ovn-k8s-overlay: Use the gateway router for North-South LB.

[shettyg]

The load-balancer on the external switch does not work when
there is a SNAT rule in the gateway router.

Signed-off-by: Gurucharan Shetty guru@ovn.org

[salv-orlando]

I guess this changes little to nothing in terms of packet flow, but fixes the issue you observed.
Is this a bug in OVN or is it just that the SNAT rule will mess up with the return traffic?

[shettyg]

The SNAT rule will mess up with the return traffic. And when it eventually comes to the place where load-balancing happened it sees a different packet and hence it will not unDNAT it. With this, since we load-balance in the router, the SNAT rule does not happen before unDNAT.

This support just got merged in OVN (i.e ability to add LB to gateway router with a fresh schema change)

[salv-orlando]

cool. lgtm then.

does this also mean the issue preventing us from testing N/S connectivity is gone?

[shettyg]

does this also mean the issue preventing us from testing N/S connectivity is gone?

Yes.