Re: [Qemu-devel] [Nbd] [PATCH v4 04/11] nbd: Improve server handling of bogus commands

[Paolo Bonzini <pbonzini@redhat.com>]

----- Original Message -----
> From: "Alex Bligh" <alex@alex.org.uk>
> To: "Wouter Verhelst" <w@uter.be>
> Cc: "Alex Bligh" <alex@alex.org.uk>, nbd-general@lists.sourceforge.net, "Paolo Bonzini" <pbonzini@redhat.com>,
> qemu-devel@nongnu.org, "qemu block" <qemu-block@nongnu.org>
> Sent: Wednesday, June 15, 2016 10:52:21 AM
> Subject: Re: [Nbd] [PATCH v4 04/11] nbd: Improve server handling of bogus commands
> 
> 
> > On 15 Jun 2016, at 09:03, Wouter Verhelst <w@uter.be> wrote:
> > 
> > On Wed, Jun 15, 2016 at 09:05:22AM +0200, Wouter Verhelst wrote:
> >> There are more clients than the Linux and qemu ones, but I think it's
> >> fair to say that those two are the most important ones. If they agree
> >> that a read reply which errors should come without payload, then I think
> >> we should update the standard to say that, too.
> > 
> > I've just pushed a commit that changes the spec (and the implementation)
> > so that if a server encounters a read error, it does not send a payload.
> > 
> > In other words, the current behaviour of qemu is correct, is now
> > documented to be correct, and should not be changed.
> 
> So what should those servers do (like 2 of mine) which don't buffer
> the entire read, if they get an error having already sent some data?

They have sent an error code of zero, and it turned out to be wrong.  So
the only thing they can do safely is disconnect.

Paolo