Some features that should be added

* Target driven iscsi-nop, to teach the library to respond to these.
  These are unsolicited nops sent from the targetr which we need to respond
  to. TGTD does not suppot these but IET should do so and could be used
  to test with.

* More efficient api for read/write commands where we read/write straight
  from the socket into the buffer the application specified instead of as now
  we pass the data to a callback and then copy it.

* More scsi marshalling and unmarshalling functions in scsi-lowlevel

* Autoconnect for session faiulures.
  When the tcp session fail,   try several times to reconnect and relogin.
  If successful re-issue any commands that were in flight.

* Task management functions

* Integrate with other relevant utilities such as 
  dvdrecord,
  ...

* Data Digest