ldpd: Fix to release MPLS label if its not used anymore

LDP should release labels allocated from zebra if its not getting used.

Signed-off-by: Binu <binu_abraham@looptelecom.com>

ldpd/lde.c

@@ -1653,6 +1653,19 @@ lde_del_label_chunk(void *val)
 	free(val);
 }
 
+static int
+lde_release_label_chunk(uint32_t start, uint32_t end)
+{
+	int		ret;
+
+	ret = lm_release_label_chunk(zclient_sync, start, end);
+	if (ret < 0) {
+		log_warnx("Error releasing label chunk!");
+		return (-1);
+	}
+	return (0);
+}
+
 static int
 lde_get_label_chunk(void)
 {
@@ -1709,6 +1722,32 @@ on_get_label_chunk_response(uint32_t start, uint32_t end)
 		current_label_chunk = listtail(label_chunk_list);
 }
 
+void
+lde_free_label(uint32_t label)
+{
+	struct listnode	*node;
+	struct label_chunk	*label_chunk;
+	uint64_t		pos;
+
+	for (ALL_LIST_ELEMENTS_RO(label_chunk_list, node, label_chunk)) {
+		if (label <= label_chunk->end && label >= label_chunk->start) {
+			pos = 1ULL << (label - label_chunk->start);
+			label_chunk->used_mask &= ~pos;
+			/* if nobody is using this chunk and it's not current_label_chunk, then free it */
+			if (!label_chunk->used_mask && (current_label_chunk != node)) {
+				if (lde_release_label_chunk(label_chunk->start, label_chunk->end) != 0)
+					log_warnx("%s: Error releasing label chunk!", __func__);
+				else {
+					listnode_delete(label_chunk_list, label_chunk);
+					lde_del_label_chunk(label_chunk);
+				}
+			}
+			break;
+		}
+	}
+	return;
+}
+
 static uint32_t
 lde_get_next_label(void)
 {

ldpd/lde.h

@@ -147,6 +147,7 @@ void		 lde_imsg_compose_parent_sync(int, pid_t, void *, uint16_t);
 int		 lde_imsg_compose_ldpe(int, uint32_t, pid_t, void *, uint16_t);
 int		 lde_acl_check(char *, int, union ldpd_addr *, uint8_t);
 uint32_t	 lde_update_label(struct fec_node *);
+void		 lde_free_label(uint32_t label);
 void		 lde_send_change_klabel(struct fec_node *, struct fec_nh *);
 void		 lde_send_delete_klabel(struct fec_node *, struct fec_nh *);
 void		 lde_fec2map(struct fec *, struct map *);

ldpd/lde_lib.c

@@ -919,6 +919,9 @@ lde_gc_timer(struct thread *thread)
 		    !RB_EMPTY(lde_map_head, &fn->upstream))
 			continue;
 
+		if (fn->local_label != NO_LABEL)
+			lde_free_label(fn->local_label);
+
 		fec_remove(&ft, &fn->fec);
 		free(fn);
 		count++;