Adguardhome: Consider using "REFUSED" or "Null IP" instead of NXDOMAIN by default

[ameshkov]

It seems that Firefox may query CF DOH when it encounters NXDOMAIN. Also, we've seen strange behavior on iOS as well.

I don't like using null IP as the default though as it may interfere with a server running locally. Let's experiment with REFUSED.

[ameshkov]

@szolin

All my experiments showed that the only approach that works 100% and does not lead to any issues with browsers using different fallbacks is "null IP".

So here's what I propose:

1. Change default to: Default: Respond with zero IP address (0.0.0.0 for A; :: for AAAA) when blocked by Adblock-style rule; respond with the IP address specified in the rule when blocked by /etc/hosts-style rule
2. Don't forget to change the English strings
3. Make sure that the strings are updated in Crowdin

[loyingEcu]

I can't filter ads when I use an Android device?

[EntropySmoke]

Why change it for AdGuard Home and not AdGuard for Android?

[ameshkov]

In the case of AdGuard for Android, we are sure that Android won't fallback to a different DNS server when it encounters an NXDOMAIN response. This is not the case with AGH, depending on how DNS is configured, the system may choose to fallback to a different DNS server.