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Re: [Xen-devel] [PATCH][qemu-xen] Change tap device mac address to prevent change of bridge's mac
On Tue, 2010-12-21 at 13:13 +0000, Miroslav Rezanina wrote:
> Qemu tap device is created with random mac address and then add to bridge.
> Due to linux kernel handlig, bridge change its mac address to tap mac in case
> tap mac is lower than bridge one. This can lead to short network breakage for
> dom0 and guests.
> This patch set tap device mac adress to FE:FF:FF:FF:FF:FF to ensure tap
> device mac is always higher then bridge one.
> Signed-off-by: Miroslav Rezanina <mrezanin@xxxxxxxxxx>
Thanks. This needed a different fix in xen-unstable.hg because tap
devices are handled by the hotplug scripts and not qemu-ifup there. See
the recent thread "tools/hotplug/Linux: Ensure tap devices receive a
dummy MAC address".
My backport to xen-4.0-testing looked a lot like yours.
> diff --git a/i386-dm/qemu-ifup-Linux b/i386-dm/qemu-ifup-Linux
> index bcbee92..c706a10 100644
> --- a/i386-dm/qemu-ifup-Linux
> +++ b/i386-dm/qemu-ifup-Linux
> @@ -33,5 +33,8 @@ then
> +# We have to change mac address of tap device to not change bridge mac
> +ip link set $1 addr fe:ff:ff:ff:ff:ff
> ifconfig $1 0.0.0.0 up
> brctl addif $bridge $1 || true
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