Net::DNS is a DNS library written in pure Ruby. It started as a port of Perl Net::DNS module, but it evolved in time into a full Ruby library.
- Complete OO interface
- Clean and intuitive API
- Modular and flexible
- Ruby >= 1.8.7
The best way to install this library is via RubyGems.
$ gem install net-dns You might need administrator privileges on your system to install the gem.
Visit the page http://rdoc.info/gems/net-dns
The simplest way to use the library is to invoke the Resolver() method:
require 'rubygems' require 'net/dns' p Resolver("www.google.com") The output is compatible with BIND zone files and it's the same you would get with the dig utility.
; Answer received from localhost:53 (212 bytes) ; ; HEADER SECTION ; id = 64075 ; qr = 1 opCode: QUERY aa = 0 tc = 0 rd = 1 ; ra = 1 ad = 0 cd = 0 rcode = NoError ; qdCount = 1 anCount = 3 nsCount = 4 arCount = 4 ; QUESTION SECTION (1 record): ; google.com. IN A ; ANSWER SECTION (3 records): google.com. 212 IN A 74.125.45.100 google.com. 212 IN A 74.125.67.100 google.com. 212 IN A 209.85.171.100 ; AUTHORITY SECTION (4 records): google.com. 345512 IN NS ns1.google.com. google.com. 345512 IN NS ns4.google.com. google.com. 345512 IN NS ns2.google.com. google.com. 345512 IN NS ns3.google.com. ; ADDITIONAL SECTION (4 records): ns1.google.com. 170275 IN A 216.239.32.10 ns2.google.com. 170275 IN A 216.239.34.10 ns3.google.com. 170275 IN A 216.239.36.10 ns4.google.com. 170275 IN A 216.239.38.10 An optional block can be passed yielding the Net::DNS::Packet object
Resolver("www.google.com"){|packet| puts packet.size + " bytes" } # => 484 bytes Same for Net::DNS::Resolver.start():
Net::DNS::Resolver.start("google.com").answer.size # => 5 As optional parameters, +TYPE+ and +CLASS+ can be specified.
p Net::DNS::Resolver.start("google.com", Net::DNS::MX) ; Answer received from localhost:53 (316 bytes) ; ; HEADER SECTION ; id = 59980 ; qr = 1 opCode: QUERY aa = 0 tc = 0 rd = 1 ; ra = 1 ad = 0 cd = 0 rcode = NoError ; qdCount = 1 anCount = 4 nsCount = 4 arCount = 8 ; QUESTION SECTION (1 record): ; google.com. IN MX ; ANSWER SECTION (4 records): google.com. 10800 IN MX 10 smtp2.google.com. google.com. 10800 IN MX 10 smtp3.google.com. google.com. 10800 IN MX 10 smtp4.google.com. google.com. 10800 IN MX 10 smtp1.google.com. The method Net::DNS::Resolver.start is a wrapper around Resolver.new. It returns a new Net::DNS::Packet object.
A DNS packet is divided into 5 sections:
- header section # => a Net::DNS::Header object
- question section # => a Net::DNS::Question object
- answer section # => an Array of Net::DNS::RR objects
- authority section # => an Array of Net::DNS::RR objects
- additional section # => an Array of Net::DNS::RR objects
You can access each section by calling the attribute with the same name on a Packet object:
packet = Net::DNS::Resolver.start("google.com") header = packet.header answer = packet.answer puts "The packet is #{packet.data.size} bytes" puts "It contains #{header.anCount} answer entries" answer.any?{|ans| p ans} The output is
The packet is 378 bytes It contains 3 answer entries google.com. 244 IN A 74.125.45.100 google.com. 244 IN A 74.125.67.100 google.com. 244 IN A 209.85.171.100 A better way to handle the answer section is to use the iterators directly on a Packet object:
packet.each_address do |ip| puts "#{ip} is alive" if Ping.pingecho(ip.to_s, 10, 80) end Gives:
74.125.45.100 is alive 74.125.67.100 is alive 209.85.171.100 is alive Net::DNS is distributed under the same license Ruby is.
- Marco Ceresa (@bluemonk)
- Simone Carletti (@weppos)