Re: [Xen-devel] Prevent vif-bridge from adding user-created tap interfaces to a bridge

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2011-10-27 at 16:12 +0100, Ian Jackson wrote:
> Jim Fehlig writes ("[Xen-devel] Prevent vif-bridge from adding user-created 
> tap interfaces to a bridge"):
> > I received a report that vif-bridge adds any tap interface to a bridge,
> > regardless if xen is running and who created the tap interface.  E.g.
> > 
> > # tunctl -p -t tap42
> > 
> > will cause vif-bridge to be executed as per the following rule in
> > xen-backend.rules
> > 
> > SUBSYSTEM=="net", KERNEL=="tap*", ACTION=="add",
> > RUN+="/etc/xen/scripts/vif-setup $env{ACTION} type_if=tap"
> 
> Urgh.  What a mess.
> 
> > I'm not sure how to improve the rule to prevent execution of vif-setup
> > in this case.  But it seems better to handle it in vif-bridge anyhow, by
> > not connecting the interface to a bridge if there is no corresponding
> > info in xenstore.  Something along the lines of the attached quick
> > patch.  Comments?
> 
> Aren't tap devices like this created by Xen's qemu ?  And as such we
> should be letting qemu run the script, and not have any hotplug
> script called by udev.

We explicitly changed away from that scheme not so long ago. The issue
is that each tap has a vif counterpart which is somewhat logically the
same device and should be setup the same way, hence via the same
mechanisms.

Ian.



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