Fix PowerDNS regex domain filter

[matusf]

Description
Regex domain filter stopped working because MatchParent method was invoked during zone partitioning. The failure occured because MatchParent included wrong zones (zones not matcing the regex) in the filtered list. Subsequently listing of those zones failed because the pdns client did not have api token with permissions to list them.

To fix this issue I disabled MatchParent functionality when matching domain using regex domain filter because MatchParent is a specific "extension" of domain filter.

Fixes #3816

Checklist

• Unit tests updated
• End user documentation update

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[mloiseleur]

It's a missing a test on domain_filter, to ensure this issue won't happen again.

[matusf]

It's a missing a test on domain_filter, to ensure this issue won't happen again.

@mloiseleur, shall I test that MatchParent returns false if the regex domain filter is set? The Match function returned correct results even before this fix. The issue was that PowerDNS provider always calls MatchParent if Match fails (here).

[mloiseleur]

@matusf Then ... 🤔 why don't you remove the invalid call on PowerDNS provider, then ?

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• ✅ login: matusf / name: Matúš Ferech (d5a1ed7, 4b771e9, 68e0451, 0df91c4)

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: matusf, mloiseleur
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[matusf]

/retest-required
Running retest required to rerun failed test. the test failed because of missing golangci-lint. This PR did not change anything regarding golangci-lint, so it may be a flaky test.

[k8s-ci-robot]

@matusf: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest-required
Running retest required to rerun failed test. the test failed because of missing golangci-lint. This PR did not change anything regarding golangci-lint, so it may be a flaky test.

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[matusf]

/cc @johngmyers @njuettner
Hi, could you please review my changes?

[mloiseleur]

@matusf The CI has been fixed with #3829. If you rebase this PR, CI should be able to pass as expected.

[matusf]

Thanks @mloiseleur, I rebased.

[mloiseleur]

/lgtm
/ok-to-test

[johngmyers]

Why are we putting the check for being a regex filter in the caller? Shouldn't it be in MatchParent like it is in Match? Then we wouldn't have to make IsRegexFilterConfigured public.

[matusf]

Firstly I put the check in the MatchParent function but then mloiseleur suggested to put it in a caller.

[johngmyers]

That's not how I interpreted that comment. I interpret it as asking why pdns is calling MatchParent at all. Perhaps @mloiseleur could clarify.

[mloiseleur]

That's not how I interpreted that comment. I interpret it as asking why pdns is calling MatchParent at all.

Yes, exactly. It seems weird to have only pdns calling MatchParent. I have not (yet) understood why it's called.

[matusf]

The MatchParent functions matches a zone if the zone is a parent zone of the filter. This functionality is only enabled in pdns provider. The implementation is a bit unfortunate, since now pdns diverges from other providers. It caused issues like breaking domain filter when trying to match one zone #3822.

For example --domain-filter=example.com will fail to match zone example.com in pdns provider (because it calls MatchParent and one might not have pdns api key with permissions for the parent zone), but it will work with every other provider (because it will not call MatchParent).

To disable this behaviour, one needs to prefix the filter with dot .. But this does not work as well because Match function treats the dot as a part of the filter and not as a "flag" to disable matching parent. As a result domain filter is broken for pdns as well.

I would suggest removing the MatchParent functionality, bacause as I said, it breaks existing filters, makes pdns behave differently than any other provider even though they have the same configuration, and the MatchParent functonality can be replaced by specifying multiple domain filters. It is also used by only one provider. I would volunteer to make this change.

Another approach might be to create a new cli flag to enable the match parent functionality and do not piggyback on the domain filter. This would also solve the abovementioned challenges.

[mhanc]

Hello, thanks for the analysis @matusf . I can confirm, that removing the MatchParent function would resolve #3822 (while making the pdns provider work the same as the rest of providers).

[mloiseleur]

@matusf @mhanc I agree with you. We should remove this MatchParent functionnality and align this provider with the others.

[matusf]

Ok, shall I remove it as part of this PR (and thereby fix the regex domain filter)?

[johngmyers]

I suppose there isn't a good way to mark MatchParent as deprecated.

I wouldn't oppose removing the functionality. We'd have to announce the behavior change in the relevant release.

[matusf]

I created new PR (#3869) which supersedes this one. It deletes the MatchParent functionality.

[mloiseleur]

/close

[k8s-ci-robot]

@mloiseleur: Closed this PR.

In response to this:

/close

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