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Networking for hosted control planes

For standalone OKD, proxy support is mainly about ensuring that workloads in the cluster are configured to use the HTTP or HTTPS proxy to access external services, honoring the NO_PROXY setting if one is configured, and accepting any trust bundle that is configured for the proxy.

For hosted control planes, proxy support involves the following additional use cases.

Control plane workloads that need to access external services

Operators that run in the control plane need to access external services through the proxy that is configured for the hosted cluster. The proxy is usually accessible only through the data plane. The control plane workloads are as follows:

  • The Control Plane Operator needs to validate and obtain endpoints from certain identity providers when it creates the OAuth server configuration.

  • The OAuth server needs non-LDAP identity provider access.

  • The OpenShift API server handles image registry metadata import.

  • The Ingress Operator needs access to validate external canary routes.

In a hosted cluster, you must send traffic that originates from the Control Plane Operator, Ingress Operator, OAuth server, and OpenShift API server pods through the data plane to the configured proxy and then to its final destination.

Some operations are not possible when a hosted cluster is reduced to zero compute nodes; for example, when you import OpenShift image streams from a registry that requires proxy access.

Compute nodes that need to access an ignition endpoint

When compute nodes need a proxy to access the ignition endpoint, you must configure the proxy in the user-data stub that is configured on the compute node when it is created. For cases where machines need a proxy to access the ignition URL, the proxy configuration is included in the stub.

The stub resembles the following example:

---
{"ignition":{"config":{"merge":[{"httpHeaders":[{"name":"Authorization","value":"Bearer ..."},{"name":"TargetConfigVersionHash","value":"a4c1b0dd"}],"source":"https://ignition.controlplanehost.example.com/ignition","verification":{}}],"replace":{"verification":{}}},"proxy":{"httpProxy":"http://proxy.example.org:3128", "httpsProxy":"https://proxy.example.org:3129", "noProxy":"host.example.org"},"security":{"tls":{"certificateAuthorities":[{"source":"...","verification":{}}]}},"timeouts":{},"version":"3.2.0"},"passwd":{},"storage":{},"systemd":{}}
---

Compute nodes that need to access the API server

This use case is relevant to self-managed hosted control planes, not to Red Hat OpenShift Service on AWS with hosted control planes.

For communication with the control plane, hosted control planes uses a local proxy in every compute node that listens on IP address 172.20.0.1 and forwards traffic to the API server. If an external proxy is required to access the API server, that local proxy needs to use the external proxy to send traffic out. When a proxy is not needed, hosted control planes uses haproxy for the local proxy, which only forwards packets via TCP. When a proxy is needed, hosted control planes uses a custom proxy, control-plane-operator-kubernetes-default-proxy, to send traffic through the external proxy.

Management clusters that need external access

The HyperShift Operator has a controller that monitors the OpenShift global proxy configuration of the management cluster and sets the proxy environment variables on its own deployment. Control plane deployments that need external access are configured with the proxy environment variables of the management cluster.

Additional resources