Re: [Qemu-devel] [Nbd] [PULL 23/28] nbd: always query export list in fixed new style protocol

[Alex Bligh <alex@alex.org.uk>]

On 17 May 2016, at 16:54, Richard W.M. Jones <rjones@redhat.com> wrote:

> On Tue, May 17, 2016 at 04:22:06PM +0100, Alex Bligh wrote:
>> nbdkit is non-compliant in that case. Support of NBD_OPT_LIST is
>> compulsory, even if you support it by returning a nameless export
>> (or default). Moreover support of export names is compulsory
>> (even if you have a single fixed one called "" or "default").
> 
> The protocol doc doesn't mention "default" (assuming you mean that
> literal string).  It says:

As per my message to Eric, I meant use an arbitrary piece of
text in your reply to NBD_OPT_LIST (it doesn't matter what it is,
'default' is not special). It doesn't matter because you ignore
what is passed in NBD_OPT_EXPORT_NAME. I was just suggesting making
things more readable for clients that did a list.

>> Whilst that is fair enough, NBD_OPT_LIST is a mandatory part of the
>> specification. If a server doesn't implement mandatory parts of
>> the specification, then bad things will happen.
> 
> It implements it, it's just that there wasn't a way to implement
> anything other than returning an error since we accept anything as an
> export name.

In which case you should just return an export name. Any
export name will work. The fact you don't have names for your
exports doesn't mean (in my book) you can error the list
request. You have one export. You don't know what it's name is,
but you should list it.

-- 
Alex Bligh