Consistently implement an interface to provide a `Virtual IP` resource to be consumed across all networking resources

[balpert89]

Summary

A NetworkInterface exposes the possibility to configure either a predefined Virtual IPresource or have it ephemerally managed by a template configuration (see https://github.com/ironcore-dev/ironcore/blob/main/api/networking/v1alpha1/networkinterface_types.go#L50-L56).

Other Networking resources such as Loadbalancers or NATGateways do not expose such an interface and therefore it is not possible to attach a predefined Virtual IP to said resources. Here we request to introduce the same contract consistently across relevant Networking resources.

Basic example

This example shows the configuration for a NATGateway to define an ephemerally managed Virtual IP. This definition is the same as omitting the configuration altogether as a NATGateway always has a public IP address allocated. The difference here is that claiming this public IP address is done by creating and claiming a Virtual IP resource.

apiVersion: networking.ironcore.dev/v1alpha1
kind: NATGateway
metadata:
  name: nat-gw
spec:
  ipFamily: IPv4
  networkRef:
    name: network
  portsPerNetworkInterface: 1024
  type: Public
  virtualIP:
    ephemeral:
      virtualIPTemplate:
        metadata:
          creationTimestamp: null
        spec:
          ipFamily: IPv4
          type: Public

The next example shows the configuration of a predefined Virtual IP resource named vip:

apiVersion: networking.ironcore.dev/v1alpha1
kind: NATGateway
metadata:
  name: nat-gw
spec:
  ipFamily: IPv4
  networkRef:
    name: network
  portsPerNetworkInterface: 1024
  type: Public
  virtualIP:
    virtualIPRef:
      name: vip

Motivation

Very strict configuration for e.g. VPN setups with well-defined IP addresses require the possibility to configure an exact prefix for Networking resources.