ClientSettingsPolicy does not work on HTTPRoutes with matching conditions

[kate-osborn]

Describe the bug
If you apply a policy to a route that has http matches with a method, params, or headers defined, the policy has no affect.

To Reproduce
Steps to reproduce the behavior:

1. Deploy edge (118488e) version of NGF
2. Apply the files from the advanced routing example.
3. Create the following policy:

apiVersion: gateway.nginx.org/v1alpha1
kind: ClientSettingsPolicy
metadata:
  name: tea
  namespace: default
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: tea
  body:
    maxSize: "50"

4. Send the following request to the tea application:

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/tea -X POST --data "this payload is greater than fifty bytes but less than seventy five"

Expected behavior
You should receive a 413 entity too large since the request body exceeds the limit

Your environment

• Version of the NGINX Gateway Fabric - edge 118488e

Additional context
The policy is correctly included in the named location block for the tea routes, but the directives are ignored by nginx. This seems to be a limitation of named locations in nginx.

For example, this config with named locations does not enforce the client max body size:

 server {
        listen 80;

        location / {
          try_files /dev/null @named;
        }

        location @named {
          client_max_body_size 50;
          return 200 "ok two";
        }
    }

however, if you change the named location to an internal location:

   server {
        listen 80;

        location / {
          try_files /dev/null /not-named;
        }

        location /not-named {
          internal;
          client_max_body_size 50;
          return 200 "ok two";
        }
    }

it does work.

[sjberman]

I'll add that I discovered this using the ObservabilityPolicy. Traces were not being sampled on requests going through the named locations (where otel_trace on; was set).