Enable IPv6 in Unbound config by default

[ThomasKramps]

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What does this PR aim to accomplish?:

Wouldn't it be a good idea to enable IPv6 by now?

How does this PR accomplish the above?:

This PR changes the unbound config to enable IPv6 by default.

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[DL6ER]

What happens if the system doesn't have IPv6? They still happens a lot today, especially worth mentioning inside most docker containers.

[rdwebdesign]

As far as I know, docker IPv6 is disabled by default and even when enabled, some features are still considered experimental:

Also, it only works in Linux (it doesn't work on Docker Desktop for Windows/Mac)

Personally, I don't think this option should be set as default.

[ThomasKramps]

Hm, I wasn't aware of the docker situation. I'm using the normal Linux installation.

I just tested the suggested config in a docker container (without IPv6-Support) and had no issues. Everything still works fine.

[jameskimmel]

Seems like unbound also has it enabled by default.
https://unbound.docs.nlnetlabs.nl/en/latest/manpages/unbound.conf.html#server-options

[yubiuser]

I think there is no harm in enabling it. Unbound will be smart enough to re-send the query via IPv4 if there is no IPv6 connectivity.
I personally run unbound with do-ip6:yes as a docker container and it works fine.

[DL6ER]

Previously, we had it disabled because debug log level showed that it always tried to send via IPv6 and this caused a lot of timeouts on non-IPv6 setups. This may have changed. Together with prefer-ip6: no it should be fine as in: not do much if anything

[yubiuser]

@ThomasKramps this branch is out-of-date. Please rebase on 'master'

[ThomasKramps]

Rebranched on master. ”prefer-ipv6: no“ is still set. So ready to merge now?