Comment 34 for bug 1988069

Reviewed: https://review.opendev.org/c/openstack/neutron/+/875809
Committed: https://opendev.org/openstack/neutron/commit/88ce859b568248a0ee2f47a5d91c1708b774d20e
Submitter: "Zuul (22348)"
Branch: master

commit 88ce859b568248a0ee2f47a5d91c1708b774d20e
Author: Brian Haley <email address hidden>
Date: Wed Mar 1 00:52:38 2023 -0500

    Change API to validate network MTU minimums

    A network's MTU is now only valid if it is the minimum value
    allowed based on the IP version of the associated subnets,
    68 for IPv4 and 1280 for IPv6.

    This minimum is now enforced in the following ways:

    1) When a subnet is associated with a network, validate
       the MTU is large enough for the IP version. Not only
       would the subnet be unusable if it was allowed, but the
       Linux kernel can fail adding addresses and configuring
       network settings like the MTU.

    2) When a network MTU is changed, validate the MTU is large
       enough for any currently associated subnets. Allowing a
       smaller MTU would render any existing subnets unusable.

    Closes-bug: #1988069
    Change-Id: Ia4017a8737f9a7c63945df546c8a7243b2673ceb