Comment 10 for bug 1871608

Reviewed: https://review.opendev.org/742872
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=8f1912a1d195dc69eed9d9aa8ff8c4ef12448b75
Submitter: Zuul
Branch: stable/train

commit 8f1912a1d195dc69eed9d9aa8ff8c4ef12448b75
Author: Maciej Józefczyk <email address hidden>
Date: Thu Apr 16 12:58:15 2020 +0000

    [OVN] Allow IP allocation with different segments for OVN service ports

    OVN creates localport [1] for each network that has metadata
    and allocate IP address from subnet within this network that has
    DHCP enabled. The traffic from this port will never go outside
    the chassis.

    While using multiple segments with subnet linked to each segment
    OVN needs to create an allocation of IP address for each of those
    subnets [2] in order to generate data for OVN NBDB IPv4 DHCP Options.

    The change [3] started to validate that condition, while multiple
    IP addresses from different segments are tried to be allocated on
    one port. We can skip this for OVN Metadata port, because there
    is no reason to prevent those kind of allocation for OVN.

    For stable branches we decide if a port is distributed or not
    by looking for DEVICE_OWNER_DHCP device owner and `ovn` device_id,
    instead DEVICE_OWNER_DISTRIBUTED device owner.

    Conflicts:
       neutron/db/ipam_backend_mixin.py
       neutron/tests/unit/db/test_ipam_pluggable_backend.py
       neutron/tests/unit/plugins/ml2/drivers/ovn/mech_driver/test_mech_driver.py

    [1] http://www.openvswitch.org/support/dist-docs/ovn-architecture.7.html
    [2] https://github.com/openstack/neutron/blob/5f42488a9a6a7a3afa55a56f53e2f5ef09365115/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py#L2279
    [3] https://review.opendev.org/#/c/709444/

    Change-Id: Ib51cde89ed873f48db4daebc27a0980da9cc0f19
    Closes-Bug: 1871608
    (cherry picked from commit 8d1512afb07a9a77958c44f2e7f5d47865c8a475)