DoT listener IPv6 Support

[brotaxt]

Hey, does the dot listener supports IPv6? I'm using the following configuration but the response from routedns is always running over ipv4!?

  address = "[::]:853"
  protocol = "dot"
  resolver = "local_resolver"
  server-crt = "/opt/routedns/fullchain.pem"
  server-key = "/opt/routedns/privkey.pem"

[folbricht]

Looks like it doesn't at the moment based on https://github.com/folbricht/routedns/blob/master/dotlistener.go#L31, but that's an easy fix.

[folbricht]

The current implementation always listens on both, so if you use address = ":853" it'll be accepting connections over IPv4 as well as IPv6

[folbricht]

The issue-355 branch adds a new option for listeners ip-version = 6 that can be used to only use IPv6. This should work for DoT as well as plain DNS listeners (tcp and udp).
Not quite sure yet if this is the right thing to do, but feel free to test it out.

[brotaxt]

This version does not start without ip-version parameter defined for all listeners
routedns[9679]: Error: ip-version must be 4 or 6

[folbricht]

Thanks, fixed that