#!/usr/bin/env ruby

# Copyright, 2009, 2012, by Samuel G. D. Williams. <http://www.codeotaku.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require 'rubygems'
require 'rubydns'
require 'rubydns/system'

# You can specify other DNS servers easily
# $R = Resolv::DNS.new(:nameserver => ["xx.xx.1.1", "xx.xx.2.2"])

R = RubyDNS::Resolver.new(RubyDNS::System.nameservers)
Name = Resolv::DNS::Name
IN = Resolv::DNS::Resource::IN
INTERFACES = [
	[:udp, '0.0.0.0', 5300],
	[:tcp, '0.0.0.0', 5300],
	# [:udp, '::0', 5300],
	# [:tcp, '::0', 5300],
]

RubyDNS.run_server(listen: INTERFACES) do
	# % dig +nocmd +noall +answer @localhost ANY dev.mydomain.org
	# dev.mydomain.org.	16000	IN	A	10.0.0.80
	# dev.mydomain.org.	16000	IN	MX	10 mail.mydomain.org.
	match(/dev.mydomain.org/, IN::ANY) do |transaction|
		transaction.append_question!

		[IN::A, IN::CNAME, IN::MX].each do |resource_class|
			logger.debug "Appending query for #{resource_class}..."
			transaction.append!(transaction.name, resource_class)
		end
	end

	# For this exact address record, return an IP address
	match('dev.mydomain.org', IN::A) do |transaction|
		transaction.respond!('10.0.0.80')
	end

	match('80.0.0.10.in-addr.arpa', IN::PTR) do |transaction|
		transaction.respond!(Name.create('dev.mydomain.org.'))
	end

	match('dev.mydomain.org', IN::MX) do |transaction|
		transaction.respond!(10, Name.create('mail.mydomain.org.'))
	end

	match(/^test([0-9]+).mydomain.org$/, IN::A) do |transaction, match_data|
		offset = match_data[1].to_i

		if offset > 0 && offset < 10
			logger.info "Responding with address #{'10.0.0.' + (90 + offset).to_s}..."
			transaction.respond!('10.0.0.' + (90 + offset).to_s)
		else
			logger.info "Address out of range: #{offset}!"
			false
		end
	end

	# Default DNS handler
	otherwise do |transaction|
		logger.info 'Passing DNS request upstream...'
		transaction.passthrough!(R)
	 end
end