Proxy DNS with debug

dns_example.rb

# frozen_string_literal: true

require 'socket'
require 'resolv'

class DNSServer

  attr_reader :port, :ttl

  def initialize(port: 5300, ttl: 60, records: {})
    @port = port
    @ttl = ttl

    # DNS Database
    @records = records
  end

  def run
    puts "Starting DNS Server on port #{@port} ..."
    ::Socket.do_not_reverse_lookup = true
    @socket = UDPSocket.new
    @socket.setsockopt(::Socket::SOL_SOCKET, ::Socket::SO_REUSEADDR, 1)
    @socket.bind('localhost', port)
    @run = true

    # Try/Catch
    begin
      while @run
        packet, addr = @socket.recvfrom(65535)

        if (packet.length == 0)
          break
        end

        sock2 = ::UDPSocket.new()
        sock2.send(packet, 0, '1.1.1.1', 53)
        packet2, addr2 = sock2.recvfrom(65535)
        sock2.close()

        real_response = Resolv::DNS::Message.decode(packet2)

        real_response.each_question { |name, typeclass|
          puts "each_question: #{name} - #{typeclass}"
        }

        real_response.each_answer { |name, ttl, data|
          puts "each_answer: #{name} - #{ttl} - #{data}"

          # case data
          #   when Resolv::DNS::Resource::IN::A
          # end
        }

        real_response.each_authority { |name, ttl, data|
          puts "each_authority: #{name} - #{ttl} - #{data}"
        }

        # request = Resolv::DNS::Message.decode(packet)

        # message = ::Resolv::DNS::Message.new(SecureRandom.random_number(2**16))
        # message.rd = 1
        # message.id = request.id
        # message.add_question 'example.com.', Resolv::DNS::Resource::IN::A

        # response_packet = message.encode()

        # @socket.send(response_packet, 0, addr[3], addr[1])

        @socket.send(real_response.encode(), 0, addr[3], addr[1])
      end
    rescue Interrupt
      puts 'Got Interrupt !'
    ensure
      if @socket
        @socket.close
        puts 'Socket Closed !'
      end
      puts 'Quiting..'
    end
  end

end

records = {
  'example.com.' => [Resolv::DNS::Resource::IN::A, '1.2.3.4'],
  'google.com.' => [Resolv::DNS::Resource::IN::MX, 'example.com']
}

DNSServer.new(ttl: 120, records: records).run