1. Proposed title of this feature request

Use OVN's transit router in the L2 UDN topologies.

2. What is the nature and description of the request?

In order to provide support for seamless live-migration of VMs between nodes, we have had to introduce a sequence of hacks into OVN-K:

• https://issues.redhat.com/browse/OCPBUGS-43354

Plus all the following, which are all related to reconciling the gateway at guest after live migration:

• ipv4:
  • https://github.com/ovn-kubernetes/ovn-kubernetes/pull/4964
• ipv6:
  • https://github.com/ovn-kubernetes/ovn-kubernetes/pull/4878
  • https://github.com/ovn-kubernetes/ovn-kubernetes/pull/4847
  • https://github.com/ovn-kubernetes/ovn-kubernetes/pull/4852

Of all these, only the IPv4 fix has any chance of landing on 4.18.0, while the IPv6 ones will be addressed in a 4.18 Z stream.

3. Why does the customer need this? (List the business requirements here)

Using transit routers would drop the need for any of these hacks, simplify the l2 topology, the primary OVN feature design, and overall, provide a simple networking topology easy to reason about.

4. List any affected packages or components.

OVN-Kubernetes