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>

1 files changed, 37 insertions, 0 deletions

diff --git a/ospf6d/ospf6_intra.c b/ospf6d/ospf6_intra.c
index 06a950156b..bea8cf0edd 100644
--- a/ospf6d/ospf6_intra.c
+++ b/ospf6d/ospf6_intra.c
@@ -47,6 +47,7 @@
 #include "ospf6_flood.h"
 #include "ospf6d.h"
 #include "ospf6_spf.h"
+#include "ospf6_gr.h"
 
 unsigned char conf_debug_ospf6_brouter = 0;
 uint32_t conf_debug_ospf6_brouter_specific_router_id;
@@ -249,6 +250,13 @@ int ospf6_router_lsa_originate(struct thread *thread)
 	oa = (struct ospf6_area *)THREAD_ARG(thread);
 	oa->thread_router_lsa = NULL;
 
+	if (oa->ospf6->gr_info.restart_in_progress) {
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"Graceful Restart in progress, don't originate LSA");
+		return 0;
+	}
+
 	if (IS_OSPF6_DEBUG_ORIGINATE(ROUTER))
 		zlog_debug("Originate Router-LSA for Area %s", oa->name);
 
@@ -532,6 +540,13 @@ int ospf6_network_lsa_originate(struct thread *thread)
 	   by ospf6_lsa_refresh (), and does not come here. */
 	assert(oi->area);
 
+	if (oi->area->ospf6->gr_info.restart_in_progress) {
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"Graceful Restart in progress, don't originate LSA");
+		return 0;
+	}
+
 	old = ospf6_lsdb_lookup(htons(OSPF6_LSTYPE_NETWORK),
 				htonl(oi->interface->ifindex),
 				oi->area->ospf6->router_id, oi->area->lsdb);
@@ -773,6 +788,14 @@ int ospf6_link_lsa_originate(struct thread *thread)
 
 	assert(oi->area);
 
+	if (oi->area->ospf6->gr_info.restart_in_progress) {
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"Graceful Restart in progress, don't originate LSA");
+		return 0;
+	}
+
+
 	/* find previous LSA */
 	old = ospf6_lsdb_lookup(htons(OSPF6_LSTYPE_LINK),
 				htonl(oi->interface->ifindex),
@@ -1009,6 +1032,13 @@ int ospf6_intra_prefix_lsa_originate_stub(struct thread *thread)
 	oa = (struct ospf6_area *)THREAD_ARG(thread);
 	oa->thread_intra_prefix_lsa = NULL;
 
+	if (oa->ospf6->gr_info.restart_in_progress) {
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"Graceful Restart in progress, don't originate LSA");
+		return 0;
+	}
+
 	/* find previous LSA */
 	old = ospf6_lsdb_lookup(htons(OSPF6_LSTYPE_INTRA_PREFIX), htonl(0),
 				oa->ospf6->router_id, oa->lsdb);
@@ -1243,6 +1273,13 @@ int ospf6_intra_prefix_lsa_originate_transit(struct thread *thread)
 
 	assert(oi->area);
 
+	if (oi->area->ospf6->gr_info.restart_in_progress) {
+		if (IS_DEBUG_OSPF6_GR)
+			zlog_debug(
+				"Graceful Restart in progress, don't originate LSA");
+		return 0;
+	}
+
 	/* find previous LSA */
 	old = ospf6_lsdb_lookup(htons(OSPF6_LSTYPE_INTRA_PREFIX),
 				htonl(oi->interface->ifindex),