RubyDNS

Author

Samuel Williams (www.oriontransfer.co.nz/)

Copyright

Copyright © 2009 Samuel Williams

License

GPLv3

RubyDNS is a simple programmatic DSL (domain specific language) for configuring and running a DNS server. RubyDNS provides a daemon that runs a DNS server which can process DNS requests depending on specific policy. Rule selection is based on pattern matching, and results can be hard-coded, computed, fetched from a remote DNS server, fetched from a local cache, etc.

RubyDNS provides a full daemon server using RExec. You can either use the built in daemon, customize it to your needs, or specify a full daemon implementation.

RubyDNS is not designed to be high-performance and uses a thread-per-request model. This is designed to make it as easy as possible to achieve concurrent performance. This is also due to the fact that many other APIs work best this way (unfortunately).

Basic Example

This is copied from test/example1.rb. It has been simplified slightly.

require 'rubygems'
require 'rubydns'

$R = Resolv::DNS.new

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

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

After starting this server you can test it using dig:

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

Todo

• Better support for logging output

• Support for more features of DNS such as zone transfer

• Support reverse records more easily

• Better support for deferred requests/concurrency.