ospf6d: introduce support for Graceful Restart (restarting mode)

RFC 5187 specifies the Graceful Restart enhancement to the OSPFv3
routing protocol. This commit implements support for the GR
restarting mode.

Here's a quick summary of how the GR restarting mode works:
* GR can be enabled on a per-instance basis using the `graceful-restart
  [grace-period (1-1800)]` command;
* To perform a graceful shutdown, the `graceful-restart prepare ipv6
  ospf` EXEC-level command needs to be issued before restarting the
  ospf6d daemon (there's no specific requirement on how the daemon
  should be restarted);
* `graceful-restart prepare ospf` will initiate the graceful restart
  for all GR-enabled instances by taking the following actions:
  o Flooding Grace-LSAs over all interfaces
  o Freezing the OSPF routes in the RIB
  o Saving the end of the grace period in non-volatile memory (a JSON
    file stored in `$frr_statedir`)
* Once ospf6d is started again, it will follow the procedures
  described in RFC 3623 until it detects it's time to exit the graceful
  restart (either successfully or unsuccessfully).

Testing done:
* New topotest featuring a multi-area OSPF topology (including stub
  and NSSA areas);
* Successful interop tests against IOS-XR routers acting as helpers.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>

configure.ac

@@ -2519,6 +2519,7 @@ AC_DEFINE_UNQUOTED([LDPD_SOCKET], ["$frr_statedir%s%s/ldpd.sock"], [ldpd control
 AC_DEFINE_UNQUOTED([ZEBRA_SERV_PATH], ["$frr_statedir%s%s/zserv.api"], [zebra api socket])
 AC_DEFINE_UNQUOTED([BFDD_CONTROL_SOCKET], ["$frr_statedir%s%s/bfdd.sock"], [bfdd control socket])
 AC_DEFINE_UNQUOTED([OSPFD_GR_STATE], ["$frr_statedir%s/ospfd-gr.json"], [ospfd GR state information])
+AC_DEFINE_UNQUOTED([OSPF6D_GR_STATE], ["$frr_statedir/ospf6d-gr.json"], [ospf6d GR state information])
 AC_DEFINE_UNQUOTED([DAEMON_VTY_DIR], ["$frr_statedir%s%s"], [daemon vty directory])
 AC_DEFINE_UNQUOTED([DAEMON_DB_DIR], ["$frr_statedir"], [daemon database directory])
 

doc/user/ospf6d.rst

@@ -264,8 +264,17 @@ 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
-=======================
+Graceful Restart
+================
+
+.. clicmd:: graceful-restart [grace-period (1-1800)]
+
+
+   Configure Graceful Restart (RFC 5187) restarting support.
+   When enabled, the default grace period is 120 seconds.
+
+   To perform a graceful shutdown, the "graceful-restart prepare ipv6 ospf"
+   EXEC-level command needs to be issued before restarting the ospf6d daemon.
 
 .. clicmd:: graceful-restart helper-only [A.B.C.D]
 
@@ -297,6 +306,16 @@ Graceful Restart Helper
    restarts. By default, it supports both planned and
    unplanned outages.
 
+.. clicmd:: graceful-restart prepare ipv6 ospf
+
+
+   Initiate a graceful restart for all OSPFv3 instances configured with the
+   "graceful-restart" command. The ospf6d daemon should be restarted during
+   the instance-specific grace period, otherwise the graceful restart will fail.
+
+   This is an EXEC-level command.
+
+
 .. _showing-ospf6-information:
 
 Showing OSPF6 information

ospf6d/ospf6_asbr.c

@@ -52,6 +52,7 @@
 #include "ospf6d.h"
 #include "ospf6_spf.h"
 #include "ospf6_nssa.h"
+#include "ospf6_gr.h"
 #include "lib/json.h"
 
 DEFINE_MTYPE_STATIC(OSPF6D, OSPF6_EXTERNAL_INFO, "OSPF6 ext. info");
@@ -102,6 +103,13 @@ struct ospf6_lsa *ospf6_as_external_lsa_originate(struct ospf6_route *route,
 	struct ospf6_as_external_lsa *as_external_lsa;
 	caddr_t p;
 
+	if (ospf6->gr_info.restart_in_progress) {
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"Graceful Restart in progress, don't originate LSA");
+		return NULL;
+	}
+
 	if (IS_OSPF6_DEBUG_ASBR || IS_OSPF6_DEBUG_ORIGINATE(AS_EXTERNAL))
 		zlog_debug("Originate AS-External-LSA for %pFX",
 			   &route->prefix);

ospf6d/ospf6_flood.c

@@ -85,7 +85,7 @@ struct ospf6_lsdb *ospf6_get_scoped_lsdb_self(struct ospf6_lsa *lsa)
 	return lsdb_self;
 }
 
-void ospf6_lsa_originate(struct ospf6_lsa *lsa)
+void ospf6_lsa_originate(struct ospf6 *ospf6, struct ospf6_lsa *lsa)
 {
 	struct ospf6_lsa *old;
 	struct ospf6_lsdb *lsdb_self;
@@ -106,7 +106,8 @@ void ospf6_lsa_originate(struct ospf6_lsa *lsa)
 
 	/* if the new LSA does not differ from previous,
 	   suppress this update of the LSA */
-	if (old && !OSPF6_LSA_IS_DIFFER(lsa, old)) {
+	if (old && !OSPF6_LSA_IS_DIFFER(lsa, old)
+	    && !ospf6->gr_info.finishing_restart) {
 		if (IS_OSPF6_DEBUG_ORIGINATE_TYPE(lsa->header->type))
 			zlog_debug("Suppress updating LSA: %s", lsa->name);
 		ospf6_lsa_delete(lsa);
@@ -134,20 +135,20 @@ void ospf6_lsa_originate(struct ospf6_lsa *lsa)
 void ospf6_lsa_originate_process(struct ospf6_lsa *lsa, struct ospf6 *process)
 {
 	lsa->lsdb = process->lsdb;
-	ospf6_lsa_originate(lsa);
+	ospf6_lsa_originate(process, lsa);
 }
 
 void ospf6_lsa_originate_area(struct ospf6_lsa *lsa, struct ospf6_area *oa)
 {
 	lsa->lsdb = oa->lsdb;
-	ospf6_lsa_originate(lsa);
+	ospf6_lsa_originate(oa->ospf6, lsa);
 }
 
 void ospf6_lsa_originate_interface(struct ospf6_lsa *lsa,
 				   struct ospf6_interface *oi)
 {
 	lsa->lsdb = oi->lsdb;
-	ospf6_lsa_originate(lsa);
+	ospf6_lsa_originate(oi->area->ospf6, lsa);
 }
 
 void ospf6_remove_id_from_external_id_table(struct ospf6 *ospf6,
@@ -326,7 +327,8 @@ void ospf6_install_lsa(struct ospf6_lsa *lsa)
 	lsa->installed = now;
 
 	/* Topo change handling */
-	if (CHECK_LSA_TOPO_CHG_ELIGIBLE(ntohs(lsa->header->type))) {
+	if (CHECK_LSA_TOPO_CHG_ELIGIBLE(ntohs(lsa->header->type))
+	    && !CHECK_FLAG(lsa->flag, OSPF6_LSA_DUPLICATE)) {
 
 		/* check if it is new lsa ? or existing lsa got modified ?*/
 		if (!old || OSPF6_LSA_IS_CHANGED(old, lsa)) {
@@ -991,6 +993,8 @@ void ospf6_receive_lsa(struct ospf6_neighbor *from,
 
 	/* if no database copy or received is more recent */
 	if (old == NULL || ismore_recent < 0) {
+		bool self_originated;
+
 		/* in case we have no database copy */
 		ismore_recent = -1;
 
@@ -1029,12 +1033,13 @@ void ospf6_receive_lsa(struct ospf6_neighbor *from,
 		reoriginated instance of the LSA not to be rejected by other
 		routers
 		due to MinLSArrival. */
-		if (new->header->adv_router
-		    != from->ospf6_if->area->ospf6->router_id)
+		self_originated = (new->header->adv_router
+				   == from->ospf6_if->area->ospf6->router_id);
+		if (!self_originated)
 			ospf6_flood(from, new);
 
-		/* Received Grace-LSA */
-		if (IS_GRACE_LSA(new)) {
+		/* Received non-self-originated Grace LSA. */
+		if (IS_GRACE_LSA(new) && !self_originated) {
 			struct ospf6 *ospf6;
 
 			ospf6 = ospf6_get_by_lsdb(new);
@@ -1088,8 +1093,16 @@ void ospf6_receive_lsa(struct ospf6_neighbor *from,
 		ospf6_acknowledge_lsa(new, ismore_recent, from);
 
 		/* (f) Self Originated LSA, section 13.4 */
-		if (new->header->adv_router
-		    == from->ospf6_if->area->ospf6->router_id) {
+		if (self_originated) {
+			if (from->ospf6_if->area->ospf6->gr_info
+				    .restart_in_progress) {
+				if (IS_DEBUG_OSPF6_GR)
+					zlog_debug(
+						"Graceful Restart in progress -- not flushing self-originated LSA: %s",
+						new->name);
+				return;
+			}
+
 			/* Self-originated LSA (newer than ours) is received
 			   from
 			   another router. We have to make a new instance of the
@@ -1105,6 +1118,11 @@ void ospf6_receive_lsa(struct ospf6_neighbor *from,
 					 &new->refresh);
 		}
 
+		struct ospf6 *ospf6 = from->ospf6_if->area->ospf6;
+		struct ospf6_area *area = from->ospf6_if->area;
+		if (ospf6->gr_info.restart_in_progress)
+			ospf6_gr_check_lsdb_consistency(ospf6, area);
+
 		return;
 	}
 

ospf6d/ospf6_flood.h

@@ -32,7 +32,7 @@ extern struct ospf6_lsdb *ospf6_get_scoped_lsdb(struct ospf6_lsa *lsa);
 extern struct ospf6_lsdb *ospf6_get_scoped_lsdb_self(struct ospf6_lsa *lsa);
 
 /* origination & purging */
-extern void ospf6_lsa_originate(struct ospf6_lsa *lsa);
+extern void ospf6_lsa_originate(struct ospf6 *ospf6, struct ospf6_lsa *lsa);
 extern void ospf6_lsa_originate_process(struct ospf6_lsa *lsa,
 					struct ospf6 *process);
 extern void ospf6_lsa_originate_area(struct ospf6_lsa *lsa,