Comment 38 for bug 1869808

Reviewed: https://review.opendev.org/742359
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=17eded13595b18ab60af5256e0f63c57c3702296
Submitter: Zuul
Branch: stable/train

commit 17eded13595b18ab60af5256e0f63c57c3702296
Author: Darragh O'Reilly <email address hidden>
Date: Mon Jul 13 14:48:10 2020 +0000

    Ensure drop flows on br-int at agent startup for DVR too

    Commit 90212b12 changed the OVS agent so adding vital drop flows on
    br-int (table 0 priority 2) for packets from physical bridges was
    deferred until DVR initialization later on. But if br-int has no flows
    from a previous run (eg after host reboot), then these packets will hit
    the NORMAL flow in table 60. And if there is more than one physical
    bridge, then the physical interfaces from the different bridges are now
    essentially connected at layer 2 and a network loop is possible in the
    time before the flows are added by DVR. Also the DVR code won't add them
    until after RPC calls to the server, so a loop is more likely if the
    server is not available.

    This patch restores adding these flows to when the physical bridges are
    first configured. Also updated a comment that was no longer correct and
    updated the unit test.

    Change-Id: I42c33fefaae6a7bee134779c840f35632823472e
    Closes-Bug: #1887148
    Related-Bug: #1869808
    (cherry picked from commit c1a77ef8b74bb9b5abbc5cb03fb3201383122eb8)
    (cherry picked from commit 143fe8ff89ba776618ed6291af9d5e28e4662bdb)