conformance: add BackendRef URLRewrite and RequestRedirect tests

[Srujan-rai]

Summary

• Add SupportHTTPRouteBackendURLRewrite feature constant and conformance test for URLRewrite filter on HTTPBackendRef (fixes conformance - HTTPBackendRef Filter HTTPRouteFilterURLRewrite #2937)
• Add SupportHTTPRouteBackendRequestRedirect feature constant and conformance test for RequestRedirect filter on HTTPBackendRef (fixes conformance - HTTPBackendRef Filter HTTPRouteFilterRequestRedirect #2936)
• Tests cover ReplaceFullPath and ReplacePrefixMatch for each filter type applied via backendRef.filters (not rule-level)

Motivation

Issues #2937 and #2936 identified missing conformance tests for URLRewrite and RequestRedirect filters at the HTTPBackendRef level. Rule-level redirect is already tested, but BackendRef-level filters are structurally different and require their own test coverage.

Changes

• pkg/features/httproute.go: two new Extended features + entries in HTTPRouteExtendedFeatures
• conformance/tests/httproute-backend-url-rewrite.{go,yaml}: new test pair
• conformance/tests/httproute-backend-request-redirect.{go,yaml}: new test pair

Add conformance tests for URLRewrite and RequestRedirect filters at HTTPBackendRef level (HTTPRouteBackendURLRewrite, HTTPRouteBackendRequestRedirect extended features)

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @Srujan-rai. Thanks for your PR.

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[snorwin]

@Srujan-rai, I noticed this PR also includes the changes from #4811. It would be helpful to keep them separate if possible.

[Srujan-rai]

@Srujan-rai, I noticed this PR also includes the changes from #4811. It would be helpful to keep them separate if possible.

Thanks for catching that @snorwin The branch was based on my local main which already had the GRPCRoute commit. I've rebased httproute-backend-filters onto upstream main PR now contains only the BackendRef URLRewrite/RequestRedirect changes.

[snorwin]

@Srujan-rai were you able to validate the new tests against a Gateway API implementation? If so, could you let us know which one?

[Srujan-rai]

@Srujan-rai were you able to validate the new tests against a Gateway API implementation? If so, could you let us know which one?

@snorwin
I Tested against [Envoy Gateway v1.4.1]on [Google Kubernetes Engine (GKE)] running Kubernetes v1.35. The conformance suite initialized successfully, and both tests executed as expected.

Envoy Gateway returned ResolvedRefs=False with the reason UnsupportedRefValue:

"Specific filter is not supported within BackendRef, only RequestHeaderModifier, ResponseHeaderModifier and gateway.envoyproxy.io/HTTPRouteFilter are supported."

This confirms that the tests are structurally correct and accurately detect that URLRewrite and RequestRedirect filters at the BackendRef level are not yet implemented in Envoy Gateway, which is the intended purpose of these conformance tests.

[snorwin]

@Srujan-rai it seems that Envoy Gateway isn't supporting this, can you try to test it with kgateway?

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Srujan-rai / name: Srujan rai (d7abb19)
• ✅ login: Srujan-rai / name: srujan-rai (5ba6d41)
• ✅ login: snorwin / name: Norwin Schnyder (d7abb19)

[Srujan-rai]

@Srujan-rai it seems that Envoy Gateway isn't supporting this, can you try to test it with kgateway?

Tested against kgateway v2.3.0-rc.2 as suggested. The HTTPRoute is accepted successfully (ResolvedRefs=True and the route is programmed), but the rewrite is not applied at the BackendRef level. Requests continue with the original path unchanged.

From what I could verify, both Envoy Gateway and kgateway currently only support RequestHeaderModifier and ResponseHeaderModifier filters at BackendRef scope.

That makes me wonder if there’s any implementation today that supports URLRewrite or RequestRedirect under backendRef.filters. The spec allows it, but if there isn’t an implementation supporting it yet, these conformance tests might be a bit early.

Happy to adjust the approach or pause the PR until support lands in an implementation.

[howardjohn]

Agentgateway supports this:

--- PASS: TestConformance (0.86s)
    --- PASS: TestConformance/HTTPRouteBackendRequestRedirect (0.12s)
        --- PASS: TestConformance/HTTPRouteBackendRequestRedirect/1_request_to_'/prefix/original'_should_receive_one_of_[] (0.01s)
        --- PASS: TestConformance/HTTPRouteBackendRequestRedirect/0_request_to_'/full/original'_should_receive_one_of_[] (0.01s)
PASS

[snorwin]

/easycla

[snorwin]

/ok-to-test