feat(source): allow to register all pods and their associated PTR record

[foyerunix]

Hello,

We have deployed multiples Kubernetes clusters on-premise. Our cluster use Cilium CNI with SNAT disabled. This mean the pods traffic will exit the cluster with their pod IP and not with the node IP (the pod IPs are then correctly routed back to Kubernetes).

This is useful for us as a SRE team as we can track easily which pod is making which connection.
The drawback is that we still have to check on Kubernetes the pod which is associated with a particular IP.

As external-dns already implemented the pod source and the creation of PTR record, I thought it would be easy to register the pods PTR record in the DNS. But the pod source seem to has been made for a very precise use case relating to kops.

I therefore implemented two new options for our use case:

• --ignore-non-host-network-pods
• --pod-source-domain

The first let us create DNS records for pods even if they aren't running with host networking enabled.
The second allow us to build a pod FQDN with a default domain even without annotations.

I'm hesitating to combine the two as only one option ("--all-pods-domain" ?) that would then bypass the original intended use case for the pod source. I worry that the combination of the kops use case and mine in the same configuration will lead to an absurd behavior. But what if someone have a legitimate use for this ?

Please can you give me your opinion on the current implementation or if you would want to refactor it in another way.

Best Regards.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: foyerunix (bf8c4c0)

[k8s-ci-robot]

Welcome @foyerunix!

It looks like this is your first PR to kubernetes-sigs/external-dns 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes-sigs/external-dns has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @foyerunix. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-triage-robot]

The Kubernetes project currently lacks enough contributors to adequately respond to all PRs.

This bot triages PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the PR is closed

You can:

• Mark this PR as fresh with /remove-lifecycle stale
• Close this PR with /close
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale

[foyerunix]

/remove-lifecycle stale

[mloiseleur]

/ok-to-test
@foyerunix The code LGTM. Would you please include in this PR documentation changes on docs/annotations/annotations.md and docs/tutorials/kops-dns-controller.md that are in #3174 ?

[foyerunix]

Hello @mloiseleur,

I included the requested documentation changes and I fixed the failing test.

Best Regards.

[mloiseleur]

/retitle feat(source): allow to register all pods and their associated PTR record

[foyerunix]

Hello @mloiseleur,

Thanks for your input.
I included it, fixed a linting issue, and squashed everything.

Best Regards.

[mloiseleur]

/lgtm

[ivankatliarchuk]

From the implemenentation no question. Looks ok.

But there are concerns around actual feature itself related but there is a problem on how certain things where implemented.

1. Why was #3588 merged? #4566
2. IPv6 internal node IPs are usable externally #3588
3. feat: allow pod IPs even for non-hostNetwork pods #3174
4. Revert #3588 "IPv6 internal node IPs are usable externally" #4574

[ivankatliarchuk]

I might missing or, not clear from flags itself.

What if I don't want this behaviour in my current setup? Will it work as is if I'm not adding any of this tags?

[ivankatliarchuk]

/assign

[foyerunix]

Hello @ivankatliarchuk,

My PR should not change the current behavior if we don't set the --no-ignore-non-host-network-pods flag. If I did change the current behavior, I would consider this an error that I have to fix.

Regarding the debate on whether IPv6 internal node IPs should be parsed as external also, I don't have a strong opinion, especially as I run an IPv4-only stack. However, I fail to see why my PR would change the current behavior for IPv6 nodes and pods.

As for PR #3174, I understood that the issue pointed out by @szuecs was that it wasn't properly shielded against a change in the current behavior, as it didn't have a feature flag to enable it. Therefore, a user who mistakenly set the annotation on some pods would have seen them being processed by External-DNS. Something that could happen for example in an Helm chart mixing HostNetwork and non-Hostnetwork pods.

Best Regards.

[ivankatliarchuk]

/lgtm

cc: @mloiseleur

[mloiseleur]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ivankatliarchuk, mloiseleur

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [mloiseleur]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment