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 along
  18  * with this program; see the file COPYING; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22
  23 #include <zebra.h>
  24
  25 #include "thread.h"
  26 #include "memory.h"
  27 #include "hash.h"
  28 #include "linklist.h"
  29 #include "prefix.h"
  30 #include "table.h"
  31 #include "log.h"
  32
  33 #include "ospfd/ospfd.h"
  34 #include "ospfd/ospf_interface.h"
  35 #include "ospfd/ospf_ism.h"
  36 #include "ospfd/ospf_asbr.h"
  37 #include "ospfd/ospf_lsa.h"
  38 #include "ospfd/ospf_lsdb.h"
  39 #include "ospfd/ospf_neighbor.h"
  40 #include "ospfd/ospf_nsm.h"
  41 #include "ospfd/ospf_spf.h"
  42 #include "ospfd/ospf_route.h"
  43 #include "ospfd/ospf_ase.h"
  44 #include "ospfd/ospf_abr.h"
  45 #include "ospfd/ospf_ia.h"
  46 #include "ospfd/ospf_dump.h"
  47
  48 static struct ospf_route *
  49 ospf_find_abr_route (struct route_table *rtrs,
  50                      struct prefix_ipv4 *abr,
  51                      struct ospf_area *area)
  52 {
  53   struct route_node *rn;
  54   struct ospf_route *or;
  55   struct listnode *node;
  56
  57   if ((rn = route_node_lookup (rtrs, (struct prefix *) abr)) == NULL)
  58     return NULL;
  59
  60   route_unlock_node (rn);
  61
  62   for (ALL_LIST_ELEMENTS_RO ((struct list *) rn->info, node, or))
  63     if (IPV4_ADDR_SAME (&or->u.std.area_id, &area->area_id)
  64         && (or->u.std.flags & ROUTER_LSA_BORDER))
  65       return or;
  66
  67   return NULL;
  68 }
  69
  70 static void
  71 ospf_ia_network_route (struct ospf *ospf, struct route_table *rt,
  72                        struct prefix_ipv4 *p, struct ospf_route *new_or,
  73                        struct ospf_route *abr_or)
  74 {
  75   struct route_node *rn1;
  76   struct ospf_route *or;
  77
  78   if (IS_DEBUG_OSPF_EVENT)
  79     zlog_debug ("ospf_ia_network_route(): processing summary route to %s/%d",
  80                inet_ntoa (p->prefix), p->prefixlen);
  81
  82   /* Find a route to the same dest */
  83   if ((rn1 = route_node_lookup (rt, (struct prefix *) p)))
  84     {
  85       int res;
  86
  87       route_unlock_node (rn1);
  88
  89       if ((or = rn1->info))
  90         {
  91           if (IS_DEBUG_OSPF_EVENT)
  92             zlog_debug ("ospf_ia_network_route(): "
  93                        "Found a route to the same network");
  94           /* Check the existing route. */
  95           if ((res = ospf_route_cmp (ospf, new_or, or)) < 0)
  96             {
  97               /* New route is better, so replace old one. */
  98               ospf_route_subst (rn1, new_or, abr_or);
  99             }
 100           else if (res == 0)
 101             {
 102               /* New and old route are equal, so next hops can be added. */
 103               route_lock_node (rn1);
 104               ospf_route_copy_nexthops (or, abr_or->paths);
 105               route_unlock_node (rn1);
 106
 107               /* new route can be deleted, because existing route has been updated. */
 108               ospf_route_free (new_or);
 109             }
 110           else
 111             {
 112               /* New route is worse, so free it. */
 113               ospf_route_free (new_or);
 114               return;
 115             }
 116         } /* if (or)*/
 117     } /*if (rn1)*/
 118   else
 119     { /* no route */
 120       if (IS_DEBUG_OSPF_EVENT)
 121         zlog_debug ("ospf_ia_network_route(): add new route to %s/%d",
 122                    inet_ntoa (p->prefix), p->prefixlen);
 123       ospf_route_add (rt, p, new_or, abr_or);
 124     }
 125 }
 126
 127 static void
 128 ospf_ia_router_route (struct ospf *ospf, struct route_table *rtrs,
 129                       struct prefix_ipv4 *p,
 130                       struct ospf_route *new_or, struct ospf_route *abr_or)
 131 {
 132   struct ospf_route *or = NULL;
 133   struct route_node *rn;
 134   int ret;
 135
 136   if (IS_DEBUG_OSPF_EVENT)
 137     zlog_debug ("ospf_ia_router_route(): considering %s/%d",
 138                inet_ntoa (p->prefix), p->prefixlen);
 139   /* Find a route to the same dest */
 140   rn = route_node_get (rtrs, (struct prefix *) p);
 141
 142   if (rn->info == NULL)
 143     /* This is a new route */
 144     rn->info = list_new ();
 145   else
 146     {
 147       struct ospf_area *or_area;
 148       or_area = ospf_area_lookup_by_area_id (ospf, new_or->u.std.area_id);
 149       assert (or_area);
 150       /* This is an additional route */
 151       route_unlock_node (rn);
 152       or = ospf_find_asbr_route_through_area (rtrs, p, or_area);
 153     }
 154
 155   if (or)
 156     {
 157       if (IS_DEBUG_OSPF_EVENT)
 158         zlog_debug ("ospf_ia_router_route(): "
 159                    "a route to the same ABR through the same area exists");
 160       /* New route is better */
 161       if ((ret = ospf_route_cmp (ospf, new_or, or)) < 0)
 162         {
 163           listnode_delete (rn->info, or);
 164           ospf_route_free (or);
 165           /* proceed down */
 166         }
 167       /* Routes are the same */
 168       else if (ret == 0)
 169         {
 170           if (IS_DEBUG_OSPF_EVENT)
 171             zlog_debug ("ospf_ia_router_route(): merging the new route");
 172
 173           ospf_route_copy_nexthops (or, abr_or->paths);
 174           ospf_route_free (new_or);
 175           return;
 176         }
 177       /* New route is worse */
 178       else
 179         {
 180           if (IS_DEBUG_OSPF_EVENT)
 181             zlog_debug ("ospf_ia_router_route(): skipping the new route");
 182           ospf_route_free (new_or);
 183           return;
 184         }
 185     }
 186
 187   ospf_route_copy_nexthops (new_or, abr_or->paths);
 188
 189   if (IS_DEBUG_OSPF_EVENT)
 190     zlog_debug ("ospf_ia_router_route(): adding the new route");
 191
 192   listnode_add (rn->info, new_or);
 193 }
 194
 195
 196 static int
 197 process_summary_lsa (struct ospf_area *area, struct route_table *rt,
 198                      struct route_table *rtrs, struct ospf_lsa *lsa)
 199 {
 200   struct ospf *ospf = area->ospf;
 201   struct ospf_area_range *range;
 202   struct ospf_route *abr_or, *new_or;
 203   struct summary_lsa *sl;
 204   struct prefix_ipv4 p, abr;
 205   u_int32_t metric;
 206
 207   if (lsa == NULL)
 208     return 0;
 209
 210   sl = (struct summary_lsa *) lsa->data;
 211
 212   if (IS_DEBUG_OSPF_EVENT)
 213     zlog_debug ("process_summary_lsa(): LS ID: %s", inet_ntoa (sl->header.id));
 214
 215   metric = GET_METRIC (sl->metric);
 216
 217   if (metric == OSPF_LS_INFINITY)
 218     return 0;
 219
 220   if (IS_LSA_MAXAGE (lsa))
 221     return 0;
 222
 223   if (ospf_lsa_is_self_originated (area->ospf, lsa))
 224     return 0;
 225
 226   p.family = AF_INET;
 227   p.prefix = sl->header.id;
 228
 229   if (sl->header.type == OSPF_SUMMARY_LSA)
 230     p.prefixlen = ip_masklen (sl->mask);
 231   else
 232     p.prefixlen = IPV4_MAX_BITLEN;
 233
 234   apply_mask_ipv4 (&p);
 235
 236   if (sl->header.type == OSPF_SUMMARY_LSA &&
 237       (range = ospf_area_range_match_any (ospf, &p)) &&
 238       ospf_area_range_active (range))
 239     return 0;
 240
 241   /* XXX: This check seems dubious to me. If an ABR has already decided
 242    * to consider summaries received in this area, then why would one wish
 243    * to exclude default?
 244    */
 245   if (IS_OSPF_ABR(ospf) &&
 246       ospf->abr_type != OSPF_ABR_STAND &&
 247       area->external_routing != OSPF_AREA_DEFAULT &&
 248       p.prefix.s_addr == OSPF_DEFAULT_DESTINATION &&
 249       p.prefixlen == 0)
 250     return 0; /* Ignore summary default from a stub area */
 251
 252   abr.family = AF_INET;
 253   abr.prefix = sl->header.adv_router;
 254   abr.prefixlen = IPV4_MAX_BITLEN;
 255   apply_mask_ipv4 (&abr);
 256
 257   abr_or = ospf_find_abr_route (rtrs, &abr, area);
 258
 259   if (abr_or == NULL)
 260     return 0;
 261
 262   new_or = ospf_route_new ();
 263   new_or->type = OSPF_DESTINATION_NETWORK;
 264   new_or->id = sl->header.id;
 265   new_or->mask = sl->mask;
 266   new_or->u.std.options = sl->header.options;
 267   new_or->u.std.origin = (struct lsa_header *) sl;
 268   new_or->cost = abr_or->cost + metric;
 269   new_or->u.std.area_id = area->area_id;
 270   new_or->u.std.external_routing = area->external_routing;
 271   new_or->path_type = OSPF_PATH_INTER_AREA;
 272
 273   if (sl->header.type == OSPF_SUMMARY_LSA)
 274     ospf_ia_network_route (ospf, rt, &p, new_or, abr_or);
 275   else
 276     {
 277       new_or->type = OSPF_DESTINATION_ROUTER;
 278       new_or->u.std.flags = ROUTER_LSA_EXTERNAL;
 279       ospf_ia_router_route (ospf, rtrs, &p, new_or, abr_or);
 280     }
 281
 282   return 0;
 283 }
 284
 285 static void
 286 ospf_examine_summaries (struct ospf_area *area,
 287                         struct route_table *lsdb_rt,
 288                         struct route_table *rt,
 289                         struct route_table *rtrs)
 290 {
 291   struct ospf_lsa *lsa;
 292   struct route_node *rn;
 293
 294   LSDB_LOOP (lsdb_rt, rn, lsa)
 295     process_summary_lsa (area, rt, rtrs, lsa);
 296 }
 297
 298 int
 299 ospf_area_is_transit (struct ospf_area *area)
 300 {
 301   return (area->transit == OSPF_TRANSIT_TRUE) ||
 302     ospf_full_virtual_nbrs(area); /* Cisco forgets to set the V-bit :( */
 303 }
 304
 305 static void
 306 ospf_update_network_route (struct ospf *ospf,
 307                            struct route_table *rt,
 308                            struct route_table *rtrs,
 309                            struct summary_lsa *lsa,
 310                            struct prefix_ipv4 *p,
 311                            struct ospf_area *area)
 312 {
 313   struct route_node *rn;
 314   struct ospf_route *or, *abr_or, *new_or;
 315   struct prefix_ipv4 abr;
 316   u_int32_t cost;
 317
 318   abr.family = AF_INET;
 319   abr.prefix =lsa->header.adv_router;
 320   abr.prefixlen = IPV4_MAX_BITLEN;
 321   apply_mask_ipv4 (&abr);
 322
 323   abr_or = ospf_find_abr_route (rtrs, &abr, area);
 324
 325   if (abr_or == NULL)
 326     {
 327       if (IS_DEBUG_OSPF_EVENT)
 328         zlog_debug ("ospf_update_network_route(): can't find a route to the ABR");
 329       return;
 330     }
 331
 332   cost = abr_or->cost + GET_METRIC (lsa->metric);
 333
 334   rn = route_node_lookup (rt, (struct prefix *) p);
 335
 336   if (! rn)
 337     {
 338       if (ospf->abr_type != OSPF_ABR_SHORTCUT)
 339         return; /* Standard ABR can update only already installed
 340                    backbone paths                                       */
 341       if (IS_DEBUG_OSPF_EVENT)
 342         zlog_debug ("ospf_update_network_route(): "
 343                    "Allowing Shortcut ABR to add new route");
 344       new_or = ospf_route_new ();
 345       new_or->type = OSPF_DESTINATION_NETWORK;
 346       new_or->id = lsa->header.id;
 347       new_or->mask = lsa->mask;
 348       new_or->u.std.options = lsa->header.options;
 349       new_or->u.std.origin = (struct lsa_header *) lsa;
 350       new_or->cost = cost;
 351       new_or->u.std.area_id = area->area_id;
 352       new_or->u.std.external_routing = area->external_routing;
 353       new_or->path_type = OSPF_PATH_INTER_AREA;
 354       ospf_route_add (rt, p, new_or, abr_or);
 355
 356       return;
 357     }
 358   else
 359     {
 360       route_unlock_node (rn);
 361       if (rn->info == NULL)
 362         return;
 363     }
 364
 365   or = rn->info;
 366
 367   if (or->path_type != OSPF_PATH_INTRA_AREA &&
 368       or->path_type != OSPF_PATH_INTER_AREA)
 369     {
 370       if (IS_DEBUG_OSPF_EVENT)
 371         zlog_debug ("ospf_update_network_route(): ERR: path type is wrong");
 372       return;
 373     }
 374
 375   if (ospf->abr_type == OSPF_ABR_SHORTCUT)
 376     {
 377       if (or->path_type == OSPF_PATH_INTRA_AREA &&
 378           !OSPF_IS_AREA_ID_BACKBONE (or->u.std.area_id))
 379         {
 380           if (IS_DEBUG_OSPF_EVENT)
 381             zlog_debug ("ospf_update_network_route(): Shortcut: "
 382                        "this intra-area path is not backbone");
 383           return;
 384         }
 385     }
 386   else   /* Not Shortcut ABR */
 387     {
 388       if (!OSPF_IS_AREA_ID_BACKBONE (or->u.std.area_id))
 389         {
 390           if (IS_DEBUG_OSPF_EVENT)
 391             zlog_debug ("ospf_update_network_route(): "
 392                        "route is not BB-associated");
 393           return; /* We can update only BB routes */
 394         }
 395     }
 396
 397   if (or->cost < cost)
 398     {
 399       if (IS_DEBUG_OSPF_EVENT)
 400         zlog_debug ("ospf_update_network_route(): new route is worse");
 401       return;
 402     }
 403
 404   if (or->cost == cost)
 405     {
 406       if (IS_DEBUG_OSPF_EVENT)
 407         zlog_debug ("ospf_update_network_route(): "
 408                    "new route is same distance, adding nexthops");
 409       ospf_route_copy_nexthops (or, abr_or->paths);
 410     }
 411
 412   if (or->cost > cost)
 413     {
 414       if (IS_DEBUG_OSPF_EVENT)
 415         zlog_debug ("ospf_update_network_route(): "
 416                    "new route is better, overriding nexthops");
 417       ospf_route_subst_nexthops (or, abr_or->paths);
 418       or->cost = cost;
 419
 420       if ((ospf->abr_type == OSPF_ABR_SHORTCUT) &&
 421           !OSPF_IS_AREA_ID_BACKBONE (or->u.std.area_id))
 422         {
 423           or->path_type = OSPF_PATH_INTER_AREA;
 424           or->u.std.area_id = area->area_id;
 425           or->u.std.external_routing = area->external_routing;
 426           /* Note that we can do this only in Shortcut ABR mode,
 427              because standard ABR must leave the route type and area
 428              unchanged
 429           */
 430         }
 431     }
 432 }
 433
 434 static void
 435 ospf_update_router_route (struct ospf *ospf,
 436                           struct route_table *rtrs,
 437                           struct summary_lsa *lsa,
 438                           struct prefix_ipv4 *p,
 439                           struct ospf_area *area)
 440 {
 441   struct ospf_route *or, *abr_or, *new_or;
 442   struct prefix_ipv4 abr;
 443   u_int32_t cost;
 444
 445   abr.family = AF_INET;
 446   abr.prefix = lsa->header.adv_router;
 447   abr.prefixlen = IPV4_MAX_BITLEN;
 448   apply_mask_ipv4 (&abr);
 449
 450   abr_or = ospf_find_abr_route (rtrs, &abr, area);
 451
 452   if (abr_or == NULL)
 453     {
 454       if (IS_DEBUG_OSPF_EVENT)
 455         zlog_debug ("ospf_update_router_route(): can't find a route to the ABR");
 456       return;
 457     }
 458
 459   cost = abr_or->cost + GET_METRIC (lsa->metric);
 460
 461   /* First try to find a backbone path,
 462      because standard ABR can update only BB-associated paths */
 463
 464   if ((ospf->backbone == NULL) &&
 465       (ospf->abr_type != OSPF_ABR_SHORTCUT))
 466      return; /* no BB area, not Shortcut ABR, exiting */
 467
 468   /* find the backbone route, if possible */
 469   if ((ospf->backbone == NULL)
 470       || !(or = ospf_find_asbr_route_through_area (rtrs, p, ospf->backbone)))
 471     {
 472       if (ospf->abr_type != OSPF_ABR_SHORTCUT)
 473
 474          /* route to ASBR through the BB not found
 475             the router is not Shortcut ABR, exiting */
 476
 477           return;
 478       else
 479         /* We're a Shortcut ABR*/
 480         {
 481           /* Let it either add a new router or update the route
 482              through the same (non-BB) area. */
 483
 484           new_or = ospf_route_new ();
 485           new_or->type = OSPF_DESTINATION_ROUTER;
 486           new_or->id = lsa->header.id;
 487           new_or->mask = lsa->mask;
 488           new_or->u.std.options = lsa->header.options;
 489           new_or->u.std.origin = (struct lsa_header *)lsa;
 490           new_or->cost = cost;
 491           new_or->u.std.area_id = area->area_id;
 492           new_or->u.std.external_routing = area->external_routing;
 493           new_or->path_type = OSPF_PATH_INTER_AREA;
 494           new_or->u.std.flags = ROUTER_LSA_EXTERNAL;
 495           ospf_ia_router_route (ospf, rtrs, p, new_or, abr_or);
 496
 497           return;
 498         }
 499     }
 500
 501   /* At this point the "or" is always bb-associated */
 502
 503   if (!(or->u.std.flags & ROUTER_LSA_EXTERNAL))
 504     {
 505       if (IS_DEBUG_OSPF_EVENT)
 506         zlog_debug ("ospf_upd_router_route(): the remote router is not an ASBR");
 507       return;
 508     }
 509
 510   if (or->path_type != OSPF_PATH_INTRA_AREA &&
 511       or->path_type != OSPF_PATH_INTER_AREA)
 512     return;
 513
 514   if (or->cost < cost)
 515     return;
 516
 517   else if (or->cost == cost)
 518     ospf_route_copy_nexthops (or, abr_or->paths);
 519
 520   else if (or->cost > cost)
 521     {
 522       ospf_route_subst_nexthops (or, abr_or->paths);
 523       or->cost = cost;
 524
 525       /* Even if the ABR runs in Shortcut mode, we can't change
 526          the path type and area, because the "or" is always bb-associated
 527          at this point and even Shortcut ABR can't change these attributes */
 528     }
 529 }
 530
 531 static int
 532 process_transit_summary_lsa (struct ospf_area *area, struct route_table *rt,
 533                              struct route_table *rtrs, struct ospf_lsa *lsa)
 534 {
 535   struct ospf *ospf = area->ospf;
 536   struct summary_lsa *sl;
 537   struct prefix_ipv4 p;
 538   u_int32_t metric;
 539
 540   if (lsa == NULL)
 541     return 0;
 542
 543   sl = (struct summary_lsa *) lsa->data;
 544
 545   if (IS_DEBUG_OSPF_EVENT)
 546     zlog_debug ("process_transit_summaries(): LS ID: %s",
 547                inet_ntoa (lsa->data->id));
 548   metric = GET_METRIC (sl->metric);
 549
 550   if (metric == OSPF_LS_INFINITY)
 551     {
 552       if (IS_DEBUG_OSPF_EVENT)
 553         zlog_debug ("process_transit_summaries(): metric is infinity, skip");
 554       return 0;
 555     }
 556
 557   if (IS_LSA_MAXAGE (lsa))
 558     {
 559       if (IS_DEBUG_OSPF_EVENT)
 560         zlog_debug ("process_transit_summaries(): This LSA is too old");
 561       return 0;
 562     }
 563
 564   if (ospf_lsa_is_self_originated (area->ospf, lsa))
 565     {
 566       if (IS_DEBUG_OSPF_EVENT)
 567         zlog_debug ("process_transit_summaries(): This LSA is mine, skip");
 568       return 0;
 569     }
 570
 571   p.family = AF_INET;
 572   p.prefix = sl->header.id;
 573
 574   if (sl->header.type == OSPF_SUMMARY_LSA)
 575     p.prefixlen = ip_masklen (sl->mask);
 576   else
 577     p.prefixlen = IPV4_MAX_BITLEN;
 578
 579   apply_mask_ipv4 (&p);
 580
 581   if (sl->header.type == OSPF_SUMMARY_LSA)
 582     ospf_update_network_route (ospf, rt, rtrs, sl, &p, area);
 583   else
 584     ospf_update_router_route (ospf, rtrs, sl, &p, area);
 585
 586   return 0;
 587 }
 588
 589 static void
 590 ospf_examine_transit_summaries (struct ospf_area *area,
 591                                 struct route_table *lsdb_rt,
 592                                 struct route_table *rt,
 593                                 struct route_table *rtrs)
 594 {
 595   struct ospf_lsa *lsa;
 596   struct route_node *rn;
 597
 598   LSDB_LOOP (lsdb_rt, rn, lsa)
 599     process_transit_summary_lsa (area, rt, rtrs, lsa);
 600 }
 601
 602 void
 603 ospf_ia_routing (struct ospf *ospf,
 604                  struct route_table *rt,
 605                  struct route_table *rtrs)
 606 {
 607   struct ospf_area * area;
 608
 609   if (IS_DEBUG_OSPF_EVENT)
 610     zlog_debug ("ospf_ia_routing():start");
 611
 612   if (IS_OSPF_ABR (ospf))
 613     {
 614       struct listnode *node;
 615       struct ospf_area *area;
 616
 617       switch (ospf->abr_type)
 618         {
 619         case OSPF_ABR_STAND:
 620           if (IS_DEBUG_OSPF_EVENT)
 621             zlog_debug ("ospf_ia_routing():Standard ABR");
 622
 623           if ((area = ospf->backbone))
 624             {
 625               struct listnode *node;
 626
 627               if (IS_DEBUG_OSPF_EVENT)
 628                 {
 629                   zlog_debug ("ospf_ia_routing():backbone area found");
 630                   zlog_debug ("ospf_ia_routing():examining summaries");
 631                 }
 632
 633               OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 634
 635               for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 636                 if (area != ospf->backbone)
 637                   if (ospf_area_is_transit (area))
 638                     OSPF_EXAMINE_TRANSIT_SUMMARIES_ALL (area, rt, rtrs);
 639             }
 640           else
 641             if (IS_DEBUG_OSPF_EVENT)
 642               zlog_debug ("ospf_ia_routing():backbone area NOT found");
 643           break;
 644         case OSPF_ABR_IBM:
 645         case OSPF_ABR_CISCO:
 646           if (IS_DEBUG_OSPF_EVENT)
 647             zlog_debug ("ospf_ia_routing():Alternative Cisco/IBM ABR");
 648           area = ospf->backbone; /* Find the BB */
 649
 650           /* If we have an active BB connection */
 651           if (area && ospf_act_bb_connection (ospf))
 652             {
 653               if (IS_DEBUG_OSPF_EVENT)
 654                 {
 655                   zlog_debug ("ospf_ia_routing(): backbone area found");
 656                   zlog_debug ("ospf_ia_routing(): examining BB summaries");
 657                 }
 658
 659               OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 660
 661               for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 662                 if (area != ospf->backbone)
 663                   if (ospf_area_is_transit (area))
 664                     OSPF_EXAMINE_TRANSIT_SUMMARIES_ALL (area, rt, rtrs);
 665             }
 666           else
 667             { /* No active BB connection--consider all areas */
 668               if (IS_DEBUG_OSPF_EVENT)
 669                 zlog_debug ("ospf_ia_routing(): "
 670                            "Active BB connection not found");
 671               for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 672                 OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 673             }
 674           break;
 675         case OSPF_ABR_SHORTCUT:
 676           if (IS_DEBUG_OSPF_EVENT)
 677             zlog_debug ("ospf_ia_routing():Alternative Shortcut");
 678           area = ospf->backbone; /* Find the BB */
 679
 680           /* If we have an active BB connection */
 681           if (area && ospf_act_bb_connection (ospf))
 682             {
 683               if (IS_DEBUG_OSPF_EVENT)
 684                 {
 685                   zlog_debug ("ospf_ia_routing(): backbone area found");
 686                   zlog_debug ("ospf_ia_routing(): examining BB summaries");
 687                 }
 688               OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 689             }
 690
 691           for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 692             if (area != ospf->backbone)
 693               if (ospf_area_is_transit (area) ||
 694                   ((area->shortcut_configured != OSPF_SHORTCUT_DISABLE) &&
 695                   ((ospf->backbone == NULL) ||
 696                   ((area->shortcut_configured == OSPF_SHORTCUT_ENABLE) &&
 697                   area->shortcut_capability))))
 698                 OSPF_EXAMINE_TRANSIT_SUMMARIES_ALL (area, rt, rtrs);
 699           break;
 700         default:
 701           break;
 702         }
 703     }
 704   else
 705     {
 706       struct listnode *node;
 707
 708       if (IS_DEBUG_OSPF_EVENT)
 709         zlog_debug ("ospf_ia_routing():not ABR, considering all areas");
 710
 711       for (ALL_LIST_ELEMENTS_RO (ospf->areas, node, area))
 712         OSPF_EXAMINE_SUMMARIES_ALL (area, rt, rtrs);
 713     }
 714 }