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

[Richard W.M. Jones]

Daniel P. Berrange wrote:
> 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.

Oh I didn't realise that.  In that case, the patch is fine.

Rich.

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