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Re: [Xen-devel] Prevent vif-bridge from adding user-created tap interfac

To: Jim Fehlig <jfehlig@xxxxxxxx>
Subject: Re: [Xen-devel] Prevent vif-bridge from adding user-created tap interfaces to a bridge
From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Date: Thu, 27 Oct 2011 16:12:57 +0100
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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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.

Ian.

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