This is tracking the upstream effort needed to deliver the feature request described below.

What's the feature?

Today OVN's BGP support allows OVN to advertise and learn routes to/from a host VRF routing table if the logical router is configured with "dynamic-routing=true" and "dynamic-routing-redistribute=....".

However, learning and advertising of routes is tightly coupled, in the sense that a logical router cannot be configured today to only advertise routes (without learning dynamic ones that were installed in the VRF).

Why is it needed?

In topologies with different routers (that are local datapaths from ovn-controller's perspective) users might want to configure OVN dynamic routing in the following way:

a. router1 configured to monitor VRF-ID=42 and learn routes from it (no advertisements)
b. router2 configured to monitor VRF-ID=42 and advertise routes to it (no learning)

This could be exposed through a new configuration option for logical routers, e.g.:
NB.Logical_Router.options:dynamic-routing-no-learning=true|false (default false)

Who will benefit? 

ovn-kubernetes when moving to OVN's native dynamic-routing integration support.