Explore separation of nbd_aio_pread/nbd_aio_submit(callback) since
current nbd_aio_pread_callback(callback) can race into the callback
before cookie is known to the user.

Explore if nbd_aio_notify_error is needed for faster response if
server goes away.

Improve python bindings to free persistent closure wrappers at time
of command completion rather than nbd close.

Bindings in other languages.

Example code integrating with glib2, APR pollset (and others?).

Example command line utils to copy in/out (like qemu-img convert).

NBD_OPT_INFO mode (like qemu-nbd -L).

NBD resize extension.

NBD_INFO_BLOCK_SIZE.

TLS should properly shut down the session (calling gnutls_bye).

Implement nbd_connect + systemd socket activation.
