Gitlab.com with private non-GKS Kubernetes

My scenario is this:

  • My repo is on gitlab.com
  • I have an existing K8S cluster, behind a firewall.

Two questions:

a) What IP addresses would gitlab.com use to connect to this cluster? What do I need to open in the firewall?

b) I’m getting the dreaded "“Something went wrong while installing Helm Tiller. Can’t start installation process.” message. Is there a definitive answer to what I need to set up in this cluster before attempting to install helm?