ospfd/ospf_ism.c

   1 /*
   2  * OSPF version 2  Interface State Machine
   3  *   From RFC2328 [OSPF Version 2]
   4  * Copyright (C) 1999, 2000 Toshiaki Takada
   5  *
   6  * This file is part of GNU Zebra.
   7  *
   8  * GNU Zebra is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the
  10  * Free Software Foundation; either version 2, or (at your option) any
  11  * later version.
  12  *
  13  * GNU Zebra is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; see the file COPYING; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <zebra.h>
  24
  25 #include "thread.h"
  26 #include "linklist.h"
  27 #include "prefix.h"
  28 #include "if.h"
  29 #include "table.h"
  30 #include "log.h"
  31
  32 #include "ospfd/ospfd.h"
  33 #include "ospfd/ospf_interface.h"
  34 #include "ospfd/ospf_ism.h"
  35 #include "ospfd/ospf_asbr.h"
  36 #include "ospfd/ospf_lsa.h"
  37 #include "ospfd/ospf_lsdb.h"
  38 #include "ospfd/ospf_neighbor.h"
  39 #include "ospfd/ospf_nsm.h"
  40 #include "ospfd/ospf_network.h"
  41 #include "ospfd/ospf_dump.h"
  42 #include "ospfd/ospf_packet.h"
  43 #include "ospfd/ospf_flood.h"
  44 #include "ospfd/ospf_abr.h"
  45
  46 DEFINE_HOOK(ospf_ism_change,
  47             (struct ospf_interface * oi, int state, int oldstate),
  48             (oi, state, oldstate))
  49
  50 /* elect DR and BDR. Refer to RFC2319 section 9.4 */
  51 static struct ospf_neighbor *ospf_dr_election_sub(struct list *routers)
  52 {
  53         struct listnode *node;
  54         struct ospf_neighbor *nbr, *max = NULL;
  55
  56         /* Choose highest router priority.
  57            In case of tie, choose highest Router ID. */
  58         for (ALL_LIST_ELEMENTS_RO(routers, node, nbr)) {
  59                 if (max == NULL)
  60                         max = nbr;
  61                 else {
  62                         if (max->priority < nbr->priority)
  63                                 max = nbr;
  64                         else if (max->priority == nbr->priority)
  65                                 if (IPV4_ADDR_CMP(&max->router_id,
  66                                                   &nbr->router_id)
  67                                     < 0)
  68                                         max = nbr;
  69                 }
  70         }
  71
  72         return max;
  73 }
  74
  75 static struct ospf_neighbor *ospf_elect_dr(struct ospf_interface *oi,
  76                                            struct list *el_list)
  77 {
  78         struct list *dr_list;
  79         struct listnode *node;
  80         struct ospf_neighbor *nbr, *dr = NULL, *bdr = NULL;
  81
  82         dr_list = list_new();
  83
  84         /* Add neighbors to the list. */
  85         for (ALL_LIST_ELEMENTS_RO(el_list, node, nbr)) {
  86                 /* neighbor declared to be DR. */
  87                 if (NBR_IS_DR(nbr))
  88                         listnode_add(dr_list, nbr);
  89
  90                 /* Preserve neighbor BDR. */
  91                 if (IPV4_ADDR_SAME(&BDR(oi), &nbr->address.u.prefix4))
  92                         bdr = nbr;
  93         }
  94
  95         /* Elect Designated Router. */
  96         if (listcount(dr_list) > 0)
  97                 dr = ospf_dr_election_sub(dr_list);
  98         else
  99                 dr = bdr;
 100
 101         /* Set DR to interface. */
 102         if (dr)
 103                 DR(oi) = dr->address.u.prefix4;
 104         else
 105                 DR(oi).s_addr = 0;
 106
 107         list_delete(&dr_list);
 108
 109         return dr;
 110 }
 111
 112 static struct ospf_neighbor *ospf_elect_bdr(struct ospf_interface *oi,
 113                                             struct list *el_list)
 114 {
 115         struct list *bdr_list, *no_dr_list;
 116         struct listnode *node;
 117         struct ospf_neighbor *nbr, *bdr = NULL;
 118
 119         bdr_list = list_new();
 120         no_dr_list = list_new();
 121
 122         /* Add neighbors to the list. */
 123         for (ALL_LIST_ELEMENTS_RO(el_list, node, nbr)) {
 124                 /* neighbor declared to be DR. */
 125                 if (NBR_IS_DR(nbr))
 126                         continue;
 127
 128                 /* neighbor declared to be BDR. */
 129                 if (NBR_IS_BDR(nbr))
 130                         listnode_add(bdr_list, nbr);
 131
 132                 listnode_add(no_dr_list, nbr);
 133         }
 134
 135         /* Elect Backup Designated Router. */
 136         if (listcount(bdr_list) > 0)
 137                 bdr = ospf_dr_election_sub(bdr_list);
 138         else
 139                 bdr = ospf_dr_election_sub(no_dr_list);
 140
 141         /* Set BDR to interface. */
 142         if (bdr)
 143                 BDR(oi) = bdr->address.u.prefix4;
 144         else
 145                 BDR(oi).s_addr = 0;
 146
 147         list_delete(&bdr_list);
 148         list_delete(&no_dr_list);
 149
 150         return bdr;
 151 }
 152
 153 static int ospf_ism_state(struct ospf_interface *oi)
 154 {
 155         if (IPV4_ADDR_SAME(&DR(oi), &oi->address->u.prefix4))
 156                 return ISM_DR;
 157         else if (IPV4_ADDR_SAME(&BDR(oi), &oi->address->u.prefix4))
 158                 return ISM_Backup;
 159         else
 160                 return ISM_DROther;
 161 }
 162
 163 static void ospf_dr_eligible_routers(struct route_table *nbrs,
 164                                      struct list *el_list)
 165 {
 166         struct route_node *rn;
 167         struct ospf_neighbor *nbr;
 168
 169         for (rn = route_top(nbrs); rn; rn = route_next(rn))
 170                 if ((nbr = rn->info) != NULL)
 171                         /* Ignore 0.0.0.0 node*/
 172                         if (nbr->router_id.s_addr != 0)
 173                                 /* Is neighbor eligible? */
 174                                 if (nbr->priority > 0)
 175                                         /* Is neighbor upper 2-Way? */
 176                                         if (nbr->state >= NSM_TwoWay)
 177                                                 listnode_add(el_list, nbr);
 178 }
 179
 180 /* Generate AdjOK? NSM event. */
 181 static void ospf_dr_change(struct ospf *ospf, struct route_table *nbrs)
 182 {
 183         struct route_node *rn;
 184         struct ospf_neighbor *nbr;
 185
 186         for (rn = route_top(nbrs); rn; rn = route_next(rn))
 187                 if ((nbr = rn->info) != NULL)
 188                         /* Ignore 0.0.0.0 node*/
 189                         if (nbr->router_id.s_addr != 0)
 190                                 /* Is neighbor upper 2-Way? */
 191                                 if (nbr->state >= NSM_TwoWay)
 192                                         /* Ignore myself. */
 193                                         if (!IPV4_ADDR_SAME(&nbr->router_id,
 194                                                             &ospf->router_id))
 195                                                 OSPF_NSM_EVENT_SCHEDULE(
 196                                                         nbr, NSM_AdjOK);
 197 }
 198
 199 static int ospf_dr_election(struct ospf_interface *oi)
 200 {
 201         struct in_addr old_dr, old_bdr;
 202         int old_state, new_state;
 203         struct list *el_list;
 204
 205         /* backup current values. */
 206         old_dr = DR(oi);
 207         old_bdr = BDR(oi);
 208         old_state = oi->state;
 209
 210         el_list = list_new();
 211
 212         /* List eligible routers. */
 213         ospf_dr_eligible_routers(oi->nbrs, el_list);
 214
 215         /* First election of DR and BDR. */
 216         ospf_elect_bdr(oi, el_list);
 217         ospf_elect_dr(oi, el_list);
 218
 219         new_state = ospf_ism_state(oi);
 220
 221         zlog_debug("DR-Election[1st]: Backup %s", inet_ntoa(BDR(oi)));
 222         zlog_debug("DR-Election[1st]: DR     %s", inet_ntoa(DR(oi)));
 223
 224         if (new_state != old_state
 225             && !(new_state == ISM_DROther && old_state < ISM_DROther)) {
 226                 ospf_elect_bdr(oi, el_list);
 227                 ospf_elect_dr(oi, el_list);
 228
 229                 new_state = ospf_ism_state(oi);
 230
 231                 zlog_debug("DR-Election[2nd]: Backup %s", inet_ntoa(BDR(oi)));
 232                 zlog_debug("DR-Election[2nd]: DR     %s", inet_ntoa(DR(oi)));
 233         }
 234
 235         list_delete(&el_list);
 236
 237         /* if DR or BDR changes, cause AdjOK? neighbor event. */
 238         if (!IPV4_ADDR_SAME(&old_dr, &DR(oi))
 239             || !IPV4_ADDR_SAME(&old_bdr, &BDR(oi)))
 240                 ospf_dr_change(oi->ospf, oi->nbrs);
 241
 242         return new_state;
 243 }
 244
 245
 246 int ospf_hello_timer(struct thread *thread)
 247 {
 248         struct ospf_interface *oi;
 249
 250         oi = THREAD_ARG(thread);
 251         oi->t_hello = NULL;
 252
 253         if (IS_DEBUG_OSPF(ism, ISM_TIMERS))
 254                 zlog_debug("ISM[%s]: Timer (Hello timer expire)", IF_NAME(oi));
 255
 256         /* Sending hello packet. */
 257         ospf_hello_send(oi);
 258
 259         /* Hello timer set. */
 260         OSPF_HELLO_TIMER_ON(oi);
 261
 262         return 0;
 263 }
 264
 265 static int ospf_wait_timer(struct thread *thread)
 266 {
 267         struct ospf_interface *oi;
 268
 269         oi = THREAD_ARG(thread);
 270         oi->t_wait = NULL;
 271
 272         if (IS_DEBUG_OSPF(ism, ISM_TIMERS))
 273                 zlog_debug("ISM[%s]: Timer (Wait timer expire)", IF_NAME(oi));
 274
 275         OSPF_ISM_EVENT_SCHEDULE(oi, ISM_WaitTimer);
 276
 277         return 0;
 278 }
 279
 280 /* Hook function called after ospf ISM event is occurred. And vty's
 281    network command invoke this function after making interface
 282    structure. */
 283 static void ism_timer_set(struct ospf_interface *oi)
 284 {
 285         switch (oi->state) {
 286         case ISM_Down:
 287                 /* First entry point of ospf interface state machine. In this
 288                    state
 289                    interface parameters must be set to initial values, and
 290                    timers are
 291                    reset also. */
 292                 OSPF_ISM_TIMER_OFF(oi->t_hello);
 293                 OSPF_ISM_TIMER_OFF(oi->t_wait);
 294                 OSPF_ISM_TIMER_OFF(oi->t_ls_ack);
 295                 break;
 296         case ISM_Loopback:
 297                 /* In this state, the interface may be looped back and will be
 298                    unavailable for regular data traffic. */
 299                 OSPF_ISM_TIMER_OFF(oi->t_hello);
 300                 OSPF_ISM_TIMER_OFF(oi->t_wait);
 301                 OSPF_ISM_TIMER_OFF(oi->t_ls_ack);
 302                 break;
 303         case ISM_Waiting:
 304                 /* The router is trying to determine the identity of DRouter and
 305                    BDRouter. The router begin to receive and send Hello Packets.
 306                    */
 307                 /* send first hello immediately */
 308                 OSPF_ISM_TIMER_MSEC_ON(oi->t_hello, ospf_hello_timer, 1);
 309                 OSPF_ISM_TIMER_ON(oi->t_wait, ospf_wait_timer,
 310                                   OSPF_IF_PARAM(oi, v_wait));
 311                 OSPF_ISM_TIMER_OFF(oi->t_ls_ack);
 312                 break;
 313         case ISM_PointToPoint:
 314                 /* The interface connects to a physical Point-to-point network
 315                    or
 316                    virtual link. The router attempts to form an adjacency with
 317                    neighboring router. Hello packets are also sent. */
 318                 /* send first hello immediately */
 319                 OSPF_ISM_TIMER_MSEC_ON(oi->t_hello, ospf_hello_timer, 1);
 320                 OSPF_ISM_TIMER_OFF(oi->t_wait);
 321                 OSPF_ISM_TIMER_ON(oi->t_ls_ack, ospf_ls_ack_timer,
 322                                   oi->v_ls_ack);
 323                 break;
 324         case ISM_DROther:
 325                 /* The network type of the interface is broadcast or NBMA
 326                    network,
 327                    and the router itself is neither Designated Router nor
 328                    Backup Designated Router. */
 329                 OSPF_HELLO_TIMER_ON(oi);
 330                 OSPF_ISM_TIMER_OFF(oi->t_wait);
 331                 OSPF_ISM_TIMER_ON(oi->t_ls_ack, ospf_ls_ack_timer,
 332                                   oi->v_ls_ack);
 333                 break;
 334         case ISM_Backup:
 335                 /* The network type of the interface is broadcast os NBMA
 336                    network,
 337                    and the router is Backup Designated Router. */
 338                 OSPF_HELLO_TIMER_ON(oi);
 339                 OSPF_ISM_TIMER_OFF(oi->t_wait);
 340                 OSPF_ISM_TIMER_ON(oi->t_ls_ack, ospf_ls_ack_timer,
 341                                   oi->v_ls_ack);
 342                 break;
 343         case ISM_DR:
 344                 /* The network type of the interface is broadcast or NBMA
 345                    network,
 346                    and the router is Designated Router. */
 347                 OSPF_HELLO_TIMER_ON(oi);
 348                 OSPF_ISM_TIMER_OFF(oi->t_wait);
 349                 OSPF_ISM_TIMER_ON(oi->t_ls_ack, ospf_ls_ack_timer,
 350                                   oi->v_ls_ack);
 351                 break;
 352         }
 353 }
 354
 355 static int ism_interface_up(struct ospf_interface *oi)
 356 {
 357         int next_state = 0;
 358
 359         /* if network type is point-to-point, Point-to-MultiPoint or virtual
 360            link,
 361            the state transitions to Point-to-Point. */
 362         if (oi->type == OSPF_IFTYPE_POINTOPOINT
 363             || oi->type == OSPF_IFTYPE_POINTOMULTIPOINT
 364             || oi->type == OSPF_IFTYPE_VIRTUALLINK)
 365                 next_state = ISM_PointToPoint;
 366         /* Else if the router is not eligible to DR, the state transitions to
 367            DROther. */
 368         else if (PRIORITY(oi) == 0) /* router is eligible? */
 369                 next_state = ISM_DROther;
 370         else
 371                 /* Otherwise, the state transitions to Waiting. */
 372                 next_state = ISM_Waiting;
 373
 374         if (oi->type == OSPF_IFTYPE_NBMA)
 375                 ospf_nbr_nbma_if_update(oi->ospf, oi);
 376
 377         /*  ospf_ism_event (t); */
 378         return next_state;
 379 }
 380
 381 static int ism_loop_ind(struct ospf_interface *oi)
 382 {
 383         /* call ism_interface_down. */
 384         /* ret = ism_interface_down (oi); */
 385
 386         return 0;
 387 }
 388
 389 /* Interface down event handler. */
 390 static int ism_interface_down(struct ospf_interface *oi)
 391 {
 392         ospf_if_cleanup(oi);
 393         return 0;
 394 }
 395
 396
 397 static int ism_backup_seen(struct ospf_interface *oi)
 398 {
 399         return ospf_dr_election(oi);
 400 }
 401
 402 static int ism_wait_timer(struct ospf_interface *oi)
 403 {
 404         return ospf_dr_election(oi);
 405 }
 406
 407 static int ism_neighbor_change(struct ospf_interface *oi)
 408 {
 409         return ospf_dr_election(oi);
 410 }
 411
 412 static int ism_ignore(struct ospf_interface *oi)
 413 {
 414         if (IS_DEBUG_OSPF(ism, ISM_EVENTS))
 415                 zlog_debug("ISM[%s]: ism_ignore called", IF_NAME(oi));
 416
 417         return 0;
 418 }
 419
 420 /* Interface State Machine */
 421 const struct {
 422         int (*func)(struct ospf_interface *);
 423         int next_state;
 424 } ISM[OSPF_ISM_STATE_MAX][OSPF_ISM_EVENT_MAX] = {
 425         {
 426                 /* DependUpon: dummy state. */
 427                 {ism_ignore, ISM_DependUpon}, /* NoEvent        */
 428                 {ism_ignore, ISM_DependUpon}, /* InterfaceUp    */
 429                 {ism_ignore, ISM_DependUpon}, /* WaitTimer      */
 430                 {ism_ignore, ISM_DependUpon}, /* BackupSeen     */
 431                 {ism_ignore, ISM_DependUpon}, /* NeighborChange */
 432                 {ism_ignore, ISM_DependUpon}, /* LoopInd        */
 433                 {ism_ignore, ISM_DependUpon}, /* UnloopInd      */
 434                 {ism_ignore, ISM_DependUpon}, /* InterfaceDown  */
 435         },
 436         {
 437                 /* Down:*/
 438                 {ism_ignore, ISM_DependUpon},       /* NoEvent        */
 439                 {ism_interface_up, ISM_DependUpon}, /* InterfaceUp    */
 440                 {ism_ignore, ISM_Down},             /* WaitTimer      */
 441                 {ism_ignore, ISM_Down},             /* BackupSeen     */
 442                 {ism_ignore, ISM_Down},             /* NeighborChange */
 443                 {ism_loop_ind, ISM_Loopback},       /* LoopInd        */
 444                 {ism_ignore, ISM_Down},             /* UnloopInd      */
 445                 {ism_interface_down, ISM_Down},     /* InterfaceDown  */
 446         },
 447         {
 448                 /* Loopback: */
 449                 {ism_ignore, ISM_DependUpon},   /* NoEvent        */
 450                 {ism_ignore, ISM_Loopback},     /* InterfaceUp    */
 451                 {ism_ignore, ISM_Loopback},     /* WaitTimer      */
 452                 {ism_ignore, ISM_Loopback},     /* BackupSeen     */
 453                 {ism_ignore, ISM_Loopback},     /* NeighborChange */
 454                 {ism_ignore, ISM_Loopback},     /* LoopInd        */
 455                 {ism_ignore, ISM_Down},         /* UnloopInd      */
 456                 {ism_interface_down, ISM_Down}, /* InterfaceDown  */
 457         },
 458         {
 459                 /* Waiting: */
 460                 {ism_ignore, ISM_DependUpon},      /* NoEvent        */
 461                 {ism_ignore, ISM_Waiting},       /* InterfaceUp    */
 462                 {ism_wait_timer, ISM_DependUpon},  /* WaitTimer      */
 463                 {ism_backup_seen, ISM_DependUpon}, /* BackupSeen     */
 464                 {ism_ignore, ISM_Waiting},       /* NeighborChange */
 465                 {ism_loop_ind, ISM_Loopback},      /* LoopInd        */
 466                 {ism_ignore, ISM_Waiting},       /* UnloopInd      */
 467                 {ism_interface_down, ISM_Down},    /* InterfaceDown  */
 468         },
 469         {
 470                 /* Point-to-Point: */
 471                 {ism_ignore, ISM_DependUpon},   /* NoEvent        */
 472                 {ism_ignore, ISM_PointToPoint}, /* InterfaceUp    */
 473                 {ism_ignore, ISM_PointToPoint}, /* WaitTimer      */
 474                 {ism_ignore, ISM_PointToPoint}, /* BackupSeen     */
 475                 {ism_ignore, ISM_PointToPoint}, /* NeighborChange */
 476                 {ism_loop_ind, ISM_Loopback},   /* LoopInd        */
 477                 {ism_ignore, ISM_PointToPoint}, /* UnloopInd      */
 478                 {ism_interface_down, ISM_Down}, /* InterfaceDown  */
 479         },
 480         {
 481                 /* DROther: */
 482                 {ism_ignore, ISM_DependUpon},     /* NoEvent        */
 483                 {ism_ignore, ISM_DROther},           /* InterfaceUp    */
 484                 {ism_ignore, ISM_DROther},           /* WaitTimer      */
 485                 {ism_ignore, ISM_DROther},           /* BackupSeen     */
 486                 {ism_neighbor_change, ISM_DependUpon}, /* NeighborChange */
 487                 {ism_loop_ind, ISM_Loopback},     /* LoopInd        */
 488                 {ism_ignore, ISM_DROther},           /* UnloopInd      */
 489                 {ism_interface_down, ISM_Down}, /* InterfaceDown  */
 490         },
 491         {
 492                 /* Backup: */
 493                 {ism_ignore, ISM_DependUpon},     /* NoEvent        */
 494                 {ism_ignore, ISM_Backup},             /* InterfaceUp    */
 495                 {ism_ignore, ISM_Backup},             /* WaitTimer      */
 496                 {ism_ignore, ISM_Backup},             /* BackupSeen     */
 497                 {ism_neighbor_change, ISM_DependUpon}, /* NeighborChange */
 498                 {ism_loop_ind, ISM_Loopback},     /* LoopInd        */
 499                 {ism_ignore, ISM_Backup},             /* UnloopInd      */
 500                 {ism_interface_down, ISM_Down}, /* InterfaceDown  */
 501         },
 502         {
 503                 /* DR: */
 504                 {ism_ignore, ISM_DependUpon},     /* NoEvent        */
 505                 {ism_ignore, ISM_DR},                  /* InterfaceUp    */
 506                 {ism_ignore, ISM_DR},                  /* WaitTimer      */
 507                 {ism_ignore, ISM_DR},                  /* BackupSeen     */
 508                 {ism_neighbor_change, ISM_DependUpon}, /* NeighborChange */
 509                 {ism_loop_ind, ISM_Loopback},     /* LoopInd        */
 510                 {ism_ignore, ISM_DR},                  /* UnloopInd      */
 511                 {ism_interface_down, ISM_Down}, /* InterfaceDown  */
 512         },
 513 };
 514
 515 static const char *const ospf_ism_event_str[] = {
 516         "NoEvent",      "InterfaceUp", "WaitTimer", "BackupSeen",
 517         "NeighborChange", "LoopInd",     "UnLoopInd", "InterfaceDown",
 518 };
 519
 520 static void ism_change_state(struct ospf_interface *oi, int state)
 521 {
 522         int old_state;
 523         struct ospf_lsa *lsa;
 524
 525         /* Logging change of state. */
 526         if (IS_DEBUG_OSPF(ism, ISM_STATUS))
 527                 zlog_debug("ISM[%s]: State change %s -> %s", IF_NAME(oi),
 528                            lookup_msg(ospf_ism_state_msg, oi->state, NULL),
 529                            lookup_msg(ospf_ism_state_msg, state, NULL));
 530
 531         old_state = oi->state;
 532         oi->state = state;
 533         oi->state_change++;
 534
 535         hook_call(ospf_ism_change, oi, state, old_state);
 536
 537         /* Set multicast memberships appropriately for new state. */
 538         ospf_if_set_multicast(oi);
 539
 540         if (old_state == ISM_Down || state == ISM_Down)
 541                 ospf_check_abr_status(oi->ospf);
 542
 543         /* Originate router-LSA. */
 544         if (state == ISM_Down) {
 545                 if (oi->area->act_ints > 0)
 546                         oi->area->act_ints--;
 547         } else if (old_state == ISM_Down)
 548                 oi->area->act_ints++;
 549
 550         /* schedule router-LSA originate. */
 551         ospf_router_lsa_update_area(oi->area);
 552
 553         /* Originate network-LSA. */
 554         if (old_state != ISM_DR && state == ISM_DR)
 555                 ospf_network_lsa_update(oi);
 556         else if (old_state == ISM_DR && state != ISM_DR) {
 557                 /* Free self originated network LSA. */
 558                 lsa = oi->network_lsa_self;
 559                 if (lsa)
 560                         ospf_lsa_flush_area(lsa, oi->area);
 561
 562                 ospf_lsa_unlock(&oi->network_lsa_self);
 563                 oi->network_lsa_self = NULL;
 564         }
 565
 566         ospf_opaque_ism_change(oi, old_state);
 567
 568         /* Check area border status.  */
 569         ospf_check_abr_status(oi->ospf);
 570 }
 571
 572 /* Execute ISM event process. */
 573 int ospf_ism_event(struct thread *thread)
 574 {
 575         int event;
 576         int next_state;
 577         struct ospf_interface *oi;
 578
 579         oi = THREAD_ARG(thread);
 580         event = THREAD_VAL(thread);
 581
 582         /* Call function. */
 583         next_state = (*(ISM[oi->state][event].func))(oi);
 584
 585         if (!next_state)
 586                 next_state = ISM[oi->state][event].next_state;
 587
 588         if (IS_DEBUG_OSPF(ism, ISM_EVENTS))
 589                 zlog_debug("ISM[%s]: %s (%s)", IF_NAME(oi),
 590                            lookup_msg(ospf_ism_state_msg, oi->state, NULL),
 591                            ospf_ism_event_str[event]);
 592
 593         /* If state is changed. */
 594         if (next_state != oi->state)
 595                 ism_change_state(oi, next_state);
 596
 597         /* Make sure timer is set. */
 598         ism_timer_set(oi);
 599
 600         return 0;
 601 }