* Listen on specific interfaces or protocols (eg. only IPv6).

* Can we do language bindings using #!'s?
  You would enter:
    nbdkit foo [args]
  where nbdkit-foo-plugin is a Perl script starting:
    #!perl
  which causes nbdkit to load the perl plugin wrapper.

* syslog? journal?

* Glance and/or cinder plugins.

* Performance - measure and improve it.

* split files plugin
    nbdkit split file=file1 file=file2 [...]
  which concatenates the files to make the virtual device.

* filters: It should be possible to layer filters over plugins to
  do things like injecting errors and adding delays (see wdelay/rdelay
  options in the file plugin).

* Factor out the nbd client in the nbd plugin and make it available
  to other consumers, so that nbdkit can be layered.
