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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.

Dan.
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