Comment 4 for bug 1933273

Reviewed: https://review.opendev.org/c/openstack/neutron/+/799226
Committed: https://opendev.org/openstack/neutron/commit/b5dd6efdca0aa6e7405a55d66c7042a49ec72214
Submitter: "Zuul (22348)"
Branch: master

commit b5dd6efdca0aa6e7405a55d66c7042a49ec72214
Author: Slawek Kaplonski <email address hidden>
Date: Fri Jul 2 17:55:26 2021 +0200

    [DVR] Fix update of the MTU in the SNAT namespace

    When network's MTU is changed, Neutron sends notification about it
    to the L3 agents. In case of DVR (and DVR HA) MTU is then changed in
    the qrouter- namespace but should be also changed on snat interfaces
    in the snat namespace. And that part was missing.

    This patch adds special implementation of the internal_network_updated()
    method in the DvrEdgeRouter class so it can configure MTU also for
    in the snat namespace.

    This patch also removed passing attributes "interface_name",
    "ip_cidrs" and "mtu" to the internal_network_updated() method and adds
    "port" dict to be passed there. It is consistent with what is already
    done in e.g. internal_network_added() method and "port" dict is actually
    necessary to configure properly snat internal interface in the snat
    namespace.

    This patch adds also functional test of update network mtu for all types
    of routers as there was no such test at all.

    There is additional issue with DVR-HA which isn't fixed with that patch
    and for which follow up will be proposed. Because of that this patch is
    marked as partial fix for the related bug.

    Related-Bug: #1933273
    Change-Id: I200acfcaaae7f056ea9a563fead9ff2de8464971