isisd: apply fast-reroute on an adjacency failure

When a adjacency falls down, the primary routes are not deleted on the
dataplane until the SPF is recomputed. Even the backup routes are
pre-installed on the dataplane, there is no fast-route optimization.

Reasons for an adjacency to come down are:
- BFD down
- Hello timer timeout
- User adjacency clear

Apply the backup route switchover for fast-reroute as soon an IS-IS
adjacency falls down before the first SPF re-computation. Pre-computed
backup routes are applied sooner.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

isisd/isis_adjacency.c

@@ -212,6 +212,36 @@ static const char *adj_level2string(int level)
 	return NULL; /* not reached */
 }
 
+static void isis_adj_route_switchover(struct isis_adjacency *adj)
+{
+	union g_addr ip = {};
+	ifindex_t ifindex;
+	unsigned int i;
+
+	if (!adj->circuit || !adj->circuit->interface)
+		return;
+
+	ifindex = adj->circuit->interface->ifindex;
+
+	for (i = 0; i < adj->ipv4_address_count; i++) {
+		ip.ipv4 = adj->ipv4_addresses[i];
+		isis_circuit_switchover_routes(adj->circuit, AF_INET, &ip,
+					       ifindex);
+	}
+
+	for (i = 0; i < adj->ll_ipv6_count; i++) {
+		ip.ipv6 = adj->ll_ipv6_addrs[i];
+		isis_circuit_switchover_routes(adj->circuit, AF_INET6, &ip,
+					       ifindex);
+	}
+
+	for (i = 0; i < adj->global_ipv6_count; i++) {
+		ip.ipv6 = adj->global_ipv6_addrs[i];
+		isis_circuit_switchover_routes(adj->circuit, AF_INET6, &ip,
+					       ifindex);
+	}
+}
+
 void isis_adj_process_threeway(struct isis_adjacency *adj,
 			       struct isis_threeway_adj *tw_adj,
 			       enum isis_adj_usage adj_usage)
@@ -298,6 +328,15 @@ void isis_adj_state_change(struct isis_adjacency **padj,
 	if (new_state == old_state)
 		return;
 
+	if (old_state == ISIS_ADJ_UP) {
+		if (IS_DEBUG_EVENTS)
+			zlog_debug(
+				"ISIS-Adj (%s): Starting fast-reroute on state change %d->%d: %s",
+				circuit->area->area_tag, old_state, new_state,
+				reason ? reason : "unspecified");
+		isis_adj_route_switchover(adj);
+	}
+
 	adj->adj_state = new_state;
 	send_hello_sched(circuit, adj->level, TRIGGERED_IIH_DELAY);
 

isisd/isis_adjacency.h

@@ -151,5 +151,4 @@ void isis_adj_build_up_list(struct list *adjdb, struct list *list);
 int isis_adj_usage2levels(enum isis_adj_usage usage);
 void isis_bfd_startup_timer(struct thread *thread);
 const char *isis_adj_name(const struct isis_adjacency *adj);
-
 #endif /* ISIS_ADJACENCY_H */

isisd/isis_circuit.c

@@ -598,6 +598,32 @@ size_t isis_circuit_pdu_size(struct isis_circuit *circuit)
 	return ISO_MTU(circuit);
 }
 
+static bool isis_circuit_lfa_enabled(struct isis_circuit *circuit, int level)
+{
+	return (circuit->lfa_protection[level - 1] ||
+		circuit->rlfa_protection[level - 1] ||
+		circuit->tilfa_protection[level - 1]);
+}
+
+void isis_circuit_switchover_routes(struct isis_circuit *circuit, int family,
+				    union g_addr *nexthop_ip, ifindex_t ifindex)
+{
+	char is_type;
+
+	if (!circuit->area)
+		return;
+
+	is_type = circuit->area->is_type;
+	if ((is_type == IS_LEVEL_1 || is_type == IS_LEVEL_1_AND_2) &&
+	    isis_circuit_lfa_enabled(circuit, IS_LEVEL_1))
+		isis_area_switchover_routes(circuit->area, family, nexthop_ip,
+					    ifindex, IS_LEVEL_1);
+	if ((is_type == IS_LEVEL_2 || is_type == IS_LEVEL_1_AND_2) &&
+	    isis_circuit_lfa_enabled(circuit, IS_LEVEL_2))
+		isis_area_switchover_routes(circuit->area, family, nexthop_ip,
+					    ifindex, IS_LEVEL_2);
+}
+
 void isis_circuit_stream(struct isis_circuit *circuit, struct stream **stream)
 {
 	size_t stream_size = isis_circuit_pdu_size(circuit);

isisd/isis_circuit.h

@@ -28,6 +28,7 @@
 #include "qobj.h"
 #include "prefix.h"
 #include "ferr.h"
+#include "nexthop.h"
 
 #include "isis_constants.h"
 #include "isis_common.h"
@@ -209,6 +210,9 @@ void isis_circuit_print_vty(struct isis_circuit *circuit, struct vty *vty,
 void isis_circuit_print_json(struct isis_circuit *circuit,
 			     struct json_object *json, char detail);
 size_t isis_circuit_pdu_size(struct isis_circuit *circuit);
+void isis_circuit_switchover_routes(struct isis_circuit *circuit, int family,
+				    union g_addr *nexthop_ip,
+				    ifindex_t ifindex);
 void isis_circuit_stream(struct isis_circuit *circuit, struct stream **stream);
 
 void isis_circuit_af_set(struct isis_circuit *circuit, bool ip_router,

isisd/isis_route.c

@@ -724,3 +724,53 @@ void isis_route_invalidate_table(struct isis_area *area,
 		UNSET_FLAG(rinfo->flag, ISIS_ROUTE_FLAG_ACTIVE);
 	}
 }
+
+void isis_route_switchover_nexthop(struct isis_area *area,
+				   struct route_table *table, int family,
+				   union g_addr *nexthop_addr,
+				   ifindex_t ifindex)
+{
+	const char *ifname = NULL, *vrfname = NULL;
+	struct isis_route_info *rinfo;
+	struct prefix_ipv6 *src_p;
+	struct route_node *rnode;
+	vrf_id_t vrf_id;
+	struct prefix *prefix;
+
+	if (IS_DEBUG_EVENTS) {
+		if (area && area->isis) {
+			vrf_id = area->isis->vrf_id;
+			vrfname = vrf_id_to_name(vrf_id);
+			ifname = ifindex2ifname(ifindex, vrf_id);
+		}
+		zlog_debug("%s: initiating fast-reroute %s on VRF %s iface %s",
+			   __func__, family2str(family), vrfname ? vrfname : "",
+			   ifname ? ifname : "");
+	}
+
+	for (rnode = route_top(table); rnode;
+	     rnode = srcdest_route_next(rnode)) {
+		if (!rnode->info)
+			continue;
+		rinfo = rnode->info;
+
+		if (!rinfo->backup)
+			continue;
+
+		if (!nexthoplookup(rinfo->nexthops, family, nexthop_addr,
+				   ifindex))
+			continue;
+
+		srcdest_rnode_prefixes(rnode, (const struct prefix **)&prefix,
+				       (const struct prefix **)&src_p);
+
+		/* Switchover route. */
+		UNSET_FLAG(rinfo->flag, ISIS_ROUTE_FLAG_ZEBRA_SYNCED);
+		isis_route_update(area, prefix, src_p, rinfo->backup);
+
+		isis_route_info_delete(rinfo);
+
+		rnode->info = NULL;
+		route_unlock_node(rnode);
+	}
+}

isisd/isis_route.h

@@ -86,4 +86,9 @@ void isis_route_invalidate_table(struct isis_area *area,
 void isis_route_node_cleanup(struct route_table *table,
 			     struct route_node *node);
 
+void isis_route_switchover_nexthop(struct isis_area *area,
+				   struct route_table *table, int family,
+				   union g_addr *nexthop_addr,
+				   ifindex_t ifindex);
+
 #endif /* _ZEBRA_ISIS_ROUTE_H */

isisd/isis_spf.c

@@ -1851,6 +1851,15 @@ void isis_spf_invalidate_routes(struct isis_spftree *tree)
 	tree->route_table_backup->cleanup = isis_route_node_cleanup;
 }
 
+void isis_spf_switchover_routes(struct isis_area *area,
+				struct isis_spftree **trees, int family,
+				union g_addr *nexthop_ip, ifindex_t ifindex,
+				int level)
+{
+	isis_route_switchover_nexthop(area, trees[level - 1]->route_table,
+				      family, nexthop_ip, ifindex);
+}
+
 static void isis_run_spf_cb(struct thread *thread)
 {
 	struct isis_spf_run *run = THREAD_ARG(thread);

isisd/isis_spf.h

@@ -60,6 +60,10 @@ struct isis_vertex *isis_spf_prefix_sid_lookup(struct isis_spftree *spftree,
 void isis_spf_invalidate_routes(struct isis_spftree *tree);
 void isis_spf_verify_routes(struct isis_area *area,
 			    struct isis_spftree **trees);
+void isis_spf_switchover_routes(struct isis_area *area,
+				struct isis_spftree **trees, int family,
+				union g_addr *nexthop_ip, ifindex_t ifindex,
+				int level);
 void isis_spftree_del(struct isis_spftree *spftree);
 void spftree_area_init(struct isis_area *area);
 void spftree_area_del(struct isis_area *area);

isisd/isisd.c

@@ -3092,6 +3092,25 @@ void isis_area_verify_routes(struct isis_area *area)
 		isis_spf_verify_routes(area, area->spftree[tree]);
 }
 
+void isis_area_switchover_routes(struct isis_area *area, int family,
+				 union g_addr *nexthop_ip, ifindex_t ifindex,
+				 int level)
+{
+	int tree;
+
+	/* TODO SPFTREE_DSTSRC */
+	if (family == AF_INET)
+		tree = SPFTREE_IPV4;
+	else if (family == AF_INET6)
+		tree = SPFTREE_IPV6;
+	else
+		return;
+
+	isis_spf_switchover_routes(area, area->spftree[tree], family,
+				   nexthop_ip, ifindex, level);
+}
+
+
 static void area_resign_level(struct isis_area *area, int level)
 {
 	isis_area_invalidate_routes(area, level);

isisd/isisd.h

@@ -291,6 +291,9 @@ struct isis_lsp *lsp_for_sysid(struct lspdb_head *head, const char *sysid_str,
 
 void isis_area_invalidate_routes(struct isis_area *area, int levels);
 void isis_area_verify_routes(struct isis_area *area);
+void isis_area_switchover_routes(struct isis_area *area, int family,
+				 union g_addr *nexthop_ip, ifindex_t ifindex,
+				 int level);
 
 void isis_area_overload_bit_set(struct isis_area *area, bool overload_bit);
 void isis_area_overload_on_startup_set(struct isis_area *area,