changing the qos policy on a network does not change the placement allocation of the bound ports in the network

[Balazs Gibizer]

1) create a network with qos policy (with min_bw rule)
2) create a port in that network without explicit qos policy (so the port inherits the policy from the network)
3) boot a server with that port
4) update the qos policy on the network

Expected either:
A)
* qos policy change is accepted
* the port resource request is updated according to the new qos policy
* the placement allocation is updated according to the new qos policy

B)
* qos policy update is rejected

Actual:
* qos policy change is accepted -> OK as in A)
* the port resource request is updated according to the new qos policy -> OK as in A)
* the placement allocation is _not_ updated -> NOT OK in A)

See the specific reproduction steps with printouts in: http://paste.openstack.org/show/802718/

[Balazs Gibizer (balazs-gibizer)]

Please note that the above scenario is relevant also for the case when there are more than one bound port exists in the network.

[Przemyslaw Szczerbik (pszczerbik)]

A) is the correct expected behavior.

Rejecting QoS policy update in B) approach, would break dataplane enforcement.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/818889

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/818889
Committed: https://opendev.org/openstack/neutron/commit/e68a2832114739264dbbd42766b4991afa2e0d0d
Submitter: "Zuul (22348)"
Branch: master

commit e68a2832114739264dbbd42766b4991afa2e0d0d
Author: Przemyslaw Szczerbik <email address hidden>
Date: Wed Nov 17 09:12:16 2021 +0100

    Update placement allocation of bound ports when network QoS policy is changed

    When QoS policy is changed on a network, placement allocation of bound
    ports in that network has to be updated. This applies only to ports
    that do not overwrite network QoS policy.

    To detect network resource change, a new callback is registered for
    AFTER_UPDATE event.

    Closes-Bug: #1915898
    Change-Id: Ibc71d26cbb0dce99ea6dad9e5ccd0966e72f3f20

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/neutron 20.0.0.0rc1 release candidate.