conformance: Coverage for request routing to TLSRoute with no valid BackendRefs

[sunjayBhatia]

What would you like to be added:

As a follow up to #2076, we should add test coverage to the TLSRoute test in that PR that makes an assertion on what a client sees when making a connection/request that match a Gateway/TLSRoute with no valid backends (due to invalid ReferenceGrant etc.)

Before we add a test, the language here likely needs a little more specificity (and we should make sure to write tests that match the new language), particularly what "reject" means:

gateway-api/apis/v1alpha2/tlsroute_types.go

Lines 104 to 108 in a5ede12

	// sent. If unspecified or invalid (refers to a non-existent resource or
	// a Service with no endpoints), the rule performs no forwarding; if no
	// filters are specified that would result in a response being sent, the
	// underlying implementation must actively reject request attempts to this
	// backend, by rejecting the connection or returning a 500 status code.

"Reject" could mean:

• Connection refused, so nothing listening on the relevant Gateway Listener port (probably not the right answer, since you could have multiple hostnames for the same port)
• Server sends TCP RST (what Envoy/Contour will do if there the Listener port is open but no proxying set up)
• Specific TLS error (seems less likely to be uniform across all implementors)
• other ideas welcome

Why this is needed:

Full coverage of TLSRoute API surface.

Related to #1579

We can probably do something similar for TCPRoute

[shaneutt]

Sounds like a reasonable improvement.

/triage accepted

Given that this is about TLSRoute, it seems like something we can do after our GA release.

/priority backlog

[k8s-triage-robot]

This issue has not been updated in over 1 year, and should be re-triaged.

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/remove-triage accepted