/*
 * OSPF version 2  Neighbor 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 "memory.h"
#include "hash.h"
#include "linklist.h"
#include "prefix.h"
#include "if.h"
#include "table.h"
#include "stream.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_packet.h"
#include "ospfd/ospf_dump.h"
#include "ospfd/ospf_flood.h"
#include "ospfd/ospf_abr.h"
#include "ospfd/ospf_snmp.h"

static void nsm_clear_adj (struct ospf_neighbor *);

/* OSPF NSM Timer functions. */
static int
ospf_inactivity_timer (struct thread *thread)
{
  struct ospf_neighbor *nbr;

  nbr = THREAD_ARG (thread);
  nbr->t_inactivity = NULL;

  if (IS_DEBUG_OSPF (nsm, NSM_TIMERS))
    zlog (NULL, LOG_DEBUG, "NSM[%s:%s]: Timer (Inactivity timer expire)",
	  IF_NAME (nbr->oi), inet_ntoa (nbr->router_id));

  OSPF_NSM_EVENT_SCHEDULE (nbr, NSM_InactivityTimer);

  return 0;
}

static int
ospf_db_desc_timer (struct thread *thread)
{
  struct ospf_neighbor *nbr;

  nbr = THREAD_ARG (thread);
  nbr->t_db_desc = NULL;

  if (IS_DEBUG_OSPF (nsm, NSM_TIMERS))
    zlog (NULL, LOG_DEBUG, "NSM[%s:%s]: Timer (DD Retransmit timer expire)",
	  IF_NAME (nbr->oi), inet_ntoa (nbr->src));

  /* resent last send DD packet. */
  assert (nbr->last_send);
  ospf_db_desc_resend (nbr);

  /* DD Retransmit timer set. */
  OSPF_NSM_TIMER_ON (nbr->t_db_desc, ospf_db_desc_timer, nbr->v_db_desc);

  return 0;
}

/* Hook function called after ospf NSM event is occured.
 *
 * Set/clear any timers whose condition is implicit to the neighbour
 * state. There may be other timers which are set/unset according to other
 * state.
 *
 * We rely on this function to properly clear timers in lower states,
 * particularly before deleting a neighbour.
 */
static void
nsm_timer_set (struct ospf_neighbor *nbr)
{
  switch (nbr->state)
    {
    case NSM_Deleted:
    case NSM_Down:
      OSPF_NSM_TIMER_OFF (nbr->t_inactivity);
      OSPF_NSM_TIMER_OFF (nbr->t_hello_reply);
    case NSM_Attempt:
    case NSM_Init:
    case NSM_TwoWay:
      OSPF_NSM_TIMER_OFF (nbr->t_db_desc);
      OSPF_NSM_TIMER_OFF (nbr->t_ls_upd);
      OSPF_NSM_TIMER_OFF (nbr->t_ls_req);
      break;
    case NSM_ExStart:
      OSPF_NSM_TIMER_ON (nbr->t_db_desc, ospf_db_desc_timer, nbr->v_db_desc);
      OSPF_NSM_TIMER_OFF (nbr->t_ls_upd);
      OSPF_NSM_TIMER_OFF (nbr->t_ls_req);
      break;
    case NSM_Exchange:
      OSPF_NSM_TIMER_ON (nbr->t_ls_upd, ospf_ls_upd_timer, nbr->v_ls_upd);
      if (!IS_SET_DD_MS (nbr->dd_flags))      
	OSPF_NSM_TIMER_OFF (nbr->t_db_desc);
      break;
    case NSM_Loading:
    case NSM_Full:
    default:
      OSPF_NSM_TIMER_OFF (nbr->t_db_desc);
      break;
    }
}

/* 10.4 of RFC2328, indicate whether an adjacency is appropriate with
 * the given neighbour
 */
static int
nsm_should_adj (struct ospf_neighbor *nbr)
{
  struct ospf_interface *oi = nbr->oi;

      /* These network types must always form adjacencies. */
  if (oi->type == OSPF_IFTYPE_POINTOPOINT
      || oi->type == OSPF_IFTYPE_POINTOMULTIPOINT
      || oi->type == OSPF_IFTYPE_VIRTUALLINK
      /* Router itself is the DRouter or the BDRouter. */
      || IPV4_ADDR_SAME (&oi->address->u.prefix4, &DR (oi))
      || IPV4_ADDR_SAME (&oi->address->u.prefix4, &BDR (oi))
      /* Neighboring Router is the DRouter or the BDRouter. */
      || IPV4_ADDR_SAME (&nbr->address.u.prefix4, &DR (oi))
      || IPV4_ADDR_SAME (&nbr->address.u.prefix4, &BDR (oi)))
    return 1;

  return 0;
}

/* OSPF NSM functions. */
static int
nsm_packet_received (struct ospf_neighbor *nbr)
{
  /* Start or Restart Inactivity Timer. */
  OSPF_NSM_TIMER_OFF (nbr->t_inactivity);
  
  OSPF_NSM_TIMER_ON (nbr->t_inactivity, ospf_inactivity_timer,
		     nbr->v_inactivity);

  if (nbr->oi->type == OSPF_IFTYPE_NBMA && nbr->nbr_nbma)
    OSPF_POLL_TIMER_OFF (nbr->nbr_nbma->t_poll);

  return 0;
}

static int
nsm_start (struct ospf_neighbor *nbr)
{
  if (nbr->nbr_nbma)
      OSPF_POLL_TIMER_OFF (nbr->nbr_nbma->t_poll);

  OSPF_NSM_TIMER_OFF (nbr->t_inactivity);
  
  OSPF_NSM_TIMER_ON (nbr->t_inactivity, ospf_inactivity_timer,
                     nbr->v_inactivity);

  return 0;
}

static int
nsm_twoway_received (struct ospf_neighbor *nbr)
{
  return (nsm_should_adj (nbr) ? NSM_ExStart : NSM_TwoWay);
}

int
ospf_db_summary_count (struct ospf_neighbor *nbr)
{
  return ospf_lsdb_count_all (&nbr->db_sum);
}

int
ospf_db_summary_isempty (struct ospf_neighbor *nbr)
{
  return ospf_lsdb_isempty (&nbr->db_sum);
}

static int
ospf_db_summary_add (struct ospf_neighbor *nbr, struct ospf_lsa *lsa)
{
#ifdef HAVE_OPAQUE_LSA
  switch (lsa->data->type)
    {
    case OSPF_OPAQUE_LINK_LSA:
      /* Exclude type-9 LSAs that does not have the same "oi" with "nbr". */
      if (nbr->oi && ospf_if_exists (lsa->oi) != nbr->oi)
          return 0;
      break;
    case OSPF_OPAQUE_AREA_LSA:
      /*
       * It is assured by the caller function "nsm_negotiation_done()"
       * that every given LSA belongs to the same area with "nbr".
       */
      break;
    case OSPF_OPAQUE_AS_LSA:
    default:
      break;
    }
#endif /* HAVE_OPAQUE_LSA */

  /* Stay away from any Local Translated Type-7 LSAs */
  if (CHECK_FLAG (lsa->flags, OSPF_LSA_LOCAL_XLT))
    return 0;

  if (IS_LSA_MAXAGE (lsa))
    ospf_ls_retransmit_add (nbr, lsa);                      
  else 
    ospf_lsdb_add (&nbr->db_sum, lsa);

  return 0;
}

void
ospf_db_summary_clear (struct ospf_neighbor *nbr)
{
  struct ospf_lsdb *lsdb;
  int i;

  lsdb = &nbr->db_sum;
  for (i = OSPF_MIN_LSA; i < OSPF_MAX_LSA; i++)
    {
      struct route_table *table = lsdb->type[i].db;
      struct route_node *rn;

      for (rn = route_top (table); rn; rn = route_next (rn))
	if (rn->info)
	  ospf_lsdb_delete (&nbr->db_sum, rn->info);
    }
}



/* The area link state database consists of the router-LSAs,
   network-LSAs and summary-LSAs contained in the area structure,
   along with the AS-external-LSAs contained in the global structure.
   AS-external-LSAs are omitted from a virtual neighbor's Database
   summary list.  AS-external-LSAs are omitted from the Database
   summary list if the area has been configured as a stub. */
static int
nsm_negotiation_done (struct ospf_neighbor *nbr)
{
  struct ospf_area *area = nbr->oi->area;
  struct ospf_lsa *lsa;
  struct route_node *rn;

  LSDB_LOOP (ROUTER_LSDB (area), rn, lsa)
    ospf_db_summary_add (nbr, lsa);
  LSDB_LOOP (NETWORK_LSDB (area), rn, lsa)
    ospf_db_summary_add (nbr, lsa);
  LSDB_LOOP (SUMMARY_LSDB (area), rn, lsa)
    ospf_db_summary_add (nbr, lsa);
  LSDB_LOOP (ASBR_SUMMARY_LSDB (area), rn, lsa)
    ospf_db_summary_add (nbr, lsa);

#ifdef HAVE_OPAQUE_LSA
  /* Process only if the neighbor is opaque capable. */
  if (CHECK_FLAG (nbr->options, OSPF_OPTION_O))
    {
      LSDB_LOOP (OPAQUE_LINK_LSDB (area), rn, lsa)
	ospf_db_summary_add (nbr, lsa);
      LSDB_LOOP (OPAQUE_AREA_LSDB (area), rn, lsa)
	ospf_db_summary_add (nbr, lsa);
    }
#endif /* HAVE_OPAQUE_LSA */

  if (CHECK_FLAG (nbr->options, OSPF_OPTION_NP))
    {
      LSDB_LOOP (NSSA_LSDB (area), rn, lsa)
	ospf_db_summary_add (nbr, lsa);
    }

  if (nbr->oi->type != OSPF_IFTYPE_VIRTUALLINK
      && area->external_routing == OSPF_AREA_DEFAULT)
    LSDB_LOOP (EXTERNAL_LSDB (nbr->oi->ospf), rn, lsa)
      ospf_db_summary_add (nbr, lsa);

#ifdef HAVE_OPAQUE_LSA
  if (CHECK_FLAG (nbr->options, OSPF_OPTION_O)
      && (nbr->oi->type != OSPF_IFTYPE_VIRTUALLINK
	  && area->external_routing == OSPF_AREA_DEFAULT))
    LSDB_LOOP (OPAQUE_AS_LSDB (nbr->oi->ospf), rn, lsa)
      ospf_db_summary_add (nbr, lsa);
#endif /* HAVE_OPAQUE_LSA */

  return 0;
}

static int
nsm_exchange_done (struct ospf_neighbor *nbr)
{
  if (ospf_ls_request_isempty (nbr))
    return NSM_Full;

  /* Send Link State Request. */
  ospf_ls_req_send (nbr);

  return NSM_Loading;
}

static int
nsm_adj_ok (struct ospf_neighbor *nbr)
{
  int next_state = nbr->state;
  int adj = nsm_should_adj (nbr);

  if (nbr->state == NSM_TwoWay && adj == 1)
    next_state = NSM_ExStart;
  else if (nbr->state >= NSM_ExStart && adj == 0)
    next_state = NSM_TwoWay;

  return next_state;
}

/* Clear adjacency related state for a neighbour, intended where nbr
 * transitions from > ExStart (i.e. a Full or forming adjacency)
 * to <= ExStart.
 */
static void
nsm_clear_adj (struct ospf_neighbor *nbr)
{
  /* Clear Database Summary list. */
  if (!ospf_db_summary_isempty (nbr))
    ospf_db_summary_clear (nbr);

  /* Clear Link State Request list. */
  if (!ospf_ls_request_isempty (nbr))
    ospf_ls_request_delete_all (nbr);

  /* Clear Link State Retransmission list. */
  if (!ospf_ls_retransmit_isempty (nbr))
    ospf_ls_retransmit_clear (nbr);

#ifdef HAVE_OPAQUE_LSA
  if (CHECK_FLAG (nbr->options, OSPF_OPTION_O))
    UNSET_FLAG (nbr->options, OSPF_OPTION_O);
#endif /* HAVE_OPAQUE_LSA */
}

static int
nsm_kill_nbr (struct ospf_neighbor *nbr)
{
  /* killing nbr_self is invalid */
  if (nbr == nbr->oi->nbr_self)
    {
      assert (nbr != nbr->oi->nbr_self);
      return 0;
    }
  
  if (nbr->oi->type == OSPF_IFTYPE_NBMA && nbr->nbr_nbma != NULL)
    {
      struct ospf_nbr_nbma *nbr_nbma = nbr->nbr_nbma;

      nbr_nbma->nbr = NULL;
      nbr_nbma->state_change = nbr->state_change;

      nbr->nbr_nbma = NULL;

      OSPF_POLL_TIMER_ON (nbr_nbma->t_poll, ospf_poll_timer,
			  nbr_nbma->v_poll);

      if (IS_DEBUG_OSPF (nsm, NSM_EVENTS))
	zlog_debug ("NSM[%s:%s]: Down (PollIntervalTimer scheduled)",
		   IF_NAME (nbr->oi), inet_ntoa (nbr->address.u.prefix4));  
    }

  return 0;
}

/* Neighbor State Machine */
struct {
  int (*func) (struct ospf_neighbor *);
  int next_state;
} NSM [OSPF_NSM_STATE_MAX][OSPF_NSM_EVENT_MAX] =
{
  {
    /* DependUpon: dummy state. */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { NULL,                    NSM_DependUpon }, /* PacketReceived    */
    { NULL,                    NSM_DependUpon }, /* Start             */
    { NULL,                    NSM_DependUpon }, /* 2-WayReceived     */
    { NULL,                    NSM_DependUpon }, /* NegotiationDone   */
    { NULL,                    NSM_DependUpon }, /* ExchangeDone      */
    { NULL,                    NSM_DependUpon }, /* BadLSReq          */
    { NULL,                    NSM_DependUpon }, /* LoadingDone       */
    { NULL,                    NSM_DependUpon }, /* AdjOK?            */
    { NULL,                    NSM_DependUpon }, /* SeqNumberMismatch */
    { NULL,                    NSM_DependUpon }, /* 1-WayReceived     */
    { NULL,                    NSM_DependUpon }, /* KillNbr           */
    { NULL,                    NSM_DependUpon }, /* InactivityTimer   */
    { NULL,                    NSM_DependUpon }, /* LLDown            */
  },
  {
    /* Deleted: dummy state. */
    { NULL,                    NSM_Deleted    }, /* NoEvent           */
    { NULL,                    NSM_Deleted    }, /* PacketReceived    */
    { NULL,                    NSM_Deleted    }, /* Start             */
    { NULL,                    NSM_Deleted    }, /* 2-WayReceived     */
    { NULL,                    NSM_Deleted    }, /* NegotiationDone   */
    { NULL,                    NSM_Deleted    }, /* ExchangeDone      */
    { NULL,                    NSM_Deleted    }, /* BadLSReq          */
    { NULL,                    NSM_Deleted    }, /* LoadingDone       */
    { NULL,                    NSM_Deleted    }, /* AdjOK?            */
    { NULL,                    NSM_Deleted    }, /* SeqNumberMismatch */
    { NULL,                    NSM_Deleted    }, /* 1-WayReceived     */
    { NULL,                    NSM_Deleted    }, /* KillNbr           */
    { NULL,                    NSM_Deleted    }, /* InactivityTimer   */
    { NULL,                    NSM_Deleted    }, /* LLDown            */
  },
  {
    /* Down: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_Init       }, /* PacketReceived    */
    { nsm_start,               NSM_Attempt    }, /* Start             */
    { NULL,                    NSM_Down       }, /* 2-WayReceived     */
    { NULL,                    NSM_Down       }, /* NegotiationDone   */
    { NULL,                    NSM_Down       }, /* ExchangeDone      */
    { NULL,                    NSM_Down       }, /* BadLSReq          */
    { NULL,                    NSM_Down       }, /* LoadingDone       */
    { NULL,                    NSM_Down       }, /* AdjOK?            */
    { NULL,                    NSM_Down       }, /* SeqNumberMismatch */
    { NULL,                    NSM_Down       }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
  {
    /* Attempt: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_Init       }, /* PacketReceived    */
    { NULL,                    NSM_Attempt    }, /* Start             */
    { NULL,                    NSM_Attempt    }, /* 2-WayReceived     */
    { NULL,                    NSM_Attempt    }, /* NegotiationDone   */
    { NULL,                    NSM_Attempt    }, /* ExchangeDone      */
    { NULL,                    NSM_Attempt    }, /* BadLSReq          */
    { NULL,                    NSM_Attempt    }, /* LoadingDone       */
    { NULL,                    NSM_Attempt    }, /* AdjOK?            */
    { NULL,                    NSM_Attempt    }, /* SeqNumberMismatch */
    { NULL,                    NSM_Attempt    }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
  {
    /* Init: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_Init      }, /* PacketReceived    */
    { NULL,                    NSM_Init       }, /* Start             */
    { nsm_twoway_received,     NSM_DependUpon }, /* 2-WayReceived     */
    { NULL,                    NSM_Init       }, /* NegotiationDone   */
    { NULL,                    NSM_Init       }, /* ExchangeDone      */
    { NULL,                    NSM_Init       }, /* BadLSReq          */
    { NULL,                    NSM_Init       }, /* LoadingDone       */
    { NULL,                    NSM_Init       }, /* AdjOK?            */
    { NULL,                    NSM_Init       }, /* SeqNumberMismatch */
    { NULL,                    NSM_Init       }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
  {
    /* 2-Way: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_TwoWay     }, /* HelloReceived     */
    { NULL,                    NSM_TwoWay     }, /* Start             */
    { NULL,                    NSM_TwoWay     }, /* 2-WayReceived     */
    { NULL,                    NSM_TwoWay     }, /* NegotiationDone   */
    { NULL,                    NSM_TwoWay     }, /* ExchangeDone      */
    { NULL,                    NSM_TwoWay     }, /* BadLSReq          */
    { NULL,                    NSM_TwoWay     }, /* LoadingDone       */
    { nsm_adj_ok,              NSM_DependUpon }, /* AdjOK?            */
    { NULL,                    NSM_TwoWay     }, /* SeqNumberMismatch */
    { NULL,                    NSM_Init       }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
  {
    /* ExStart: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_ExStart    }, /* PacaketReceived   */
    { NULL,                    NSM_ExStart    }, /* Start             */
    { NULL,                    NSM_ExStart    }, /* 2-WayReceived     */
    { nsm_negotiation_done,    NSM_Exchange   }, /* NegotiationDone   */
    { NULL,                    NSM_ExStart    }, /* ExchangeDone      */
    { NULL,                    NSM_ExStart    }, /* BadLSReq          */
    { NULL,                    NSM_ExStart    }, /* LoadingDone       */
    { nsm_adj_ok,              NSM_DependUpon }, /* AdjOK?            */
    { NULL,                    NSM_ExStart    }, /* SeqNumberMismatch */
    { NULL,                    NSM_Init       }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
  {
    /* Exchange: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_Exchange   }, /* PacketReceived    */
    { NULL,                    NSM_Exchange   }, /* Start             */
    { NULL,                    NSM_Exchange   }, /* 2-WayReceived     */
    { NULL,                    NSM_Exchange   }, /* NegotiationDone   */
    { nsm_exchange_done,       NSM_DependUpon }, /* ExchangeDone      */
    { NULL,                    NSM_ExStart    }, /* BadLSReq          */
    { NULL,                    NSM_Exchange   }, /* LoadingDone       */
    { nsm_adj_ok,              NSM_DependUpon }, /* AdjOK?            */
    { NULL,                    NSM_ExStart    }, /* SeqNumberMismatch */
    { NULL,                    NSM_Init       }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
  {
    /* Loading: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_Loading    }, /* PacketReceived    */
    { NULL,                    NSM_Loading    }, /* Start             */
    { NULL,                    NSM_Loading    }, /* 2-WayReceived     */
    { NULL,                    NSM_Loading    }, /* NegotiationDone   */
    { NULL,                    NSM_Loading    }, /* ExchangeDone      */
    { NULL,                    NSM_ExStart    }, /* BadLSReq          */
    { NULL,                    NSM_Full       }, /* LoadingDone       */
    { nsm_adj_ok,              NSM_DependUpon }, /* AdjOK?            */
    { NULL,                    NSM_ExStart    }, /* SeqNumberMismatch */
    { NULL,                    NSM_Init       }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
  { /* Full: */
    { NULL,                    NSM_DependUpon }, /* NoEvent           */
    { nsm_packet_received,     NSM_Full       }, /* PacketReceived    */
    { NULL,                    NSM_Full       }, /* Start             */
    { NULL,                    NSM_Full       }, /* 2-WayReceived     */
    { NULL,                    NSM_Full       }, /* NegotiationDone   */
    { NULL,                    NSM_Full       }, /* ExchangeDone      */
    { NULL,                    NSM_ExStart    }, /* BadLSReq          */
    { NULL,                    NSM_Full       }, /* LoadingDone       */
    { nsm_adj_ok,              NSM_DependUpon }, /* AdjOK?            */
    { NULL,                    NSM_ExStart    }, /* SeqNumberMismatch */
    { NULL,                    NSM_Init       }, /* 1-WayReceived     */
    { nsm_kill_nbr,            NSM_Deleted    }, /* KillNbr           */
    { nsm_kill_nbr,            NSM_Deleted    }, /* InactivityTimer   */
    { nsm_kill_nbr,            NSM_Deleted    }, /* LLDown            */
  },
};

static const char *ospf_nsm_event_str[] =
{
  "NoEvent",
  "PacketReceived",
  "Start",
  "2-WayReceived",
  "NegotiationDone",
  "ExchangeDone",
  "BadLSReq",
  "LoadingDone",
  "AdjOK?",
  "SeqNumberMismatch",
  "1-WayReceived",
  "KillNbr",
  "InactivityTimer",
  "LLDown",
};

static void
nsm_notice_state_change (struct ospf_neighbor *nbr, int next_state, int event)
{
  /* Logging change of status. */
  if (IS_DEBUG_OSPF (nsm, NSM_STATUS))
    zlog_debug ("NSM[%s:%s]: State change %s -> %s (%s)",
               IF_NAME (nbr->oi), inet_ntoa (nbr->router_id),
               LOOKUP (ospf_nsm_state_msg, nbr->state),
               LOOKUP (ospf_nsm_state_msg, next_state),
               ospf_nsm_event_str [event]);

  /* Optionally notify about adjacency changes */
  if (CHECK_FLAG(nbr->oi->ospf->config, OSPF_LOG_ADJACENCY_CHANGES) &&
      (CHECK_FLAG(nbr->oi->ospf->config, OSPF_LOG_ADJACENCY_DETAIL) ||
       (next_state == NSM_Full) || (next_state < nbr->state)))
    zlog_notice("AdjChg: Nbr %s on %s: %s -> %s (%s)",
                inet_ntoa (nbr->router_id), IF_NAME (nbr->oi),
                LOOKUP (ospf_nsm_state_msg, nbr->state),
                LOOKUP (ospf_nsm_state_msg, next_state),
                ospf_nsm_event_str [event]);

  /* Advance in NSM */
  if (next_state > nbr->state)
    nbr->ts_last_progress = recent_relative_time ();
  else /* regression in NSM */
    {
      nbr->ts_last_regress = recent_relative_time ();
      nbr->last_regress_str = ospf_nsm_event_str [event];
    }

#ifdef HAVE_SNMP
  /* Terminal state or regression */ 
  if ((next_state == NSM_Full) 
      || (next_state == NSM_TwoWay)
      || (next_state < nbr->state))
    {
      /* ospfVirtNbrStateChange */
      if (nbr->oi->type == OSPF_IFTYPE_VIRTUALLINK)
        ospfTrapVirtNbrStateChange(nbr);
      /* ospfNbrStateChange trap  */
      else	
        /* To/From FULL, only managed by DR */
        if (((next_state != NSM_Full) && (nbr->state != NSM_Full)) 
            || (nbr->oi->state == ISM_DR))
          ospfTrapNbrStateChange(nbr);
    }
#endif
}

static void
nsm_change_state (struct ospf_neighbor *nbr, int state)
{
  struct ospf_interface *oi = nbr->oi;
  struct ospf_area *vl_area = NULL;
  u_char old_state;
  int x;
  int force = 1;
  
  /* Preserve old status. */
  old_state = nbr->state;

  /* Change to new status. */
  nbr->state = state;

  /* Statistics. */
  nbr->state_change++;

  if (oi->type == OSPF_IFTYPE_VIRTUALLINK)
    vl_area = ospf_area_lookup_by_area_id (oi->ospf, oi->vl_data->vl_area_id);

  /* Generate NeighborChange ISM event.
   *
   * In response to NeighborChange, DR election is rerun. The information
   * from the election process is required by the router-lsa construction.
   *
   * Therefore, trigger the event prior to refreshing the LSAs. */
  switch (oi->state) {
  case ISM_DROther:
  case ISM_Backup:
  case ISM_DR:
    if ((old_state < NSM_TwoWay && state >= NSM_TwoWay) ||
        (old_state >= NSM_TwoWay && state < NSM_TwoWay))
      OSPF_ISM_EVENT_EXECUTE (oi, ISM_NeighborChange);
    break;
  default:
    /* ISM_PointToPoint -> ISM_Down, ISM_Loopback -> ISM_Down, etc. */
    break;
  }

  /* One of the neighboring routers changes to/from the FULL state. */
  if ((old_state != NSM_Full && state == NSM_Full) ||
      (old_state == NSM_Full && state != NSM_Full))
    {
      if (state == NSM_Full)
	{
	  oi->full_nbrs++;
	  oi->area->full_nbrs++;

          ospf_check_abr_status (oi->ospf);

	  if (oi->type == OSPF_IFTYPE_VIRTUALLINK && vl_area)
            if (++vl_area->full_vls == 1)
	      ospf_schedule_abr_task (oi->ospf);

	  /* kevinm: refresh any redistributions */
	  for (x = ZEBRA_ROUTE_SYSTEM; x < ZEBRA_ROUTE_MAX; x++)
	    {
	      if (x == ZEBRA_ROUTE_OSPF || x == ZEBRA_ROUTE_OSPF6)
		continue;
	      ospf_external_lsa_refresh_type (oi->ospf, x, force);
	    }
          /* XXX: Clearly some thing is wrong with refresh of external LSAs
           * this added to hack around defaults not refreshing after a timer
           * jump.
           */
          ospf_external_lsa_refresh_default (oi->ospf);
	}
      else
	{
	  oi->full_nbrs--;
	  oi->area->full_nbrs--;

          ospf_check_abr_status (oi->ospf);

	  if (oi->type == OSPF_IFTYPE_VIRTUALLINK && vl_area)
	    if (vl_area->full_vls > 0)
	      if (--vl_area->full_vls == 0)
		ospf_schedule_abr_task (oi->ospf);
	}

      zlog_info ("nsm_change_state(%s, %s -> %s): "
		 "scheduling new router-LSA origination",
		 inet_ntoa (nbr->router_id),
		 LOOKUP(ospf_nsm_state_msg, old_state),
		 LOOKUP(ospf_nsm_state_msg, state));

      ospf_router_lsa_update_area (oi->area);

      if (oi->type == OSPF_IFTYPE_VIRTUALLINK)
	{
	  struct ospf_area *vl_area =
	    ospf_area_lookup_by_area_id (oi->ospf, oi->vl_data->vl_area_id);
	  
	  if (vl_area)
	    ospf_router_lsa_update_area (vl_area);
	}

      /* Originate network-LSA. */
      if (oi->state == ISM_DR)
	{
	  if (oi->network_lsa_self && oi->full_nbrs == 0)
	    {
	      ospf_lsa_flush_area (oi->network_lsa_self, oi->area);
	      ospf_lsa_unlock (&oi->network_lsa_self);
	      oi->network_lsa_self = NULL;
	    }
	  else
	    ospf_network_lsa_update (oi);
	}
    }

#ifdef HAVE_OPAQUE_LSA
  ospf_opaque_nsm_change (nbr, old_state);
#endif /* HAVE_OPAQUE_LSA */

  /* State changes from > ExStart to <= ExStart should clear any Exchange
   * or Full/LSA Update related lists and state.
   * Potential causal events: BadLSReq, SeqNumberMismatch, AdjOK?
   */
  if ((old_state > NSM_ExStart) && (state <= NSM_ExStart))
    nsm_clear_adj (nbr);

  /* Start DD exchange protocol */
  if (state == NSM_ExStart)
    {
      if (nbr->dd_seqnum == 0)
	nbr->dd_seqnum = quagga_time (NULL);
      else
	nbr->dd_seqnum++;

      nbr->dd_flags = OSPF_DD_FLAG_I|OSPF_DD_FLAG_M|OSPF_DD_FLAG_MS;
      ospf_db_desc_send (nbr);
    }

  /* clear cryptographic sequence number */
  if (state == NSM_Down)
    nbr->crypt_seqnum = 0;
  
  /* Preserve old status? */
}

/* Execute NSM event process. */
int
ospf_nsm_event (struct thread *thread)
{
  int event;
  int next_state;
  struct ospf_neighbor *nbr;

  nbr = THREAD_ARG (thread);
  event = THREAD_VAL (thread);

  if (IS_DEBUG_OSPF (nsm, NSM_EVENTS))
    zlog_debug ("NSM[%s:%s]: %s (%s)", IF_NAME (nbr->oi),
	       inet_ntoa (nbr->router_id),
	       LOOKUP (ospf_nsm_state_msg, nbr->state),
	       ospf_nsm_event_str [event]);
  
  next_state = NSM [nbr->state][event].next_state;

  /* Call function. */
  if (NSM [nbr->state][event].func != NULL)
    {
      int func_state = (*(NSM [nbr->state][event].func))(nbr);
      
      if (NSM [nbr->state][event].next_state == NSM_DependUpon)
        next_state = func_state;
      else if (func_state)
        {
          /* There's a mismatch between the FSM tables and what an FSM
           * action/state-change function returned. State changes which
           * do not have conditional/DependUpon next-states should not
           * try set next_state.
           */
          zlog_warn ("NSM[%s:%s]: %s (%s): "
                     "Warning: action tried to change next_state to %s",
                     IF_NAME (nbr->oi), inet_ntoa (nbr->router_id),
                     LOOKUP (ospf_nsm_state_msg, nbr->state),
                     ospf_nsm_event_str [event],
                     LOOKUP (ospf_nsm_state_msg, func_state));
        }
    }

  assert (next_state != NSM_DependUpon);
  
  /* If state is changed. */
  if (next_state != nbr->state)
    {
      nsm_notice_state_change (nbr, next_state, event);
      nsm_change_state (nbr, next_state);
    }

  /* Make sure timer is set. */
  nsm_timer_set (nbr);

  /* When event is NSM_KillNbr, InactivityTimer or LLDown, the neighbor
   * is deleted.
   *
   * Rather than encode knowledge here of which events lead to NBR
   * delete, we take our cue from the NSM table, via the dummy
   * 'Deleted' neighbour state.
   */
  if (nbr->state == NSM_Deleted)
    ospf_nbr_delete (nbr);

  return 0;
}

/* Check loading state. */
void
ospf_check_nbr_loading (struct ospf_neighbor *nbr)
{
  if (nbr->state == NSM_Loading)
    {
      if (ospf_ls_request_isempty (nbr))
	OSPF_NSM_EVENT_SCHEDULE (nbr, NSM_LoadingDone);
      else if (nbr->ls_req_last == NULL)
	ospf_ls_req_event (nbr);
    }
}