Merge pull request #8841 from volta-networks/fix_ospf6_bad_seqnum

ospf6: Drop LSA with bad seqnumber

ospf6d/ospf6_flood.c

@@ -811,6 +811,18 @@ void ospf6_receive_lsa(struct ospf6_neighbor *from,
 	ismore_recent = 1;
 	assert(from);
 
+	/* if we receive a LSA with invalid seqnum drop it */
+	if (ntohl(lsa_header->seqnum) - 1 == OSPF_MAX_SEQUENCE_NUMBER) {
+		if (IS_OSPF6_DEBUG_EXAMIN_TYPE(lsa_header->type)) {
+			zlog_debug(
+				"received lsa [%s Id:%pI4 Adv:%pI4] with invalid seqnum 0x%x, ignore",
+				ospf6_lstype_name(lsa_header->type),
+				&lsa_header->id, &lsa_header->adv_router,
+				ntohl(lsa_header->seqnum));
+		}
+		return;
+	}
+
 	/* make lsa structure for received lsa */
 	new = ospf6_lsa_create(lsa_header);