Adding upstream version 9.1.upstream/9.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 875 insertions, 0 deletions

diff --git a/ospfd/ospf_nsm.c b/ospfd/ospf_nsm.c
new file mode 100644
index 0000000..bcbe028
--- /dev/null
+++ b/ospfd/ospf_nsm.c
@@ -0,0 +1,875 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * OSPF version 2  Neighbor State Machine
+ * From RFC2328 [OSPF Version 2]
+ * Copyright (C) 1999, 2000 Toshiaki Takada
+ */
+
+#include <zebra.h>
+
+#include "frrevent.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 "command.h"
+#include "network.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_bfd.h"
+#include "ospfd/ospf_gr.h"
+#include "ospfd/ospf_errors.h"
+
+DEFINE_HOOK(ospf_nsm_change,
+	    (struct ospf_neighbor * on, int state, int oldstate),
+	    (on, state, oldstate));
+
+static void nsm_clear_adj(struct ospf_neighbor *);
+
+/* OSPF NSM Timer functions. */
+static void ospf_inactivity_timer(struct event *thread)
+{
+	struct ospf_neighbor *nbr;
+
+	nbr = EVENT_ARG(thread);
+	nbr->t_inactivity = NULL;
+
+	if (IS_DEBUG_OSPF(nsm, NSM_TIMERS))
+		zlog_debug("NSM[%s:%pI4:%s]: Timer (Inactivity timer expire)",
+			   IF_NAME(nbr->oi), &nbr->router_id,
+			   ospf_get_name(nbr->oi->ospf));
+
+	/* Dont trigger NSM_InactivityTimer event , if the current
+	 * router acting as HELPER for this neighbour.
+	 */
+	if (!OSPF_GR_IS_ACTIVE_HELPER(nbr))
+		OSPF_NSM_EVENT_SCHEDULE(nbr, NSM_InactivityTimer);
+	else {
+		if (IS_DEBUG_OSPF_GR)
+			zlog_debug(
+				"%s, Acting as HELPER for this neighbour, So restart the dead timer",
+				__func__);
+		OSPF_NSM_TIMER_ON(nbr->t_inactivity, ospf_inactivity_timer,
+				  nbr->v_inactivity);
+	}
+}
+
+static void ospf_db_desc_timer(struct event *thread)
+{
+	struct ospf_neighbor *nbr;
+
+	nbr = EVENT_ARG(thread);
+	nbr->t_db_desc = NULL;
+
+	if (IS_DEBUG_OSPF(nsm, NSM_TIMERS))
+		zlog_debug("NSM[%s:%pI4:%s]: Timer (DD Retransmit timer expire)",
+			   IF_NAME(nbr->oi), &nbr->src,
+			   ospf_get_name(nbr->oi->ospf));
+
+	/* 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);
+}
+
+/* Hook function called after ospf NSM event is occurred.
+ *
+ * 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:
+		EVENT_OFF(nbr->t_inactivity);
+		EVENT_OFF(nbr->t_hello_reply);
+	/* fallthru */
+	case NSM_Attempt:
+	case NSM_Init:
+	case NSM_TwoWay:
+		EVENT_OFF(nbr->t_db_desc);
+		EVENT_OFF(nbr->t_ls_upd);
+		EVENT_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);
+		EVENT_OFF(nbr->t_ls_upd);
+		EVENT_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))
+			EVENT_OFF(nbr->t_db_desc);
+		break;
+	case NSM_Loading:
+	case NSM_Full:
+	default:
+		EVENT_OFF(nbr->t_db_desc);
+		break;
+	}
+}
+
+/* 10.4 of RFC2328, indicate whether an adjacency is appropriate with
+ * the given neighbour
+ */
+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_hello_received(struct ospf_neighbor *nbr)
+{
+	/* Start or Restart Inactivity Timer. */
+	EVENT_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)
+		EVENT_OFF(nbr->nbr_nbma->t_poll);
+
+	/* Send proactive ARP requests */
+	if (nbr->state < NSM_Exchange)
+		ospf_proactively_arp(nbr);
+
+	return 0;
+}
+
+static int nsm_start(struct ospf_neighbor *nbr)
+{
+	if (nbr->nbr_nbma)
+		EVENT_OFF(nbr->nbr_nbma->t_poll);
+
+	EVENT_OFF(nbr->t_inactivity);
+
+	OSPF_NSM_TIMER_ON(nbr->t_inactivity, ospf_inactivity_timer,
+			  nbr->v_inactivity);
+
+	/* Send proactive ARP requests */
+	ospf_proactively_arp(nbr);
+
+	return 0;
+}
+
+static int nsm_twoway_received(struct ospf_neighbor *nbr)
+{
+	int adj = nsm_should_adj(nbr);
+
+	/* Send proactive ARP requests */
+	if (adj)
+		ospf_proactively_arp(nbr);
+
+	return (adj ? 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)
+{
+	switch (lsa->data->type) {
+	case OSPF_OPAQUE_LINK_LSA:
+		/* Exclude type-9 LSAs that does not have the same "oi" with
+		 * "nbr". */
+		if (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;
+	}
+
+	/* 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;
+
+	/* Send proactive ARP requests */
+	ospf_proactively_arp(nbr);
+
+	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);
+
+	/* 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);
+	}
+
+	if (CHECK_FLAG(nbr->options, OSPF_OPTION_NP)) {
+		LSDB_LOOP (NSSA_LSDB(area), rn, lsa)
+			ospf_db_summary_add(nbr, lsa);
+	}
+
+	/* For Stub/NSSA area, we should not send Type-4 and Type-5 LSAs */
+	if (nbr->oi->type != OSPF_IFTYPE_VIRTUALLINK
+	    && area->external_routing == OSPF_AREA_DEFAULT) {
+		LSDB_LOOP (ASBR_SUMMARY_LSDB(area), rn, lsa)
+			ospf_db_summary_add(nbr, lsa);
+		LSDB_LOOP (EXTERNAL_LSDB(nbr->oi->ospf), rn, lsa)
+			ospf_db_summary_add(nbr, 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);
+
+	return 0;
+}
+
+static int nsm_exchange_done(struct ospf_neighbor *nbr)
+{
+	if (ospf_ls_request_isempty(nbr))
+		return NSM_Full;
+
+	/* Send Link State Request. */
+	if (nbr->t_ls_req == NULL)
+		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;
+
+		/* Send proactive ARP requests */
+		ospf_proactively_arp(nbr);
+	} 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);
+
+	if (CHECK_FLAG(nbr->options, OSPF_OPTION_O))
+		UNSET_FLAG(nbr->options, OSPF_OPTION_O);
+}
+
+static int nsm_kill_nbr(struct ospf_neighbor *nbr)
+{
+	struct ospf_interface *oi = nbr->oi;
+	struct ospf_neighbor *on;
+	struct route_node *rn;
+
+	/* 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:%pI4:%s]: Down (PollIntervalTimer scheduled)",
+				IF_NAME(nbr->oi),
+				&nbr->address.u.prefix4,
+				ospf_get_name(nbr->oi->ospf));
+	}
+
+	/*
+	 * Do we have any neighbors that are also operating
+	 * on this interface?
+	 */
+	for (rn = route_top(oi->nbrs); rn; rn = route_next(rn)) {
+		on = rn->info;
+
+		if (!on)
+			continue;
+
+		if (on == nbr || on == oi->nbr_self)
+			continue;
+
+		/*
+		 * on is in some state where we might be
+		 * sending packets on this interface
+		 */
+		if (on->state > NSM_Down) {
+			route_unlock_node(rn);
+			return 0;
+		}
+	}
+	/*
+	 * If we get here we know that this interface
+	 * has no neighbors in a state where we could
+	 * be sending packets.  Let's flush anything
+	 * we got.
+	 */
+	ospf_interface_fifo_flush(oi);
+	return 0;
+}
+
+/* Neighbor State Machine */
+const 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}, /* HelloReceived     */
+		{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}, /* HelloReceived     */
+		{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_hello_received, NSM_Init},  /* HelloReceived     */
+		{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_hello_received, NSM_Init},  /* HelloReceived     */
+		{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_hello_received, NSM_Init},        /* HelloReceived     */
+		{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_hello_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_hello_received, NSM_ExStart},    /* HelloReceived     */
+		{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_hello_received, NSM_Exchange},  /* HelloReceived     */
+		{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_hello_received, NSM_Loading},  /* HelloReceived     */
+		{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_hello_received, NSM_Full},  /* HelloReceived     */
+		{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 *const ospf_nsm_event_str[] = {
+	"NoEvent",	   "HelloReceived",  "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:%pI4:%s]: State change %s -> %s (%s)",
+			   IF_NAME(nbr->oi), &nbr->router_id,
+			   ospf_get_name(nbr->oi->ospf),
+			   lookup_msg(ospf_nsm_state_msg, nbr->state, NULL),
+			   lookup_msg(ospf_nsm_state_msg, next_state, NULL),
+			   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 %pI4, NbrIP %pI4 (%s) on %s: %s -> %s (%s)",
+			&nbr->router_id, &nbr->src,
+			ospf_get_name(nbr->oi->ospf), IF_NAME(nbr->oi),
+			lookup_msg(ospf_nsm_state_msg, nbr->state, NULL),
+			lookup_msg(ospf_nsm_state_msg, next_state, NULL),
+			ospf_nsm_event_str[event]);
+
+	/* Advance in NSM */
+	if (next_state > nbr->state)
+		monotime(&nbr->ts_last_progress);
+	else /* regression in NSM */
+	{
+		monotime(&nbr->ts_last_regress);
+		nbr->last_regress_str = ospf_nsm_event_str[event];
+	}
+}
+
+static void nsm_change_state(struct ospf_neighbor *nbr, int state)
+{
+	struct ospf_interface *oi = nbr->oi;
+	struct ospf_area *vl_area = NULL;
+	uint8_t old_state;
+
+	/* 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);
+		} 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);
+		}
+
+		if (CHECK_FLAG(oi->ospf->config, OSPF_LOG_ADJACENCY_DETAIL))
+			zlog_info(
+				"%s:[%pI4:%s], %s -> %s): scheduling new router-LSA origination",
+				__func__, &nbr->router_id,
+				ospf_get_name(oi->ospf),
+				lookup_msg(ospf_nsm_state_msg, old_state, NULL),
+				lookup_msg(ospf_nsm_state_msg, state, NULL));
+
+		/* Dont originate router LSA if the current
+		 * router is acting as a HELPER for this neighbour.
+		 */
+		if (!OSPF_GR_IS_ACTIVE_HELPER(nbr))
+			ospf_router_lsa_update_area(oi->area);
+
+		if (oi->type == OSPF_IFTYPE_VIRTUALLINK) {
+			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);
+		}
+
+		/* Dont originate/flush network LSA if the current
+		 * router is acting as a HELPER for this neighbour.
+		 */
+		if (!OSPF_GR_IS_ACTIVE_HELPER(nbr)) {
+			/* 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);
+			}
+		}
+
+		if (state == NSM_Full && oi->ospf->gr_info.restart_in_progress)
+			ospf_gr_check_adjs(oi->ospf);
+	}
+
+	ospf_opaque_nsm_change(nbr, old_state);
+
+	/* 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 = (uint32_t)frr_weak_random();
+		else
+			nbr->dd_seqnum++;
+
+		nbr->dd_flags =
+			OSPF_DD_FLAG_I | OSPF_DD_FLAG_M | OSPF_DD_FLAG_MS;
+		if (CHECK_FLAG(oi->ospf->config, OSPF_LOG_ADJACENCY_DETAIL))
+			zlog_info(
+				"%s: Initializing [DD]: %pI4 with seqnum:%x , flags:%x",
+				ospf_get_name(oi->ospf), &nbr->router_id,
+				nbr->dd_seqnum, nbr->dd_flags);
+		ospf_db_desc_send(nbr);
+	}
+
+	/* clear cryptographic sequence number */
+	if (state == NSM_Down)
+		nbr->crypt_seqnum = 0;
+
+	if (nbr->bfd_session)
+		ospf_bfd_trigger_event(nbr, old_state, state);
+
+	/* Preserve old status? */
+}
+
+/* Execute NSM event process. */
+void ospf_nsm_event(struct event *thread)
+{
+	int event;
+	int next_state;
+	struct ospf_neighbor *nbr;
+
+	nbr = EVENT_ARG(thread);
+	event = EVENT_VAL(thread);
+
+	if (IS_DEBUG_OSPF(nsm, NSM_EVENTS))
+		zlog_debug("NSM[%s:%pI4:%s]: %s (%s)", IF_NAME(nbr->oi),
+			   &nbr->router_id,
+			   ospf_get_name(nbr->oi->ospf),
+			   lookup_msg(ospf_nsm_state_msg, nbr->state, NULL),
+			   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.
+			 */
+			flog_err(
+				EC_OSPF_FSM_INVALID_STATE,
+				"NSM[%s:%pI4:%s]: %s (%s): Warning: action tried to change next_state to %s",
+				IF_NAME(nbr->oi), &nbr->router_id,
+				ospf_get_name(nbr->oi->ospf),
+				lookup_msg(ospf_nsm_state_msg, nbr->state,
+					   NULL),
+				ospf_nsm_event_str[event],
+				lookup_msg(ospf_nsm_state_msg, func_state,
+					   NULL));
+		}
+	}
+
+	assert(next_state != NSM_DependUpon);
+
+	/* If state is changed. */
+	if (next_state != nbr->state) {
+		int old_state = nbr->state;
+
+		nsm_notice_state_change(nbr, next_state, event);
+		nsm_change_state(nbr, next_state);
+
+		hook_call(ospf_nsm_change, nbr, next_state, old_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);
+}
+
+/* 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);
+	}
+}