Merge pull request #8935 from rgirada/ospfv3_gr_helper

ospf6d: Support for ospfv3  graceful restart  helper functionality

doc/user/ospf6d.rst

@@ -258,6 +258,39 @@ Redistribute routes to OSPF6
    argument injects the default route regardless of it being present in the
    router. Metric values and route-map can also be specified optionally.
 
+Graceful Restart Helper
+=======================
+
+.. clicmd:: graceful-restart helper-only [A.B.C.D]
+
+
+   Configure Graceful Restart (RFC 5187) helper support.
+   By default, helper support is disabled for all neighbours.
+   This config enables/disables helper support on this router
+   for all neighbours.
+   To enable/disable helper support for a specific
+   neighbour, the router-id (A.B.C.D) has to be specified.
+
+.. clicmd:: graceful-restart helper strict-lsa-checking
+
+
+   If 'strict-lsa-checking' is configured then the helper will
+   abort the Graceful Restart when a LSA change occurs which
+   affects the restarting router.
+   By default 'strict-lsa-checking' is enabled"
+
+.. clicmd:: graceful-restart helper supported-grace-time (10-1800)
+
+
+   Supports as HELPER for configured grace period.
+
+.. clicmd:: graceful-restart helper planned-only
+
+
+   It helps to support as HELPER only for planned
+   restarts. By default, it supports both planned and
+   unplanned outages.
+
 .. _showing-ospf6-information:
 
 Showing OSPF6 information
@@ -351,6 +384,19 @@ Showing OSPF6 information
    JSON object, with each router having "cost", "isLeafNode" and "children" as
    arguments.
 
+.. clicmd:: show ipv6 ospf6 graceful-restart helper [detail] [json]
+
+   This command shows the graceful-restart helper details including helper
+   configuration parameters.
+
+Debugging OSPF6
+===============
+
+.. clicmd:: debug ospf6 graceful-restart
+
+   This command enables/disables debug information for ospf6 graceful restart
+   helper functionality.
+
 
 .. _ospf6-debugging:
 

ospf6d/ospf6_flood.c

@@ -41,6 +41,7 @@
 
 #include "ospf6_flood.h"
 #include "ospf6_nssa.h"
+#include "ospf6_gr.h"
 
 unsigned char conf_debug_ospf6_flooding;
 
@@ -323,6 +324,22 @@ void ospf6_install_lsa(struct ospf6_lsa *lsa)
 
 	/* actually install */
 	lsa->installed = now;
+
+	/* Topo change handling */
+	if (CHECK_LSA_TOPO_CHG_ELIGIBLE(ntohs(lsa->header->type))) {
+
+		/* check if it is new lsa ? or existing lsa got modified ?*/
+		if (!old || OSPF6_LSA_IS_CHANGED(old, lsa)) {
+			struct ospf6 *ospf6;
+
+			ospf6 = ospf6_get_by_lsdb(lsa);
+
+			assert(ospf6);
+
+			ospf6_helper_handle_topo_chg(ospf6, lsa);
+		}
+	}
+
 	ospf6_lsdb_add(lsa, lsa->lsdb);
 
 	if (ntohs(lsa->header->type) == OSPF6_LSTYPE_TYPE_7) {
@@ -1016,6 +1033,50 @@ void ospf6_receive_lsa(struct ospf6_neighbor *from,
 		    != from->ospf6_if->area->ospf6->router_id)
 			ospf6_flood(from, new);
 
+		/* Received Grace-LSA */
+		if (IS_GRACE_LSA(new)) {
+			struct ospf6 *ospf6;
+
+			ospf6 = ospf6_get_by_lsdb(new);
+
+			assert(ospf6);
+
+			if (OSPF6_LSA_IS_MAXAGE(new)) {
+
+				if (IS_DEBUG_OSPF6_GR)
+					zlog_debug(
+						"%s, Received a maxage GraceLSA from router %pI4",
+						__func__,
+						&new->header->adv_router);
+				if (old) {
+					ospf6_process_maxage_grace_lsa(
+						ospf6, new, from);
+				} else {
+					if (IS_DEBUG_OSPF6_GR)
+						zlog_debug(
+							"%s, GraceLSA doesn't exist in lsdb, so discarding GraceLSA",
+							__func__);
+					return;
+				}
+			} else {
+
+				if (IS_DEBUG_OSPF6_GR)
+					zlog_debug(
+						"%s, Received a GraceLSA from router %pI4",
+						__func__,
+						&new->header->adv_router);
+
+				if (ospf6_process_grace_lsa(ospf6, new, from)
+				    == OSPF6_GR_NOT_HELPER) {
+					if (IS_DEBUG_OSPF6_GR)
+						zlog_debug(
+							"%s, Not moving to HELPER role, So dicarding GraceLSA",
+							__func__);
+					return;
+				}
+			}
+		}
+
 		/* (d), installing lsdb, which may cause routing
 			table calculation (replacing database copy) */
 		ospf6_install_lsa(new);

ospf6d/ospf6_gr.h

@@ -0,0 +1,161 @@
+/*
+ * OSPF6 Graceful Retsart helper functions.
+ *
+ * Copyright (C) 2021-22 Vmware, Inc.
+ * Rajesh Kumar Girada
+ *
+ * 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 this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef OSPF6_GR_H
+#define OSPF6_GR_H
+
+#define OSPF6_GR_NOT_HELPER 0
+#define OSPF6_GR_ACTIVE_HELPER 1
+
+#define OSPF6_GR_HELPER_NO_LSACHECK 0
+#define OSPF6_GR_HELPER_LSACHECK 1
+
+#define OSPF6_MAX_GRACE_INTERVAL 1800
+#define OSPF6_MIN_GRACE_INTERVAL 1
+
+/* Debug option */
+extern unsigned char conf_debug_ospf6_gr;
+
+#define OSPF6_DEBUG_GR 0x01
+
+#define OSPF6_DEBUG_GR_ON() (conf_debug_ospf6_gr |= OSPF6_DEBUG_GR)
+
+#define OSPF6_DEBUG_GR_OFF() (conf_debug_ospf6_gr &= ~OSPF6_DEBUG_GR)
+
+#define IS_DEBUG_OSPF6_GR conf_debug_ospf6_gr
+
+
+enum ospf6_helper_exit_reason {
+	OSPF6_GR_HELPER_EXIT_NONE = 0,
+	OSPF6_GR_HELPER_INPROGRESS,
+	OSPF6_GR_HELPER_TOPO_CHG,
+	OSPF6_GR_HELPER_GRACE_TIMEOUT,
+	OSPF6_GR_HELPER_COMPLETED
+};
+
+enum ospf6_gr_restart_reason {
+	OSPF6_GR_UNKNOWN_RESTART = 0,
+	OSPF6_GR_SW_RESTART = 1,
+	OSPF6_GR_SW_UPGRADE = 2,
+	OSPF6_GR_SWITCH_REDUNDANT_CARD = 3,
+	OSPF6_GR_INVALID_REASON_CODE = 4
+};
+
+enum ospf6_gr_helper_rejected_reason {
+	OSPF6_HELPER_REJECTED_NONE,
+	OSPF6_HELPER_SUPPORT_DISABLED,
+	OSPF6_HELPER_NOT_A_VALID_NEIGHBOUR,
+	OSPF6_HELPER_PLANNED_ONLY_RESTART,
+	OSPF6_HELPER_TOPO_CHANGE_RTXMT_LIST,
+	OSPF6_HELPER_LSA_AGE_MORE
+};
+
+#ifdef roundup
+#define ROUNDUP(val, gran) roundup(val, gran)
+#else /* roundup */
+#define ROUNDUP(val, gran) (((val)-1 | (gran)-1) + 1)
+#endif /* roundup */
+
+/*
+ * Generic TLV (type, length, value) macros
+ */
+struct tlv_header {
+	uint16_t type;   /* Type of Value */
+	uint16_t length; /* Length of Value portion only, in bytes */
+};
+
+#define TLV_HDR_SIZE (sizeof(struct tlv_header))
+
+#define TLV_BODY_SIZE(tlvh) (ROUNDUP(ntohs((tlvh)->length), sizeof(uint32_t)))
+
+#define TLV_SIZE(tlvh) (TLV_HDR_SIZE + TLV_BODY_SIZE(tlvh))
+
+#define TLV_HDR_TOP(lsah)                                                      \
+	(struct tlv_header *)((char *)(lsah) + OSPF6_LSA_HEADER_SIZE)
+
+#define TLV_HDR_NEXT(tlvh)                                                     \
+	(struct tlv_header *)((char *)(tlvh) + TLV_SIZE(tlvh))
+
+/* Ref RFC5187 appendix-A */
+/* Grace period TLV */
+#define GRACE_PERIOD_TYPE 1
+#define GRACE_PERIOD_LENGTH 4
+struct grace_tlv_graceperiod {
+	struct tlv_header header;
+	uint32_t interval;
+};
+#define GRACE_PERIOD_TLV_SIZE sizeof(struct grace_tlv_graceperiod)
+
+/* Restart reason TLV */
+#define RESTART_REASON_TYPE 2
+#define RESTART_REASON_LENGTH 1
+struct grace_tlv_restart_reason {
+	struct tlv_header header;
+	uint8_t reason;
+	uint8_t reserved[3];
+};
+#define GRACE_RESTART_REASON_TLV_SIZE sizeof(struct grace_tlv_restart_reason)
+
+#define OSPF6_GRACE_LSA_MIN_SIZE                                               \
+	GRACE_PERIOD_TLV_SIZE + GRACE_RESTART_REASON_TLV_SIZE
+
+struct advRtr {
+	in_addr_t advRtrAddr;
+};
+
+#define OSPF6_HELPER_ENABLE_RTR_COUNT(ospf)                                    \
+	(ospf6->ospf6_helper_cfg.enable_rtr_list->count)
+
+/* Check , it is a planned restart */
+#define OSPF6_GR_IS_PLANNED_RESTART(reason)                                    \
+	((reason == OSPF6_GR_SW_RESTART) || (reason == OSPF6_GR_SW_UPGRADE))
+
+/* Check the router is HELPER for current neighbour */
+#define OSPF6_GR_IS_ACTIVE_HELPER(N)                                           \
+	((N)->gr_helper_info.gr_helper_status == OSPF6_GR_ACTIVE_HELPER)
+
+/* Check the LSA is GRACE LSA */
+#define IS_GRACE_LSA(lsa) (ntohs(lsa->header->type) == OSPF6_LSTYPE_GRACE_LSA)
+
+/* Check neighbour is in FULL state */
+#define IS_NBR_STATE_FULL(nbr) (nbr->state == OSPF6_NEIGHBOR_FULL)
+
+extern const char *ospf6_exit_reason_desc[];
+extern const char *ospf6_restart_reason_desc[];
+extern const char *ospf6_rejected_reason_desc[];
+
+extern void ospf6_gr_helper_config_init(void);
+extern void ospf6_gr_helper_init(struct ospf6 *ospf6);
+extern void ospf6_gr_helper_deinit(struct ospf6 *ospf6);
+extern void ospf6_gr_helper_exit(struct ospf6_neighbor *nbr,
+				 enum ospf6_helper_exit_reason reason);
+extern int ospf6_process_grace_lsa(struct ospf6 *ospf6, struct ospf6_lsa *lsa,
+				   struct ospf6_neighbor *nbr);
+extern void ospf6_process_maxage_grace_lsa(struct ospf6 *ospf,
+					   struct ospf6_lsa *lsa,
+					   struct ospf6_neighbor *nbr);
+extern void ospf6_helper_handle_topo_chg(struct ospf6 *ospf6,
+					 struct ospf6_lsa *lsa);
+extern int config_write_ospf6_gr_helper(struct vty *vty, struct ospf6 *ospf6);
+extern int config_write_ospf6_debug_gr_helper(struct vty *vty);
+#endif /* OSPF6_GR_H */

ospf6d/ospf6_interface.c

@@ -44,9 +44,10 @@
 #include "ospf6d.h"
 #include "ospf6_bfd.h"
 #include "ospf6_zebra.h"
+#include "ospf6_gr.h"
 #include "lib/json.h"
 
-DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_IF,       "OSPF6 interface");
+DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_IF, "OSPF6 interface");
 DEFINE_MTYPE_STATIC(OSPF6D, CFG_PLIST_NAME, "configured prefix list names");
 DEFINE_QOBJ_TYPE(ospf6_interface);
 DEFINE_HOOK(ospf6_interface_change,
@@ -59,6 +60,22 @@ const char *const ospf6_interface_state_str[] = {
 	"None",    "Down", "Loopback", "Waiting", "PointToPoint",
 	"DROther", "BDR",  "DR",       NULL};
 
+int ospf6_interface_neighbor_count(struct ospf6_interface *oi)
+{
+	int count = 0;
+	struct ospf6_neighbor *nbr = NULL;
+	struct listnode *node;
+
+	for (ALL_LIST_ELEMENTS_RO(oi->neighbor_list, node, nbr)) {
+		/* Down state is not shown. */
+		if (nbr->state == OSPF6_NEIGHBOR_DOWN)
+			continue;
+		count++;
+	}
+
+	return count;
+}
+
 struct ospf6_interface *ospf6_interface_lookup_by_ifindex(ifindex_t ifindex,
 							  vrf_id_t vrf_id)
 {
@@ -579,7 +596,7 @@ static struct ospf6_neighbor *better_drouter(struct ospf6_neighbor *a,
 	return a;
 }
 
-static uint8_t dr_election(struct ospf6_interface *oi)
+uint8_t dr_election(struct ospf6_interface *oi)
 {
 	struct listnode *node, *nnode;
 	struct ospf6_neighbor *on, *drouter, *bdrouter, myself;
@@ -896,6 +913,17 @@ int interface_down(struct thread *thread)
 	/* Stop trying to set socket options. */
 	THREAD_OFF(oi->thread_sso);
 
+	/* Cease the HELPER role for all the neighbours
+	 * of this interface.
+	 */
+	if (ospf6_interface_neighbor_count(oi)) {
+		struct listnode *ln;
+		struct ospf6_neighbor *nbr = NULL;
+
+		for (ALL_LIST_ELEMENTS_RO(oi->neighbor_list, ln, nbr))
+			ospf6_gr_helper_exit(nbr, OSPF6_GR_HELPER_TOPO_CHG);
+	}
+
 	for (ALL_LIST_ELEMENTS(oi->neighbor_list, node, nnode, on))
 		ospf6_neighbor_delete(on);
 

ospf6d/ospf6_interface.h

@@ -218,6 +218,8 @@ extern void install_element_ospf6_clear_interface(void);
 
 extern int config_write_ospf6_debug_interface(struct vty *vty);
 extern void install_element_ospf6_debug_interface(void);
+extern int ospf6_interface_neighbor_count(struct ospf6_interface *oi);
+extern uint8_t dr_election(struct ospf6_interface *oi);
 
 DECLARE_HOOK(ospf6_interface_change,
 	     (struct ospf6_interface * oi, int state, int old_state),

ospf6d/ospf6_lsa.h

@@ -70,7 +70,8 @@
 #define OSPF6_LSTYPE_TYPE_7           0x2007
 #define OSPF6_LSTYPE_LINK             0x0008
 #define OSPF6_LSTYPE_INTRA_PREFIX     0x2009
-#define OSPF6_LSTYPE_SIZE             0x000a
+#define OSPF6_LSTYPE_GRACE_LSA	      0x000b
+#define OSPF6_LSTYPE_SIZE             0x000c
 
 /* Masks for LS Type : RFC 2740 A.4.2.1 "LS type" */
 #define OSPF6_LSTYPE_UBIT_MASK        0x8000
@@ -146,6 +147,9 @@ struct ospf6_lsa {
 
 	/* lsa instance */
 	struct ospf6_lsa_header *header;
+
+	/*For topo chg detection in HELPER role*/
+	bool tobe_acknowledged;
 };
 
 #define OSPF6_LSA_HEADERONLY 0x01
@@ -210,6 +214,14 @@ extern vector ospf6_lsa_handler_vector;
 		continue;                                                      \
 	}
 
+#define CHECK_LSA_TOPO_CHG_ELIGIBLE(type)		\
+	((type == OSPF6_LSTYPE_ROUTER)			\
+	 || (type == OSPF6_LSTYPE_NETWORK)		\
+	 || (type == OSPF6_LSTYPE_INTER_PREFIX)		\
+	 || (type == OSPF6_LSTYPE_INTER_ROUTER)		\
+	 || (type == OSPF6_LSTYPE_AS_EXTERNAL)		\
+	 || (type == OSPF6_LSTYPE_TYPE_7)		\
+	 || (type == OSPF6_LSTYPE_INTRA_PREFIX))
 
 /* Function Prototypes */
 extern const char *ospf6_lstype_name(uint16_t type);

ospf6d/ospf6_message.c

@@ -46,7 +46,7 @@
 
 #include "ospf6_flood.h"
 #include "ospf6d.h"
-
+#include "ospf6_gr.h"
 #include <netinet/ip6.h>
 
 DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_MESSAGE, "OSPF6 message");
@@ -84,7 +84,9 @@ const uint16_t ospf6_lsa_minlen[OSPF6_LSTYPE_SIZE] = {
 	/* 0x2006 */ 0,
 	/* 0x2007 */ OSPF6_AS_EXTERNAL_LSA_MIN_SIZE,
 	/* 0x0008 */ OSPF6_LINK_LSA_MIN_SIZE,
-	/* 0x2009 */ OSPF6_INTRA_PREFIX_LSA_MIN_SIZE};
+	/* 0x2009 */ OSPF6_INTRA_PREFIX_LSA_MIN_SIZE,
+	/* 0x200a */ 0,
+	/* 0x000b */ OSPF6_GRACE_LSA_MIN_SIZE};
 
 /* print functions */
 
@@ -512,8 +514,44 @@ static void ospf6_hello_recv(struct in6_addr *src, struct in6_addr *dst,
 	thread_execute(master, hello_received, on, 0);
 	if (twoway)
 		thread_execute(master, twoway_received, on, 0);
-	else
+	else {
-		thread_execute(master, oneway_received, on, 0);
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"%s, Received oneway hello from RESTARTER so ignore here.",
+				__PRETTY_FUNCTION__);
+
+		if (!OSPF6_GR_IS_ACTIVE_HELPER(on)) {
+			/* If the router is DR_OTHER, RESTARTER will not wait
+			 * until it receives the hello from it if it receives
+			 * from DR and BDR.
+			 * So, helper might receives ONE_WAY hello from
+			 * RESTARTER. So not allowing to change the state if it
+			 * receives one_way hellow when it acts as HELPER for
+			 * that specific neighbor.
+			 */
+			thread_execute(master, oneway_received, on, 0);
+		}
+	}
+
+	if (OSPF6_GR_IS_ACTIVE_HELPER(on)) {
+		/* As per the GR Conformance Test Case 7.2. Section 3
+		 * "Also, if X was the Designated Router on network segment S
+		 * when the helping relationship began, Y maintains X as the
+		 * Designated Router until the helping relationship is
+		 * terminated."
+		 * When it is a helper for this neighbor, It should not trigger
+		 * the ISM Events. Also Intentionally not setting the priority
+		 * and other fields so that when the neighbor exits the Grace
+		 * period, it can handle if there is any change before GR and
+		 * after GR.
+		 */
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"%s, Neighbor is under GR Restart, hence ignoring the ISM Events",
+				__PRETTY_FUNCTION__);
+
+		return;
+	}
 
 	/* Schedule interface events */
 	if (backupseen)
@@ -1260,7 +1298,15 @@ static unsigned ospf6_lsa_examin(struct ospf6_lsa_header *lsah,
 			lsalen - OSPF6_LSA_HEADER_SIZE
 				- OSPF6_INTRA_PREFIX_LSA_MIN_SIZE,
 			ntohs(intra_prefix_lsa->prefix_num) /* 16 bits */
-			);
+		);
+	case OSPF6_LSTYPE_GRACE_LSA:
+		if (lsalen < OSPF6_LSA_HEADER_SIZE + GRACE_PERIOD_TLV_SIZE
+				     + GRACE_RESTART_REASON_TLV_SIZE) {
+			if (IS_DEBUG_OSPF6_GR)
+				zlog_debug("%s: Undersized GraceLSA.",
+					   __func__);
+			return MSG_NG;
+		}
 	}
 	/* No additional validation is possible for unknown LSA types, which are
 	   themselves valid in OPSFv3, hence the default decision is to accept.

ospf6d/ospf6_neighbor.c

@@ -45,6 +45,7 @@
 #include "ospf6_lsa.h"
 #include "ospf6_spf.h"
 #include "ospf6_zebra.h"
+#include "ospf6_gr.h"
 #include "lib/json.h"
 
 DEFINE_MTYPE(OSPF6D, OSPF6_NEIGHBOR, "OSPF6 neighbor");
@@ -151,6 +152,7 @@ void ospf6_neighbor_delete(struct ospf6_neighbor *on)
 	THREAD_OFF(on->thread_send_lsreq);
 	THREAD_OFF(on->thread_send_lsupdate);
 	THREAD_OFF(on->thread_send_lsack);
+	THREAD_OFF(on->gr_helper_info.t_grace_timer);
 
 	bfd_sess_free(&on->bfd_session);
 	XFREE(MTYPE_OSPF6_NEIGHBOR, on);
@@ -192,19 +194,24 @@ static void ospf6_neighbor_state_change(uint8_t next_state,
 
 	if (prev_state == OSPF6_NEIGHBOR_FULL
 	    || next_state == OSPF6_NEIGHBOR_FULL) {
-		OSPF6_ROUTER_LSA_SCHEDULE(on->ospf6_if->area);
+		if (!OSPF6_GR_IS_ACTIVE_HELPER(on)) {
-		if (on->ospf6_if->state == OSPF6_INTERFACE_DR) {
+			OSPF6_ROUTER_LSA_SCHEDULE(on->ospf6_if->area);
-			OSPF6_NETWORK_LSA_SCHEDULE(on->ospf6_if);
+			if (on->ospf6_if->state == OSPF6_INTERFACE_DR) {
-			OSPF6_INTRA_PREFIX_LSA_SCHEDULE_TRANSIT(on->ospf6_if);
+				OSPF6_NETWORK_LSA_SCHEDULE(on->ospf6_if);
+				OSPF6_INTRA_PREFIX_LSA_SCHEDULE_TRANSIT(
+					on->ospf6_if);
+			}
 		}
 		if (next_state == OSPF6_NEIGHBOR_FULL)
 			on->ospf6_if->area->intra_prefix_originate = 1;
 
-		OSPF6_INTRA_PREFIX_LSA_SCHEDULE_STUB(on->ospf6_if->area);
+		if (!OSPF6_GR_IS_ACTIVE_HELPER(on))
+			OSPF6_INTRA_PREFIX_LSA_SCHEDULE_STUB(
+				on->ospf6_if->area);
 
-		if ((prev_state == OSPF6_NEIGHBOR_LOADING ||
+		if ((prev_state == OSPF6_NEIGHBOR_LOADING
-		     prev_state == OSPF6_NEIGHBOR_EXCHANGE) &&
+		     || prev_state == OSPF6_NEIGHBOR_EXCHANGE)
-		    next_state == OSPF6_NEIGHBOR_FULL) {
+		    && next_state == OSPF6_NEIGHBOR_FULL) {
 			OSPF6_AS_EXTERN_LSA_SCHEDULE(on->ospf6_if);
 			on->ospf6_if->area->full_nbrs++;
 		}
@@ -601,12 +608,29 @@ int inactivity_timer(struct thread *thread)
 	on->drouter = on->prev_drouter = 0;
 	on->bdrouter = on->prev_bdrouter = 0;
 
-	ospf6_neighbor_state_change(OSPF6_NEIGHBOR_DOWN, on,
+	if (!OSPF6_GR_IS_ACTIVE_HELPER(on)) {
-				    OSPF6_NEIGHBOR_EVENT_INACTIVITY_TIMER);
+		on->drouter = on->prev_drouter = 0;
-	thread_add_event(master, neighbor_change, on->ospf6_if, 0, NULL);
+		on->bdrouter = on->prev_bdrouter = 0;
 
-	listnode_delete(on->ospf6_if->neighbor_list, on);
+		ospf6_neighbor_state_change(
-	ospf6_neighbor_delete(on);
+			OSPF6_NEIGHBOR_DOWN, on,
+			OSPF6_NEIGHBOR_EVENT_INACTIVITY_TIMER);
+		thread_add_event(master, neighbor_change, on->ospf6_if, 0,
+				 NULL);
+
+		listnode_delete(on->ospf6_if->neighbor_list, on);
+		ospf6_neighbor_delete(on);
+
+	} else {
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"%s, Acting as HELPER for this neighbour, So restart the dead timer.",
+				__PRETTY_FUNCTION__);
+
+		thread_add_timer(master, inactivity_timer, on,
+				 on->ospf6_if->dead_interval,
+				 &on->inactivity_timer);
+	}
 
 	return 0;
 }

ospf6d/ospf6_neighbor.h

@@ -32,6 +32,38 @@ extern unsigned char conf_debug_ospf6_neighbor;
 #define IS_OSPF6_DEBUG_NEIGHBOR(level)                                         \
 	(conf_debug_ospf6_neighbor & OSPF6_DEBUG_NEIGHBOR_##level)
 
+struct ospf6_helper_info {
+
+	/* Grace interval received from
+	 * Restarting Router.
+	 */
+	uint32_t recvd_grace_period;
+
+	/* Grace interval used for grace
+	 * gracetimer.
+	 */
+	uint32_t actual_grace_period;
+
+	/* Grace timer,This Router acts as
+	 * helper until this timer until
+	 * this timer expires.
+	 */
+	struct thread *t_grace_timer;
+
+	/* Helper status */
+	uint32_t gr_helper_status;
+
+	/* Helper exit reason*/
+	uint32_t helper_exit_reason;
+
+	/* Planned/Unplanned restart*/
+	uint32_t gr_restart_reason;
+
+
+	/* Helper rejected reason */
+	uint32_t rejected_reason;
+};
+
 /* Neighbor structure */
 struct ospf6_neighbor {
 	/* Neighbor Router ID String */
@@ -104,6 +136,9 @@ struct ospf6_neighbor {
 
 	/* BFD information */
 	struct bfd_session_params *bfd_session;
+
+	/* ospf6 graceful restart HELPER info */
+	struct ospf6_helper_info gr_helper_info;
 };
 
 /* Neighbor state */

ospf6d/ospf6_top.c

@@ -51,6 +51,7 @@
 #include "ospf6_intra.h"
 #include "ospf6_spf.h"
 #include "ospf6d.h"
+#include "ospf6_gr.h"
 #include "lib/json.h"
 #include "ospf6_nssa.h"
 
@@ -440,6 +441,7 @@ static struct ospf6 *ospf6_create(const char *name)
 
 	o->oi_write_q = list_new();
 
+	ospf6_gr_helper_init(o);
 	QOBJ_REG(o, ospf6);
 
 	/* Make ospf protocol socket. */
@@ -485,6 +487,7 @@ void ospf6_delete(struct ospf6 *o)
 
 	QOBJ_UNREG(o);
 
+	ospf6_gr_helper_deinit(o);
 	ospf6_flush_self_originated_lsas_now(o);
 	ospf6_disable(o);
 	ospf6_del(o);
@@ -2233,7 +2236,7 @@ static int config_write_ospf6(struct vty *vty)
 		ospf6_distance_config_write(vty, ospf6);
 		ospf6_distribute_config_write(vty, ospf6);
 		ospf6_asbr_summary_config_write(vty, ospf6);
-
+		config_write_ospf6_gr_helper(vty, ospf6);
 		vty_out(vty, "!\n");
 	}
 	return 0;

ospf6d/ospf6_top.h

@@ -60,6 +60,43 @@ struct ospf6_redist {
 #define ROUTEMAP(R) (R->route_map.map)
 };
 
+struct ospf6_gr_helper {
+	/* Gracefull restart Helper supported configs*/
+	/* Supported grace interval*/
+	uint32_t supported_grace_time;
+
+	/* Helper support
+	 * Supported : True
+	 * Not Supported : False.
+	 */
+	bool is_helper_supported;
+
+	/* Support for strict LSA check.
+	 * if it is set,Helper aborted
+	 * upon a TOPO change.
+	 */
+	bool strict_lsa_check;
+
+	/* Support as HELPER only for
+	 * planned restarts.
+	 */
+	bool only_planned_restart;
+
+	/* This list contains the advertisement
+	 * routerids for which Helper support is
+	 * enabled.
+	 */
+	struct hash *enable_rtr_list;
+
+	/* HELPER for number of active
+	 * RESTARTERs.
+	 */
+	int active_restarter_cnt;
+
+	/* last HELPER exit reason */
+	uint32_t last_exit_reason;
+};
+
 /* OSPFv3 top level data structure */
 struct ospf6 {
 	/* The relevant vrf_id */
@@ -154,6 +191,10 @@ struct ospf6 {
 	 * to support ECMP.
 	 */
 	uint16_t max_multipath;
+
+	/*ospf6 Graceful restart helper info */
+	struct ospf6_gr_helper ospf6_helper_cfg;
+
 	/* Count of NSSA areas */
 	uint8_t anyNSSA;
 	struct thread *t_abr_task; /* ABR task timer. */

ospf6d/ospf6d.c

@@ -45,6 +45,7 @@
 #include "ospf6_flood.h"
 #include "ospf6d.h"
 #include "ospf6_bfd.h"
+#include "ospf6_gr.h"
 #include "lib/json.h"
 #include "ospf6_nssa.h"
 
@@ -96,6 +97,7 @@ static int config_write_ospf6_debug(struct vty *vty)
 	config_write_ospf6_debug_abr(vty);
 	config_write_ospf6_debug_flood(vty);
 	config_write_ospf6_debug_nssa(vty);
+	config_write_ospf6_debug_gr_helper(vty);
 
 	return 0;
 }
@@ -1402,6 +1404,7 @@ void ospf6_init(struct thread_master *master)
 	ospf6_intra_init();
 	ospf6_asbr_init();
 	ospf6_abr_init();
+	ospf6_gr_helper_config_init();
 
 	/* initialize hooks for modifying filter rules */
 	prefix_list_add_hook(ospf6_plist_add);

ospf6d/ospf6d.h

@@ -108,6 +108,12 @@ extern struct thread_master *master;
 		vrf_name = VRF_DEFAULT_NAME;                                   \
 	}
 
+#define OSPF6_FALSE false
+#define OSPF6_TRUE true
+#define OSPF6_SUCCESS 1
+#define OSPF6_FAILURE 0
+#define OSPF6_INVALID -1
+
 extern struct zebra_privs_t ospf6d_privs;
 
 /* Function Prototypes */

ospf6d/subdir.am

@@ -12,6 +12,7 @@ vtysh_scan += \
 	ospf6d/ospf6_area.c \
 	ospf6d/ospf6_bfd.c \
 	ospf6d/ospf6_flood.c \
+	ospf6d/ospf6_gr_helper.c \
 	ospf6d/ospf6_interface.c \
 	ospf6d/ospf6_intra.c \
 	ospf6d/ospf6_lsa.c \
@@ -39,6 +40,7 @@ ospf6d_libospf6_a_SOURCES = \
 	ospf6d/ospf6_routemap_nb_config.c \
 	ospf6d/ospf6_bfd.c \
 	ospf6d/ospf6_flood.c \
+	ospf6d/ospf6_gr_helper.c \
 	ospf6d/ospf6_interface.c \
 	ospf6d/ospf6_intra.c \
 	ospf6d/ospf6_lsa.c \
@@ -61,6 +63,7 @@ noinst_HEADERS += \
 	ospf6d/ospf6_asbr.h \
 	ospf6d/ospf6_bfd.h \
 	ospf6d/ospf6_flood.h \
+	ospf6d/ospf6_gr.h \
 	ospf6d/ospf6_interface.h \
 	ospf6d/ospf6_intra.h \
 	ospf6d/ospf6_lsa.h \
@@ -91,6 +94,7 @@ clippy_scan += \
 	ospf6d/ospf6_top.c \
 	ospf6d/ospf6_asbr.c \
 	ospf6d/ospf6_lsa.c \
+	ospf6d/ospf6_gr_helper.c \
 	# end
 
 nodist_ospf6d_ospf6d_SOURCES = \