[libvirt] vnet<X>'s & interfaceStats().. KVM device numbering confusion?

Hi libirt-list, I am attempting to migrate from Xen->KVM and am having a little trouble understanding the new vnet<X> interface numbering scheme and how to use it to collect statistics of the interface using the interfaceStats() function. In Xen, the ID for a given domain was know, and a corresponding vif<ID>.0 interface was brought up so it was easy to grab the stats (amongst other things). Under my new KVM config I've realised that vnet<X> is brought up in a 'first free' fashion as opposed to a counter in the Xen case. This leaves me scratching my head a little bit, say I have a domain which has ended up with ID = 8, but may for instance have network 'vnet1' associated with it. I'm not sure how I can determine any association between the domain & which interface belongs to it! (e.g. a call to domain.interfaceStats() requires the correct network interface as a parameter). Surely I must be missing something here? Anyone have any advice/workaround for this situation? Ideally I would like to either be able to hardcode vnet-labels in the XML description (tried but it's ignored), or otherwise keep vnet numbering in sync with domain ID. Thanks in advance, Ravi