Mac address on linux bridge can change depending on taps plugged in

[Andrew Melton]

When the linux bridge nova-network driver creates it's bridge, it makes an assumption that the bridge's mac will be the mac from the first device plugged into it. This is the case at first, when there is only one device. But, when more devices are plugged in, the default behavior is to take the lowest mac from all devices plugged in. This is a problem because there may be rules on the switch the initial interface is plugged into that prohibit traffic from anything but that interface's initial mac.

What should happen is immediately after creating the bridge, if there is an interface available, the bridge's mac should be explicitly set to that interface's mac. This will effectively lock the mac on the bridge, and it will not try to use the lowest mac of all devices plugged in.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/216895

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/216895
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=33fba4872634738f6c02e3607a25f6bd6a13a59d
Submitter: Jenkins
Branch: master

commit 33fba4872634738f6c02e3607a25f6bd6a13a59d
Author: Andrew Melton <email address hidden>
Date: Tue Aug 25 16:02:10 2015 -0700

    net: explicitly set mac on linux bridge

    The default behavior on a linux bridge is to use the lowest mac of
    all attached interface. This isn't a problem when the bridge is first
    set up, because the bridged interface is the only interface attached.
    But, when instance interfaces are attached, there is a chance a lower
    mac could be assigned and the bridge will switch macs. This patch
    always sets the mac on the bridge to the mac of the bridged interface.

    Change-Id: Ibf5333516a4c5487a3ee7c662e07028789bdd286
    Closes-bug: #1488686