* Add DNS list argument for mobile client
* Write testable code
Many places are checked the wgInterface != nil condition.
It is doing it just because to avoid the real wgInterface creation for tests.
Instead of this involve a wgInterface interface what is moc-able.
* Refactor the DNS server internal code structure
With the fake resolver has been involved several
if-else statement and generated some unused
variables to distinguish the listener and fake
resolver solutions at running time. With this
commit the fake resolver and listener based
solution has been moved into two separated
structure. Name of this layer is the 'service'.
With this modification the unit test looks
simpler and open the option to add new logic for
the permanent DNS service usage for mobile
systems.
* Remove is running check in test
We can not ensure the state well so remove this
check. The test will fail if the server is not
running well.
* Disable upstream DNS resolver after several tries and fails
* Add tests for upstream fails
* Use an extra flag to disable domains in DNS upstreams
* Fix hashing IPs of nameservers for updates.
Added host configurators for Linux, Windows, and macOS.
The host configurator will update the peer system configuration
directing DNS queries according to its capabilities.
Some Linux distributions don't support split (match) DNS or custom ports,
and that will be reported to our management system in another PR
