ospfd: Add support for TI-LFA node protection

Signed-off-by: GalaxyGorilla <sascha@netdef.org>
2020-10-26 11:27:09 +00:00 · 2020-10-26 11:27:09 +00:00 · 385a1e07b1
parent cc1725bd34
commit 385a1e07b1
12 changed files with 535 additions and 98 deletions
--- a/doc/user/ospfd.rst
+++ b/doc/user/ospfd.rst
@ -1233,7 +1233,6 @@ Summary Route will be originated on-behalf of all matched external LSAs.
   Show configuration for display all configured summary routes with
   matching external LSA information.

-======
 TI-LFA
 ======

@ -1241,11 +1240,10 @@ Experimental support for Topology Independent LFA (Loop-Free Alternate), see
 for example 'draft-bashandy-rtgwg-segment-routing-ti-lfa-05'. Note that
 TI-LFA requires a proper Segment Routing configuration.

-.. index:: fast-reroute ti-lfa
-.. clicmd:: fast-reroute ti-lfa
+.. index:: fast-reroute ti-lfa [node-protection]
+.. clicmd:: fast-reroute ti-lfa [node-protection]

   Configured on the router level. Activates TI-LFA for all interfaces.
-   Currently just link protection for P2P interfaces is supported.

 Debugging OSPF
 ==============
--- a/ospfd/ospf_spf.c
+++ b/ospfd/ospf_spf.c
@ -142,7 +142,7 @@ static void ospf_canonical_nexthops_free(struct vertex *root)
 			ospf_canonical_nexthops_free(child);

 		/* Free child nexthops pointing back to this root vertex */
-		for (ALL_LIST_ELEMENTS(child->parents, n2, nn2, vp))
+		for (ALL_LIST_ELEMENTS(child->parents, n2, nn2, vp)) {
 			if (vp->parent == root && vp->nexthop) {
 				vertex_nexthop_free(vp->nexthop);
 				vp->nexthop = NULL;
@ -151,6 +151,7 @@ static void ospf_canonical_nexthops_free(struct vertex *root)
 					vp->local_nexthop = NULL;
 				}
 			}
+		}
 	}
 }

@ -320,6 +321,22 @@ struct vertex_parent *ospf_spf_vertex_parent_find(struct in_addr id,
 	return NULL;
 }

+struct vertex *ospf_spf_vertex_by_nexthop(struct vertex *root,
+					  struct in_addr *nexthop)
+{
+	struct listnode *node;
+	struct vertex *child;
+	struct vertex_parent *vertex_parent;
+
+	for (ALL_LIST_ELEMENTS_RO(root->children, node, child)) {
+		vertex_parent = ospf_spf_vertex_parent_find(root->id, child);
+		if (vertex_parent->nexthop->router.s_addr == nexthop->s_addr)
+			return child;
+	}
+
+	return NULL;
+}
+
 /* Create a deep copy of a SPF vertex without children and parents */
 static struct vertex *ospf_spf_vertex_copy(struct vertex *vertex)
 {
@ -345,10 +362,9 @@ ospf_spf_vertex_parent_copy(struct vertex_parent *vertex_parent)

 	vertex_parent_copy =
 		XCALLOC(MTYPE_OSPF_VERTEX, sizeof(struct vertex_parent));
-	nexthop_copy =
-		XCALLOC(MTYPE_OSPF_VERTEX, sizeof(struct vertex_nexthop));
-	local_nexthop_copy =
-		XCALLOC(MTYPE_OSPF_VERTEX, sizeof(struct vertex_nexthop));
+
+	nexthop_copy = vertex_nexthop_new();
+	local_nexthop_copy = vertex_nexthop_new();

 	memcpy(vertex_parent_copy, vertex_parent, sizeof(struct vertex_parent));
 	memcpy(nexthop_copy, vertex_parent->nexthop,
@ -459,8 +475,8 @@ static void ospf_spf_remove_branch(struct vertex_parent *vertex_parent,
 	}
 }

-int ospf_spf_remove_link(struct vertex *vertex, struct list *vertex_list,
-			 struct router_lsa_link *link)
+static int ospf_spf_remove_link(struct vertex *vertex, struct list *vertex_list,
+				struct router_lsa_link *link)
 {
 	struct listnode *node, *inner_node;
 	struct vertex *child;
@ -494,6 +510,39 @@ int ospf_spf_remove_link(struct vertex *vertex, struct list *vertex_list,
 	return 1;
 }

+void ospf_spf_remove_resource(struct vertex *vertex, struct list *vertex_list,
+			      struct protected_resource *resource)
+{
+	struct listnode *node, *nnode;
+	struct vertex *found;
+	struct vertex_parent *vertex_parent;
+
+	switch (resource->type) {
+	case OSPF_TI_LFA_LINK_PROTECTION:
+		ospf_spf_remove_link(vertex, vertex_list, resource->link);
+		break;
+	case OSPF_TI_LFA_NODE_PROTECTION:
+		found = ospf_spf_vertex_find(resource->router_id, vertex_list);
+		if (!found)
+			break;
+
+		/*
+		 * Remove the node by removing all links from its parents. Note
+		 * that the child is automatically removed here with the last
+		 * link from a parent, hence no explicit removal of the node.
+		 */
+		for (ALL_LIST_ELEMENTS(found->parents, node, nnode,
+				       vertex_parent))
+			ospf_spf_remove_branch(vertex_parent, found,
+					       vertex_list);
+
+		break;
+	default:
+		/* do nothing */
+		break;
+	}
+}
+
 static void ospf_spf_init(struct ospf_area *area, struct ospf_lsa *root_lsa,
 			  bool is_dry_run, bool is_root_node)
 {
@ -1098,18 +1147,83 @@ static unsigned int ospf_nexthop_calculation(struct ospf_area *area,
 	return added;
 }

-static int ospf_spf_is_protected_link(struct ospf_area *area,
-				      struct router_lsa_link *link)
+static int ospf_spf_is_protected_resource(struct ospf_area *area,
+					  struct router_lsa_link *link,
+					  struct lsa_header *lsa)
 {
+	uint8_t *p, *lim;
 	struct router_lsa_link *p_link;
+	struct router_lsa_link *l = NULL;
+	struct in_addr router_id;
+	int link_type;

-	p_link = area->spf_protected_link;
-	if (!p_link)
+	if (!area->spf_protected_resource)
 		return 0;

-	if ((p_link->link_id.s_addr & p_link->link_data.s_addr)
-	    == (link->link_data.s_addr & p_link->link_data.s_addr))
-		return 1;
+	link_type = link->m[0].type;
+
+	switch (area->spf_protected_resource->type) {
+	case OSPF_TI_LFA_LINK_PROTECTION:
+		p_link = area->spf_protected_resource->link;
+		if (!p_link)
+			return 0;
+
+		/* For P2P: check if the link belongs to the same subnet */
+		if (link_type == LSA_LINK_TYPE_POINTOPOINT
+		    && (p_link->link_id.s_addr & p_link->link_data.s_addr)
+			       == (link->link_data.s_addr
+				   & p_link->link_data.s_addr))
+			return 1;
+
+		/* For stub: check if this the same subnet */
+		if (link_type == LSA_LINK_TYPE_STUB
+		    && (p_link->link_id.s_addr == link->link_id.s_addr)
+		    && (p_link->link_data.s_addr == link->link_data.s_addr))
+			return 1;
+
+		break;
+	case OSPF_TI_LFA_NODE_PROTECTION:
+		router_id = area->spf_protected_resource->router_id;
+		if (router_id.s_addr == INADDR_ANY)
+			return 0;
+
+		/* For P2P: check if the link leads to the protected node */
+		if (link_type == LSA_LINK_TYPE_POINTOPOINT
+		    && link->link_id.s_addr == router_id.s_addr)
+			return 1;
+
+		/* The rest is about stub links! */
+		if (link_type != LSA_LINK_TYPE_STUB)
+			return 0;
+
+		/*
+		 * Check if there's a P2P link in the router LSA with the
+		 * corresponding link data in the same subnet.
+		 */
+
+		p = ((uint8_t *)lsa) + OSPF_LSA_HEADER_SIZE + 4;
+		lim = ((uint8_t *)lsa) + ntohs(lsa->length);
+
+		while (p < lim) {
+			l = (struct router_lsa_link *)p;
+			p += (OSPF_ROUTER_LSA_LINK_SIZE
+			      + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));
+
+			/* We only care about P2P with the proper link id */
+			if ((l->m[0].type != LSA_LINK_TYPE_POINTOPOINT)
+			    || (l->link_id.s_addr != router_id.s_addr))
+				continue;
+
+			/* Link data in the subnet given by the link? */
+			if ((link->link_id.s_addr & link->link_data.s_addr)
+			    == (l->link_data.s_addr & link->link_data.s_addr))
+				return 1;
+		}
+
+		break;
+	case OSPF_TI_LFA_UNDEFINED_PROTECTION:
+		break;
+	}

 	return 0;
 }
@ -1217,13 +1331,13 @@ static void ospf_spf_next(struct vertex *v, struct ospf_area *area,
 				continue;

 			/*
-			 * Don't process TI-LFA protected links.
+			 * Don't process TI-LFA protected resources.
 			 *
 			 * TODO: Replace this by a proper solution, e.g. remove
 			 * corresponding links from the LSDB and run the SPF
 			 * algo with the stripped-down LSDB.
 			 */
-			if (ospf_spf_is_protected_link(area, l))
+			if (ospf_spf_is_protected_resource(area, l, v->lsa))
 				continue;

 			/*
@ -1475,9 +1589,9 @@ static void ospf_spf_process_stubs(struct ospf_area *area, struct vertex *v,
 			p += (OSPF_ROUTER_LSA_LINK_SIZE
 			      + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

-			/* Don't process TI-LFA protected links */
+			/* Don't process TI-LFA protected resources */
 			if (l->m[0].type == LSA_LINK_TYPE_STUB
-			    && !ospf_spf_is_protected_link(area, l))
+			    && !ospf_spf_is_protected_resource(area, l, v->lsa))
 				ospf_intra_add_stub(rt, l, v, area,
 						    parent_is_root, lsa_pos);
 			lsa_pos++;
@ -1534,7 +1648,6 @@ void ospf_rtrs_free(struct route_table *rtrs)

 void ospf_spf_cleanup(struct vertex *spf, struct list *vertex_list)
 {
-
 	/*
 	 * Free nexthop information, canonical versions of which are
 	 * attached the first level of router vertices attached to the
@ -1721,7 +1834,8 @@ void ospf_spf_calculate_area(struct ospf *ospf, struct ospf_area *area,
 			   false, true);

 	if (ospf->ti_lfa_enabled)
-		ospf_ti_lfa_compute(area, new_table);
+		ospf_ti_lfa_compute(area, new_table,
+				    ospf->ti_lfa_protection_type);

 	ospf_spf_cleanup(area->spf, area->spf_vertex_list);
 }
--- a/ospfd/ospf_spf.h
+++ b/ospfd/ospf_spf.h
@ -86,10 +86,13 @@ extern void ospf_spf_calculate_areas(struct ospf *ospf,
 extern void ospf_rtrs_free(struct route_table *);
 extern void ospf_spf_cleanup(struct vertex *spf, struct list *vertex_list);
 extern void ospf_spf_copy(struct vertex *vertex, struct list *vertex_list);
-extern int ospf_spf_remove_link(struct vertex *vertex, struct list *vertex_list,
-				struct router_lsa_link *link);
+extern void ospf_spf_remove_resource(struct vertex *vertex,
+				     struct list *vertex_list,
+				     struct protected_resource *resource);
 extern struct vertex *ospf_spf_vertex_find(struct in_addr id,
 					   struct list *vertex_list);
+extern struct vertex *ospf_spf_vertex_by_nexthop(struct vertex *root,
+						 struct in_addr *nexthop);
 extern struct vertex_parent *ospf_spf_vertex_parent_find(struct in_addr id,
 							 struct vertex *vertex);
 extern int vertex_parent_cmp(void *aa, void *bb);
--- a/ospfd/ospf_ti_lfa.c
+++ b/ospfd/ospf_ti_lfa.c
@ -24,6 +24,7 @@

 #include "prefix.h"
 #include "table.h"
+#include "printfrr.h"

 #include "ospfd/ospfd.h"
 #include "ospfd/ospf_asbr.h"
@ -39,6 +40,29 @@ DECLARE_RBTREE_UNIQ(p_spaces, struct p_space, p_spaces_item,
 DECLARE_RBTREE_UNIQ(q_spaces, struct q_space, q_spaces_item,
 		    q_spaces_compare_func)

+void ospf_print_protected_resource(
+	struct protected_resource *protected_resource, char *buf)
+{
+	struct router_lsa_link *link;
+
+	switch (protected_resource->type) {
+	case OSPF_TI_LFA_LINK_PROTECTION:
+		link = protected_resource->link;
+		snprintfrr(buf, PROTECTED_RESOURCE_STRLEN,
+			   "protected link: %pI4 %pI4", &link->link_id,
+			   &link->link_data);
+		break;
+	case OSPF_TI_LFA_NODE_PROTECTION:
+		snprintfrr(buf, PROTECTED_RESOURCE_STRLEN,
+			   "protected node: %pI4",
+			   &protected_resource->router_id);
+		break;
+	case OSPF_TI_LFA_UNDEFINED_PROTECTION:
+		snprintfrr(buf, PROTECTED_RESOURCE_STRLEN,
+			   "undefined protected resource");
+		break;
+	}
+}

 static void ospf_ti_lfa_find_p_node(struct vertex *pc_node,
 				    struct p_space *p_space,
@ -263,7 +287,23 @@ static void ospf_ti_lfa_generate_q_spaces(struct ospf_area *area,
 	struct vertex *child;
 	struct route_table *new_table, *new_rtrs;
 	struct q_space *q_space, q_space_search;
-	char buf[MPLS_LABEL_STRLEN];
+	char label_buf[MPLS_LABEL_STRLEN];
+	char res_buf[PROTECTED_RESOURCE_STRLEN];
+
+	ospf_print_protected_resource(p_space->protected_resource, res_buf);
+
+	/*
+	 * If node protection is used, don't build a Q space for the protected
+	 * node of that particular P space. Move on with children instead.
+	 */
+	if (p_space->protected_resource->type == OSPF_TI_LFA_NODE_PROTECTION
+	    && dest->id.s_addr
+		       == p_space->protected_resource->router_id.s_addr) {
+		/* Recursively generate Q spaces for all children */
+		for (ALL_LIST_ELEMENTS_RO(dest->children, node, child))
+			ospf_ti_lfa_generate_q_spaces(area, p_space, child);
+		return;
+	}

 	/* Check if we already have a Q space for this destination */
 	q_space_search.root = dest;
@ -289,9 +329,9 @@ static void ospf_ti_lfa_generate_q_spaces(struct ospf_area *area,
 	q_space->vertex_list = area->spf_vertex_list;
 	q_space->label_stack = NULL;

-	/* 'Cut' the branch of the protected link out of the new SPF tree */
-	ospf_spf_remove_link(q_space->root, q_space->vertex_list,
-			     p_space->protected_link);
+	/* 'Cut' the protected resource out of the new SPF tree */
+	ospf_spf_remove_resource(q_space->root, q_space->vertex_list,
+				 p_space->protected_resource);

 	/*
 	 * Generate the smallest possible label stack from the root of the P
@ -299,19 +339,20 @@ static void ospf_ti_lfa_generate_q_spaces(struct ospf_area *area,
 	 */
 	ospf_ti_lfa_generate_label_stack(p_space, q_space);

+
 	if (q_space->label_stack) {
 		mpls_label2str(q_space->label_stack->num_labels,
-			       q_space->label_stack->label, buf,
+			       q_space->label_stack->label, label_buf,
 			       MPLS_LABEL_STRLEN, true);
 		zlog_info(
-			"%s: Generated label stack %s for root %pI4 and destination %pI4 for protected link %pI4",
-			__func__, buf, &p_space->root->id, &q_space->root->id,
-			&p_space->protected_link->link_id);
+			"%s: Generated label stack %s for root %pI4 and destination %pI4 for %s",
+			__func__, label_buf, &p_space->root->id,
+			&q_space->root->id, res_buf);
 	} else {
 		zlog_info(
-			"%s: NO label stack generated for root %pI4 and destination %pI4 for protected link %pI4",
+			"%s: NO label stack generated for root %pI4 and destination %pI4 for %s",
 			__func__, &p_space->root->id, &q_space->root->id,
-			&p_space->protected_link->link_id);
+			res_buf);
 	}

 	/* We are finished, store the new Q space in the P space struct */
@ -330,20 +371,22 @@ static void ospf_ti_lfa_generate_post_convergence_spf(struct ospf_area *area,
 	new_table = route_table_init();
 	new_rtrs = route_table_init();

-	area->spf_protected_link = p_space->protected_link;
+	area->spf_protected_resource = p_space->protected_resource;

 	/*
 	 * The 'post convergence' SPF tree is generated here
 	 * dry run true, root node false
 	 *
 	 * So how does this work? During the SPF calculation the algorithm
-	 * checks if a link belongs to a protected stub and then just ignores
-	 * it. This is actually _NOT_ a good way to calculate the post
+	 * checks if a link belongs to a protected resource and then just
+	 * ignores it.
+	 * This is actually _NOT_ a good way to calculate the post
 	 * convergence SPF tree. The preferred way would be to delete the
-	 * relevant links from a copy of the LSDB and then just run the SPF
-	 * algorithm on that as usual. However, removing links from router
-	 * LSAs appears to be its own endeavour (because LSAs are stored as a
-	 * 'raw' stream), so we go with this rather hacky way for now.
+	 * relevant links (and nodes) from a copy of the LSDB and then just run
+	 * the SPF algorithm on that as usual.
+	 * However, removing links from router LSAs appears to be its own
+	 * endeavour (because LSAs are stored as a 'raw' stream), so we go with
+	 * this rather hacky way for now.
 	 */
 	ospf_spf_calculate(area, area->router_lsa_self, new_table, new_rtrs,
 			   true, false);
@ -351,12 +394,12 @@ static void ospf_ti_lfa_generate_post_convergence_spf(struct ospf_area *area,
 	p_space->pc_spf = area->spf;
 	p_space->pc_vertex_list = area->spf_vertex_list;

-	area->spf_protected_link = NULL;
+	area->spf_protected_resource = NULL;
 }

-static void ospf_ti_lfa_generate_p_space(struct ospf_area *area,
-					 struct vertex *child,
-					 struct router_lsa_link *link)
+static void
+ospf_ti_lfa_generate_p_space(struct ospf_area *area, struct vertex *child,
+			     struct protected_resource *protected_resource)
 {
 	struct vertex *spf_orig;
 	struct list *vertex_list, *vertex_list_orig;
@ -369,16 +412,16 @@ static void ospf_ti_lfa_generate_p_space(struct ospf_area *area,
 	ospf_spf_copy(area->spf, vertex_list);
 	p_space->root = listnode_head(vertex_list);
 	p_space->vertex_list = vertex_list;
-	p_space->protected_link = link;
+	p_space->protected_resource = protected_resource;

-	/* Initialize the Q spaces for this P space and protected link */
+	/* Initialize the Q spaces for this P space and protected resource */
 	p_space->q_spaces =
 		XCALLOC(MTYPE_OSPF_Q_SPACE, sizeof(struct q_spaces_head));
 	q_spaces_init(p_space->q_spaces);

-	/* 'Cut' the child branch out of the new SPF tree */
-	ospf_spf_remove_link(p_space->root, p_space->vertex_list,
-			     p_space->protected_link);
+	/* 'Cut' the protected resource out of the new SPF tree */
+	ospf_spf_remove_resource(p_space->root, p_space->vertex_list,
+				 p_space->protected_resource);

 	/*
 	 * Since we are going to calculate more SPF trees for Q spaces, keep the
@ -401,7 +444,8 @@ static void ospf_ti_lfa_generate_p_space(struct ospf_area *area,
 	p_spaces_add(area->p_spaces, p_space);
 }

-void ospf_ti_lfa_generate_p_spaces(struct ospf_area *area)
+void ospf_ti_lfa_generate_p_spaces(struct ospf_area *area,
+				   enum protection_type protection_type)
 {
 	struct listnode *node, *inner_node;
 	struct vertex *root, *child;
@ -409,6 +453,7 @@ void ospf_ti_lfa_generate_p_spaces(struct ospf_area *area)
 	uint8_t *p, *lim;
 	struct router_lsa_link *l = NULL;
 	struct prefix stub_prefix, child_prefix;
+	struct protected_resource *protected_resource;

 	area->p_spaces =
 		XCALLOC(MTYPE_OSPF_P_SPACE, sizeof(struct p_spaces_head));
@ -439,6 +484,30 @@ void ospf_ti_lfa_generate_p_spaces(struct ospf_area *area)
 		p += (OSPF_ROUTER_LSA_LINK_SIZE
 		      + (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));

+		/* First comes node protection */
+		if (protection_type == OSPF_TI_LFA_NODE_PROTECTION) {
+			if (l->m[0].type == LSA_LINK_TYPE_POINTOPOINT) {
+				protected_resource = XCALLOC(
+					MTYPE_OSPF_P_SPACE,
+					sizeof(struct protected_resource));
+				protected_resource->type = protection_type;
+				protected_resource->router_id = l->link_id;
+				child = ospf_spf_vertex_find(
+					protected_resource->router_id,
+					root->children);
+				if (child)
+					ospf_ti_lfa_generate_p_space(
+						area, child,
+						protected_resource);
+			}
+
+			continue;
+		}
+
+		/* The rest is about link protection */
+		if (protection_type != OSPF_TI_LFA_LINK_PROTECTION)
+			continue;
+
 		if (l->m[0].type != LSA_LINK_TYPE_STUB)
 			continue;

@ -467,26 +536,50 @@ void ospf_ti_lfa_generate_p_spaces(struct ospf_area *area)
 					zlog_info(
 						"%s: Generating P space for %pI4",
 						__func__, &l->link_id);
-					ospf_ti_lfa_generate_p_space(area,
-								     child, l);
+
+					protected_resource = XCALLOC(
+						MTYPE_OSPF_P_SPACE,
+						sizeof(struct
+						       protected_resource));
+					protected_resource->type =
+						protection_type;
+					protected_resource->link = l;
+
+					ospf_ti_lfa_generate_p_space(
+						area, child,
+						protected_resource);
 				}
 			}
 		}
 	}
 }

-static struct p_space *
-ospf_ti_lfa_get_p_space_by_nexthop(struct ospf_area *area,
-				   struct in_addr *nexthop)
+static struct p_space *ospf_ti_lfa_get_p_space_by_path(struct ospf_area *area,
+						       struct ospf_path *path)
 {
 	struct p_space *p_space;
 	struct router_lsa_link *link;
+	struct vertex *child;
+	int type;

 	frr_each(p_spaces, area->p_spaces, p_space) {
-		link = p_space->protected_link;
-		if ((nexthop->s_addr & link->link_data.s_addr)
-		    == (link->link_id.s_addr & link->link_data.s_addr))
-			return p_space;
+		type = p_space->protected_resource->type;
+
+		if (type == OSPF_TI_LFA_LINK_PROTECTION) {
+			link = p_space->protected_resource->link;
+			if ((path->nexthop.s_addr & link->link_data.s_addr)
+			    == (link->link_id.s_addr & link->link_data.s_addr))
+				return p_space;
+		}
+
+		if (type == OSPF_TI_LFA_NODE_PROTECTION) {
+			child = ospf_spf_vertex_by_nexthop(area->spf,
+							   &path->nexthop);
+			if (child
+			    && p_space->protected_resource->router_id.s_addr
+				       == child->id.s_addr)
+				return p_space;
+		}
 	}

 	return NULL;
@ -502,6 +595,7 @@ void ospf_ti_lfa_insert_backup_paths(struct ospf_area *area,
 	struct p_space *p_space;
 	struct q_space *q_space, q_space_search;
 	struct vertex root_search;
+	char label_buf[MPLS_LABEL_STRLEN];

 	for (rn = route_top(new_table); rn; rn = route_next(rn)) {
 		or = rn->info;
@ -510,12 +604,22 @@ void ospf_ti_lfa_insert_backup_paths(struct ospf_area *area,

 		/* Insert a backup path for all OSPF paths */
 		for (ALL_LIST_ELEMENTS_RO(or->paths, node, path)) {
-			p_space = ospf_ti_lfa_get_p_space_by_nexthop(
-				area, &path->nexthop);
+
+			if (path->adv_router.s_addr == INADDR_ANY
+			    || path->nexthop.s_addr == INADDR_ANY)
+				continue;
+
+			zlog_debug(
+				"%s: attempting to insert backup path for prefix %pFX, router id %pI4 and nexthop %pI4.",
+				__func__, &rn->p, &path->adv_router,
+				&path->nexthop);
+
+			p_space = ospf_ti_lfa_get_p_space_by_path(area, path);
 			if (!p_space) {
 				zlog_debug(
-					"%s: P space not found for nexthop %pI4.",
-					__func__, &path->nexthop);
+					"%s: P space not found for router id %pI4 and nexthop %pI4.",
+					__func__, &path->adv_router,
+					&path->nexthop);
 				continue;
 			}

@ -532,6 +636,22 @@ void ospf_ti_lfa_insert_backup_paths(struct ospf_area *area,

 			path->srni.backup_label_stack = q_space->label_stack;
 			path->srni.backup_nexthop = q_space->nexthop;
+
+			if (path->srni.backup_label_stack) {
+				mpls_label2str(q_space->label_stack->num_labels,
+					       q_space->label_stack->label,
+					       label_buf, MPLS_LABEL_STRLEN,
+					       true);
+				zlog_debug(
+					"%s: inserted backup path %s for prefix %pFX, router id %pI4 and nexthop %pI4.",
+					__func__, label_buf, &rn->p,
+					&path->adv_router, &path->nexthop);
+			} else {
+				zlog_debug(
+					"%s: inserted NO backup path for prefix %pFX, router id %pI4 and nexthop %pI4.",
+					__func__, &rn->p, &path->adv_router,
+					&path->nexthop);
+			}
 		}
 	}
 }
@ -554,6 +674,7 @@ void ospf_ti_lfa_free_p_spaces(struct ospf_area *area)
 		}
 		ospf_spf_cleanup(p_space->root, p_space->vertex_list);
 		ospf_spf_cleanup(p_space->pc_spf, p_space->pc_vertex_list);
+		XFREE(MTYPE_OSPF_P_SPACE, p_space->protected_resource);

 		q_spaces_fini(p_space->q_spaces);
 		XFREE(MTYPE_OSPF_Q_SPACE, p_space->q_spaces);
@ -563,13 +684,15 @@ void ospf_ti_lfa_free_p_spaces(struct ospf_area *area)
 	XFREE(MTYPE_OSPF_P_SPACE, area->p_spaces);
 }

-void ospf_ti_lfa_compute(struct ospf_area *area, struct route_table *new_table)
+void ospf_ti_lfa_compute(struct ospf_area *area, struct route_table *new_table,
+			 enum protection_type protection_type)
 {
 	/*
-	 * Generate P spaces per protected link and their respective Q spaces,
-	 * generate backup paths (MPLS label stacks) by finding P/Q nodes.
+	 * Generate P spaces per protected link/node and their respective Q
+	 * spaces, generate backup paths (MPLS label stacks) by finding P/Q
+	 * nodes.
 	 */
-	ospf_ti_lfa_generate_p_spaces(area);
+	ospf_ti_lfa_generate_p_spaces(area, protection_type);

 	/* Insert the generated backup paths into the routing table. */
 	ospf_ti_lfa_insert_backup_paths(area, new_table);
--- a/ospfd/ospf_ti_lfa.h
+++ b/ospfd/ospf_ti_lfa.h
@ -23,13 +23,19 @@
 #ifndef _OSPF_TI_LFA_H
 #define _OSPF_TI_LFA_H

+#define PROTECTED_RESOURCE_STRLEN 100
+
 extern void ospf_ti_lfa_compute(struct ospf_area *area,
-				struct route_table *new_table);
+				struct route_table *new_table,
+				enum protection_type protection_type);

 /* unit testing */
-extern void ospf_ti_lfa_generate_p_spaces(struct ospf_area *area);
+extern void ospf_ti_lfa_generate_p_spaces(struct ospf_area *area,
+					  enum protection_type protection_type);
 extern void ospf_ti_lfa_insert_backup_paths(struct ospf_area *area,
 					    struct route_table *new_table);
 extern void ospf_ti_lfa_free_p_spaces(struct ospf_area *area);
+void ospf_print_protected_resource(
+	struct protected_resource *protected_resource, char *buf);

 #endif /* _OSPF_TI_LFA_H */
--- a/ospfd/ospf_vty.c
+++ b/ospfd/ospf_vty.c
@ -2602,28 +2602,38 @@ ALIAS(no_ospf_write_multiplier, no_write_multiplier_cmd,
      "Write multiplier\n"
      "Maximum number of interface serviced per write\n")

-DEFUN(ospf_ti_lfa, ospf_ti_lfa_cmd, "fast-reroute ti-lfa",
+DEFUN(ospf_ti_lfa, ospf_ti_lfa_cmd, "fast-reroute ti-lfa [node-protection]",
      "Fast Reroute for MPLS and IP resilience\n"
-      "Topology Independent LFA (Loop-Free Alternate)\n")
+      "Topology Independent LFA (Loop-Free Alternate)\n"
+      "TI-LFA node protection (default is link protection)\n")
 {
 	VTY_DECLVAR_INSTANCE_CONTEXT(ospf, ospf);

 	ospf->ti_lfa_enabled = true;

+	if (argc == 3)
+		ospf->ti_lfa_protection_type = OSPF_TI_LFA_NODE_PROTECTION;
+	else
+		ospf->ti_lfa_protection_type = OSPF_TI_LFA_LINK_PROTECTION;
+
 	ospf_spf_calculate_schedule(ospf, SPF_FLAG_CONFIG_CHANGE);

 	return CMD_SUCCESS;
 }

-DEFUN(no_ospf_ti_lfa, no_ospf_ti_lfa_cmd, "no fast-reroute ti-lfa",
+DEFUN(no_ospf_ti_lfa, no_ospf_ti_lfa_cmd,
+      "no fast-reroute ti-lfa [node-protection]",
      NO_STR
      "Fast Reroute for MPLS and IP resilience\n"
-      "Topology Independent LFA (Loop-Free Alternate)\n")
+      "Topology Independent LFA (Loop-Free Alternate)\n"
+      "TI-LFA node protection (default is link protection)\n")
 {
 	VTY_DECLVAR_INSTANCE_CONTEXT(ospf, ospf);

 	ospf->ti_lfa_enabled = false;

+	ospf->ti_lfa_protection_type = OSPF_TI_LFA_UNDEFINED_PROTECTION;
+
 	ospf_spf_calculate_schedule(ospf, SPF_FLAG_CONFIG_CHANGE);

 	return CMD_SUCCESS;
@ -12389,8 +12399,12 @@ static int ospf_config_write_one(struct vty *vty, struct ospf *ospf)
 	}

 	/* TI-LFA print. */
-	if (ospf->ti_lfa_enabled)
-		vty_out(vty, " fast-reroute ti-lfa\n");
+	if (ospf->ti_lfa_enabled) {
+		if (ospf->ti_lfa_protection_type == OSPF_TI_LFA_NODE_PROTECTION)
+			vty_out(vty, " fast-reroute ti-lfa node-protection\n");
+		else
+			vty_out(vty, " fast-reroute ti-lfa\n");
+	}

 	/* Network area print. */
 	config_write_network_area(vty, ospf);
--- a/ospfd/ospfd.c
+++ b/ospfd/ospfd.c
@ -89,8 +89,18 @@ static void ospf_finish_final(struct ospf *);

 int p_spaces_compare_func(const struct p_space *a, const struct p_space *b)
 {
-	return (a->protected_link->link_id.s_addr
-		- b->protected_link->link_id.s_addr);
+	if (a->protected_resource->type == OSPF_TI_LFA_LINK_PROTECTION
+	    && b->protected_resource->type == OSPF_TI_LFA_LINK_PROTECTION)
+		return (a->protected_resource->link->link_id.s_addr
+			- b->protected_resource->link->link_id.s_addr);
+
+	if (a->protected_resource->type == OSPF_TI_LFA_NODE_PROTECTION
+	    && b->protected_resource->type == OSPF_TI_LFA_NODE_PROTECTION)
+		return (a->protected_resource->router_id.s_addr
+			- b->protected_resource->router_id.s_addr);
+
+	/* This should not happen */
+	return 0;
 }

 int q_spaces_compare_func(const struct q_space *a, const struct q_space *b)
--- a/ospfd/ospfd.h
+++ b/ospfd/ospfd.h
@ -127,6 +127,13 @@ enum {
 	OSPF_LOG_ADJACENCY_DETAIL =	(1 << 4),
 };

+/* TI-LFA */
+enum protection_type {
+	OSPF_TI_LFA_UNDEFINED_PROTECTION,
+	OSPF_TI_LFA_LINK_PROTECTION,
+	OSPF_TI_LFA_NODE_PROTECTION,
+};
+
 /* OSPF instance structure. */
 struct ospf {
 	/* OSPF's running state based on the '[no] router ospf [<instance>]'
@ -377,6 +384,7 @@ struct ospf {

 	/* TI-LFA support for all interfaces. */
 	bool ti_lfa_enabled;
+	enum protection_type ti_lfa_protection_type;

 	QOBJ_FIELDS
 };
@ -395,6 +403,16 @@ struct ospf_ti_lfa_node_info {
 	struct in_addr nexthop;
 };

+struct protected_resource {
+	enum protection_type type;
+
+	/* Link Protection */
+	struct router_lsa_link *link;
+
+	/* Node Protection */
+	struct in_addr router_id;
+};
+
 PREDECL_RBTREE_UNIQ(q_spaces)
 struct q_space {
 	struct vertex *root;
@ -407,7 +425,7 @@ struct q_space {
 PREDECL_RBTREE_UNIQ(p_spaces)
 struct p_space {
 	struct vertex *root;
-	struct router_lsa_link *protected_link;
+	struct protected_resource *protected_resource;
 	struct q_spaces_head *q_spaces;
 	struct list *vertex_list;
 	struct vertex *pc_spf;
@ -513,7 +531,7 @@ struct ospf_area {
 			       root node of the SPF tree */

 	/* TI-LFA protected link for SPF calculations */
-	struct router_lsa_link *spf_protected_link;
+	struct protected_resource *spf_protected_resource;

 	/* P/Q spaces for TI-LFA */
 	struct p_spaces_head *p_spaces;
--- a/tests/ospfd/common.c
+++ b/tests/ospfd/common.c
@ -27,6 +27,8 @@ struct ospf_topology *test_find_topology(const char *name)
 		return &topo2;
 	else if (strmatch(name, "topo3"))
 		return &topo3;
+	else if (strmatch(name, "topo4"))
+		return &topo4;

 	return NULL;
 }
--- a/tests/ospfd/common.h
+++ b/tests/ospfd/common.h
@ -34,6 +34,7 @@ extern struct thread_master *master;
 extern struct ospf_topology topo1;
 extern struct ospf_topology topo2;
 extern struct ospf_topology topo3;
+extern struct ospf_topology topo4;
 extern struct zebra_privs_t ospfd_privs;

 #endif /* _COMMON_OSPF_H */
--- a/tests/ospfd/test_ospf_spf.c
+++ b/tests/ospfd/test_ospf_spf.c
@ -47,13 +47,15 @@ static struct ospf *test_init(struct ospf_test_node *root)
 	return ospf;
 }

-static void test_run_spf(struct vty *vty, struct ospf *ospf)
+static void test_run_spf(struct vty *vty, struct ospf *ospf,
+			 enum protection_type protection_type)
 {
 	struct route_table *new_table, *new_rtrs;
 	struct ospf_area *area;
 	struct p_space *p_space;
 	struct q_space *q_space;
-	char buf[MPLS_LABEL_STRLEN];
+	char label_buf[MPLS_LABEL_STRLEN];
+	char res_buf[PROTECTED_RESOURCE_STRLEN];

 	/* Just use the backbone for testing */
 	area = ospf->backbone;
@ -69,13 +71,15 @@ static void test_run_spf(struct vty *vty, struct ospf *ospf)
 	ospf_route_table_print(vty, new_table);

 	/* TI-LFA testrun */
-	ospf_ti_lfa_generate_p_spaces(area);
+	ospf_ti_lfa_generate_p_spaces(area, protection_type);
 	ospf_ti_lfa_insert_backup_paths(area, new_table);

 	/* Print P/Q space information */
 	frr_each(p_spaces, area->p_spaces, p_space) {
-		vty_out(vty, "\n\nP Space for root %pI4 and link %pI4:\n",
-			&p_space->root->id, &p_space->protected_link->link_id);
+		ospf_print_protected_resource(p_space->protected_resource,
+					      res_buf);
+		vty_out(vty, "\n\nP Space for root %pI4 and %s\n",
+			&p_space->root->id, res_buf);
 		ospf_spf_print(vty, p_space->root, 0);

 		frr_each(q_spaces, p_space->q_spaces, q_space) {
@ -84,17 +88,17 @@ static void test_run_spf(struct vty *vty, struct ospf *ospf)
 			ospf_spf_print(vty, q_space->root, 0);
 			if (q_space->label_stack) {
 				mpls_label2str(q_space->label_stack->num_labels,
-					       q_space->label_stack->label, buf,
-					       MPLS_LABEL_STRLEN, true);
-				vty_out(vty, "\nLabel stack: %s\n", buf);
+					       q_space->label_stack->label,
+					       label_buf, MPLS_LABEL_STRLEN,
+					       true);
+				vty_out(vty, "\nLabel stack: %s\n", label_buf);
 			} else {
 				vty_out(vty, "\nLabel stack not generated!\n");
 			}
 		}

-		vty_out(vty,
-			"\nPost-convergence path for root %pI4 and link %pI4:\n",
-			&p_space->root->id, &p_space->protected_link->link_id);
+		vty_out(vty, "\nPost-convergence path for root %pI4 and %s\n",
+			&p_space->root->id, res_buf);
 		ospf_spf_print(vty, p_space->pc_spf, 0);
 	}

@ -111,7 +115,8 @@ static void test_run_spf(struct vty *vty, struct ospf *ospf)
 }

 static int test_run(struct vty *vty, struct ospf_topology *topology,
-		    struct ospf_test_node *root)
+		    struct ospf_test_node *root,
+		    enum protection_type protection_type)
 {
 	struct ospf *ospf;

@ -126,21 +131,25 @@ static int test_run(struct vty *vty, struct ospf_topology *topology,
 	vty_out(vty, "\n");
 	show_ip_ospf_database_summary(vty, ospf, 0, NULL);

-	test_run_spf(vty, ospf);
+	test_run_spf(vty, ospf, protection_type);

 	return 0;
 }

-DEFUN(test_ospf, test_ospf_cmd, "test ospf topology WORD root HOSTNAME",
+DEFUN(test_ospf, test_ospf_cmd,
+      "test ospf topology WORD root HOSTNAME ti-lfa [node-protection]",
      "Test mode\n"
      "Choose OSPF for SPF testing\n"
      "Network topology to choose\n"
      "Name of the network topology to choose\n"
      "Root node to choose\n"
-      "Hostname of the root node to choose\n")
+      "Hostname of the root node to choose\n"
+      "Use Topology-Independent LFA\n"
+      "Use node protection (default is link protection)\n")
 {
 	struct ospf_topology *topology;
 	struct ospf_test_node *root;
+	enum protection_type protection_type;
 	int idx = 0;

 	/* Parse topology. */
@ -158,7 +167,12 @@ DEFUN(test_ospf, test_ospf_cmd, "test ospf topology WORD root HOSTNAME",
 		return CMD_WARNING;
 	}

-	return test_run(vty, topology, root);
+	if (argc == 8)
+		protection_type = OSPF_TI_LFA_NODE_PROTECTION;
+	else
+		protection_type = OSPF_TI_LFA_LINK_PROTECTION;
+
+	return test_run(vty, topology, root, protection_type);
 }

 static void vty_do_exit(int isexit)
--- a/tests/ospfd/topologies.c
+++ b/tests/ospfd/topologies.c
@ -26,8 +26,12 @@
 * |         |
 * +---------+
 *
+ * Link Protection:
 * P and Q spaces overlap here, hence just one P/Q node regardless of which
 * link is protected. Hence the backup label stack just has one label.
+ *
+ * Node Protection:
+ * Obviously no backup paths involved.
 */
 struct ospf_topology topo1 = {
 	.nodes =
@ -121,10 +125,15 @@ struct ospf_topology topo1 = {
 * |         |
 * +---------+
 *
+ * Link Protection:
 * Regarding the subnet 10.0.1.0/24, the P space of RT1 is just RT1 itself
 * while the Q space of RT3 consists of RT3 and RT2. Hence the P and Q
 * nodes are disjunct (tricky: the root node is the P node here). For the
 * backup label stack just one label is necessary.
+ *
+ * Node Protection:
+ * For protected node RT2 and route from RT1 to RT3 there is just the backup
+ * path consisting of the label 15002.
 */
 struct ospf_topology topo2 = {
 	.nodes =
@ -217,11 +226,16 @@ struct ospf_topology topo2 = {
 * |         |                     |         |
 * +---------+                     +---------+
 *
+ * Link Protection:
 * Regarding the protected subnet 10.0.4.0/24, the P and Q spaces for root RT1
 * and destination RT4 are disjunct and the P node is RT2 while RT3 is the Q
 * node. Hence the backup label stack here is 16020/15004. Note that here the
 * P and Q nodes are neither the root nor the destination nodes, so this is a
 * case where you really need a label stack consisting of two labels.
+ *
+ * Node Protection:
+ * For the protected node RT4 and the route from RT1 to RT3 there is a backup
+ * path with the single label 15001.
 */
 struct ospf_topology topo3 = {
 	.nodes =
@ -316,3 +330,123 @@ struct ospf_topology topo3 = {
 			},
 		},
 };
+
+/*
+ * +---------+                     +---------+
+ * |         |                     |         |
+ * |   RT1   |eth-rt4       eth-rt1|   RT5   |
+ * | 1.1.1.1 +---------------------+ 4.4.4.4 |
+ * |         |  10.0.4.0/24 (10)   |         |
+ * +---------+                     +---------+
+ *      |eth+rt2                 eth-rt3|
+ *      |                               |
+ *      |10.0.1.0/24 (10)               |
+ *      |              10.0.3.0/24 (10) |
+ *      |eth-rt1                 eth-rt4|
+ * +---------+                     +---------+
+ * |         |eth-rt3       eth-rt2|         |
+ * |   RT2   +---------------------+   RT3   |
+ * | 2.2.2.2 |  10.0.2.0/24 (40)   | 3.3.3.3 |
+ * |         |                     |         |
+ * +---------+                     +---------+
+ *
+ * This case was specifically created for Node Protection with RT4 as
+ * protected node from the perspective of RT1. Note the weight of 40
+ * on the link between RT2 and RT3.
+ * The P space of RT1 is just RT2 while the Q space of RT3 is empty.
+ * This means that the P and Q spaces are disjunct and there are two
+ * labels needed to get from RT1 to RT3.
+ */
+struct ospf_topology topo4 = {
+	.nodes =
+		{
+			{
+				.hostname = "rt1",
+				.router_id = "1.1.1.1",
+				.label = 10,
+				.adjacencies =
+					{
+						{
+							.hostname = "rt2",
+							.network =
+								"10.0.1.1/24",
+							.metric = 10,
+							.label = 1,
+						},
+						{
+							.hostname = "rt4",
+							.network =
+								"10.0.4.1/24",
+							.metric = 10,
+							.label = 2,
+						},
+					},
+			},
+			{
+				.hostname = "rt2",
+				.router_id = "2.2.2.2",
+				.label = 20,
+				.adjacencies =
+					{
+						{
+							.hostname = "rt1",
+							.network =
+								"10.0.1.2/24",
+							.metric = 10,
+							.label = 3,
+						},
+						{
+							.hostname = "rt3",
+							.network =
+								"10.0.2.1/24",
+							.metric = 50,
+							.label = 4,
+						},
+					},
+			},
+			{
+				.hostname = "rt3",
+				.router_id = "3.3.3.3",
+				.label = 30,
+				.adjacencies =
+					{
+						{
+							.hostname = "rt2",
+							.network =
+								"10.0.2.2/24",
+							.metric = 50,
+							.label = 5,
+						},
+						{
+							.hostname = "rt4",
+							.network =
+								"10.0.3.1/24",
+							.metric = 10,
+							.label = 6,
+						},
+					},
+			},
+			{
+				.hostname = "rt4",
+				.router_id = "4.4.4.4",
+				.label = 40,
+				.adjacencies =
+					{
+						{
+							.hostname = "rt3",
+							.network =
+								"10.0.3.2/24",
+							.metric = 10,
+							.label = 7,
+						},
+						{
+							.hostname = "rt1",
+							.network =
+								"10.0.4.2/24",
+							.metric = 10,
+							.label = 8,
+						},
+					},
+			},
+		},
+};