Prefer IPv6 over IPv4 during endpoint resolution

[userunkn4wn]

I know this repository is only a mirror, but I would still like to use this pull request to start a discussion.

I noticed that WireGuard on iOS appears to prefer IPv4 DNS records over IPv6 records. This behavior is not suitable for my use case and may reflect a more traditional or legacy address-selection approach.

The proposed change demonstrates one possible way to prefer IPv6 over IPv4:

1. First, resolve the hostname using AF_INET6 together with AI_ADDRCONFIG.
2. If a usable IPv6 address is returned, use it as the resolved endpoint.
3. Otherwise, fall back to the original resolution logic, which prefers IPv4.

Please note that AI_ADDRCONFIG does not verify actual IPv6 connectivity. It only ensures that IPv6 results are returned when IPv6 is configured on the local system.

This code has not been tested because I do not currently have access to the Apple Developer Program. I would therefore appreciate feedback, testing, or suggestions for a better implementation.

I would also be interested in discussing whether there are still technical reasons for preferring IPv4 over IPv6 on current iOS versions.

[celyr]

+1, if not this at least give us an option to prefer ipv6 if available!