ospf6d: GR helper exit scenarios

Description:
	Changes to cover all the following  GR helper exit scenarios.
	1. Upon receiving max age grace lsa.( successful graceful restart)
	2. Topo change
	3. Grace timer expiry.
	4. User changes( like config deletion , interface down)

Signed-off-by: Rajesh Girada <rgirada@vmware.com>

1 files changed, 180 insertions, 1 deletions

diff --git a/ospf6d/ospf6_gr_helper.c b/ospf6d/ospf6_gr_helper.c
index d03517115..60c62a934 100644
--- a/ospf6d/ospf6_gr_helper.c
+++ b/ospf6d/ospf6_gr_helper.c
@@ -191,7 +191,7 @@ static int ospf6_handle_grace_timer_expiry(struct thread *thread)
 
 	nbr->gr_helper_info.t_grace_timer = NULL;
 
-	// ospf6_gr_helper_exit(nbr, OSPF6_GR_HELPER_GRACE_TIMEOUT);
+	ospf6_gr_helper_exit(nbr, OSPF6_GR_HELPER_GRACE_TIMEOUT);
 	return OSPF6_SUCCESS;
 }
 
@@ -403,6 +403,185 @@ int ospf6_process_grace_lsa(struct ospf6 *ospf6, struct ospf6_lsa *lsa,
 	return OSPF6_GR_ACTIVE_HELPER;
 }
 
+/*
+ * Api to exit from HELPER role to take all actions
+ * required at exit.
+ * Ref rfc3623 section 3. and rfc51872
+ *
+ * ospf6
+ *    Ospf6 pointer.
+ *
+ * nbr
+ *    Ospf6 neighbour for which it is acting as HELPER.
+ *
+ * reason
+ *    The reason for exiting from HELPER.
+ *
+ * Returns:
+ *    Nothing.
+ */
+void ospf6_gr_helper_exit(struct ospf6_neighbor *nbr,
+			  enum ospf6_helper_exit_reason reason)
+{
+	struct ospf6_interface *oi = nbr->ospf6_if;
+	struct ospf6 *ospf6;
+
+	if (!oi)
+		return;
+
+	ospf6 = oi->area->ospf6;
+
+	if (!OSPF6_GR_IS_ACTIVE_HELPER(nbr))
+		return;
+
+	if (IS_DEBUG_OSPF6_GR_HELPER)
+		zlog_debug("%s, Exiting from HELPER support to %pI6, due to %s",
+			   __func__, &nbr->linklocal_addr,
+			   ospf6_exit_reason_desc[reason]);
+
+	/* Reset helper status*/
+	nbr->gr_helper_info.gr_helper_status = OSPF6_GR_NOT_HELPER;
+	nbr->gr_helper_info.helper_exit_reason = reason;
+	nbr->gr_helper_info.actual_grace_period = 0;
+	nbr->gr_helper_info.recvd_grace_period = 0;
+	nbr->gr_helper_info.gr_restart_reason = 0;
+	ospf6->ospf6_helper_cfg.last_exit_reason = reason;
+
+	/* If the exit not triggered due to grace timer
+	 * expairy , stop the grace timer.
+	 */
+	if (reason != OSPF6_GR_HELPER_GRACE_TIMEOUT)
+		THREAD_OFF(nbr->gr_helper_info.t_grace_timer);
+
+	if (ospf6->ospf6_helper_cfg.active_restarter_cnt <= 0) {
+		zlog_err(
+			"OSPF6 GR-Helper: Number of active Restarters should be greater than zero.");
+		return;
+	}
+	/* Decrement active Restarter count */
+	ospf6->ospf6_helper_cfg.active_restarter_cnt--;
+
+	/* check exit triggered due to successful completion
+	 * of graceful restart.
+	 */
+	if (reason != OSPF6_GR_HELPER_COMPLETED) {
+		if (IS_DEBUG_OSPF6_GR_HELPER)
+			zlog_debug("%s, Unsuccessful GR exit. RESTARTER : %pI6",
+				   __func__, &nbr->linklocal_addr);
+	}
+
+	/*Recalculate the DR for the network segment */
+	dr_election(oi);
+
+	/* Originate a router LSA */
+	OSPF6_ROUTER_LSA_SCHEDULE(nbr->ospf6_if->area);
+
+	/* Originate network lsa if it is an DR in the LAN */
+	if (nbr->ospf6_if->state == OSPF6_INTERFACE_DR)
+		OSPF6_NETWORK_LSA_SCHEDULE(nbr->ospf6_if);
+}
+
+/*
+ * Process Maxage Grace LSA.
+ * It is a indication for successfull completion of GR.
+ * If router acting as HELPER, It exits from helper role.
+ *
+ * ospf6
+ *    Ospf6 pointer.
+ *
+ * lsa
+ *    Grace LSA received from RESTARTER.
+ *
+ * nbr
+ *    ospf6 neighbour which requets the router to act as
+ *    HELPER.
+ *
+ * Returns:
+ *    Nothing.
+ */
+void ospf6_process_maxage_grace_lsa(struct ospf6 *ospf6, struct ospf6_lsa *lsa,
+				    struct ospf6_neighbor *restarter)
+{
+	uint8_t restart_reason = 0;
+	uint32_t grace_interval = 0;
+	int ret;
+
+	/* Extract the grace lsa packet fields */
+	ret = ospf6_extract_grace_lsa_fields(lsa, &grace_interval,
+					     &restart_reason);
+	if (ret != OSPF6_SUCCESS) {
+		if (IS_DEBUG_OSPF6_GR_HELPER)
+			zlog_debug("%s, Wrong Grace LSA packet.",
+				   __func__);
+		return;
+	}
+
+	if (IS_DEBUG_OSPF6_GR_HELPER)
+		zlog_debug("%s, GraceLSA received for neighbour %pI4.",
+			   __func__, &restarter->router_id);
+
+	ospf6_gr_helper_exit(restarter, OSPF6_GR_HELPER_COMPLETED);
+}
+
+/*
+ * Actions to be taken  when topo change detected
+ * HELPER will be exited upon a topo change.
+ *
+ * ospf6
+ *    ospf6 pointer
+ * lsa
+ *    topo change occured due to this lsa(type (1-5  and 7)
+ *
+ * Returns:
+ *    Nothing
+ */
+void ospf6_helper_handle_topo_chg(struct ospf6 *ospf6, struct ospf6_lsa *lsa)
+{
+	struct listnode *i, *j, *k;
+	struct ospf6_neighbor *nbr = NULL;
+	struct ospf6_area *oa = NULL;
+	struct ospf6_interface *oi = NULL;
+
+	if (!ospf6->ospf6_helper_cfg.active_restarter_cnt)
+		return;
+
+	/* Topo change not required to be hanlded if strict
+	 * LSA check is disbaled for this router.
+	 */
+	if (!ospf6->ospf6_helper_cfg.strict_lsa_check)
+		return;
+
+	if (IS_DEBUG_OSPF6_GR_HELPER)
+		zlog_debug(
+			"%s, Topo change detected due to lsa details : %s",
+			__func__, lsa->name);
+
+	lsa->tobe_acknowledged = OSPF6_TRUE;
+
+	for (ALL_LIST_ELEMENTS_RO(ospf6->area_list, i, oa))
+		for (ALL_LIST_ELEMENTS_RO(oa->if_list, j, oi)) {
+
+			/* Ref rfc3623 section 3.2.3.b and rfc5187
+			 * If change due to external LSA and if the area is
+			 * stub, then it is not a topo change. Since Type-5
+			 * lsas will not be flooded in stub area.
+			 */
+			if (IS_AREA_STUB(oi->area)
+			    && ((lsa->header->type == OSPF6_LSTYPE_AS_EXTERNAL)
+				|| (lsa->header->type == OSPF6_LSTYPE_TYPE_7)
+				|| (lsa->header->type
+				    == OSPF6_LSTYPE_INTER_ROUTER))) {
+				continue;
+			}
+
+			for (ALL_LIST_ELEMENTS_RO(oi->neighbor_list, k, nbr)) {
+
+				ospf6_gr_helper_exit(nbr,
+						     OSPF6_GR_HELPER_TOPO_CHG);
+			}
+		}
+}
+
 /* Debug commands */
 DEFPY(debug_ospf6_gr,
       debug_ospf6_gr_cmd,