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

On Mon, Dec 07, 2015 at 10:59:32PM -0700, Jim Fehlig wrote: > On 12/07/2015 11:52 AM, Daniel P. Berrange wrote: >> 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. > AFAIK, XML parsing is all that's in play here. > >> 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. > This seems like the best option, since a post-parse callback doesn't solve the > problem in virDomainNetDefFormat. It also has the upshot of making the prefix > visible and known to users. But I doubt such a change is suitable during 1.3.0 > freeze. With the freeze in mind, seems the best solution to the libxl migration > regression is revert d2e5538b1. It can be added again post-1.3.0 release, after > adding the prefix to capabilities. > > DV, since you may be making the release soon, feel free to revert d2e5538b1 if > you agree. Yeah, just go ahead & revert it Jim, DV isn't doing the releae until tomorrow morning