Router's external gateway isn't properly updated when new subnet is added

[Slawek Kaplonski]

Steps to reproduce the issue:

1. Enable scope enforcement and new secure RBAC default policies in Neutron,
2. As project A create external network and IPv4 subnet
3. As project B create router and set external gateway using network created above,
4. As project A create IPv6 subnet in external network
5. Router's external gateway should be updated but it isn't.

The issue happens after patch https://review.opendev.org/c/openstack/neutron/+/821208 was merged.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/826828

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/neutron/+/826828
Committed: https://opendev.org/openstack/neutron/commit/0fd168ae93176573575c61eab370e13a4cee34ce
Submitter: "Zuul (22348)"
Branch: master

commit 0fd168ae93176573575c61eab370e13a4cee34ce
Author: Slawek Kaplonski <email address hidden>
Date: Fri Jan 28 09:32:47 2022 +0100

    Use elevated context to update router's external gateway

    When new defaults and scope enforcement are used in Neutron, elevated
    context needs to be used to update router's external gateway when new
    subnet is added to the external network. Otherwise, router can belongs
    to the other project than external network and it will not be updated at
    all.

    Closes-Bug: #1959331
    Change-Id: I888ddf66a15cd20039ff26baccd170da128e1eb7

[OpenStack Infra (hudson-openstack)]

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