BlockdevOptionsNbd has a member SocketAddress, and nbd_config() doesn't restrict variants. Thus, all four SOCKET_ADDRESS_KIND_ can occur.
Now have a look at nbd_refresh_filename(). s->saddr->type is If SOCKET_ADDRESS_KIND_VSOCK or SOCKET_ADDRESS_KIND_FD, then @host, @port and @path all remain null, and bs->exact_filename[] is not touched. Does this work as intended?
