Mesh Config controller is a pretty simple controller, reading from `ConfigMap`(s) (multiple if `SHARED_MESH_CONFIG` is used), processing and merging these into a the typed `MeshConfig`. It then exposes this over a simple `mesh.Watcher`, which just exposes a way to access the current `MeshConfig` and get notified when it changes.

#### Ingress

  held off after the release. Hiding/Showing documentation does not require TOC approval.
* Cases for other API changes require TOC approval
    * Simple `meshConfig` changes have been approved in the past. Functionality should not be enabled by default.
* For large API changes, 2 members of the TOC must approve the PR before release manager approval in the release branch

- Helm is for configuration that is expected to be set at install-time only. If the change is a dynamic runtime configuration, it probably belongs in the [MeshConfig API](https://github.com/istio/api/blob/master/mesh/v1alpha1/config.proto). This allows configuration without re-installing or restarting deployments.

		return err
	}
	if err != nil {
		// not found
		return nil
	}
	// found
	res := ObjectToInstance(svc)
	messages.Add(msg.NewUpdateIncompatibility(res,
		"meshConfig.defaultConfig.tracer", "1.21",
		"tracing is no longer by default enabled to send to 'zipkin.istio-system.svc'; "+
			"follow https://istio.io/latest/docs/tasks/observability/distributed-tracing/telemetry-api/",
		"1.21"))

		for port, mode := range pa.PerPort {
			fmt.Fprintf(writer, "      %d: %s\n", port, mode.String())
		}
	}
}

func getMeshConfig(kubeClient kube.CLIClient, istioNamespace string) (*meshconfig.MeshConfig, error) {
	rev := kubeClient.Revision()
	meshConfigMapName := istioctlutil.DefaultMeshConfigMapName

	// if the revision is not "default", render mesh config map name with revision