[libvirt] RFC: Introduce API to query IP addresses for given domain

[Daniel P. Berrange]

On Fri, Jun 28, 2013 at 03:56:10PM +0530, Nehal J. Wani wrote:
> Hello, fellow developers!
>       I am a GSoC candidate this year working for libvirt.org. My
> project is "Introduce API to query IP addresses for given domain".
> The discussion regarding this feature had started here:
> http://www.mail-archive.com/libvir-list@redhat.com/msg51857.html and
> then Michal had sent a patch too (refer:
> http://www.mail-archive.com/libvir-list@redhat.com/msg57141.html). But
> it was not pushed upstream due to lack of extensibility.
> 
> So far I've come up with an API and I want to get your opinion before
> I start writing the rest so I don't follow the wrong direction.
> 
> Following are the valid commands:
> 
> domifaddr <domain-name>
> domifaddr <domain-name> <interface-name>
> domifaddr <domain-name> <interface-name> <method>
> domifaddr <domain-name> <method>

What are valid values for '<method>' here ?

> 
> methods:
> (i) Querying qemu-guest-agent
> (ii) Getting info from dnsmasq.leases file
> (iii) Using the nwfilter to snoop the traffic
> 
> If no method is mentioned, qemu-guest-agent will be used.
> 
> Previous attempts by Michal had used structs and xml. Structs bring in
> restrictions and xml has to be parsed. Hence I am not planning to
> continue with either of these.
> 
> As a start, I would like to know your comments about my API which
> queries the qemu-guest-agent and returns the results in
> virTypedParameter **params.
> 
> Format(JSON) in which the qemu guest agent returns info:
> 
> [{"name":"lo",
> 	"ip-addresses":
> 		[{"ip-address-type":"ipv4","ip-address":"127.0.0.1","prefix":8},
>          	{"ip-address-type":"ipv6","ip-address":"::1","prefix":128}],
>         "hardware-address":"00:00:00:00:00:00"},
> {"name":"eth0",
> 	"ip-addresses":
>         	[{"ip-address-type":"ipv4","ip-address":"192.168.122.42","prefix":24},
>          	{"ip-address-type":"ipv6","ip-address":"fe80::5054:ff:fe09:d240","prefix":64}],
>         "hardware-address":"52:54:00:09:d2:40"}]
> 
> //Possible 1-D Structure (A little hassle to maintain)
> 
> params[0] = {"iface-count",int,2}
> params[1] = {"iface-name",string,"lo"}
> params[2] = {"iface-hwaddr",string,"00:00:00:00:00:00"}
> params[3] = {"iface-addr-count",int,2}
> params[4] = {"iface-addr-type",string,"ipv4"}
> params[5] = {"iface-addr",string,"127.0.0.1"}
> params[6] = {"iface-addr-prefix",int,8}
> params[7] = {"iface-addr-type",string,"ipv6"}
> params[8] = {"iface-addr",string,"::1"}
> params[9] = {"iface-addr-prefix",int,128}
> ....
> ....
> ....
> 
> //2D Structure: (Not very hasslefree, but easier to maintain as one
> interface per row)
> 
> params[0] = {"iface-name",string,"lo"}{"iface-hwaddr",string,"00:00:00:00:00:00"}{"iface-addr-type",string,"ipv4"}{"iface-addr",string,"127.0.0.1"}{"iface-addr-prefix",int,8}{"iface-addr-type",string,"ipv6"}{"iface-addr",string,"::1"}{"iface-addr-prefix",int,128}
> params[1] = {"iface-name",string,"eth0"}{"iface-hwaddr",string,"52:54:00:09:d2:40"}{"iface-addr-type",string,"ipv4"}{"iface-addr",string,"192.168.122.42"}{"iface-addr-prefix",int,8}{"iface-addr-type",string,"ipv6"}{"iface-addr",string,"fe80::5054:ff:fe09:d240"}{"iface-addr-prefix",int,64}

IMHO both of these approaches to encoding the data in virTypedParameter
are seriously unpleasant for an app to deal with. Now this is a true for
virTypedParameter in general, but I think that the need to deal with a
list of objects here, each containing a list of typed parameters makes
it even worse than normal. I wouldn't really like this as an application
developer.

Looking at this possible approach of virTypedParameter, I'm think I am
preferring either the XML or fixed struct approach to this API as was
proposed in the past, with a bias towards a fixed struct for simplicity
of use by app developers.

Regards,
Danuiel
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