[libvirt] [PATCH] Set a stable & high MAC addr for guest TAP devices on host
Daniel Veillard
veillard at redhat.com
Wed Jul 21 10:39:08 UTC 2010
On Wed, Jul 21, 2010 at 11:15:05AM +0100, Daniel P. Berrange wrote:
> A Linux software bridge will assume the MAC address of the enslaved
> interface with the numerically lowest MAC addr. When the bridge
> changes MAC address there is a period of network blackout, so a
> change should be avoided. The kernel gives TAP devices a completely
> random MAC address. Occassionally the random TAP device MAC is lower
> than that of the physical interface (eth0, eth1etc) that is enslaved,
> causing the bridge to change its MAC.
Ah, that's the reason why it was hiding !
> This change sets an explicit MAC address for all TAP devices created
> using the configured MAC from the XML, but with the high byte set
> to 0xFE. This should ensure TAP device MACs are higher than any
> physical interface MAC.
>
> * src/qemu/qemu_conf.c, src/uml/uml_conf.c: Pass in a MAC addr
> for the TAP device with high byte set to 0xFE
> * src/util/bridge.c, src/util/bridge.h: Set a MAC when creating
> the TAP device to override random MAC
> ---
> src/qemu/qemu_conf.c | 11 +++++++++--
> src/uml/uml_conf.c | 11 +++++++++--
> src/util/bridge.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> src/util/bridge.h | 3 ++-
> 4 files changed, 62 insertions(+), 5 deletions(-)
Patch looks fine,
ACK,
Daniel
--
Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
daniel at veillard.com | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library http://libvirt.org/
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