Kubernetes masters and API calls to active master

We have a 3 master cluster and want to use haproxy external to the cluster to handle API calls to the master nodes. Since only one master is active and the others are on standby, how can I have haproxy direct traffic to only the active master in the cluster? It would have to know which master is currently the active master while directing the calls. I thought I seen some discussion on this in the past but have been unable to find more information.

Thanks for any help!