isisd: When adjacencies go up and down add support to modify attached-bit

When adjacencies change state the attached-bits in LSPs in other areas
on the router may need to be modified.

 1. If a router no longer has a L2 adjacency to another area the
    attached-bit must no longer be sent in the LSP
 2. If a new L2 adjacency comes up in a different area then the
    attached-bit should be sent in the LSP

Signed-off-by: Lynne Morrison <lynne@voltanet.io>

4 files changed, 90 insertions, 17 deletions

diff --git a/isisd/isis_lsp.c b/isisd/isis_lsp.c
index 4c70bd12b..6d2303817 100644
--- a/isisd/isis_lsp.c
+++ b/isisd/isis_lsp.c
@@ -417,22 +417,18 @@ static bool isis_level2_adj_up(struct isis_area *curr_area)
 		for (ALL_LIST_ELEMENTS_RO(area->circuit_list, cnode, circuit)) {
 			if (circuit->circ_type == CIRCUIT_T_BROADCAST) {
 				adjdb = circuit->u.bc.adjdb[1];
-				if (adjdb && adjdb->count) {
-					for (ALL_LIST_ELEMENTS_RO(adjdb, node,
-								  adj))
-						if ((adj->level
-							     == ISIS_ADJ_LEVEL2
-						     || adj->level
-								== ISIS_ADJ_LEVEL1AND2)
-						    && adj->adj_state
-							       == ISIS_ADJ_UP)
-							return true;
+				if (!adjdb || !adjdb->count)
+					continue;
+
+				for (ALL_LIST_ELEMENTS_RO(adjdb, node, adj)) {
+					if (adj->level != ISIS_ADJ_LEVEL1
+					    && adj->adj_state == ISIS_ADJ_UP)
+						return true;
 				}
 			} else if (circuit->circ_type == CIRCUIT_T_P2P
 				   && circuit->u.p2p.neighbor) {
 				adj = circuit->u.p2p.neighbor;
-				if ((adj->level == ISIS_ADJ_LEVEL2
-				     || adj->level == ISIS_ADJ_LEVEL1AND2)
+				if (adj->level != ISIS_ADJ_LEVEL1
 				    && adj->adj_state == ISIS_ADJ_UP)
 					return true;
 			}
@@ -441,6 +437,58 @@ static bool isis_level2_adj_up(struct isis_area *curr_area)
 	return false;
 }
 
+static void isis_reset_attach_bit(struct isis_adjacency *curr_adj)
+{
+	struct listnode *node;
+	struct isis_area *curr_area = curr_adj->circuit->area;
+	struct isis *isis = curr_area->isis;
+	struct isis_area *area;
+	struct lspdb_head *head;
+	struct isis_lsp *lsp;
+	uint8_t lspid[ISIS_SYS_ID_LEN + 2];
+
+	/* If new adjaceny is up and area is level2 or level1and2 verify if
+	 * we have LSPs in other areas that should now set the attach bit.
+	 *
+	 * If adjacenty is down, verify if we no longer have another level2
+	 * or level1and2 areas so that we should now remove the attach bit.
+	 */
+	if (curr_area->is_type == IS_LEVEL_1)
+		return;
+
+	for (ALL_LIST_ELEMENTS_RO(isis->area_list, node, area)) {
+		if (area->area_tag
+		    && strcmp(area->area_tag, curr_area->area_tag) == 0)
+			continue;
+
+		if (!area->attached_bit_send)
+			continue;
+
+		head = &area->lspdb[IS_LEVEL_1 - 1];
+		memset(lspid, 0, ISIS_SYS_ID_LEN + 2);
+		memcpy(lspid, area->isis->sysid, ISIS_SYS_ID_LEN);
+
+		lsp = lsp_search(head, lspid);
+		if (!lsp)
+			continue;
+
+		if (curr_adj->adj_state == ISIS_ADJ_UP
+		    && !(lsp->hdr.lsp_bits & LSPBIT_ATT)) {
+			sched_debug(
+				"ISIS (%s): adj going up regenerate lsp-bits",
+				area->area_tag);
+			lsp_regenerate_schedule(area, IS_LEVEL_1, 0);
+		} else if (curr_adj->adj_state == ISIS_ADJ_DOWN
+			   && lsp->hdr.lsp_bits & LSPBIT_ATT
+			   && !isis_level2_adj_up(area)) {
+			sched_debug(
+				"ISIS (%s): adj going down regenerate lsp-bits",
+				area->area_tag);
+			lsp_regenerate_schedule(area, IS_LEVEL_1, 0);
+		}
+	}
+}
+
 static uint8_t lsp_bits_generate(int level, int overload_bit, int attached_bit,
 				 struct isis_area *area)
 {
@@ -2087,6 +2135,12 @@ void _lsp_flood(struct isis_lsp *lsp, struct isis_circuit *circuit,
 static int lsp_handle_adj_state_change(struct isis_adjacency *adj)
 {
 	lsp_regenerate_schedule(adj->circuit->area, IS_LEVEL_1 | IS_LEVEL_2, 0);
+
+	/* when an adjacency state changes determine if we need to
+	 * change attach_bits in other area's LSPs
+	 */
+	isis_reset_attach_bit(adj);
+
 	return 0;
 }
 
diff --git a/isisd/isis_spf.c b/isisd/isis_spf.c
index ec0313f21..22dfee994 100644
--- a/isisd/isis_spf.c
+++ b/isisd/isis_spf.c
@@ -1047,15 +1047,17 @@ lspfragloop:
 
 end:
 
-	/* if attach bit set and we are a level-1 router
-	 * and attach-bit-rcv-ignore is not configured
-	 * add a default route toward this neighbor
+	/* if attach bit set in LSP, attached-bit receive ignore is
+	 * not configured, we are a level-1 area and we have no other
+	 * level-2 | level1-2 areas then add a default route toward
+	 * this neighbor
 	 */
 	if ((lsp->hdr.lsp_bits & LSPBIT_ATT) == LSPBIT_ATT
 	    && !spftree->area->attached_bit_rcv_ignore
-	    && spftree->area->is_type == IS_LEVEL_1) {
+	    && spftree->area->is_type == IS_LEVEL_1
+	    && !isis_area_count(spftree->area->isis, IS_LEVEL_2)) {
 		struct prefix_pair ip_info = { {0} };
-		if (IS_DEBUG_SPF_EVENTS)
+		if (IS_DEBUG_RTE_EVENTS)
 			zlog_debug("ISIS-Spf (%s): add default %s route",
 				   rawlspid_print(lsp->hdr.lsp_id),
 				   spftree->family == AF_INET ? "ipv4"
diff --git a/isisd/isisd.c b/isisd/isisd.c
index d45690f4d..a802bac13 100644
--- a/isisd/isisd.c
+++ b/isisd/isisd.c
@@ -424,6 +424,22 @@ int isis_area_get(struct vty *vty, const char *area_tag)
 	return CMD_SUCCESS;
 }
 
+/* return the number of Level1 and level-1-2 routers or
+ * the number of Level2 and level-1-2 routers configured
+ */
+int isis_area_count(const struct isis *isis, int levels)
+{
+	struct isis_area *area;
+	struct listnode *node;
+	int count = 0;
+
+	for (ALL_LIST_ELEMENTS_RO(isis->area_list, node, area))
+		if (area->is_type & levels)
+			count++;
+
+	return count;
+}
+
 void isis_area_destroy(struct isis_area *area)
 {
 	struct listnode *node, *nnode;
diff --git a/isisd/isisd.h b/isisd/isisd.h
index a09f74152..22d9c6236 100644
--- a/isisd/isisd.h
+++ b/isisd/isisd.h
@@ -243,6 +243,7 @@ struct isis_area *isis_area_lookup(const char *, vrf_id_t vrf_id);
 struct isis_area *isis_area_lookup_by_vrf(const char *area_tag,
 					  const char *vrf_name);
 int isis_area_get(struct vty *vty, const char *area_tag);
+int isis_area_count(const struct isis *isis, int levels);
 void isis_area_destroy(struct isis_area *area);
 void isis_filter_update(struct access_list *access);
 void isis_prefix_list_update(struct prefix_list *plist);