Re: [Qemu-devel] [BUG] Monitor QMP is broken ?

[Daniel P. Berrange]

On Fri, Jun 05, 2015 at 04:58:46PM +0300, Pavel Fedin wrote:
>  Hello! 
> 
> >  I have updated my qemu to the recent version and it seems to have lost 
> > compatibility
> with
> > libvirt. The error message is:
> > --- cut ---
> > internal error: unable to execute QEMU command 'qmp_capabilities': QMP 
> > input object
> > member
> > 'id' is unexpected
> > --- cut ---
> >  What does it mean? Is it intentional or not?
> 
>  I have found the problem. It is caused by commit
> 65207c59d99f2260c5f1d3b9c491146616a522aa. libvirt does not seem to use the 
> removed
> asynchronous interface but it still feeds in JSONs with 'id' field set to 
> something. So i
> think the related fragment in qmp_check_input_obj() function should be 
> brought back

If QMP is rejecting the 'id' parameter that is a regression bug.

[quote]
The QMP spec says

2.3 Issuing Commands
--------------------

The format for command execution is:

{ "execute": json-string, "arguments": json-object, "id": json-value }

 Where,

- The "execute" member identifies the command to be executed by the Server
- The "arguments" member is used to pass any arguments required for the
  execution of the command, it is optional when no arguments are
  required. Each command documents what contents will be considered
  valid when handling the json-argument
- The "id" member is a transaction identification associated with the
  command execution, it is optional and will be part of the response if
  provided. The "id" member can be any json-value, although most
  clients merely use a json-number incremented for each successive
  command


2.4 Commands Responses
----------------------

There are two possible responses which the Server will issue as the result
of a command execution: success or error.

2.4.1 success
-------------

The format of a success response is:

{ "return": json-value, "id": json-value }

 Where,

- The "return" member contains the data returned by the command, which
  is defined on a per-command basis (usually a json-object or
  json-array of json-objects, but sometimes a json-number, json-string,
  or json-array of json-strings); it is an empty json-object if the
  command does not return data
- The "id" member contains the transaction identification associated
  with the command execution if issued by the Client

[/quote]

And as such, libvirt chose to /always/ send an 'id' parameter in all
commands it issues.

We don't however validate the id in the reply, though arguably we
should have done so.

Regards,
Daniel
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