provide option to include private IP addresses

[tylervick]

Hello!

I use caddy-dynamicdns to enable ddns on my private network/VPN (via Tailscale). Unfortunately, the change in #61 regresses my use case since private IPs are no longer returned by ip_source interface.

I'm able to work around this with a custom caddy module to provide a new IPSource. However, after seeing @jm355 call out my exact use case #59 (comment)_ I wanted to track this for posterity should anyone else run into this!

@Monviech's suggestion in #59 to include a include_private_ips flag sounds good to me. I'm happy to get started on a PR, unless maintainers have a better idea 🙂

[mholt]

Heh, I guess that will work then. 👍 Want to submit a PR?

[jm355]

I'm not sure what happens if both a public and private ip gets returned. Based on the name include_private_ips, I'm guessing it would return both, so maybe calling it something else like only_private_ips and only returning a private ip might be better? Just a minor nitpick/pointer, and it's been a while since I looked at this so I'm not sure

[mholt]

Good point. It's almost like you'd need to toggle public/private, but not have both.