Comment 5 for bug 1196963

Reviewed: https://review.openstack.org/41239
Committed: http://github.com/openstack/neutron/commit/a369f9e39691c01a4e4f7f8668cb37fc17ba03b3
Submitter: Jenkins
Branch: master

commit a369f9e39691c01a4e4f7f8668cb37fc17ba03b3
Author: Francois Eleouet <email address hidden>
Date: Wed Aug 7 11:19:46 2013 +0200

    Enable GRE and VXLAN with the same ID

    Current packet processing in br-tun is based on tun-id,
    as a consequence, two networks using different tunnel
    types but sharing the same tun-id would not be properly isolated.

    To ensure proper isolation within a single bridge, NORMAL action
    can't be used any more as it floods unknown unicasts on all
    bridges ports. It is replaced by a learn action that dynamically
    sets-up flows when packets are recieved from tunnel ports. As mac
    address are learnt in explicit flows (in table 20), we can use a
    default action in that table to flood unknown unicasts to the
    right set of ports, like broadcasts and multicasts packets.

    See https://wiki.openstack.org/wiki/Ovs-flow-logic for a more
    detailled explanation of the flow logic

    Another alternative could have been to use distinct bridges for
    each tunnel type (whithout modifying the current flow logic),
    but previous alternative may be preferable as it paves the way
    for new tunneling optimisations (like RPC based mac learning and
    partial-mesh flooding proposed in bp/l2-population)

    Change-Id: I1dfe74f96680c2c6fe4d8d4aac4821c6b020c005
    Closes-Bug: #1196963