The function vnet_delete_sub_interface() in src/vnet/ethernet/interface.c is missing hash-unset of hi->sub_interface_sw_if_index_by_id which can cause later call of vnet_delete_hw_interface() to corrupt sw_if_index usage or crash as it cleanup sub-interfaces which are already deleted. There is also a memory leak from the hash_unset_mem() call without freeing the key memory.