allow coredns override extensions

[ghost]

Proposed Changes

Allow CoreDNS override extensions in default Corefile

Other K8s implementations such as AKS[1] and DigitalOcean[2] have similar configuration

This would enable ConfigMaps to adjust the CoreDNS settings without creating a whole copy of coredns.yaml.

1: https://learn.microsoft.com/en-us/azure/aks/coredns-custom
2: https://docs.digitalocean.com/products/kubernetes/how-to/customize-coredns/

Types of Changes

New Feature

Verification

1. Patch Corefile with import /etc/coredns/custom/*.override in the .:53 default server block
2. Create a coredns-custom ConfigMap with some custom settings for the default server block, e.g. rewrite name substring svc.example.com svc.cluster.local
3. Restart CoreDNS pod
4. Test that the custom config has taken effect. For my example, run nslookup my-pod.my-svc.my-namespace.svc.example.com or getent hosts ... in a pod and confirm it resolves to the same name as my-pod.my-svc.my-namespace.svc.cluster.local

Testing

Linked Issues

• Allow adding configuration to coredns .:53 block via *.override keys in coredns-custom ConfigMap #7639

User-Facing Change

Further Comments

[brandond]

Thanks for the PR! You need to make download generate and check in the resulting changes.

[cwayne18]

Also as a CNCF project we need to have commits signed, can you please make sure to commit with -s so the DCO check passes? Thanks a lot for the PR!

[ghost]

Thanks for checking @cwayne18 @brandond. I've just updated the commit with my signature and checked in the re-generated Go artifact.

[brandond]

@andrewroffey your commits are signed (-S/--gpg-sign), but not signed off (-s/--signoff). DCO requires signoff, not signature.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.17 ⚠️

Comparison is base (d069a85) 47.71% compared to head (71b5001) 47.55%.

❗ Current head 71b5001 differs from pull request most recent head 6872eb6. Consider uploading reports for the commit 6872eb6 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7583      +/-   ##
==========================================
- Coverage   47.71%   47.55%   -0.17%     
==========================================
  Files         140      140              
  Lines       14284    14284              
==========================================
- Hits         6816     6793      -23     
- Misses       6399     6413      +14     
- Partials     1069     1078       +9     

Flag	Coverage Δ
inttests	44.91% <ø> (-0.17%)	⬇️
unittests	19.83% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/deploy/zz_generated_bindata.go	51.49% <ø> (ø)

... and 6 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
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[ghost]

@andrewroffey your commits are signed (-S/--gpg-sign), but not signed off (-s/--signoff). DCO requires signoff, not signature.

@brandond oops, third time lucky, TIL about the -s flag. I've updated that with both this time.

[dereknola]

We are still in code freeze for May releases, but this will get in after that, should be in all June releases.

[cwayne18]

Thanks a lot for the PR, and for signing your commits :) Like Derek said we'll get this in as soon as code freeze is thawed

[ghost]

Cheers! That's just around the corner, sounds great.