How do I set the kgateway LoadBalancer to RequireDualStack?

[tomalexander]

I have a self-hosted kubernetes cluster with cilium for the CNI, MetalLB for the IPAM, and kgateway for the gateway controller. If I deploy a test nginx service and expose it through a gateway:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  namespace: default
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - image: nginx
          name: nginx
---
apiVersion: v1
kind: Service
metadata:
  name: nginx
  namespace: default
  labels:
    app: nginx
spec:
  ipFamilyPolicy: RequireDualStack
  ipFamilies:
    - IPv6
    - IPv4
  ports:
    - name: http
      port: 80
      protocol: TCP
      targetPort: 80
  selector:
    app: nginx
  type: ClusterIP
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: nginx-gateway
  namespace: default
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-stg
spec:
  gatewayClassName: kgateway
  listeners:
    - name: http-1
      protocol: HTTP
      port: 80
      hostname: "my.subdomain.here"
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: https-app-route-1
  namespace: default
spec:
  parentRefs:
    - name: nginx-gateway
  hostnames:
    - "my.subdomain.here"
  rules:
    - matches:
        - path:
            type: PathPrefix
            value: /
      backendRefs:
        - name: nginx
          port: 80

Then that creates a LoadBalancer named nginx-gateway which is configured as:

  ipFamilies:
  - IPv6
  ipFamilyPolicy: SingleStack

I can manually patch that LoadBalancer to dual stack, and then it gets both an ipv4 and ipv6 address and everything works:

kubectl patch svc nginx-gateway -p '{"spec": {"ipFamilyPolicy": "RequireDualStack","ipFamilies":["IPv6","IPv4"]}}'

I'm under the impression that kgateway, as the gateway API controller, is creating the LoadBalancer resource, but I cannot find a setting in kgateway to tell it to create a dual stack LoadBalancer instead of a single stack one.

I've found the controller.service.ipFamilyPolicy setting in the helm chart but based on the name, I'm guessing that is meant to configure the controller's service rather than the LoadBalancers that the controller creates (I haven't tested it myself since that helm option has not been part of a stable release yet).

Searching the docs for "ipFamilyPolicy", "ipFamilies", "RequireDualStack", "PreferDualStack", "dual stack" turned up nothing except for "dual stack" returning some open telemetry pages.

Grepping for ipFamilyPolicy in the kgateway repo only turned up the helm chart and some test files.

Searching for "ipFamilies" in discussions, pull requests, and issues didn't turn up anything that seemed relevant (except for this issue which might be tangentially related but it seems to be more about health checks rather than about setting up dual stack LoadBalancers).