my-dns-resolver.rb

my-dns-resolver.rb

#!/usr/bin/env ruby

# Purpose : Extremely stupid dns resolver for laptop
# Author  : Ky-Anh Huynh
# License : MIT

# Requirements
#
#   * dnscrypt-proxy, or another upstream listen on 127.0.0.1:52
#   * NetworkManager
#   * Enable this dns resolver and make /etc/resolv.conf immutable
#      ( rm /etc/resolv.conf; echo nameserver 127.0.0.1 > /etc/resolv.conf; chattr +i /etc/resolv.conf ;)
#
# Dealing with captive portal (Remember to remove them after you're connected :D)
#
#   $ sudo touch /root/enable_isp
#

require 'rubydns'

LISTEN_PORT = (ENV["MDNS_PORT"].to_s.empty? ? 53 : ENV["MDNS_PORT"].to_i)
# Where we are listening on
INTERFACES = [
  [:udp, "0.0.0.0", LISTEN_PORT],
  [:tcp, "0.0.0.0", LISTEN_PORT],
]

# Alias
IN = Resolv::DNS::Resource::IN

# The main upstream
UPSTREAM = RubyDNS::Resolver.new(
  [
    [:udp, "127.0.0.1", 52],
    [:tcp, "127.0.0.1", 52],
  ])


# To use the ISP/router resolvers, just touch a file
#   $ sudo touch /root/enable_isp
#
# FIXME: We don't have cache here, so it's a bit slow ;)
def next_upstream
  isp_resolv_conf = "/run/NetworkManager/resolv.conf"
  resolvers = []
  if File.exist?("/root/enable_isp") and File.exist?(isp_resolv_conf)
    STDERR.puts "using isp dns resolvers..."
    lines = File.open(isp_resolv_conf, "r").readlines
    lines.each do |line|
      if gs = line.match(/^nameserver (.+)/)
        STDERR.puts "found isp dns resolver: #{gs[1]}"
        resolvers << gs[1]
      end
    end
  end
  if resolvers.size > 0
    STDERR.puts "using upstream: #{resolvers}"
    ret = RubyDNS::Resolver.new(resolvers.map{|ip| [:udp, ip, 53]})
  else
    STDERR.puts "using default upstream on your localhost"
    ret = UPSTREAM
  end
  return ret
end

RubyDNS::run_server(INTERFACES) do
  # This is just an example for fun
  match("incoming.telemetry.mozilla.org") do |t|
    t.respond!("127.0.0.1")
  end

  # Your own domains
  match(%r{kyanh.net}, IN::A) do |t|
    my_ip = "192.168.192.168"
    my_ip = "127.0.0.1"
    STDERR.puts "client #{t.options[:remote_address].ip_address} asked #{t.question} got #{my_ip}"
    t.respond!(my_ip)
  end

  otherwise do |t|
    t.passthrough!(next_upstream)
  end
end