Add the option to select blocking type

[admitrevskiy]

Please, add ability to select blocking type by analogue with go-dnsproxy and AG Home

There are several options:

• Default
  ||example.com^ rule should block both A and AAAA requests to example.com with NXDomain
  0.0.0.0 example.com rule should block both A and AAAA requests to example.com with unspecified ip (0.0.0.0 or [::]) response
  1.2.3.4 example.com should be used only for A requests to example.com

• NXDomain
  ||example.com^, 0.0.0.0 example.com should block both A and AAAA requests with NXDomain

• Unspecified IP
  ||example.com^, 0.0.0.0 example.com should block both A and AAAA requests with unspecified ip (0.0.0.0 or [::]) response

[sfionov]

1.2.3.4 example.com should be used only for A requests to example.com

Current /etc/hosts logic differs, if there is any host rule with specific IP, only this set of IPs will be used to resolve both IPv4 and IPv6 addresses.

So if /etc/hosts are:

1.2.3.4 example.org

A will return 1.2.3.4
AAAA will return no addresses, request will not be forwarded.
If /etc/hosts are:

1.2.3.4 example.org
1234::5678 example.org

A will return 1.2.3.4
AAAA will return 1234::5678

I think we should use this logic for specific IPs in host rules.

[ameshkov]

Please do it as explained here:
AdguardTeam/AdGuardHome#1284 (comment)

[sfionov]

So we should threat both "0.0.0.0" and "127.0.0.1" hosts records as blocking

[ngorskikh]

dns-libs/pull-requests/60