Contour ignores key field of genericKey for global rateLimitPolicy

[SimonVHB]

What steps did you take and what happened:
When applying a rateLimitPolicy on an HTTPProxy using a genericKey entry, the key field of the genericKey is ignored and the default value (generic_key) is passed on to the RLS.

Example configuration (using a kuard deployment as example and the envoy ratelimit service).

HTTPProxy

apiVersion: projectcontour.io/v1
kind: HTTPProxy
metadata:
  name: kuard
  labels:
    app: kuard
spec:
  virtualhost:
    fqdn: local.projectcontour.io
    rateLimitPolicy:
      global:
        descriptors:
          - entries:
            - genericKey:
                key: foo
                value: bar
  routes:
  - services:
    - name: kuard
      port: 80

Envoy ratelimit config

domain: contour
descriptors:
  - key: foo
    value: bar
    rate_limit:
      unit: minute
      requests_per_unit: 100

Envoy ratelimit debug logs

level=debug msg="starting cache lookup"
level=debug msg="returning normal response"
level=debug msg="got descriptor: (generic_key=bar)"
level=debug msg="starting get limit lookup"
level=debug msg="looking up key: generic_key_bar"
level=debug msg="looking up key: generic_key"
level=debug msg="descriptor does not match any limit, no limits applied"

What did you expect to happen:
Contour should set the genericKey key value properly and pass that value on to the RLS.
The RLS should get the following descriptor:

descriptor: (foo=bar)

instead of

descriptor: (generic_key=bar)

Anything else you would like to add:
This happens for a RL policy defined on the virtualhost as well for a RL policy defined at the route.

Environment:

• Contour version: v1.13.1
• Kubernetes version: (use kubectl version): v1.19.4+k3s1
• Kubernetes installer & version: k3d
• Cloud provider or hardware configuration: k3d local test cluster
• OS (e.g. from /etc/os-release): /

[skriss]

👀