On Tue, May 17, 2016 at 09:59:02AM -0600, Eric Blake wrote: > On 05/17/2016 09:52 AM, Eric Blake wrote: > >>> Perhaps nbdkit should implement NBD_OPT_LIST returning just "" (the > >>> default name) as its only list entry? > >> > >> Or "default". > > > > As I read the protocol, I don't see "default" as a permissible name of > > the default export, just "". > > > > Also, we currently state that NBD_OPT_LIST has zero or more > > NBD_REP_SERVER replies, which means that it is valid for the command to > > succeed with NBD_REP_ACK _without_ advertising any exports at all > > (rather annoying in that it tells you nothing about whether > > NBD_OPT_EXPORT_NAME/NBD_OPT_GO will succeed anyways). Should we reword > > that to require that if NBD_REP_ACK is sent, then at least one > > NBD_REP_SERVER reply was given (where "" is the obvious name, but at the > > same time where "" is not mandatory if some other name is given)? > > Okay, I just downloaded nbdkit code and checked; nbdkit is sending 0 > entries and NBD_REP_ACK (for success), and NOT an error code; so it is > implying that there are NO known export names but that the command was > recognized.
Bleah you are right. I misread the code I wrote :-( We can add a empty string list entry there easily enough. Rich. > >> > >> My interpretation of NBD_OPT_LIST failing would be 'this server > >> doesn't have anything it can export'. > > > > Indeed, and that's why qemu as a client is currently dropping the > > connection with nbdkit. > > Except that nbdkit is NOT failing NBD_OPT_LIST, just merely listing 0 > replies. > > > But I would also make that interpretation for > > NBD_OPT_LIST succeeding with NBD_REP_ACK with 0 NBD_REP_SERVER replies - > > which is the nbdkit behavior > > > so maybe it is worth a note in the protocol how to detect servers that > > are exporting exactly one volume and don't care what name you pass, then > > tweaking either nbdkit, qemu, or both to comply to that added protocol > > wording. > > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/ ------------------------------------------------------------------------------ Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data untouched! https://ad.doubleclick.net/ddm/clk/304595813;131938128;j _______________________________________________ Nbd-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/nbd-general
