Comment 9 for bug 1951559

Reviewed: https://review.opendev.org/c/openstack/neutron/+/819581
Committed: https://opendev.org/openstack/neutron/commit/41703c0a56e87d54d87b1e470fbc694abd570807
Submitter: "Zuul (22348)"
Branch: stable/ussuri

commit 41703c0a56e87d54d87b1e470fbc694abd570807
Author: Elvira García <email address hidden>
Date: Thu Nov 18 18:08:13 2021 +0100

    [OVN] Fix gateway_mtu option should not always be set

    OVN Driver currently fixes gateway_mtu MTU to the provider MTU value
    without considering if the private networks in the associated router
    have greater MTU values than the provider. This is unnecesary and
    adds extra actions for each packet. This patch fixes that, as now
    gateway_mtu is only set in case the provider MTU is smaller than the
    private MTU.

    The changes in create_router_port and delete_router_port were necessary
    as there could be a use case when the user first sets the gateway
    router and later adds subnets from networks with greater MTU, so this
    parameter needs to be checked after adding a subnet.

    Closes-Bug: #1951559

    Signed-off-by: Elvira García <email address hidden>
    Change-Id: If56f1a3dcdc8c57303d5641df79ea919ba7c170d
    (cherry picked from commit 0725533a6fa6a42d361e518b027f69da8e1e1ec5)