RubyDNS

RubyDNS is a tool that allows you to intercept and modify DNS requests. It can provide most typical DNS server functionality, including the ability to pull DNS records from any data source.

Documentation

  1. Installation
  2. Examples
  3. rd-dns-check
  4. rd-resolve-test
  5. Latest RDOC

Example

#!/usr/bin/env ruby

# Copyright (c) 2009 Samuel Williams. Released under the GNU GPLv3.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

require 'rubygems'

require 'rexec'
require 'rexec/daemon'

require 'rubygems'
require 'rubydns'

require 'timeout'

# UDP Socket does per packet reverse lookups unless this is set.
UDPSocket.do_not_reverse_lookup = true

Thread.abort_on_exception = true

# Run as user "dns"
RUN_AS="dns"

# Cache DNS entries for 5 minutes
CACHE_TIME=60*5

# We need to be root in order to bind to privileged port
if RExec.current_user != "root"
	$stderr.puts "Sorry, this command needs to be run as root!"
	exit 1
end

# Helper
Name = Resolv::DNS::Name

HARU_A = "10.0.0.80"
SCOOTER_A = "10.0.0.10"

# The Daemon itself
class Server < RExec::Daemon::Base
	@@var_directory = File.dirname(__FILE__)

	def self.run
		# Bind to port 53 (UDP)
		socket = UDPSocket.new
		socket.bind("0.0.0.0", 53)

		# Drop priviledges
		RExec.change_user(RUN_AS)

		# Don't buffer output (for debug purposes)
		$stderr.sync = true

		# Use upstream DNS for name resolution
		# Scooter DNS
		$R = Resolv::DNS.new(:nameserver => SCOOTER_A)

		$CACHE = {}

		# Start the RubyDNS server
		RubyDNS::run_server(:listen => [socket]) do
			@logger.level = Logger::INFO

			match(/(gems|git|svn).oriontransfer.org$/, :A) do |match, transaction|
				transaction.respond!(HARU_A)
			end

			match("haru.oriontransfer.org", :A) do |transaction|
				transaction.respond!(HARU_A)
			end

			match("80.0.0.10.in-addr.arpa", :PTR) do |transaction|
				transaction.respond!(Name.create("haru.oriontransfer.org."))
			end

			# Default DNS handler
			otherwise do |transaction|
				key = [transaction.name, transaction.resource_class]
				cache = $CACHE[key]

				if cache and (Time.now - cache[1]) < CACHE_TIME
					logger.info "Cached: #{transaction.name}..."
					transaction.answer.merge!(cache[0])
				else
					logger.info "Lookup: #{transaction.question.to_s}"
					transaction.passthrough!($R) do |reply, reply_name|
						$CACHE[key] = [reply, Time.now]
					end
				end
			end
		end
	end
end

# RExec daemon runner
Server.daemonize