On Thu, Mar 24, 2016 at 12:37:33PM +0100, Paolo Bonzini wrote: > > > On 24/03/2016 09:26, Wouter Verhelst wrote: > >> > > >> > No, there is no specific reason. Looks like NBD_CMD_FLAG_ZEROES fits the > >> > spec and implementations nicely. So I'll rewrite the extension and add > >> > the flag instead of the whole command. > > Actually, having given this some more thought... > > > > There is at least one server-side implementation of nbd (mine) which > > silently ignores flags it doesn't know about. This isn't a problem for > > non-critical flags, but it could be a problem for a flag like this. Of > > course, a client shouldn't send a flag to a server which that server > > hasn't heard of, but mistakes do happen. > > > > Do we want to keep that in mind? If so, we might want to keep it as a > > separate command after all. > > > > OTOH, it could be said that silently ignoring unknown messages is a bug. > > I should probably just fix my implementation instead. > > Even if it is a bug, it does suggest that the payload format should not > be changed by flags. For example ignoring flags is a bug for an NBD > server, but not for a Wireshark protocol dissector.
Agreed. Let's make this a different command then, instead. -- < ron> I mean, the main *practical* problem with C++, is there's like a dozen people in the world who think they really understand all of its rules, and pretty much all of them are just lying to themselves too. -- #debian-devel, OFTC, 2016-02-12