bgpd/bgp_label.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* BGP carrying label information
   3  * Copyright (C) 2013 Cumulus Networks, Inc.
   4  */
   5
   6 #include <zebra.h>
   7
   8 #include "command.h"
   9 #include "frrevent.h"
  10 #include "prefix.h"
  11 #include "zclient.h"
  12 #include "stream.h"
  13 #include "network.h"
  14 #include "log.h"
  15 #include "memory.h"
  16 #include "nexthop.h"
  17 #include "mpls.h"
  18
  19 #include "bgpd/bgpd.h"
  20 #include "bgpd/bgp_table.h"
  21 #include "bgpd/bgp_route.h"
  22 #include "bgpd/bgp_attr.h"
  23 #include "bgpd/bgp_label.h"
  24 #include "bgpd/bgp_packet.h"
  25 #include "bgpd/bgp_debug.h"
  26 #include "bgpd/bgp_errors.h"
  27
  28 extern struct zclient *zclient;
  29
  30 int bgp_parse_fec_update(void)
  31 {
  32         struct stream *s;
  33         struct bgp_dest *dest;
  34         struct bgp *bgp;
  35         struct bgp_table *table;
  36         struct prefix p;
  37         uint32_t label;
  38         afi_t afi;
  39         safi_t safi;
  40
  41         s = zclient->ibuf;
  42
  43         memset(&p, 0, sizeof(p));
  44         p.family = stream_getw(s);
  45         p.prefixlen = stream_getc(s);
  46         stream_get(p.u.val, s, PSIZE(p.prefixlen));
  47         label = stream_getl(s);
  48
  49         /* hack for the bgp instance & SAFI = have to send/receive it */
  50         afi = family2afi(p.family);
  51         safi = SAFI_UNICAST;
  52         bgp = bgp_get_default();
  53         if (!bgp) {
  54                 zlog_debug("no default bgp instance");
  55                 return -1;
  56         }
  57
  58         table = bgp->rib[afi][safi];
  59         if (!table) {
  60                 zlog_debug("no %u unicast table", p.family);
  61                 return -1;
  62         }
  63         dest = bgp_node_lookup(table, &p);
  64         if (!dest) {
  65                 zlog_debug("no node for the prefix");
  66                 return -1;
  67         }
  68
  69         /* treat it as implicit withdraw - the label is invalid */
  70         if (label == MPLS_INVALID_LABEL)
  71                 bgp_unset_valid_label(&dest->local_label);
  72         else {
  73                 dest->local_label = mpls_lse_encode(label, 0, 0, 1);
  74                 bgp_set_valid_label(&dest->local_label);
  75         }
  76         SET_FLAG(dest->flags, BGP_NODE_LABEL_CHANGED);
  77         bgp_process(bgp, dest, afi, safi);
  78         bgp_dest_unlock_node(dest);
  79         return 1;
  80 }
  81
  82 mpls_label_t bgp_adv_label(struct bgp_dest *dest, struct bgp_path_info *pi,
  83                            struct peer *to, afi_t afi, safi_t safi)
  84 {
  85         struct peer *from;
  86         mpls_label_t remote_label;
  87         int reflect;
  88
  89         if (!dest || !pi || !to)
  90                 return MPLS_INVALID_LABEL;
  91
  92         remote_label = pi->extra ? pi->extra->label[0] : MPLS_INVALID_LABEL;
  93         from = pi->peer;
  94         reflect =
  95                 ((from->sort == BGP_PEER_IBGP) && (to->sort == BGP_PEER_IBGP));
  96
  97         if (reflect
  98             && !CHECK_FLAG(to->af_flags[afi][safi],
  99                            PEER_FLAG_FORCE_NEXTHOP_SELF))
 100                 return remote_label;
 101
 102         if (CHECK_FLAG(to->af_flags[afi][safi], PEER_FLAG_NEXTHOP_UNCHANGED))
 103                 return remote_label;
 104
 105         return dest->local_label;
 106 }
 107
 108 static void bgp_send_fec_register_label_msg(struct bgp_dest *dest, bool reg,
 109                                             uint32_t label_index)
 110 {
 111         struct stream *s;
 112         int command;
 113         const struct prefix *p;
 114         uint16_t flags = 0;
 115         size_t flags_pos = 0;
 116         mpls_label_t *local_label = &(dest->local_label);
 117         uint32_t ttl = 0;
 118         uint32_t bos = 0;
 119         uint32_t exp = 0;
 120         mpls_label_t label = MPLS_INVALID_LABEL;
 121         bool have_label_to_reg;
 122
 123         mpls_lse_decode(*local_label, &label, &ttl, &exp, &bos);
 124
 125         have_label_to_reg = bgp_is_valid_label(local_label) &&
 126                             label != MPLS_LABEL_IMPLICIT_NULL;
 127
 128         p = bgp_dest_get_prefix(dest);
 129
 130         /* Check socket. */
 131         if (!zclient || zclient->sock < 0)
 132                 return;
 133
 134         if (BGP_DEBUG(labelpool, LABELPOOL))
 135                 zlog_debug("%s: FEC %sregister %pRN label_index=%u label=%u",
 136                            __func__, reg ? "" : "un", bgp_dest_to_rnode(dest),
 137                            label_index, label);
 138         /* If the route node has a local_label assigned or the
 139          * path node has an MPLS SR label index allowing zebra to
 140          * derive the label, proceed with registration. */
 141         s = zclient->obuf;
 142         stream_reset(s);
 143         command = (reg) ? ZEBRA_FEC_REGISTER : ZEBRA_FEC_UNREGISTER;
 144         zclient_create_header(s, command, VRF_DEFAULT);
 145         flags_pos = stream_get_endp(s); /* save position of 'flags' */
 146         stream_putw(s, flags);          /* initial flags */
 147         stream_putw(s, PREFIX_FAMILY(p));
 148         stream_put_prefix(s, p);
 149         if (reg) {
 150                 /* label index takes precedence over auto-assigned label. */
 151                 if (label_index != 0) {
 152                         flags |= ZEBRA_FEC_REGISTER_LABEL_INDEX;
 153                         stream_putl(s, label_index);
 154                 } else if (have_label_to_reg) {
 155                         flags |= ZEBRA_FEC_REGISTER_LABEL;
 156                         stream_putl(s, label);
 157                 }
 158                 SET_FLAG(dest->flags, BGP_NODE_REGISTERED_FOR_LABEL);
 159         } else
 160                 UNSET_FLAG(dest->flags, BGP_NODE_REGISTERED_FOR_LABEL);
 161
 162         /* Set length and flags */
 163         stream_putw_at(s, 0, stream_get_endp(s));
 164
 165         /*
 166          * We only need to write new flags if this is a register
 167          */
 168         if (reg)
 169                 stream_putw_at(s, flags_pos, flags);
 170
 171         zclient_send_message(zclient);
 172 }
 173
 174 /**
 175  * This is passed as the callback function to bgp_labelpool.c:bgp_lp_get()
 176  * by bgp_reg_dereg_for_label() when a label needs to be obtained from
 177  * label pool.
 178  * Note that it will reject the allocated label if a label index is found,
 179  * because the label index supposes predictable labels
 180  */
 181 int bgp_reg_for_label_callback(mpls_label_t new_label, void *labelid,
 182                                bool allocated)
 183 {
 184         struct bgp_dest *dest;
 185
 186         dest = labelid;
 187
 188         /*
 189          * if the route had been removed or the request has gone then reject
 190          * the allocated label. The requesting code will have done what is
 191          * required to allocate the correct label
 192          */
 193         if (!CHECK_FLAG(dest->flags, BGP_NODE_LABEL_REQUESTED)) {
 194                 bgp_dest_unlock_node(dest);
 195                 return -1;
 196         }
 197
 198         bgp_dest_unlock_node(dest);
 199
 200         if (BGP_DEBUG(labelpool, LABELPOOL))
 201                 zlog_debug("%s: FEC %pRN label=%u, allocated=%d", __func__,
 202                            bgp_dest_to_rnode(dest), new_label, allocated);
 203
 204         if (!allocated) {
 205                 /*
 206                  * previously-allocated label is now invalid, set to implicit
 207                  * null until new label arrives
 208                  */
 209                 if (CHECK_FLAG(dest->flags, BGP_NODE_REGISTERED_FOR_LABEL)) {
 210                         UNSET_FLAG(dest->flags, BGP_NODE_LABEL_REQUESTED);
 211                         dest->local_label = mpls_lse_encode(
 212                                 MPLS_LABEL_IMPLICIT_NULL, 0, 0, 1);
 213                         bgp_set_valid_label(&dest->local_label);
 214                 }
 215         }
 216
 217         dest->local_label = mpls_lse_encode(new_label, 0, 0, 1);
 218         bgp_set_valid_label(&dest->local_label);
 219
 220         /*
 221          * Get back to registering the FEC
 222          */
 223         bgp_send_fec_register_label_msg(dest, true, 0);
 224
 225         return 0;
 226 }
 227
 228 void bgp_reg_dereg_for_label(struct bgp_dest *dest, struct bgp_path_info *pi,
 229                              bool reg)
 230 {
 231         bool with_label_index = false;
 232         const struct prefix *p;
 233         bool have_label_to_reg;
 234         uint32_t ttl = 0;
 235         uint32_t bos = 0;
 236         uint32_t exp = 0;
 237         mpls_label_t label = MPLS_INVALID_LABEL;
 238
 239         mpls_lse_decode(dest->local_label, &label, &ttl, &exp, &bos);
 240
 241         have_label_to_reg = bgp_is_valid_label(&dest->local_label) &&
 242                             label != MPLS_LABEL_IMPLICIT_NULL;
 243
 244         p = bgp_dest_get_prefix(dest);
 245
 246         if (BGP_DEBUG(labelpool, LABELPOOL))
 247                 zlog_debug("%s: %pFX: %s ", __func__, p,
 248                            (reg ? "reg" : "dereg"));
 249
 250         if (reg) {
 251                 assert(pi);
 252                 /*
 253                  * Determine if we will let zebra should derive label from
 254                  * label index instead of bgpd requesting from label pool
 255                  */
 256                 if (CHECK_FLAG(pi->attr->flag,
 257                             ATTR_FLAG_BIT(BGP_ATTR_PREFIX_SID))
 258                         && pi->attr->label_index != BGP_INVALID_LABEL_INDEX) {
 259                         with_label_index = true;
 260                         UNSET_FLAG(dest->flags, BGP_NODE_LABEL_REQUESTED);
 261                 } else {
 262                         /*
 263                          * If no label has been registered -- assume any label
 264                          * from label pool will do. This means that label index
 265                          * always takes precedence over auto-assigned labels.
 266                          */
 267                         if (!have_label_to_reg) {
 268                                 SET_FLAG(dest->flags, BGP_NODE_LABEL_REQUESTED);
 269                                 if (BGP_DEBUG(labelpool, LABELPOOL))
 270                                         zlog_debug(
 271                                                 "%s: Requesting label from LP for %pFX",
 272                                                 __func__, p);
 273                                 /* bgp_reg_for_label_callback() will deal with
 274                                  * fec registration when it gets a label from
 275                                  * the pool. This means we'll never register
 276                                  * FECs withoutvalid labels.
 277                                  */
 278                                 bgp_lp_get(LP_TYPE_BGP_LU, dest,
 279                                            bgp_reg_for_label_callback);
 280                                 return;
 281                         }
 282                 }
 283         } else {
 284                 UNSET_FLAG(dest->flags, BGP_NODE_LABEL_REQUESTED);
 285                 bgp_lp_release(LP_TYPE_BGP_LU, dest, label);
 286         }
 287
 288         bgp_send_fec_register_label_msg(
 289                 dest, reg, with_label_index ? pi->attr->label_index : 0);
 290 }
 291
 292 static int bgp_nlri_get_labels(struct peer *peer, uint8_t *pnt, uint8_t plen,
 293                                mpls_label_t *label)
 294 {
 295         uint8_t *data = pnt;
 296         uint8_t *lim = pnt + plen;
 297         uint8_t llen = 0;
 298         uint8_t label_depth = 0;
 299
 300         if (plen < BGP_LABEL_BYTES)
 301                 return 0;
 302
 303         for (; data < lim; data += BGP_LABEL_BYTES) {
 304                 memcpy(label, data, BGP_LABEL_BYTES);
 305                 llen += BGP_LABEL_BYTES;
 306
 307                 bgp_set_valid_label(label);
 308                 label_depth += 1;
 309
 310                 if (bgp_is_withdraw_label(label) || label_bos(label))
 311                         break;
 312         }
 313
 314         /* If we RX multiple labels we will end up keeping only the last
 315          * one. We do not yet support a label stack greater than 1. */
 316         if (label_depth > 1)
 317                 zlog_info("%pBP rcvd UPDATE with label stack %d deep", peer,
 318                           label_depth);
 319
 320         if (!(bgp_is_withdraw_label(label) || label_bos(label)))
 321                 flog_warn(
 322                         EC_BGP_INVALID_LABEL_STACK,
 323                         "%pBP rcvd UPDATE with invalid label stack - no bottom of stack",
 324                         peer);
 325
 326         return llen;
 327 }
 328
 329 int bgp_nlri_parse_label(struct peer *peer, struct attr *attr,
 330                          struct bgp_nlri *packet)
 331 {
 332         uint8_t *pnt;
 333         uint8_t *lim;
 334         struct prefix p;
 335         int psize = 0;
 336         int prefixlen;
 337         afi_t afi;
 338         safi_t safi;
 339         bool addpath_capable;
 340         uint32_t addpath_id;
 341         mpls_label_t label = MPLS_INVALID_LABEL;
 342         uint8_t llen;
 343
 344         pnt = packet->nlri;
 345         lim = pnt + packet->length;
 346         afi = packet->afi;
 347         safi = packet->safi;
 348         addpath_id = 0;
 349
 350         addpath_capable = bgp_addpath_encode_rx(peer, afi, safi);
 351
 352         for (; pnt < lim; pnt += psize) {
 353                 /* Clear prefix structure. */
 354                 memset(&p, 0, sizeof(p));
 355
 356                 if (addpath_capable) {
 357
 358                         /* When packet overflow occurs return immediately. */
 359                         if (pnt + BGP_ADDPATH_ID_LEN > lim)
 360                                 return BGP_NLRI_PARSE_ERROR_PACKET_OVERFLOW;
 361
 362                         memcpy(&addpath_id, pnt, BGP_ADDPATH_ID_LEN);
 363                         addpath_id = ntohl(addpath_id);
 364                         pnt += BGP_ADDPATH_ID_LEN;
 365
 366                         if (pnt >= lim)
 367                                 return BGP_NLRI_PARSE_ERROR_PACKET_OVERFLOW;
 368                 }
 369
 370                 /* Fetch prefix length. */
 371                 prefixlen = *pnt++;
 372                 p.family = afi2family(packet->afi);
 373                 psize = PSIZE(prefixlen);
 374
 375                 /* sanity check against packet data */
 376                 if ((pnt + psize) > lim) {
 377                         flog_err(
 378                                 EC_BGP_UPDATE_RCV,
 379                                 "%s [Error] Update packet error / L-U (prefix length %d exceeds packet size %u)",
 380                                 peer->host, prefixlen, (uint)(lim - pnt));
 381                         return BGP_NLRI_PARSE_ERROR_PACKET_OVERFLOW;
 382                 }
 383
 384                 /* Fill in the labels */
 385                 llen = bgp_nlri_get_labels(peer, pnt, psize, &label);
 386                 if (llen == 0) {
 387                         flog_err(
 388                                 EC_BGP_UPDATE_RCV,
 389                                 "%s [Error] Update packet error (wrong label length 0)",
 390                                 peer->host);
 391                         return BGP_NLRI_PARSE_ERROR_LABEL_LENGTH;
 392                 }
 393                 p.prefixlen = prefixlen - BSIZE(llen);
 394
 395                 /* There needs to be at least one label */
 396                 if (prefixlen < 24) {
 397                         flog_err(EC_BGP_UPDATE_RCV,
 398                                  "%s [Error] Update packet error (wrong label length %d)",
 399                                  peer->host, prefixlen);
 400                         return BGP_NLRI_PARSE_ERROR_LABEL_LENGTH;
 401                 }
 402
 403                 if ((afi == AFI_IP && p.prefixlen > IPV4_MAX_BITLEN)
 404                     || (afi == AFI_IP6 && p.prefixlen > IPV6_MAX_BITLEN))
 405                         return BGP_NLRI_PARSE_ERROR_PREFIX_LENGTH;
 406
 407                 /* Fetch prefix from NLRI packet */
 408                 memcpy(&p.u.prefix, pnt + llen, psize - llen);
 409
 410                 /* Check address. */
 411                 if (afi == AFI_IP && safi == SAFI_LABELED_UNICAST) {
 412                         if (IN_CLASSD(ntohl(p.u.prefix4.s_addr))) {
 413                                 /* From RFC4271 Section 6.3:
 414                                  *
 415                                  * If a prefix in the NLRI field is semantically
 416                                  * incorrect
 417                                  * (e.g., an unexpected multicast IP address),
 418                                  * an error SHOULD
 419                                  * be logged locally, and the prefix SHOULD be
 420                                  * ignored.
 421                                   */
 422                                 flog_err(
 423                                         EC_BGP_UPDATE_RCV,
 424                                         "%s: IPv4 labeled-unicast NLRI is multicast address %pI4, ignoring",
 425                                         peer->host, &p.u.prefix4);
 426                                 continue;
 427                         }
 428                 }
 429
 430                 /* Check address. */
 431                 if (afi == AFI_IP6 && safi == SAFI_LABELED_UNICAST) {
 432                         if (IN6_IS_ADDR_LINKLOCAL(&p.u.prefix6)) {
 433                                 flog_err(
 434                                         EC_BGP_UPDATE_RCV,
 435                                         "%s: IPv6 labeled-unicast NLRI is link-local address %pI6, ignoring",
 436                                         peer->host, &p.u.prefix6);
 437
 438                                 continue;
 439                         }
 440
 441                         if (IN6_IS_ADDR_MULTICAST(&p.u.prefix6)) {
 442                                 flog_err(
 443                                         EC_BGP_UPDATE_RCV,
 444                                         "%s: IPv6 unicast NLRI is multicast address %pI6, ignoring",
 445                                         peer->host, &p.u.prefix6);
 446
 447                                 continue;
 448                         }
 449                 }
 450
 451                 if (attr) {
 452                         bgp_update(peer, &p, addpath_id, attr, packet->afi,
 453                                    safi, ZEBRA_ROUTE_BGP, BGP_ROUTE_NORMAL,
 454                                    NULL, &label, 1, 0, NULL);
 455                 } else {
 456                         bgp_withdraw(peer, &p, addpath_id, packet->afi,
 457                                      SAFI_UNICAST, ZEBRA_ROUTE_BGP,
 458                                      BGP_ROUTE_NORMAL, NULL, &label, 1, NULL);
 459                 }
 460         }
 461
 462         /* Packet length consistency check. */
 463         if (pnt != lim) {
 464                 flog_err(
 465                         EC_BGP_UPDATE_RCV,
 466                         "%s [Error] Update packet error / L-U (%td data remaining after parsing)",
 467                         peer->host, lim - pnt);
 468                 return BGP_NLRI_PARSE_ERROR_PACKET_LENGTH;
 469         }
 470
 471         return BGP_NLRI_PARSE_OK;
 472 }