dns kube-dns doesn't expose service scoped dns names for pod IPs

Problem statement

As described in https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#a-aaaa-records-1:

Any Pods exposed by a Service have the following DNS resolution available: pod-ipv4-address.service-name.my-namespace.svc.cluster-domain.example

This is not the case for kube-dns. We're using (generating) those dns names from EndpointSlices for inter cluster communication between services. It does work with coredns.

This is relevant for a number of users since GKE by default uses kube-dns.

Usage of service scoped dns names is preferred because it allows for wildcard certificates like *.service-name.my-namespace.svc.cluster-domain.example to be used.

Proposed solution

Serve service scoped dns names.

May 22 '24 10:05 pmalek

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/lifecycle stale

Aug 20 '24 10:08 k8s-triage-robot

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/lifecycle rotten

Sep 19 '24 10:09 k8s-triage-robot

/remove-lifecycle rotten

Sep 19 '24 12:09 programmer04

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/lifecycle stale

Dec 18 '24 12:12 k8s-triage-robot

/remove-lifecycle stale

Dec 18 '24 12:12 pmalek

Seems like a bug in the documentation, as according to the DNS specification mentioned in the section linked in the issue, section 2.4.1, it's only provided for headless services (clusterIP: None) and with pod hostnames rather than IP addresses as the subdomain.

Dec 18 '24 15:12 Michcioperz

As @Michcioperz brought up, I wonder if kube-dns is supposed to provide these A records or if it's a bug in the docs. Perhaps a maintainer can comment if kube-dns will ever provide this functionality?

In the meantime, I made a PR to update the docs.

Jan 22 '25 21:01 davidxia

I'm in favor of changing the behavior to fulfill what OP described, because

CoreDNS that is popular does it
GKE Autopilot uses Cloud DNS which also behaves the same as CoreDNS

thus we're currently in Hyrum's Law to expect this behavior from the K8s cluster as a whole (no matter the underlying DNS and official specs, etc.)

Jan 23 '25 13:01 programmer04

Can you provide a repro Deployment+Service where CoreDNS and Cloud DNS do what OP described? I'm pretty confident that, like I said, Cloud DNS only does it for headless services.

Jan 23 '25 14:01 Michcioperz

I made tests and support for the availability of DNS resolution like e.g. 10-96-2-4.example-service.default.svc for Pods exposed by a Service depends on a DNS provider and it looks like that

	Cloud DNS	Core DNS	kube-dns
ClusterIP	❌	✔️	❌
Headless	✔️	✔️	❌

tested with the below configuration

apiVersion: apps/v1
kind: Deployment
metadata:
  name: example-deployment
  labels:
    app: example-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: example-app
  template:
    metadata:
      labels:
        app: example-app
    spec:
      containers:
        - name: example-container
          image: nginx:latest
          ports:
            - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: example-service
spec:
  clusterIP: None # To comment/un-comment
  selector:
    app: example-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80

Jan 23 '25 16:01 programmer04

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Apr 23 '25 16:04 k8s-triage-robot

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/lifecycle rotten

May 23 '25 16:05 k8s-triage-robot

/remove-lifecycle rotten

I still want to figure this out in free time

May 23 '25 17:05 Michcioperz

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Aug 21 '25 17:08 k8s-triage-robot

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Sep 20 '25 17:09 k8s-triage-robot

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/close not-planned

Oct 20 '25 17:10 k8s-triage-robot

@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

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/close not-planned

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Oct 20 '25 17:10 k8s-ci-robot