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).
This is copied from test/examples/test-dns-2.rb. It has been simplified slightly.
require 'rubydns' 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 |transaction| transaction.respond!("10.0.0.80") end # Default DNS handler otherwise do |transaction| transaction.passthrough!(UPSTREAM) end 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 For examples and documentation please see the main project page.
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) 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.
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.
- Support for more features of DNS such as zone transfer.
- Support reverse records more easily.
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Copyright, 2009, 2012, by Samuel G. D. Williams.
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