ospf_ism.c

router source code for the ospdf.

/*
 * OSPF version 2  Interface State Machine
 *   From RFC2328 [OSPF Version 2] 
 * Copyright (C) 1999, 2000 Toshiaki Takada
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * GNU Zebra is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Zebra; see the file COPYING.  If not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <zebra.h>

#include "thread.h"
#include "linklist.h"
#include "prefix.h"
#include "if.h"
#include "table.h"
#include "log.h"

#include "ospfd/ospfd.h"
#include "ospfd/ospf_interface.h"
#include "ospfd/ospf_ism.h"
#include "ospfd/ospf_asbr.h"
#include "ospfd/ospf_lsa.h"
#include "ospfd/ospf_lsdb.h"
#include "ospfd/ospf_neighbor.h"
#include "ospfd/ospf_nsm.h"
#include "ospfd/ospf_network.h"
#include "ospfd/ospf_dump.h"
#include "ospfd/ospf_packet.h"
#include "ospfd/ospf_flood.h"
#include "ospfd/ospf_abr.h"

/* elect DR and BDR. Refer to RFC2319 section 9.4 */
struct ospf_neighbor *
ospf_dr_election_sub (list routers)
{
  listnode node;
  struct ospf_neighbor *nbr, *max = NULL;

  /* Choose highest router priority.
     In case of tie, choose highest Router ID. */
  for (node = listhead (routers); node; nextnode (node))
    {
      nbr = getdata (node);

      if (max == NULL)
	max = nbr;
      else
	{
	  if (max->priority < nbr->priority)
	    max = nbr;
	  else if (max->priority == nbr->priority)
	    if (IPV4_ADDR_CMP (&max->router_id, &nbr->router_id) < 0)
	      max = nbr;
	}
    }

  return max;
}

struct ospf_neighbor *
ospf_elect_dr (struct ospf_interface *oi, list el_list)
{
  list dr_list;
  listnode node;
  struct ospf_neighbor *nbr, *dr = NULL, *bdr = NULL;

  dr_list = list_new ();

  /* Add neighbors to the list. */
  for (node = listhead (el_list); node; nextnode (node))
    {
      nbr = getdata (node);

      /* neighbor declared to be DR. */
      if (NBR_IS_DR (nbr))
	listnode_add (dr_list, nbr);

      /* Preserve neighbor BDR. */
      if (IPV4_ADDR_SAME (&BDR (oi), &nbr->address.u.prefix4))
	bdr = nbr;
    }

  /* Elect Designated Router. */
  if (listcount (dr_list) > 0)
    dr = ospf_dr_election_sub (dr_list);
  else
    dr = bdr;

  /* Set DR to interface. */
  if (dr)
    {
      DR (oi) = dr->address.u.prefix4;
      dr->d_router = dr->address.u.prefix4;
    }
  else
      DR (oi).s_addr = 0;

  list_delete (dr_list);

  return dr;
}

struct ospf_neighbor *
ospf_elect_bdr (struct ospf_interface *oi, list el_list)
{
  list bdr_list, no_dr_list;
  listnode node;
  struct ospf_neighbor *nbr, *bdr = NULL;

  bdr_list = list_new ();
  no_dr_list = list_new ();

  /* Add neighbors to the list. */
  for (node = listhead (el_list); node; nextnode (node))
    {
      nbr = getdata (node);

      /* neighbor declared to be DR. */
      if (NBR_IS_DR (nbr))
	continue;

      /* neighbor declared to be BDR. */
      if (NBR_IS_BDR (nbr))
	listnode_add (bdr_list, nbr);

      listnode_add (no_dr_list, nbr);
    }

  /* Elect Backup Designated Router. */
  if (listcount (bdr_list) > 0)
    bdr = ospf_dr_election_sub (bdr_list);
  else
    bdr = ospf_dr_election_sub (no_dr_list);

  /* Set BDR to interface. */
  if (bdr)
    {
      BDR (oi) = bdr->address.u.prefix4;
      bdr->bd_router = bdr->address.u.prefix4;
    }
  else
    BDR (oi).s_addr = 0;

  list_delete (bdr_list);
  list_delete (no_dr_list);

  return bdr;
}

int
ospf_ism_state (struct ospf_interface *oi)
{
  if (IPV4_ADDR_SAME (&DR (oi), &oi->address->u.prefix4))
    return ISM_DR;
  else if (IPV4_ADDR_SAME (&BDR (oi), &oi->address->u.prefix4))
    return ISM_Backup;
  else
    return ISM_DROther;
}

void
ospf_dr_eligible_routers (struct route_table *nbrs, list el_list)
{
  struct route_node *rn;
  struct ospf_neighbor *nbr;

  for (rn = route_top (nbrs); rn; rn = route_next (rn))
    if ((nbr = rn->info) != NULL)
      /* Ignore 0.0.0.0 node*/
      if (nbr->router_id.s_addr != 0)
	/* Is neighbor eligible? */
	if (nbr->priority != 0)
	  /* Is neighbor upper 2-Way? */
	  if (nbr->state >= NSM_TwoWay)
	    listnode_add (el_list, nbr);
}

/* Generate AdjOK? NSM event. */
void
ospf_dr_change (struct ospf *ospf, struct route_table *nbrs)
{
  struct route_node *rn;
  struct ospf_neighbor *nbr;

  for (rn = route_top (nbrs); rn; rn = route_next (rn))
    if ((nbr = rn->info) != NULL)
      /* Ignore 0.0.0.0 node*/
      if (nbr->router_id.s_addr != 0)
	/* Is neighbor upper 2-Way? */
	if (nbr->state >= NSM_TwoWay)
	  /* Ignore myself. */
	  if (!IPV4_ADDR_SAME (&nbr->router_id, &ospf->router_id))
	    OSPF_NSM_EVENT_SCHEDULE (nbr, NSM_AdjOK);
}

int
ospf_dr_election (struct ospf_interface *oi)
{
  struct in_addr old_dr, old_bdr;
  int old_state, new_state;
  list el_list;
  struct ospf_neighbor *dr, *bdr;

  /* backup current values. */
  old_dr = DR (oi);
  old_bdr = BDR (oi);
  old_state = oi->state;

  el_list = list_new ();

  /* List eligible routers. */
  ospf_dr_eligible_routers (oi->nbrs, el_list);

  /* First election of DR and BDR. */
  bdr = ospf_elect_bdr (oi, el_list);
  dr = ospf_elect_dr (oi, el_list);

  new_state = ospf_ism_state (oi);

  zlog_info ("DR-Election[1st]: Backup %s", inet_ntoa (BDR (oi)));
  zlog_info ("DR-Election[1st]: DR     %s", inet_ntoa (DR (oi)));

  if (new_state != old_state &&
      !(new_state == ISM_DROther && old_state < ISM_DROther))
    {
      ospf_elect_bdr (oi, el_list);
      ospf_elect_dr (oi, el_list); 

      new_state = ospf_ism_state (oi);

      zlog_info ("DR-Election[2nd]: Backup %s", inet_ntoa (BDR (oi)));
      zlog_info ("DR-Election[2nd]: DR     %s", inet_ntoa (DR (oi)));
    }

  list_delete (el_list);

  /* if DR or BDR changes, cause AdjOK? neighbor event. */
  if (!IPV4_ADDR_SAME (&old_dr, &DR (oi)) ||
      !IPV4_ADDR_SAME (&old_bdr, &BDR (oi)))
    ospf_dr_change (oi->ospf, oi->nbrs);

  if (oi->type == OSPF_IFTYPE_BROADCAST || oi->type == OSPF_IFTYPE_POINTOPOINT)
    {
      /* Multicast group change. */
      if ((old_state != ISM_DR && old_state != ISM_Backup) &&
	  (new_state == ISM_DR || new_state == ISM_Backup))
	ospf_if_add_alldrouters (oi->ospf, oi->address, oi->ifp->ifindex);
      else if ((old_state == ISM_DR || old_state == ISM_Backup) &&
	       (new_state != ISM_DR && new_state != ISM_Backup))
	ospf_if_drop_alldrouters (oi->ospf, oi->address, oi->ifp->ifindex);
    }

  return new_state;
}


int
ospf_hello_timer (struct thread *thread)
{
  struct ospf_interface *oi;

  oi = THREAD_ARG (thread);
  oi->t_hello = NULL;

  if (IS_DEBUG_OSPF (ism, ISM_TIMERS))
    zlog (NULL, LOG_DEBUG, "ISM[%s]: Timer (Hello timer expire)",
	  IF_NAME (oi));

  /* Sending hello packet. */
  ospf_hello_send (oi);

  /* Hello timer set. */
  OSPF_ISM_TIMER_ON (oi->t_hello, ospf_hello_timer,
		     OSPF_IF_PARAM (oi, v_hello));

  return 0;
}

int
ospf_wait_timer (struct thread *thread)
{
  struct ospf_interface *oi;

  oi = THREAD_ARG (thread);
  oi->t_wait = NULL;

  if (IS_DEBUG_OSPF (ism, ISM_TIMERS))
    zlog (NULL, LOG_DEBUG, "ISM[%s]: Timer (Wait timer expire)",
	  IF_NAME (oi));

  OSPF_ISM_EVENT_SCHEDULE (oi, ISM_WaitTimer);

  return 0;
}

/* Hook function called after ospf ISM event is occured. And vty's
   network command invoke this function after making interface
   structure. */
void
ism_timer_set (struct ospf_interface *oi)
{
  switch (oi->state)
    {
    case ISM_Down:
      /* First entry point of ospf interface state machine. In this state
	 interface parameters must be set to initial values, and timers are
	 reset also. */
      OSPF_ISM_TIMER_OFF (oi->t_hello);
      OSPF_ISM_TIMER_OFF (oi->t_wait);
      OSPF_ISM_TIMER_OFF (oi->t_ls_ack);
      break;
    case ISM_Loopback:
      /* In this state, the interface may be looped back and will be
	 unavailable for regular data traffic. */
      OSPF_ISM_TIMER_OFF (oi->t_hello);