implement dnstap

[weyrick]

Implement support for https://dnstap.info

Unix domain sockets and TCP streams are supported. Sample config:

version: "1.0"

visor:
  taps:
    unix_dnstap:
      input_type: dnstap
      config:
        socket: "/tmp/dnstap.sock"
    tcp_dnstap:
      input_type: dnstap
      config:
        tcp: "127.0.0.1:53053"
  policies:
    mysocket:
      kind: collection
      input:
        tap: unix_dnstap
        input_type: dnstap
      handlers:
        modules:
          default_net:
            type: net
          default_dns:
            type: dns
    mytcp:
      kind: collection
      input:
        tap: tcp_dnstap
        input_type: dnstap
      handlers:
        modules:
          default_net:
            type: net
          default_dns:
            type: dns

There is also a new tool pktvisor-dnstap which is analogous to pktvisor-pcap and can read dnstap binary save files written by https://github.com/dnstap/golang-dnstap

[jroyalty]

Thanks for the heads up @weyrick