa_count)
  72                         flags |= F_HELLO_REQ_TARG;
  73                 fd = (ldp_af_global_get(&global, af))->ldp_edisc_socket;
  74
  75                 /* unicast destination address */
  76                 dst = tnbr->addr;
  77                 break;
  78         default:
  79                 fatalx("send_hello: unknown hello type");
  80         }
  81
  82         /* calculate message size */
  83         size = LDP_HDR_SIZE + LDP_MSG_SIZE + sizeof(struct hello_prms_tlv);
  84         switch (af) {
  85         case AF_INET:
  86                 size += sizeof(struct hello_prms_opt4_tlv);
  87                 break;
  88         case AF_INET6:
  89                 size += sizeof(struct hello_prms_opt16_tlv);
  90                 break;
  91         default:
  92                 fatalx("send_hello: unknown af");
  93         }
  94         size += sizeof(struct hello_prms_opt4_tlv);
  95         if (ldp_is_dual_stack(leconf))
  96                 size += sizeof(struct hello_prms_opt4_tlv);
  97
  98         /* generate message */
  99         if ((buf = ibuf_open(size)) == NULL)
 100                 fatal(__func__);
 101
 102         err |= gen_ldp_hdr(buf, size);
 103         size -= LDP_HDR_SIZE;
 104         err |= gen_msg_hdr(buf, MSG_TYPE_HELLO, size);
 105         err |= gen_hello_prms_tlv(buf, holdtime, flags);
 106
 107         /*
 108          * RFC 7552 - Section 6.1:
 109          * "An LSR MUST include only the transport address whose address
 110          * family is the same as that of the IP packet carrying the Hello
 111          * message".
 112          */
 113         switch (af) {
 114         case AF_INET:
 115                 err |= gen_opt4_hello_prms_tlv(buf, TLV_TYPE_IPV4TRANSADDR,
 116                     leconf->ipv4.trans_addr.v4.s_addr);
 117                 break;
 118         case AF_INET6:
 119                 err |= gen_opt16_hello_prms_tlv(buf, TLV_TYPE_IPV6TRANSADDR,
 120                     leconf->ipv6.trans_addr.v6.s6_addr);
 121                 break;
 122         default:
 123                 fatalx("send_hello: unknown af");
 124         }
 125
 126         err |= gen_opt4_hello_prms_tlv(buf, TLV_TYPE_CONFIG,
 127             htonl(global.conf_seqnum));
 128
 129         /*
 130          * RFC 7552 - Section 6.1.1:
 131          * "A Dual-stack LSR (i.e., an LSR supporting Dual-stack LDP for a peer)
 132          * MUST include the Dual-Stack capability TLV in all of its LDP Hellos".
 133          */
 134         if (ldp_is_dual_stack(leconf))
 135                 err |= gen_ds_hello_prms_tlv(buf, leconf->trans_pref);
 136
 137         if (err) {
 138                 ibuf_free(buf);
 139                 return (-1);
 140         }
 141
 142         switch (type) {
 143         case HELLO_LINK:
 144                 debug_hello_send("iface %s (%s) holdtime %u", ia->iface->name,
 145                     af_name(ia->af), holdtime);
 146                 break;
 147         case HELLO_TARGETED:
 148                 debug_hello_send("targeted-neighbor %s (%s) holdtime %u",
 149                     log_addr(tnbr->af, &tnbr->addr), af_name(tnbr->af),
 150                     holdtime);
 151                 break;
 152         default:
 153                 fatalx("send_hello: unknown hello type");
 154         }
 155
 156         send_packet(fd, af, &dst, ia, buf->buf, buf->wpos);
 157         ibuf_free(buf);
 158
 159         return (0);
 160 }
 161
 162 void
 163 recv_hello(struct in_addr lsr_id, struct ldp_msg *msg, int af,
 164     union ldpd_addr *src, struct iface *iface, int multicast, char *buf,
 165     uint16_t len)
 166 {
 167         struct adj              *adj = NULL;
 168         struct nbr              *nbr, *nbrt;
 169         uint16_t                 holdtime = 0, flags = 0;
 170         int                      tlvs_rcvd;
 171         int                      ds_tlv;
 172         union ldpd_addr          trans_addr;
 173         ifindex_t                scope_id = 0;
 174         uint32_t                 conf_seqnum;
 175         uint16_t                 trans_pref;
 176         int                      r;
 177         struct hello_source      source;
 178         struct iface_af         *ia = NULL;
 179         struct tnbr             *tnbr = NULL;
 180
 181         r = tlv_decode_hello_prms(buf, len, &holdtime, &flags);
 182         if (r == -1) {
 183                 log_debug("%s: lsr-id %pI4: failed to decode params", __func__,
 184                     &lsr_id);
 185                 return;
 186         }
 187         /* safety checks */
 188         if (holdtime != 0 && holdtime < MIN_HOLDTIME) {
 189                 log_debug("%s: lsr-id %pI4: invalid hello holdtime (%u)",
 190                     __func__, &lsr_id, holdtime);
 191                 return;
 192         }
 193         if (multicast && (flags & F_HELLO_TARGETED)) {
 194                 log_debug("%s: lsr-id %pI4: multicast targeted hello", __func__,
 195                     &lsr_id);
 196                 return;
 197         }
 198         if (!multicast && !((flags & F_HELLO_TARGETED))) {
 199                 log_debug("%s: lsr-id %pI4: unicast link hello", __func__,
 200                     &lsr_id);
 201                 return;
 202         }
 203         buf += r;
 204         len -= r;
 205
 206         r = tlv_decode_opt_hello_prms(buf, len, &tlvs_rcvd, af, &trans_addr,
 207             &conf_seqnum, &trans_pref);
 208         if (r == -1) {
 209                 log_debug("%s: lsr-id %pI4: failed to decode optional params",
 210                     __func__, &lsr_id);
 211                 return;
 212         }
 213         if (r != len) {
 214                 log_debug("%s: lsr-id %pI4: unexpected data in message",
 215                     __func__, &lsr_id);
 216                 return;
 217         }
 218         ds_tlv = (tlvs_rcvd & F_HELLO_TLV_RCVD_DS) ? 1 : 0;
 219
 220         /* implicit transport address */
 221         if (!(tlvs_rcvd & F_HELLO_TLV_RCVD_ADDR))
 222                 trans_addr = *src;
 223         if (bad_addr(af, &trans_addr)) {
 224                 log_debug("%s: lsr-id %pI4: invalid transport address %s",
 225                     __func__, &lsr_id, log_addr(af, &trans_addr));
 226                 return;
 227         }
 228         if (af == AF_INET6 && IN6_IS_SCOPE_EMBED(&trans_addr.v6)) {
 229                 /*
 230                  * RFC 7552 - Section 6.1:
 231                  * "An LSR MUST use a global unicast IPv6 address in an IPv6
 232                  * Transport Address optional object of outgoing targeted
 233                  * Hellos and check for the same in incoming targeted Hellos
 234                  * (i.e., MUST discard the targeted Hello if it failed the
 235                  * check)".
 236                  */
 237                 if (flags & F_HELLO_TARGETED) {
 238                         log_debug("%s: lsr-id %pI4: invalid targeted hello transport address %s", __func__, &lsr_id,
 239                              log_addr(af, &trans_addr));
 240                         return;
 241                 }
 242                 scope_id = iface->ifindex;
 243         }
 244
 245         memset(&source, 0, sizeof(source));
 246         if (flags & F_HELLO_TARGETED) {
 247                 /*
 248                  * RFC 7552 - Section 5.2:
 249                 * "The link-local IPv6 addresses MUST NOT be used as the
 250                 * targeted LDP Hello packet's source or destination addresses".
 251                 */
 252                 if (af == AF_INET6 && IN6_IS_SCOPE_EMBED(&src->v6)) {
 253                         log_debug("%s: lsr-id %pI4: targeted hello with link-local source address", __func__,
 254                             &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         debug_hello_recv("%s lsr-id %pI4 transport-address %s holdtime %u%s",
 295             log_hello_src(&source), &lsr_id, log_addr(af, &trans_addr),
 296              holdtime, (ds_tlv) ? " (dual stack TLV present)" : "");
 297
 298         adj = adj_find(lsr_id, &source);
 299         if (adj && adj->ds_tlv != ds_tlv) {
 300                 /*
 301                  * Transient condition, ignore packet and wait until adjacency
 302                  * times out.
 303                  */
 304                 return;
 305         }
 306         nbr = nbr_find_ldpid(lsr_id.s_addr);
 307
 308         /* check dual-stack tlv */
 309         if (ds_tlv && trans_pref != leconf->trans_pref) {
 310                 /*
 311                  * RFC 7552 - Section 6.1.1:
 312                  * "If the Dual-Stack capability TLV is present and the remote
 313                  * preference does not match the local preference (or does not
 314                  * get recognized), then the LSR MUST discard the Hello message
 315                  * and log an error.
 316                  * If an LDP session was already in place, then the LSR MUST
 317                  * send a fatal Notification message with status code of
 318                  * 'Transport Connection Mismatch' and reset the session".
 319                  */
 320                 log_debug("%s: lsr-id %pI4: remote transport preference does not match the local preference", __func__, &lsr_id);
 321                 if (nbr)
 322                         session_shutdown(nbr, S_TRANS_MISMTCH, msg->id,
 323                             msg->type);
 324                 if (adj)
 325                         adj_del(adj, S_SHUTDOWN);
 326                 return;
 327         }
 328
 329         /*
 330          * Check for noncompliant dual-stack neighbor according to
 331          * RFC 7552 section 6.1.1.
 332          */
 333         if (nbr && !ds_tlv) {
 334                 switch (af) {
 335                 case AF_INET:
 336                         if (nbr_adj_count(nbr, AF_INET6) > 0) {
 337                                 session_shutdown(nbr, S_DS_NONCMPLNCE,
 338                                     msg->id, msg->type);
 339                                 return;
 340                         }
 341                         break;
 342                 case AF_INET6:
 343                         if (nbr_adj_count(nbr, AF_INET) > 0) {
 344                                 session_shutdown(nbr, S_DS_NONCMPLNCE,
 345                                     msg->id, msg->type);
 346                                 return;
 347                         }
 348                         break;
 349                 default:
 350                         fatalx("recv_hello: unknown af");
 351                 }
 352         }
 353
 354         /*
 355          * Protections against misconfigured networks and buggy implementations.
 356          */
 357         if (nbr && nbr->af == af &&
 358             (ldp_addrcmp(af, &nbr->raddr, &trans_addr) ||
 359             nbr->raddr_scope != scope_id)) {
 360                 log_warnx("%s: lsr-id %pI4: hello packet advertising a different transport address", __func__, &lsr_id);
 361                 if (adj)
 362                         adj_del(adj, S_SHUTDOWN);
 363                 return;
 364         }
 365         if (nbr == NULL) {
 366                 nbrt = nbr_find_addr(af, &trans_addr);
 367                 if (nbrt) {
 368                         log_debug("%s: transport address %s is already being used by lsr-id %pI4", __func__, log_addr(af,
 369                             &trans_addr), &nbrt->id);
 370                         if (adj)
 371                                 adj_del(adj, S_SHUTDOWN);
 372                         return;
 373                 }
 374         }
 375
 376         if (adj == NULL) {
 377                 adj = adj_new(lsr_id, &source, &trans_addr);
 378                 if (nbr) {
 379                         adj->nbr = nbr;
 380                         RB_INSERT(nbr_adj_head, &nbr->adj_tree, adj);
 381                 }
 382                 ldp_sync_fsm_adj_event(adj, LDP_SYNC_EVT_ADJ_NEW);
 383         }
 384         adj->ds_tlv = ds_tlv;
 385
 386         /*
 387          * If the hello adjacency's address-family doesn't match the local
 388          * preference, then an adjacency is still created but we don't attempt
 389          * to start an LDP session.
 390          */
 391         if (nbr == NULL && (!ds_tlv ||
 392             ((trans_pref == DUAL_STACK_LDPOV4 && af == AF_INET) ||
 393             (trans_pref == DUAL_STACK_LDPOV6 && af == AF_INET6))))
 394                 nbr = nbr_new(lsr_id, af, ds_tlv, &trans_addr, scope_id);
 395
 396         /* dynamic LDPv4 GTSM negotiation as per RFC 6720 */
 397         if (nbr) {
 398                 if (flags & F_HELLO_GTSM)
 399                         nbr->flags |= F_NBR_GTSM_NEGOTIATED;
 400                 else
 401                         nbr->flags &= ~F_NBR_GTSM_NEGOTIATED;
 402         }
 403
 404         /* update neighbor's configuration sequence number */
 405         if (nbr && (tlvs_rcvd & F_HELLO_TLV_RCVD_CONF)) {
 406                 if (conf_seqnum > nbr->conf_seqnum &&
 407                     nbr_pending_idtimer(nbr))
 408                         nbr_stop_idtimer(nbr);
 409                 nbr->conf_seqnum = conf_seqnum;
 410         }
 411
 412         /* always update the holdtime to properly handle runtime changes */
 413         switch (source.type) {
 414         case HELLO_LINK:
 415                 if (holdtime == 0)
 416                         holdtime = LINK_DFLT_HOLDTIME;
 417
 418                 adj->holdtime = MIN(if_get_hello_holdtime(ia), holdtime);
 419                 break;
 420         case HELLO_TARGETED:
 421                 if (holdtime == 0)
 422                         holdtime = TARGETED_DFLT_HOLDTIME;
 423
 424                 adj->holdtime = MIN(tnbr_get_hello_holdtime(tnbr), holdtime);
 425         }
 426         if (adj->holdtime != INFINITE_HOLDTIME)
 427                 adj_start_itimer(adj);
 428         else
 429                 adj_stop_itimer(adj);
 430
 431         if (nbr && nbr->state == NBR_STA_PRESENT && !nbr_pending_idtimer(nbr) &&
 432             nbr_session_active_role(nbr) && !nbr_pending_connect(nbr))
 433                 nbr_establish_connection(nbr);
 434 }
 435
 436 static int
 437 gen_hello_prms_tlv(struct ibuf *buf, uint16_t holdtime, uint16_t flags)
 438 {
 439         struct hello_prms_tlv   parms;
 440
 441         memset(&parms, 0, sizeof(parms));
 442         parms.type = htons(TLV_TYPE_COMMONHELLO);
 443         parms.length = htons(sizeof(parms.holdtime) + sizeof(parms.flags));
 444         parms.holdtime = htons(holdtime);
 445         parms.flags = htons(flags);
 446
 447         return (ibuf_add(buf, &parms, sizeof(parms)));
 448 }
 449
 450 static int
 451 gen_opt4_hello_prms_tlv(struct ibuf *buf, uint16_t type, uint32_t value)
 452 {
 453         struct hello_prms_opt4_tlv      parms;
 454
 455         memset(&parms, 0, sizeof(parms));
 456         parms.type = htons(type);
 457         parms.length = htons(sizeof(parms.value));
 458         parms.value = value;
 459
 460         return (ibuf_add(buf, &parms, sizeof(parms)));
 461 }
 462
 463 static int
 464 gen_opt16_hello_prms_tlv(struct ibuf *buf, uint16_t type, uint8_t *value)
 465 {
 466         struct hello_prms_opt16_tlv     parms;
 467
 468         memset(&parms, 0, sizeof(parms));
 469         parms.type = htons(type);
 470         parms.length = htons(sizeof(parms.value));
 471         memcpy(&parms.value, value, sizeof(parms.value));
 472
 473         return (ibuf_add(buf, &parms, sizeof(parms)));
 474 }
 475
 476 static int
 477 gen_ds_hello_prms_tlv(struct ibuf *buf, uint32_t value)
 478 {
 479         if (leconf->flags & F_LDPD_DS_CISCO_INTEROP)
 480                 value = htonl(value);
 481         else
 482                 value = htonl(value << 28);
 483
 484         return (gen_opt4_hello_prms_tlv(buf, TLV_TYPE_DUALSTACK, value));
 485 }
 486
 487 static int
 488 tlv_decode_hello_prms(char *buf, uint16_t len, uint16_t *holdtime,
 489     uint16_t *flags)
 490 {
 491         struct hello_prms_tlv   tlv;
 492
 493         if (len < sizeof(tlv))
 494                 return (-1);
 495         memcpy(&tlv, buf, sizeof(tlv));
 496
 497         if (tlv.type != htons(TLV_TYPE_COMMONHELLO))
 498                 return (-1);
 499         if (ntohs(tlv.length) != sizeof(tlv) - TLV_HDR_SIZE)
 500                 return (-1);
 501
 502         *holdtime = ntohs(tlv.holdtime);
 503         *flags = ntohs(tlv.flags);
 504
 505         return (sizeof(tlv));
 506 }
 507
 508 static int
 509 tlv_decode_opt_hello_prms(char *buf, uint16_t len, int *tlvs_rcvd, int af,
 510     union ldpd_addr *addr, uint32_t *conf_number, uint16_t *trans_pref)
 511 {
 512         struct tlv      tlv;
 513         uint16_t        tlv_len;
 514         int             total = 0;
 515
 516         *tlvs_rcvd = 0;
 517         memset(addr, 0, sizeof(*addr));
 518         *conf_number = 0;
 519         *trans_pref = 0;
 520
 521         /*
 522          * RFC 7552 - Section 6.1:
 523          * "An LSR SHOULD accept the Hello message that contains both IPv4 and
 524          * IPv6 Transport Address optional objects but MUST use only the
 525          * transport address whose address family is the same as that of the
 526          * IP packet carrying the Hello message.  An LSR SHOULD accept only
 527          * the first Transport Address optional object for a given address
 528          * family in the received Hello message and ignore the rest if the
 529          * LSR receives more than one Transport Address optional object for a
 530          * given address family".
 531          */
 532         while (len >= sizeof(tlv)) {
 533                 memcpy(&tlv, buf, TLV_HDR_SIZE);
 534                 tlv_len = ntohs(tlv.length);
 535                 if (tlv_len + TLV_HDR_SIZE > len)
 536                         return (-1);
 537                 buf += TLV_HDR_SIZE;
 538                 len -= TLV_HDR_SIZE;
 539                 total += TLV_HDR_SIZE;
 540
 541                 switch (ntohs(tlv.type)) {
 542                 case TLV_TYPE_IPV4TRANSADDR:
 543                         if (tlv_len != sizeof(addr->v4))
 544                                 return (-1);
 545                         if (af != AF_INET)
 546                                 return (-1);
 547                         if (*tlvs_rcvd & F_HELLO_TLV_RCVD_ADDR)
 548                                 break;
 549                         memcpy(&addr->v4, buf, sizeof(addr->v4));
 550                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_ADDR;
 551                         break;
 552                 case TLV_TYPE_IPV6TRANSADDR:
 553                         if (tlv_len != sizeof(addr->v6))
 554                                 return (-1);
 555                         if (af != AF_INET6)
 556                                 return (-1);
 557                         if (*tlvs_rcvd & F_HELLO_TLV_RCVD_ADDR)
 558                                 break;
 559                         memcpy(&addr->v6, buf, sizeof(addr->v6));
 560                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_ADDR;
 561                         break;
 562                 case TLV_TYPE_CONFIG:
 563                         if (tlv_len != sizeof(uint32_t))
 564                                 return (-1);
 565                         memcpy(conf_number, buf, sizeof(uint32_t));
 566                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_CONF;
 567                         break;
 568                 case TLV_TYPE_DUALSTACK:
 569                         if (tlv_len != sizeof(uint32_t))
 570                                 return (-1);
 571                         /*
 572                          * RFC 7552 - Section 6.1:
 573                          * "A Single-stack LSR does not need to use the
 574                          * Dual-Stack capability in Hello messages and SHOULD
 575                          * ignore this capability if received".
 576                          */
 577                         if (!ldp_is_dual_stack(leconf))
 578                                 break;
 579                         /* Shame on you, Cisco! */
 580                         if (leconf->flags & F_LDPD_DS_CISCO_INTEROP) {
 581                                 memcpy(trans_pref, buf + sizeof(uint16_t),
 582                                     sizeof(uint16_t));
 583                                 *trans_pref = ntohs(*trans_pref);
 584                         } else {
 585                                 memcpy(trans_pref, buf , sizeof(uint16_t));
 586                                 *trans_pref = ntohs(*trans_pref) >> 12;
 587                         }
 588                         *tlvs_rcvd |= F_HELLO_TLV_RCVD_DS;
 589                         break;
 590                 default:
 591                         /* if unknown flag set, ignore TLV */
 592                         if (!(ntohs(tlv.type) & UNKNOWN_FLAG))
 593                                 return (-1);
 594                         break;
 595                 }
 596                 buf += tlv_len;
 597                 len -= tlv_len;
 598                 total += tlv_len;
 599         }
 600
 601         return (total);
 602 }