Add whitelist regex support

[DL6ER]

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10

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Implement regex support for the whitelist. Just as with blacklists, whitelist regex support is intended for few, specialized filters. For mass-whitelisting, the known exact whitelisting should be used*.

Regex whitelist filter will affect the entire blocking Pi-hole is performing:

• Gravity: Domains from the blocklists that a match whitelist regex filter will not be imported.
• Blacklist: Blacklisted domains that match a whitelist regex filter will not be imported.
• Regex blacklist: Domains matching both, blacklist and whitelist regex filters will be permitted as the whitelist is given a higher importance in FTL.

Using whitelist regex filters can slow down the startup process of FTL, however it can also result in improved performance when fewer blocking domains have to be imported.

Performance examples on a NanoPi NEO:

• No regex whitelist:

  Database (gravity): imported 114851 domains (took 3269.0 ms)  
  

• One regex whitelist filter (not matching):

  Database (gravity): imported 114851 domains (took 3707.6 ms)
  

• Five regex whitelist filter (none of them matching anything):

  Database (gravity): imported 114851 domains (took 4374.3 ms) 
  

• One whitelist regex (\.com$, matching all .com addresses):

  Database (gravity): imported 86736 domains (took 2182.2 ms)
  

  Note the reduced number of imported domains and the reduced time it takes to import gravity.

The used not-matching filters are long filters of medium complexity (containing a few character groups and alternations).

This pull request also adds eight new tests around blocking and whitelisting.

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*) Pi-hole v5.0 ships with a massively improved exact whitelist performance. Up to millions of domains on the whitelist are now possible even on low-end hardware.

[DL6ER]

Discourse feature request: Wildcard and regex support for whitelisting

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/filter-blocklist-on-update/21679/8

[dschaper]

Is this a WIP?

[DL6ER]

No, it is ready for review (and possible discussions based thereon).

[AzureMarker]

@DL6ER As this is ready to review, the core PR should also be made ready for review (un-draft).

Requested changes were made, will re-review once Core changes are finalized