DNS filtering: block cloaked trackers

[ameshkov]

See the original task in the mobile API:
AdguardTeam/dnsproxy#76

[admitrevskiy]

Done. Testing instructions for QA:

• Reinstall AG
• Find some DNS upstream which has CNAME record for some host. For example:

dig @8.8.8.8 mail.google.com

should return CNAME record googlemail.l.google.com.

• Enable DNS filtering and select chosen upstream
• Add DNS filtering rule for CNAME:0.0.0.0 cname or ||cname^. For mail.google.com valid rule is ||googlemail.l.google.com^` (please note that cname record has a dot in the end. You shouldn't include this dot to the filtering rule)
• Try to reach selected domain

Expected result:

• Domain is blocked
• Go to the filtering log
• DNS request is blocked with CNAME filtering rule.

[TPS]

It seems not to be working clearly (correctly). IIUC, this is implemented in v3.3n25(166). However, my userfilter ||c. blocks m.media-amazon.com & images-na.ssl-images-amazon.com, but the log doesn't show how/why.…
Here's another: my ||trafficman unclearly blocks www.bing.com.

[admitrevskiy]

Done.
Original answer with CNAME was added to Filtering Log