ospfd: introduce a 'dry run' into SPF code

in OSPF interface data is used for the nexthop resolution
during the SPF algorithm, see RFC2328 16.1.1. However, for
certain technologies like TI-LFA it is desirable to be able
to calculate SPFs for arbitrary root nodes, not just the
calculating node. Since interface data is not available for
other nodes it is necessary to remove this dependency and
make its usage optional, depending on the intent of
changing the RIB with the generated tree (or not).

To signal that a SPF run is used without the intent to
change the RIB an additional flag `spf_dry_run` is
introduced to the ospf_area struct. This flag is currently
only used within the pure SPF code but will be extended
to the SPF postprocessing later on.

Signed-off-by: GalaxyGorilla <sascha@netdef.org>

1 files changed, 44 insertions, 22 deletions

diff --git a/ospfd/ospf_route.c b/ospfd/ospf_route.c
index 776f50b33a..487275beec 100644
--- a/ospfd/ospf_route.c
+++ b/ospfd/ospf_route.c
@@ -375,7 +375,7 @@ void ospf_intra_add_router(struct route_table *rt, struct vertex *v,
 	else
 		route_unlock_node(rn);
 
-	ospf_route_copy_nexthops_from_vertex(or, v);
+	ospf_route_copy_nexthops_from_vertex(area, or, v);
 
 	listnode_add(rn->info, or);
 
@@ -438,7 +438,7 @@ void ospf_intra_add_transit(struct route_table *rt, struct vertex *v,
 	or->type = OSPF_DESTINATION_NETWORK;
 	or->u.std.origin = (struct lsa_header *)lsa;
 
-	ospf_route_copy_nexthops_from_vertex(or, v);
+	ospf_route_copy_nexthops_from_vertex(area, or, v);
 
 	rn->info = or ;
 }
@@ -453,7 +453,7 @@ void ospf_intra_add_stub(struct route_table *rt, struct router_lsa_link *link,
 	struct ospf_route * or ;
 	struct prefix_ipv4 p;
 	struct router_lsa *lsa;
-	struct ospf_interface *oi;
+	struct ospf_interface *oi = NULL;
 	struct ospf_path *path;
 
 	if (IS_DEBUG_OSPF_EVENT)
@@ -538,7 +538,7 @@ void ospf_intra_add_stub(struct route_table *rt, struct router_lsa_link *link,
 				zlog_debug(
 					"ospf_intra_add_stub(): routes are equal, merge");
 
-			ospf_route_copy_nexthops_from_vertex(cur_or, v);
+			ospf_route_copy_nexthops_from_vertex(area, cur_or, v);
 
 			if (IPV4_ADDR_CMP(&cur_or->u.std.origin->id,
 					  &lsa->header.id)
@@ -563,7 +563,7 @@ void ospf_intra_add_stub(struct route_table *rt, struct router_lsa_link *link,
 
 			list_delete_all_node(cur_or->paths);
 
-			ospf_route_copy_nexthops_from_vertex(cur_or, v);
+			ospf_route_copy_nexthops_from_vertex(area, cur_or, v);
 
 			cur_or->u.std.origin = (struct lsa_header *)lsa;
 			return;
@@ -588,24 +588,35 @@ void ospf_intra_add_stub(struct route_table *rt, struct router_lsa_link *link,
 		if (IS_DEBUG_OSPF_EVENT)
 			zlog_debug(
 				"ospf_intra_add_stub(): this network is on remote router");
-		ospf_route_copy_nexthops_from_vertex(or, v);
+		ospf_route_copy_nexthops_from_vertex(area, or, v);
 	} else {
 		if (IS_DEBUG_OSPF_EVENT)
 			zlog_debug(
 				"ospf_intra_add_stub(): this network is on this router");
 
-		if ((oi = ospf_if_lookup_by_lsa_pos(area, lsa_pos))) {
+		/*
+		 * Only deal with interface data when we
+		 * don't do a dry run
+		 */
+		if (!area->spf_dry_run)
+			oi = ospf_if_lookup_by_lsa_pos(area, lsa_pos);
+
+		if (oi || area->spf_dry_run) {
 			if (IS_DEBUG_OSPF_EVENT)
 				zlog_debug(
-					"ospf_intra_add_stub(): the interface is %s",
-					IF_NAME(oi));
+					"ospf_intra_add_stub(): the lsa pos is %d",
+					lsa_pos);
 
 			path = ospf_path_new();
 			path->nexthop.s_addr = INADDR_ANY;
-			path->ifindex = oi->ifp->ifindex;
-			if (CHECK_FLAG(oi->connected->flags,
-				       ZEBRA_IFA_UNNUMBERED))
-				path->unnumbered = 1;
+
+			if (oi) {
+				path->ifindex = oi->ifp->ifindex;
+				if (CHECK_FLAG(oi->connected->flags,
+					       ZEBRA_IFA_UNNUMBERED))
+					path->unnumbered = 1;
+			}
+
 			listnode_add(or->paths, path);
 		} else {
 			if (IS_DEBUG_OSPF_EVENT)
@@ -734,30 +745,41 @@ static int ospf_path_exist(struct list *plist, struct in_addr nexthop,
 	return 0;
 }
 
-void ospf_route_copy_nexthops_from_vertex(struct ospf_route *to,
+void ospf_route_copy_nexthops_from_vertex(struct ospf_area *area,
+					  struct ospf_route *to,
 					  struct vertex *v)
 {
 	struct listnode *node;
 	struct ospf_path *path;
 	struct vertex_nexthop *nexthop;
 	struct vertex_parent *vp;
+	struct ospf_interface *oi = NULL;
 
 	assert(to->paths);
 
 	for (ALL_LIST_ELEMENTS_RO(v->parents, node, vp)) {
 		nexthop = vp->nexthop;
 
-		if (nexthop->oi != NULL) {
-			if (!ospf_path_exist(to->paths, nexthop->router,
-					     nexthop->oi)) {
-				path = ospf_path_new();
-				path->nexthop = nexthop->router;
-				path->ifindex = nexthop->oi->ifp->ifindex;
-				if (CHECK_FLAG(nexthop->oi->connected->flags,
+		/*
+		 * Only deal with interface data when we
+		 * don't do a dry run
+		 */
+		if (!area->spf_dry_run)
+			oi = ospf_if_lookup_by_lsa_pos(area, nexthop->lsa_pos);
+
+		if ((oi && !ospf_path_exist(to->paths, nexthop->router, oi))
+		    || area->spf_dry_run) {
+			path = ospf_path_new();
+			path->nexthop = nexthop->router;
+
+			if (oi) {
+				path->ifindex = oi->ifp->ifindex;
+				if (CHECK_FLAG(oi->connected->flags,
 					       ZEBRA_IFA_UNNUMBERED))
 					path->unnumbered = 1;
-				listnode_add(to->paths, path);
 			}
+
+			listnode_add(to->paths, path);
 		}
 	}
 }