Add $client modifier support

[ameshkov]

The idea is to allow adding rules for specific clients as easy as possible.

Spec

The $client modifier allows specifying clients this rule will be working for. It accepts both client names or IP addresses.

The syntax is:

$client=value1|value2|...

You can also specify "restricted" clients by adding a ~ character before the client IP or name. In this case, the rule will not be applied to this client's DNS requests.

$client=~value1

Specifying client names

Client names usually contain spaces or other special characters, that's why you should enclose the name in quotes (both double-quotes and single-quotes are supported). If the client name contains quotes, use \ to escape them. Also, you need to escape commas (,) and pipes (|).

Please note, that when specifying a "restricted" client, you must keep ~ out of the quotes.

Examples

• @@||*^$client=127.0.0.1 -- unblock everything for localhost
• ||example.org^$client='Frank\'s laptop' -- block example.org for the client named Frank's laptop only. Note that quote (') must be escaped.
• ||example.org^$client=~'Mary\'s\, John\'s\, and Boris\s laptops' -- block example.org for everyone except the client named Mary, John, and Boris. Note that comma (,) must be escaped as well.
• ||example.org^$client=~Mom|~Dad|Kids -- block example.org for Kids, but not for Mom and Dad. This example demonstrates how to specify multiple clients in one rule.