RubyDNS

RubyDNS is a high-performance DNS server which can be easily integrated into other projects or used as a stand-alone daemon (via RExec). By default it uses rule-based pattern matching. Results can be hard-coded, computed, fetched from a remote DNS server or fetched from a local cache, depending on requirements.

In addition, RubyDNS includes a high-performance asynchronous DNS resolver built on top of EventMachine. This module can be used by itself in client applications without using the full RubyDNS server stack.

For examples and documentation please see the main project page.

Installation

Add this line to your application's Gemfile:

gem 'rubydns'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rubydns

Usage

This is copied from test/examples/test-dns-2.rb. It has been simplified slightly.

#!/usr/bin/env ruby
require 'rubydns'

INTERFACES = [
	[:udp, "0.0.0.0", 53],
	[:tcp, "0.0.0.0", 53]
]
Name = Resolv::DNS::Name
IN = Resolv::DNS::Resource::IN

# Use upstream DNS for name resolution.
UPSTREAM = RubyDNS::Resolver.new([[:udp, "8.8.8.8", 53], [:tcp, "8.8.8.8", 53]])

def self.run
    # Start the RubyDNS server
    RubyDNS::run_server(:listen => INTERFACES) do
        match(/test.mydomain.org/, IN::A) do |_host, transaction|
            transaction.respond!("10.0.0.80")
        end

        # Default DNS handler
        otherwise do |transaction|
            transaction.passthrough!(UPSTREAM)
        end
    end
end
run

Start the server using rvmsudo ./test.rb. You can then test it using dig:

$ dig @localhost test1.mydomain.org
$ dig @localhost dev.mydomain.org
$ dig @localhost google.com

Compatibility

Migrating from RubyDNS 0.3.x to 0.4.x

Due to changes in resolv.rb, superficial parts of RubyDNS have changed. Rather than using :A to specify A-records, one must now use the class name.

match(..., :A)

becomes

IN = Resolv::DNS::Resource::IN
match(..., IN::A)

Migrating from RubyDNS 0.4.x to 0.5.x

The system standard resolver was synchronous, and this could stall the server when making upstream requests to other DNS servers. A new resolver RubyDNS::Resolver now provides an asynchronous interface and the Transaction::passthrough makes exclusive use of this to provide high performance asynchonous resolution.

Here is a basic example of how to use the new resolver in full. It is important to provide both :udp and :tcp connection specifications, so that large requests will be handled correctly:

resolver = RubyDNS::Resolver.new([[:udp, "8.8.8.8", 53], [:tcp, "8.8.8.8", 53]])

EventMachine::run do
  resolver.query('google.com', IN::A) do |response|
		case response
		when RubyDNS::Message
			puts "Got response: #{response.answers.first}"
		else
			# Response is of class RubyDNS::ResolutionFailure
			puts "Failed: #{response.message}"
		end

		EventMachine::stop
	end
end

Existing code that uses Resolv::DNS as a resolver will need to be updated:

# 1/ Add this at the top of your file; Host specific system information:
require 'rubydns/system'
	
# 2/ Change from R = Resolv::DNS.new to:
R = RubyDNS::Resolver.new(RubyDNS::System::nameservers)

Everything else in the server can remain the same. You can see a complete example in test/test_resolver.rb.

Deferred Transactions

The implementation of the above depends on a new feature which was added in 0.5.0:

transaction.defer!

Once you call this, the transaction won't complete until you call either transaction.succeed or transaction.fail.

RubyDNS::run_server(:listen => SERVER_PORTS) do
	match(/\.*.com/, IN::A) do |match, transaction|
		transaction.defer!
		
		# No domain exists, after 5 seconds:
		EventMachine::Timer.new(5) do
			transaction.failure!(:NXDomain)
		end
	end

	otherwise do
		transaction.failure!(:NXDomain)
	end
end

You can see a complete example in test/test_slow_server.rb.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Desired Features

• Support for more features of DNS such as zone transfer.
• Support reverse records more easily.

License

Released under the MIT license.

Copyright, 2009, 2012, by Samuel G. D. Williams.

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.