Re: [Qemu-devel] [PATCH v4] qemu-ga: Add guest-network-info command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Mon, 27 Feb 2012 20:07:28 -0600
Michael Roth <mdroth@linux.vnet.ibm.com> wrote:

> What about something like this instead:
> 
> { 'enum': 'GuestIpAddressType',
>   'data': [ 'ipv4', 'ipv6' ] }
> 
> { 'type': 'GuestIpAddress',
>   'data': {'ip-address': 'str',
>            'ip-address-type': 'GuestIpAddressType',
>            'prefix': 'int'} }
> 
> { 'type': 'GuestNetworkInterface',
>   'data': {'interface': {'name': 'str',
>                          '*hardware-address': 'str',
>                          '*ip-addresses': ['GuestIpAddress'] } } }
> 
> { 'type': 'GuestNetworkInfo',
>   'data': { 'interfaces': ['GuestNetworkInterfaces'] } }
> 
> { 'command': 'guest-network-info',
>   'returns': 'GuestNetworkInfo' }
> 
> In the future we might have:
> 
> { 'type': 'GuestNetworkInfo',
>   'data': { 'interfaces': ['GuestNetworkInterfaces'],
>             'routes': ['GuestNetworkRoute'],
>             'bridges': ['GuestNetworkBridge'],
>             'firewall-rules': ['firewall-rule'], # yikes
>             etc. } }

Both approaches are fine to me, but another possibility is to split this into
multiple commands, like guest-interfaces-info, guest-routes-info etc. This would
allow for simpler commands with less clutter.

> > Once we settle down on this I can send another version for review.
> > Personally, if guest agent would report description (see my other e-mail
> > [1]) I don't see big advantage in introducing dozens of error codes here.
> 
> descriptions are mapped to QERRs though, so it'd only be useful if you
> defined specific errors for these cases. I agree with Luiz, but at the
> same time it's not exactly tractable to enumerate all possible errors for every
> command into a unique QERR except for common things like FD_NOT_FOUND. So maybe
> just a QERR_QGA_INTERFACE_ENUMERATION_FAILED, that took a stringified error
> message? I don't really have a strong opinion either way.

Well, turns out I'm not sure what to do here either. On the one hand it's a
huge work (and probably unnecessary) to add all possible errors. On the other
hand, it's really hard to debug a problem when all information you have is
a generic error.

As this a relatively simple query command, I'm fine with simple/generic errors.