Fix(ipv6): support ipv6 shortener and expander equal

[dongjiang1989]

Description

Fixes #4326

Support Short and Long IPv6 addresses to be recognized as the same.

Checklist

• Unit tests updated
• End user documentation updated

[k8s-ci-robot]

Hi @dongjiang1989. Thanks for your PR.

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[dongjiang1989]

cc @d-honeybadger

[dongjiang1989]

/ok-to-test

[k8s-ci-robot]

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[mloiseleur]

/ok-to-test

[mloiseleur]

@dongjiang1989 🤔 Instead of keeping it as a string, wdyt of storing it as Addr instead of string ?

[dongjiang1989]

@dongjiang1989 🤔 Instead of keeping it as a string, wdyt of storing it as Addr instead of string ?

Thanks for your review. @mloiseleur
Hmmm... In my opinion, it is more appropriate to use string type for Target. Target is not only Addr, but also domain type, link example.org

[mloiseleur]

Mmmh You're right, it's not a good idea to replace string with Addr, considering its usage.

Nonetheless, with this PR + the existing code in IsLess, it may call ParseAddr many times for the same target.
So let's give us one more chance to avoid that. I have an other idea.

Wdyt about converting Target from a string to a struct with a string and Addr* ?
It would mean it may use Addr when it's relevant and keep string comparison when it's not an IP ?

[szuecs]

this looks wrong, if t[j] is not parseable, or ?

Example which would be wrong:

t[j] := 2600.com 
t[i] := 1.1.1.1 // or use 3.3.3.3 if the dot1 is the one that is good

[dongjiang1989]

Sorry. I don't understand it.Less just for sort[]Target.
Add new unittest case, PTAL recheck, thanks.
ref: f3c1e32

[dongjiang1989]

Mmmh You're right, it's not a good idea to replace string with Addr, considering its usage.

Nonetheless, with this PR + the existing code in IsLess, it may call ParseAddr many times for the same target. So let's give us one more change to avoid that. I have an other idea.

Wdyt about converting Target from a string to a struct with a string and Addr* ? It would mean it may use Addr when it's relevant and keep string comparison when it's not an IP ?

Thanks. I Got it. Change Targets []string to Targets []struct, impact on use of IsLess(x Targets) and Same(x Targets) methods. Maybe merge it first, I'll add a follow-up PR to change it to struct and change all provider usage.
@mloiseleur Wdyt? or change it in this PR?

[mloiseleur]

It's better to do it in one PR, so yes, in this PR.

[mloiseleur]

@dongjiang1989 In fact, we have discussed of this PR with @szuecs .

Even if it will increase cpu time, on external-dns we should focus to keep the state as tiny and simple as possible.

So this PR is good as it is currently. Thanks.

/lgtm

[szuecs]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: szuecs

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[dongjiang1989]

Thanks. I'll add a follow-up PR