ospfd/ospf_ia.c

   1 /*
   2  * OSPF inter-area routing.
   3  * Copyright (C) 1999, 2000 Alex Zinin, Toshiaki Takada
   4  *
   5  * This file is part of GNU Zebra.
   6  *
   7  * GNU Zebra is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License as published by the
   9  * Free Software Foundation; either version 2, or (at your option) any
  10  * later version.
  11  *
  12  * GNU Zebra is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with GNU Zebra; see the file COPYING.  If not, write to the Free
  19  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20  * 02111-1307, USA.
  21  */
  22
  23
  24 #include <zebra.h>
  25
  26 #include "thread.h"
  27 #include "memory.h"
  28 #include "hash.h"
  29 #include "linklist.h"
  30 #include "prefix.h"
  31 #include "table.h"
  32 #include "log.h"
  33
  34 #include "ospfd/ospfd.h"
  35 #include "ospfd/ospf_interface.h"
  36 #include "ospfd/ospf_ism.h"
  37 #include "ospfd/ospf_asbr.h"
  38 #include "ospfd/ospf_lsa.h"
  39 #include "ospfd/ospf_lsdb.h"
  40 #include "ospfd/ospf_neighbor.h"
  41 #include "ospfd/ospf_nsm.h"
  42 #include "ospfd/ospf_spf.h"
  43 #include "ospfd/ospf_route.h"
  44 #include "ospfd/ospf_ase.h"
  45 #include "ospfd/ospf_abr.h"
  46 #include "ospfd/ospf_ia.h"
  47 #include "ospfd/ospf_dump.h"
  48
  49 static struct ospf_route *
  50 ospf_find_abr_route (struct route_table *rtrs,
  51                      struct prefix_ipv4 *abr,
  52                      struct ospf_area *area)
  53 {
  54   struct route_node *rn;
  55   struct ospf_route *or;
  56   struct listnode *node;
  57
  58   if ((rn = route_node_lookup (rtrs, (struct prefix *) abr)) == NULL)
  59     return NULL;
  60
  61   route_unlock_node (rn);
  62
  63   for (ALL_LIST_ELEMENTS_RO ((struct list *) rn->info, node, or))
  64     if (IPV4_ADDR_SAME (&or->u.std.area_id, &area->area_id)
  65         && (or->u.std.flags & ROUTER_LSA_BORDER))
  66       return or;
  67
  68   return NULL;
  69 }
  70
  71 static void
  72 ospf_ia_network_route (struct ospf *ospf, struct route_table *rt,
  73                        struct prefix_ipv4 *p, struct ospf_route *new_or,
  74                        struct ospf_route *abr_or)
  75 {
  76   struct route_node *rn1;
  77   struct ospf_route *or;
  78
  79   if (IS_DEBUG_OSPF_EVENT)
  80     zlog_debug ("ospf_ia_network_route(): processing summary route to %s/%d",
  81                inet_ntoa (p->prefix), p->prefixlen);
  82
  83   /* Find a route to the same dest */
  84   if ((rn1 = route_node_lookup (rt, (struct prefix *) p)))
  85     {
  86       int res;
  87
  88       route_unlock_node (rn1);
  89
  90       if ((or = rn1->info))
  91         {
  92           if (IS_DEBUG_OSPF_EVENT)
  93             zlog_debug ("ospf_ia_network_route(): "
  94                        "Found a route to the same network");
  95           /* Check the existing route. */
  96           if ((res = ospf_route_cmp (ospf, new_or, or)) < 0)
  97             {
  98               /* New route is better, so replace old one. */
  99               ospf_route_subst (rn1, new_or, abr_or);
 100             }
 101           else if (res == 0)
 102             {
 103               /* New and old route are equal, so next hops can be added. */
 104               route_lock_node (rn1);
 105               ospf_route_copy_nexthops (or, abr_or->paths);
 106               route_unlock_node (rn1);
 107
 108               /* new route can be deleted, because existing route has been updated. */
 109               ospf_route_free (new_or);
 110             }
 111           else
 112             {
 113               /* New route is worse, so free it. */
 114               ospf_route_free (new_or);
 115               return;
 116             }
 117         } /* if (or)*/
 118     } /*if (rn1)*/
 119   else
 120     { /* no route */
 121       if (IS_DEBUG_OSPF_EVENT)
 122         zlog_debug ("ospf_ia_network_route(): add new route to %s/%d",
 123                    inet_ntoa (p->prefix), p->prefixlen);
 124       ospf_route_add (rt, p, new_or, abr_or);
 125     }
 126 }
 127
 128 static void
 129 ospf_ia_router_route (struct ospf *ospf, struct route_table *rtrs,
 130                       struct prefix_ipv4 *p,
 131                       struct ospf_route *new_or, struct ospf_route *abr_or)
 132 {
 133   struct ospf_route *or = NULL;
 134   struct route_node *rn;
 135   int ret;
 136
 137   if (IS_DEBUG_OSPF_EVENT)
 138     zlog_debug ("ospf_ia_router_route(): considering %s/%d",
 139                inet_ntoa (p->prefix), p->prefixlen);
 140   /* Find a route to the same dest */
 141   rn = route_node_get (rtrs, (struct prefix *) p);
 142
 143   if (rn->info == NULL)
 144     /* This is a new route */
 145     rn->info = list_new ();
 146   else
 147     {
 148       struct ospf_area *or_area;
 149       or_area = ospf_area_lookup_by_area_id (ospf, new_or->u.std.area_id);
 150       assert (or_area);
 151       /* This is an additional route */
 152       route_unlock_node (rn);
 153       or = ospf_find_asbr_route_through_area (rtrs, p, or_area);
 154     }
 155
 156   if (or)
 157     {
 158       if (IS_DEBUG_OSPF_EVENT)
 159         zlog_debug ("ospf_ia_router_route(): "
 160                    "a route to the same ABR through the same area exists");
 161       /* New route is better */
 162       if ((ret = ospf_route_cmp (ospf, new_or, or)) < 0)
 163         {
 164           listnode_delete (rn->info, or);
 165           ospf_route_free (or);
 166           /* proceed down */
 167         }
 168       /* Routes are the same */
 169       else if (ret == 0)
 170         {
 171           if (IS_DEBUG_OSPF_EVENT)
 172             zlog_debug ("ospf_ia_router_route(): merging the new route");
 173
 174           ospf_route_copy_nexthops (or, abr_or->paths);
 175           ospf_route_free (new_or);
 176           return;
 177         }
 178       /* New route is worse */
 179       else
 180         {
 181           if (IS_DEBUG_OSPF_EVENT)
 182             zlog_debug ("ospf_ia_router_route(): skipping the new route");
 183           ospf_route_free (new_or);
 184           return;
 185         }
 186     }
 187
 188   ospf_route_copy_nexthops (new_or, abr_or->paths);
 189
 190   if (IS_DEBUG_OSPF_EVENT)
 191     zlog_debug ("ospf_ia_router_route(): adding the new route");
 192
 193   listnode_add (rn->info, new_or);
 194 }
 195
 196 \f
 197 static int
 198 process_summary_lsa (struct ospf_area *area, struct route_table *rt,
 199                      struct route_table *rtrs, struct ospf_lsa *lsa)
 200 {
 201   struct ospf *ospf = area->ospf;
 202   struct ospf_area_range *range;
 203   struct ospf_route *abr_or, *new_or;
 204   struct summary_lsa *sl;
 205   struct prefix_ipv4 p, abr;
 206   u_int32_t metric;
 207
 208   if (lsa == NULL)
 209     return 0;
 210
 211   sl = (struct summary_lsa *) lsa->data;
 212
 213   if (IS_DEBUG_OSPF_EVENT)
 214     zlog_debug ("process_summary_lsa(): LS ID: %s", inet_ntoa (sl->header.id));
 215
 216   metric = GET_METRIC (sl->metric);
 217
 218   if (metric == OSPF_LS_INFINITY)
 219     return 0;
 220
 221   if (IS_LSA_MAXAGE (lsa))
 222     return 0;
 223
 224   if (ospf_lsa_is_self_originated (area->ospf, lsa))
 225     return 0;
 226
 227   p.family = AF_INET;
 228   p.prefix = sl->header.id;
 229
 230   if (sl->header.type == OSPF_SUMMARY_LSA)
 231     p.prefixlen = ip_masklen (sl->mask);
 232   else
 233     p.prefixlen = IPV4_MAX_BITLEN;
 234
 235   apply_mask_ipv4 (&p);
 236
 237   if (sl->header.type == OSPF_SUMMARY_LSA &&
 238       (range = ospf_area_range_match_any (ospf, &p)) &&
 239       ospf_area_range_active (range))
 240     return 0;
 241
 242   /* XXX: This check seems dubious to me. If an ABR has already decided
 243    * to consider summaries received in this area, then why would one wish
 244    * to exclude default?
 245    */
 246   if (IS_OSPF_ABR(ospf) &&
 247       ospf->abr_type != OSPF_ABR_STAND &&
 248       area->external_routing != OSPF_AREA_DEFAULT &&
 249       p.prefix.s_addr == OSPF_DEFAULT_DESTINATION &&
 250       p.prefixlen == 0)
 251     return 0; /* Ignore summary default from a stub area */
 252
 253   abr.family = AF_INET;
 254   abr.prefix = sl->header.adv_router;
 255   abr.prefixlen = IPV4_MAX_BITLEN;
 256   apply_mask_ipv4 (&abr);
 257
 258   abr_or = ospf_find_abr_route (rtrs, &abr, area);
 259
 260   if (abr_or == NULL)
 261     return 0;
 262
 263   new_or = ospf_route_new ();
 264   new_or->type = OSPF_DESTINATION_NETWORK;
 265   new_or->id = sl->header.id;
 266   new_or->mask = sl->mask;
 267   new_or->u.std.options = sl->header.options;
 268   new_or->u.std.origin = (struct lsa_header *) sl;
 269   new_or->cost = abr_or->cost + metric;
 270   new_or->u.std.area_id = area->area_id;
 271   new_or->u.std.external_routing = area->external_routing;
 272   new_or->path_type = OSPF_PATH_INTER_AREA;
 273
 274   if (sl->header.type == OSPF_SUMMARY_LSA)
 275     ospf_ia_network_route (ospf, rt, &p, new_or, abr_or);
 276   else
 277     {
 278       new_or->type = OSPF_DESTINATION_ROUTER;
 279       new_or->u.std.flags = ROUTER_LSA_EXTERNAL;
 280       ospf_ia_router_route (ospf, rtrs, &p, new_or, abr_or);
 281     }
 282
 283   return 0;
 284 }
 285
 286 static void
 287 ospf_examine_summaries (struct ospf_area *area,
 288                         struct route_table *lsdb_rt,
 289                         struct route_table *rt,
 290                         struct route_table *rtrs)
 291 {
 292   struct ospf_lsa *lsa;
 293   struct route_node *rn;
 294
 295   LSDB_LOOP (lsdb_rt, rn, lsa)
 296     process_summary_lsa (area, rt, rtrs, lsa);
 297 }
 298
 299 int
 300 ospf_area_is_transit (struct ospf_area *area)
 301 {
 302   return (area->transit == OSPF_TRANSIT_TRUE) ||
 303     ospf_full_virtual_nbrs(area); /* Cisco forgets to set the V-bit :( */
 304 }
 305
 306 static void
 307 ospf_update_network_route (struct ospf *ospf,
 308                            struct route_table *rt,
 309                            struct route_table *rtrs,
 310                            struct summary_lsa *lsa,
 311                            struct prefix_ipv4 *p,
 312                            struct ospf_area *area)
 313 {
 314   struct route_node *rn;
 315   struct ospf_route *or, *abr_or, *new_or;
 316   struct prefix_ipv4 abr;
 317   u_int32_t cost;
 318
 319   abr.family = AF_INET;
 320   abr.prefix =lsa->header.adv_router;
 321   abr.prefixlen = IPV4_MAX_BITLEN;
 322   apply_mask_ipv4 (&abr);
 323
 324   abr_or = ospf_find_abr_route (rtrs, &abr, area);
 325
 326   if (abr_or == NULL)
 327     {
 328       if (IS_DEBUG_OSPF_EVENT)
 329         zlog_debug ("ospf_update_network_route(): can't find a route to the ABR");
 330       return;
 331     }
 332
 333   cost = abr_or->cost + GET_METRIC (lsa->metric);
 334
 335   rn = route_node_lookup (rt, (struct prefix *) p);
 336
 337   if (! rn)
 338     {
 339       if (ospf->abr_type != OSPF_ABR_SHORTCUT)
 340         return; /* Standard ABR can update only already installed
 341                    backbone paths                                       */
 342       if (IS_DEBUG_OSPF_EVENT)
 343         zlog_debug ("ospf_update_network_route(): "
 344                    "Allowing Shortcut ABR to add new route");
 345       new_or = ospf_route_new ();
 346       new_or->type = OSPF_DESTINATION_NETWORK;
 347       new_or->id = lsa->header.id;
 348       new_or->mask = lsa->mask;
 349       new_or->u.std.options = lsa->header.options;
 350       new_or->u.std.origin = (struct lsa_header *) lsa;
 351       new_or->cost = cost;
 352       new_or->u.std.area_id = area->area_id;
 353       new_or->u.std.external_routing = area->external_routing;
 354       new_or->path_type = OSPF_PATH_INTER_AREA;
 355       ospf_route_add (rt, p, new_or, abr_or);
 356
 357       return;
 358     }
 359   else
 360     {
 361       route_unlock_node (rn);
 362       if (rn->info == NULL)
 363         return;
 364     }
 365
 366   or = rn->info;
 367
 368   if (or->path_type != OSPF_PATH_INTRA_AREA &&
 369       or->path_type != OSPF_PATH_INTER_AREA)
 370     {
 371       if (IS_DEBUG_OSPF_EVENT)
 372         zlog_debug ("ospf_update_network_route(): ERR: path type is wrong");
 373       return;
 374     }
 375
 376   if (ospf->abr_type == OSPF_ABR_SHORTCUT)
 377     {
 378       if (or->path_type == OSPF_PATH_INTRA_AREA &&
 379           !OSPF_IS_AREA_ID_BACKBONE (or->u.std.area_id))
 380         {
 381           if (IS_DEBUG_OSPF_EVENT)
 382             zlog_debug ("ospf_update_network_route(): Shortcut: "
 383                        "this intra-area path is not backbone");
 384           return;
 385         }
 386     }
 387   else   /* Not Shortcut ABR */
 388     {
 389       if (!OSPF_IS_AREA_ID_BACKBONE (or->u.std.area_id))
 390         {
 391           if (IS_DEBUG_OSPF_EVENT)
 392             zlog_debug ("ospf_update_network_route(): "
 393                        "route is not BB-associated");
 394           return; /* We can update only BB routes */
 395         }
 396     }
 397
 398   if (or->cost < cost)
 399     {
 400       if (IS_DEBUG_OSPF_EVENT)
 401         zlog_debug ("ospf_update_network_route(): new route is worse");
 402       return;
 403     }
 404
 405   if (or->cost == cost)
 406     {
 407       if (IS_DEBUG_OSPF_EVENT)
 408         zlog_debug ("ospf_update_network_route(): "
 409                    "new route is same distance, adding nexthops");
 410       ospf_route_copy_nexthops (or, abr_or->paths);
 411     }
 412
 413   if (or->cost > cost)
 414     {
 415       if (IS_DEBUG_OSPF_EVENT)
 416         zlog_debug ("ospf_update_network_route(): "
 417                    "new route is better, overriding nexthops");
 418       ospf_route_subst_nexthops (or, abr_or->paths);
 419       or->cost = cost;
 420
 421       if ((ospf->abr_type == OSPF_ABR_SHORTCUT) &&
 422           !OSPF_IS_AREA_ID_BACKBONE (or->u.std.area_id))
 423         {
 424           or->path_type = OSPF_PATH_INTER_AREA;
 425           or->u.std.area_id = area->area_id;
 426           or->u.std.external_routing = area->external_routing;
 427           /* Note that we can do this only in Shortcut ABR mode,
 428              because standard ABR must leave the route type and area
 429              unchanged
 430           */
 431         }
 432     }
 433 }
 434
 435 static void
 436 ospf_update_router_route (struct ospf *ospf,
 437                           struct route_table *rtrs,
 438                           struct summary_lsa *lsa,
 439                           struct prefix_ipv4 *p,
 440                           struct ospf_area *area)
 441 {
 442   struct ospf_route *or, *abr_or, *new_or;
 443   struct prefix_ipv4 abr;
 444   u_int32_t cost;
 445
 446   abr.family = AF_INET;
 447   abr.prefix = lsa->header.adv_router;
 448   abr.prefixlen = IPV4_MAX_BITLEN;
 449   apply_mask_ipv4 (&abr);
 450
 451   abr_or = ospf_find_abr_route (rtrs, &abr, area);
 452
 453   if (abr_or == NULL)
 454     {
 455       if (IS_DEBUG_OSPF_EVENT)
 456         zlog_debug ("ospf_update_router_route(): can't find a route to the ABR");
 457       return;
 458     }
 459
 460   cost = abr_or->cost + GET_METRIC (lsa->metric);
 461
 462   /* First try to find a backbone path,
 463      because standard ABR can update only BB-associated paths */
 464
 465   if ((ospf->backbone == NULL) &&
 466       (ospf->abr_type != OSPF_ABR_SHORTCUT))
 467      return; /* no BB area, not Shortcut ABR, exiting */
 468
 469   /* find the backbone route, if possible */
 470   if ((ospf->backbone == NULL)
 471       || !(or = ospf_find_asbr_route_through_area (rtrs, p, ospf->backbone)))
 472     {
 473       if (ospf->abr_type != OSPF_ABR_SHORTCUT)
 474
 475          /* route to ASBR through the BB not found
 476             the router is not Shortcut ABR, exiting */
 477
 478           return;
 479       else
 480         /* We're a Shortcut ABR*/
 481         {
 482           /* Let it either add a new router or update the route
 483              through the same (non-BB) area. */
 484
 485           new_or = ospf_route_new ();
 486           new_or->type = OSPF_DESTINATION_ROUTER;
 487           new_or->id = lsa->header.id;
 488           new_or->mask = lsa->mask;
 489           new_or->u.std.options = lsa->header.options;
 490           new_or->u.std.origin = (struct lsa_header *)lsa;
 491           new_or->cost = cost;
 492           new_or->u.std.area_id = area->area_id;
 493           new_or->u.std.external_routing = area->external_routing;
 494           new_or->path_type = OSPF_PATH_INTER_AREA;
 495           new_or->u.std.flags = ROUTER_LSA_EXTERNAL;
 496           ospf_ia_router_route (ospf, rtrs, p, new_or, abr_or);
 497
 498           return;
 499         }
 500     }
 501
 502   /* At this point the "or" is always bb-associated */
 503
 504   if (!(or->u.std.flags & ROUTER_LSA_EXTERNAL))
 505     {
 506       if (IS_DEBUG_OSPF_EVENT)
 507         zlog_debug ("ospf_upd_router_route(): the remote router is not an ASBR");
 508       return;
 509     }
 510
 511   if (or->path_type != OSPF_PATH_INTRA_AREA &&
 512       or->path_type != OSPF_PATH_INTER_AREA)
 513     return;
 514
 515   if (or->cost < cost)
 516     return;
 517
 518   else if (or->cost == cost)
 519     ospf_route_copy_nexthops (or, abr_or->paths);
 520
 521   else if (or->cost > cost)
 522     {
 523       ospf_route_subst_nexthops (or, abr_or->paths);
 524       or->cost = cost;
 525
 526       /* Even if the ABR runs in Shortcut mode, we can't change
 527          the path type and area, because the "or" is always bb-associated
 528          at this point and even Shortcut ABR can't change these attributes */
 529     }
 530 }
 531
 532 static int
 533 process_transit_summary_lsa (struct ospf_area *area, struct route_table *rt,
 534                              struct route_table *rtrs, struct ospf_lsa *lsa)
 535 {
 536   struct ospf *ospf = area->ospf;
 537   struct summary_lsa *sl;
 538   struct prefix_ipv4 p;
 539   u_int32_t metric;
 540
 541   if (lsa == NULL)
 542     return 0;
 543
 544   sl = (struct summary_lsa *) lsa->data;
 545
 546   if (IS_DEBUG_OSPF_EVENT)
 547     zlog_debug ("process_transit_summaries(): LS ID: %s",
 548                inet_ntoa (lsa->data->id));
 549   metric = GET_METRIC (sl->metric);
 550
 551   if (metric == OSPF_LS_INFINITY)
 552     {
 553       if (IS_DEBUG_OSPF_EVENT)
 554         zlog_debug ("process_transit_summaries(): metric is infinity, skip");
 555       return 0;
 556     }
 557
 558   if (IS_LSA_MAXAGE (lsa))
 559     {
 560       if (IS_DEBUG_OSPF_EVENT)
 561         zlog_debug ("process_transit_summaries(): This LSA is too old");
 562       return 0;
 563     }
 564
 565   if (ospf_lsa_is_self_originated (area->ospf, lsa))
 566     {
 567       if (IS_DEBUG_OSPF_EVENT)
 568         zlog_debug ("process_transit_summaries(): This LSA is mine, skip");
 569       return 0;
 570     }
 571
 572   p.family = AF_INET;
 573   p.prefix = sl->header.id;
 574
 575   if (sl->header.type == OSPF_SUMMARY_LSA)
 576     p.prefixlen = ip_masklen (sl->mask);
 577   else
 578     p.prefixlen = IPV4_MAX_BITLEN;
 579
 580   apply_mask_ipv4 (&p);
 581
 582   if (sl->header.type == OSPF_SUMMARY_LSA)
 583     ospf_update_network_route (ospf, rt, rtrs, sl, &p, area);
 584   else
 585     ospf_update_router_route (ospf, rtrs, sl, &p, area);
 586
 587   return 0;
 588 }
 589
 590 static void
 591 ospf_examine_transit_summaries (struct ospf_area *area,
 592                                 struct route_table *lsdb_rt,
 593                                 struct route_table *rt,
 594                                 struct route_table *rtrs)
 595 {
 596   struct ospf_lsa *lsa;
 597   struct route_node *rn;
 598
 599   LSDB_LOOP (lsdb_rt, rn, lsa)
 600     process_transit_summary_lsa (area, rt, rtrs, lsa);
 601 }
 602
 603 void
 604 ospf_ia_routing (struct ospf *ospf,
 605                  struct route_table *rt,
 606                  struct route_table *rtrs)
 607 {
 608   struct ospf_area * area;
 609
 610   if (IS_DEBUG_OSPF_EVENT)
 611     zlog_debug ("ospf_ia_routing():start");
 612
 613   if (IS_OSPF_ABR (ospf))
 614     {
 615       struct listnode *node;
 616       struct ospf_area *area;
 617
 618       switch (ospf->abr_type)
 619         {
 620         case OSPF_ABR_STAND:
 621           if (IS_DEBUG_OSPF_EVENT)
 622             zlog_debug ("ospf_ia_routing():Standard ABR");
 623
 624           if ((area = ospf->backbone))
 625             {
 626               struct listnode *node;
 627
 628               if (IS_DEBUG_OSPF_EVENT)
 629                 {
 630                   zlog_debug ("ospf_ia_routing():backbone area found");
 631                   zlog_debug ("ospf_ia_routing():examining summaries");
 632                 }
 633
 634               OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 635
 636               for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 637                 if (area != ospf->backbone)
 638                   if (ospf_area_is_transit (area))
 639                     OSPF_EXAMINE_TRANSIT_SUMMARIES_ALL (area, rt, rtrs);
 640             }
 641           else
 642             if (IS_DEBUG_OSPF_EVENT)
 643               zlog_debug ("ospf_ia_routing():backbone area NOT found");
 644           break;
 645         case OSPF_ABR_IBM:
 646         case OSPF_ABR_CISCO:
 647           if (IS_DEBUG_OSPF_EVENT)
 648             zlog_debug ("ospf_ia_routing():Alternative Cisco/IBM ABR");
 649           area = ospf->backbone; /* Find the BB */
 650
 651           /* If we have an active BB connection */
 652           if (area && ospf_act_bb_connection (ospf))
 653             {
 654               if (IS_DEBUG_OSPF_EVENT)
 655                 {
 656                   zlog_debug ("ospf_ia_routing(): backbone area found");
 657                   zlog_debug ("ospf_ia_routing(): examining BB summaries");
 658                 }
 659
 660               OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 661
 662               for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 663                 if (area != ospf->backbone)
 664                   if (ospf_area_is_transit (area))
 665                     OSPF_EXAMINE_TRANSIT_SUMMARIES_ALL (area, rt, rtrs);
 666             }
 667           else
 668             { /* No active BB connection--consider all areas */
 669               if (IS_DEBUG_OSPF_EVENT)
 670                 zlog_debug ("ospf_ia_routing(): "
 671                            "Active BB connection not found");
 672               for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 673                 OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 674             }
 675           break;
 676         case OSPF_ABR_SHORTCUT:
 677           if (IS_DEBUG_OSPF_EVENT)
 678             zlog_debug ("ospf_ia_routing():Alternative Shortcut");
 679           area = ospf->backbone; /* Find the BB */
 680
 681           /* If we have an active BB connection */
 682           if (area && ospf_act_bb_connection (ospf))
 683             {
 684               if (IS_DEBUG_OSPF_EVENT)
 685                 {
 686                   zlog_debug ("ospf_ia_routing(): backbone area found");
 687                   zlog_debug ("ospf_ia_routing(): examining BB summaries");
 688                 }
 689               OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 690             }
 691
 692           for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 693             if (area != ospf->backbone)
 694               if (ospf_area_is_transit (area) ||
 695                   ((area->shortcut_configured != OSPF_SHORTCUT_DISABLE) &&
 696                   ((ospf->backbone == NULL) ||
 697                   ((area->shortcut_configured == OSPF_SHORTCUT_ENABLE) &&
 698                   area->shortcut_capability))))
 699                 OSPF_EXAMINE_TRANSIT_SUMMARIES_ALL (area, rt, rtrs);
 700           break;
 701         default:
 702           break;
 703         }
 704     }
 705   else
 706     {
 707       struct listnode *node;
 708
 709       if (IS_DEBUG_OSPF_EVENT)
 710         zlog_debug ("ospf_ia_routing():not ABR, considering all areas");
 711
 712       for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 713         OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 714     }
 715 }