Comment 4 for bug 1945306

From:
https://docs.openstack.org/releasenotes/neutron/queens.html

It states:
"A new config option explicitly_egress_direct, with default value False, was added for the aim of distinguishing clouds which are running the network node mixed with compute services, upstream neutron CI should be an example. In such situation, this explicitly_egress_direct should be set to False, because there are numerous cases from HA routers which can not be covered, particularly when you have centralized floating IPs running in such mixed hosts."

The documentation is not super clear when it says "which are running the network node mixed with compute services". I think the original use case simply meant running the neutron l3 routers and compute on the same node (even in non-dvr, non-ha mode) but without dvr-snat (which has always been possible, although for the Ubuntu use case: charm-neutron-gateway did not have a way to do it).

But seems that might also include a DVR environment (which effectively mixes network and compute functions more by design). In that case, it seems explicitly_egress_direct=True should not be used. Neutron should probably prevent this combination.

charm-neutron-openvswitch now always enables explicitly_egress_direct=True on usurri which is a bug if the above is true:
https://review.opendev.org/c/openstack/charm-neutron-openvswitch/+/798072
https://bugs.launchpad.net/charm-neutron-openvswitch/+bug/1931696