[Libvir] [PATCH] Add a default network

Hey, So, we want to install a default network which guests can connect to. This can be seen as e.g. a replacement for xenbr0 as the default bridge for xen guests. A few things concern me about the patch, see below for my thinking. However, I'm happy to punt on all of these issues for now and go ahead with the patch. 1) Ordering - we want the default network to have a predictable bridge name, so instead of relying on it being the first network and ending up auto-allocated vnet0, we use virbr0. The alternative is to actually have an ordering scheme, e.g. #define LIBVIRT_AUTOSTART_PRIORITY_DISABLE -1 #define LIBVIRT_AUTOSTART_PRIORITY_FIRST 0 #define LIBVIRT_AUTOSTART_PRIORITY_LAST 99 #define LIBVIRT_AUTOSTART_PRIORITY_DEFAULT 50 int virNetworkSetAutostart(virDomainPtr domain, int priority); autostart/00-default.xml -> ../default.xml autostart/99-MyNetwork.xml -> ../MyNetwork.xml Maybe that's useful, but probably moreso for guests than networks. The "virbr0" solution is fine, IMHO. 2) IP address choice - I've randomly chosen 192.168.122.1/24 as the IP address for the network, and this could happen to clash with an existing network. Since we masquerade outgoing traffic, I think the only problem this would cause in practice would be where the host machine is already on a 192.168.122/24 subnet and it could find itself connecting to a guest rather than another machine on the physical subnet. It's a default configuration choice which admins can change, and I don't see it causing huge problems in practice, so I'm not overly concerned. If it did turn out to be a problem, I'd probably add something like: <ip type="auto" /> But I'm not anxious to go down that route right now. 3) UUID generation - there's no UUID specified, so the default network will have a different UUID across reboots. We could trivially save the UUID at first boot, but we'd really need to put it in /var then. IMHO, it's something we can fix later if it turns out to be important. Cheers, Mark.