Re: [Libvir] PATCH: strip auto-generated VIF names from XML

For the QEMU / KVM driver, if the user doesn't specify an explicit name for the TAP device associated with a virtual NIC, we auto-generate one with a name vnetXXX. You can see this if you dump XML for a running QEMU guest. Unfortunately if you dump XML, make a change and then feed it back in with the define XML API, you have now persisted this auto-generated VIF name. Do this for several domains at varying times and you'll eventually get 2 domains which have persisted the same auto-generated vnetXXX device name. You can now not start both of these VMs at once. The fix for this is simple - simply strip any TAP device name starting with the string 'vnet' when defining a new VM. It will thus get assigned a new automatically generate name which doesn't clash. The patch also strips out hardcoded vnetXXX names when starting a VM to proactively deal with any existing VMs whose config has been broken in this way.