[libvirt] default virtual network race with NetworkManager in a VM

Hi all, There's a long standing issue with running libvirt inside a VM: https://bugzilla.redhat.com/show_bug.cgi?id=811967 Summary: Run a VM using the default virtual network with IP address 192.168.122.XXX. Install libvirtd inside the VM, reboot. On startup, libvirtd in the VM can bring up its copy of the default virtual network, before NetworkManager has a chance to run. The nested network grabs the route for 192.168.122.0 before NetworkManager can claim it for the VM's normal networking. Result is the VM doesn't have any network connectivity to the outside world. If NetworkManager starts first, a libvirt check at virtual network startup time will refuse to override the existing route and avoid the problem. This is from https://bugzilla.redhat.com/show_bug.cgi?id=235961 The past few Fedora releases haven't generated that many complaints about this, but we've had reports that it's happening quite frequently with rawhide/f21, see the last comments of that first bug report. There's some suggestions in the bug about possible fixes, like listening to NetworkManager API events and stopping the virtual network if needed. But they are just ideas that no one has really researched. Anyone have a novel solution and/or some cycles to poke at this? (FWIW no one has tried to determine what has changed that's tickling this issue more often, but regardless the root issue should be dealt with) Thanks, Cole