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

On Tue, Dec 04, 2007 at 05:40:44PM +0000, Richard W.M. Jones wrote: > Daniel P. Berrange wrote: > >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. > > Hang about though, don't we sometimes want to explicitly set the name of > some interfaces to vnetXXX? No, if you want to manually set interface names, you have to use something other than a 'vnet' prefix. 'vnet' is the prefix for auto-generated names in same way as 'vif' is the prefix for Xen auto-generated names.