Unable to set or at least view additional http response headers via ResponseHeaderModifier

[davildaran]

Description:
I am setting a filter ResponseHeaderModifier for an HTTPRoute resource but am not seeing the additional headers in the response with a verbose output.

Here is a snippet of the configuration

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
...
    filters:
    - type: ResponseHeaderModifier
      responseHeaderModifier:
        add:
        - name: Content-Security-Policy
          value: default-src 'self' 
        - name: Strict-Transport-Security
          value: max-age=31536000; includeSubDomains; preload
        - name: X-Content-Type-Options
          value: nosniff

Then curl -v <http://...> returns

* Request completely sent off
< HTTP/1.1 200 OK
< Content-Type: application/json; charset=utf-8
< Date: Wed, 05 Feb 2025 18:49:12 GMT
< Content-Length: 7

I would have expected but I may be misunderstanding the filter modifier?

* Request completely sent off
< HTTP/1.1 200 OK
< Content-Type: application/json; charset=utf-8
< Date: Wed, 05 Feb 2025 18:49:12 GMT
< Content-Length: 7
< Content-Security-Policy: default-src 'self' 
< Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
< X-Content-Type-Options: nosniff

[optional Relevant Links:]
Envoy proxy adding response headers

Using envoy v 1.1.x

[zirain]

can you try with latest version, there're serval tests around ResponseHeaderModifier in conformance test.