[libvirt] Network device abstraction aka virtual switch - V3

[Neil Wilson]

> The current modes are:
> 
> <forward layer='network' mode='route|nat'/>
> 
> (in addition to not listing any mode, which equates to "isolated")
> 
> Here are suggested new modes:

Has anybody considered the migration requirements of networks in this
new layout?

If you move a machine attached to a 'route|nat' network to another Host
you need to extend the network to the new Host and eventually you need
to move the supporting processes that hand out the IP addresses/DNS
addresses etc (if you're decommissioning a Host server for example).  

If you try to start a copy of the network on the new host, then it
generally clashes with the pre-existing routing 

It would be useful to be able to extend a network onto another Host
somehow and be able to migrate the supporting processes (DNSMasq, IP
addressing, etc) between Hosts. (And obviously remove extensions as
required as well).

Perhaps this suggests that the address and route management systems need
separating from the definition of the bridge network. (There's no real
reason why the address management systems couldn't be attached to
macvtap and vepa networks as well as basic bridges). 

Rgs

Neil Wilson