Re: [libvirt] [FOR 1.3.0 PATCH] conf: add net device prefix for Xen

On Mon, Dec 07, 2015 at 09:42:21AM -0700, Jim Fehlig wrote: > In commit d2e5538b1, the libxl driver was changed to copy interface > names autogenerated by libxl to the corresponding network def in the > domain's virDomainDef object. The copied name is freed when the domain > transitions to the shutoff state. But when migrating a domain, the > autogenerated name is included in the XML sent to the destination host. > It is possible an interface with the same name already exists on the > destination host, causing migration to fail. Indeed the Xen project's > OSSTEST CI already encountered such a failure. > > This patch defines another VIR_NET_GENERATED_PREFIX for Xen, allowing > the autogenerated names to be excluded when parsing and formatting > inactive config. > > Signed-off-by: Jim Fehlig <jfehlig(a)suse.com&gt; > --- > > This is an alternative approach to Joao's fix for this regression > > https://www.redhat.com/archives/libvir-list/2015-December/msg00197.html > > I think it is the same approach used by the qemu driver. My only > reservation is that it expands the potential for clashes with > user-defined names. I.e. with this change both 'vnet' and 'vif' are > reserved prefixes. Hmm, yes, tricky one. If we only care about XML parsing, then you could register a post parse callback instead to do this.

I'm not clear why we also have it in the virDomainNetDefFormat method - and we can't solve that with a post-parse callback. The other option would be to make the reserved prefix be a capability that the parser/formatter could read.