Convert vxlan and gre network types to geneve on upgrade

[Richard Theis]

The vxlan and gre network types are not supported by OVN and networking-ovn enforces this during network creation and update (see https://review.openstack.org/#/c/366945/). However, the upgrade path from neutron ML2 OVS may result in unsupported network types existing. These networks should be converted to geneve as part of the upgrade process and future port bindings should prevent invalid network types.

[s10 (vlad-esten)]

Could it be possible not to remove vxlan support in OVN? Not all NIC support geneve offloading...

[Russell Bryant (russellb)]

No, OVN makes use of additional metadata that doesn't fit in vxlan.

Search for "DESIGN DECISIONS" on this document for discussion of "Tunnel Ecapsulations": http://openvswitch.org/support/dist-docs/ovn-architecture.7.html

[Russell Bryant (russellb)]

Fixing this depends on first rebuilding our upgrade+migration grenade job to use OVN L3 instead of the NeutronL3 agent.

[Lucas Alvares Gomes (lucasagomes)]

I believe we shouldn't just convert things silently. Geneve as @Russell pointed out is used because of the metadata we can carry with it.