feat(gateway) add support for gateway api experimental ListenerSet

[bmhughes]

What does it do ?

Support the use of ListenerSetswith Gateway API.

Motivation

Using Gateway API and TLS without ListenerSets requires either wildcard certs or all hosts to be known when creating the gateway, ListenerSets removes with requirement but external-dns does not support them currently.

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests
• Yes, I updated end user documentation accordingly

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[mloiseleur]

Would you please also complete the example just below accordingly?

[mloiseleur]

/ok-to-test

[coveralls]

Pull Request Test Coverage Report for Build 20622387398

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 165 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.1%) to 78.722%

---

Files with Coverage Reduction	New Missed Lines	%
apis/externaldns/types.go	1	99.62%
store.go	58	39.85%
gateway.go	106	79.39%

Totals
Change from base Build 20617539960:	-0.1%
Covered Lines:	15890
Relevant Lines:	20185

---

💛 - Coveralls

[szuecs]

Until gateway-api people have defined what to do for DNS we should stop changing. ListenerSet is likely the right thing to do, but not sure about the x-api. Likely gateway-api should stabilize the API before we change the DNS configuration sources.

[szuecs]

/hold likely we will not integrate HTTPRoute in the future , but ListenerSet as told by gateway-api. We should wait until they finalized the API and what external-dns should do to integrate.

[sfqzlm]

Hi Team,

With ingress-nginx reaching EOL and no further updates expected beyond March, many of us are actively migrating off the Ingress API and toward Gateway API as the long-term path.

In practice, Gateway API today still lacks a viable multi-tenancy story using only standard CRDs. The experimental ListenerSet (a.k.a. XListenerSet) is currently the only workable solution we’ve found for shared gateways with delegated ownership, especially when TLS and hostname isolation are required. We’ve successfully validated this model using Istio’s Gateway API implementation.

While ListenerSet is experimental, it’s rapidly becoming a de-facto building block. cert-manager has publicly acknowledged the gap and committed to adding ListenerSet support (targeting Feb):
https://cert-manager.io/announcements/2025/11/26/ingress-nginx-eol-and-gateway-api/#listenerset-the-missing-building-block

Without ExternalDNS support, ListenerSet-based Gateway API deployments remain incomplete for production use, forcing teams either to maintain custom DNS automation or to delay migration away from Ingress altogether.

Given the Ingress deprecation timeline and the ecosystem momentum around ListenerSet, I’d strongly encourage reconsidering the /hold. Even guarded or experimental support in ExternalDNS would meaningfully unblock real-world Gateway API adoption and align with the direction other core tooling (e.g., cert-manager) is already taking.

Happy to help test or validate behavior against Istio Gateway API if that’s useful.