Comment 14 for bug 2016198

Reviewed: https://review.opendev.org/c/openstack/neutron/+/881826
Committed: https://opendev.org/openstack/neutron/commit/e6fb32e27d1141ca4b00c3758ee44bfe2f060ccf
Submitter: "Zuul (22348)"
Branch: master

commit e6fb32e27d1141ca4b00c3758ee44bfe2f060ccf
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Fri Apr 28 13:56:02 2023 +0000

    Fix race condition when creating two routers without HA network

    When a HA router is created and the HA is not yet, before creating
    the router, the Neutron server creates the HA network and the
    corresponding subnet.

    The HA network cannot be duplicated (see previous patches related to
    this bug). But the subnet, that is created in another database
    transaction, cannot be present when the router creation call tries
    to create the HA port.

    This patch adds a HA subnet check before creating the router and the
    HA port. Even if the subnet check fails and the worker tries to
    create this subnet, if the process fails with ``InvalidInput``, that
    means other worker created the subnet before and the current one
    fails because tries to create the same subnet with the same CIDR.
    In this case, we dismiss the exception and continue with the router
    creation.

    Closes-Bug: #2016198

    Change-Id: I82225fcc6248bb0fd68959ceb1daabff423d81ff