Neutron fail to create networks because of MTU value

[Alfredo Moralejo]

After https://github.com/openstack/neutron/commit/ebb866310b48cbad2ae772e0551aaf994858a51e when creating a tenant neutron without specifying mtu size with ovn driver, it fails with error:

osc_lib.exceptions.CommandError: Error while executing command: BadRequestException: 400, Invalid input for operation: Requested MTU is too big, maximum is 1442.
clean_up CreateNetwork: Error while executing command: BadRequestException: 400, Invalid input for operation: Requested MTU is too big, maximum is 1442.

Checking at neutron server logs, i see:

2020-10-26 11:17:15.592 61398 DEBUG neutron.api.extensions [req-1904932b-3ce6-48e5-8601-a746e3a546da - - - - -] Ext name="Network MTU (writable)" alias="net-mtu-writable" description="Provid
es a writable MTU attribute for a network resource." updated="2017-07-12T00:00:00-00:00" _check_extension /usr/lib/python3.6/site-packages/neutron/api/extensions.py:413
2020-10-26 11:17:15.593 61398 INFO neutron.api.extensions [req-1904932b-3ce6-48e5-8601-a746e3a546da - - - - -] Extension net-mtu-writable not supported by any of loaded plugins

I've realized that in devstack tests, this is working fine because it's enabling logger mechanism driver in addition to ovn. I understand this driver is intended for testing and debug only and should not included in production deployments so this is a real issue.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/759673

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/759673
Committed: https://opendev.org/openstack/neutron/commit/323781d9f0992dc3691620ca0a366afae4ed34ee
Submitter: Zuul
Branch: master

commit 323781d9f0992dc3691620ca0a366afae4ed34ee
Author: Daniel Alvarez <email address hidden>
Date: Mon Oct 26 13:15:48 2020 +0100

    [ovn] Add 'net-mtu-writable' to supported extensions

    This patch is adding the 'net-mtu-writable' extension to the
    supported extensions list of the OVN plugin.

    Without it, network creation with an MTU different from the
    default (1500) will fail. Right now, devstack is working
    because this extension gets loaded as a side effect of loading
    'logger' but we should enable it by default.

    Closes-Bug: #1901534

    Depends-On: https://review.opendev.org/760446
    Change-Id: I9ff47d8f678c95a6d6594f47ebca6175fdcc5453
    Signed-off-by: Daniel Alvarez <email address hidden>

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 18.0.0.0rc1 release candidate.