Comment 11 for bug 1670666

Reviewed: https://review.openstack.org/539901
Committed: https://git.openstack.org/cgit/openstack/networking-ovn/commit/?id=e7fc4edc9412c1ef489f578feeb3dd39fedd4fd7
Submitter: Zuul
Branch: stable/pike

commit e7fc4edc9412c1ef489f578feeb3dd39fedd4fd7
Author: Dong Jun <email address hidden>
Date: Wed Jan 17 19:04:21 2018 +0800

    Use metadata IP as DHCP service IP for subnet without gateway IP

    Currently, OVN does not support DHCP for subnet without gateway IP.
    This is an important feature for VMs having multi ports on multi
    subnets, because two conflicting default routes should be avoided.
    In the patch[1] in OVN, router option was changed from mandatory to
    optional, then we can add DHCP without router option to OVN. But,
    without gateway IP, we still need an IP address as DHCP service IP,
    using the same IP with metadata is a choice.
    This patch does not solve all the problems, a TODO is added in the
    code and bug is still opening to track it.

    [1]https://github.com/openvswitch/ovs/commit/b89d25e5694bc9bb0a1fbb2a025d18a2a231c633

    Conflicts:
            networking_ovn/common/ovn_client.py

    Change-Id: Icd93101bf8834a56f80184f0584a73a36b16b483
    Partial-Bug: #1670666
    Signed-off-by: Dong Jun <email address hidden>
    (cherry picked from commit 48c3fbb8b830b4fb33fa63b1e7628c8d364509c2)