On 01/24/2017 10:42 AM, Richard W.M. Jones wrote:
Also, the NBD spec DOES allow for the server to send a string error message alongside the error code; we aren't utilizing that yet, but it would be worth exploring how easy it would be to let the plugin's error message be reflected through to the client.
I didn't know that, but yes.
Correction - error replies to NBD_OPT_ (during handshake) are easy, but error replies during transmission are trickier - they require the negotiation of structured replies between server and client, which is still marked as an experimental feature rather an official part of the NBD spec in part because there is no implementation yet (but I'm trying to get qemu to be the first such implementation, and getting nbdkit to do it as well to prove interoperability can't hurt). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org