socketry/rubydns

#!/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(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