Linode dynamic DNS updater v0.0.3

linode_dns.rb

#! /usr/bin/env ruby

# 
# Linode dynamic DNS updater
# Version 0.0.3
# August 21, 2012
#
# By Rockwell Schrock
# schrockwell@gmail.com
# https://gist.github.com/3415112
#
# This Ruby script updates a Linode DNS listing with your public IP
# address. Think of it as a personalized dynamic DNS service. Throw
# it in a crontab or a system init script for +1 effectiveness.
#
# You only have to set two constants:
#
# RedirectDomain: This is the fully-qualified domain you wish to
#   forward, of the form "[subdomain].[domain].[tld]". The script
#   will automatically figure out the Linode DomainID and ResourceID
#   for you! If the subdomain A record does not yet exist, it will be
#   created. Nifty, huh?
#
# APIKey: This is the Linode developer API key from the 'my profile' 
#   link at the top-right of the Linode Manager. Mmm, copypasta.
#
# Enjoy!

require 'uri'
require 'net/http'
require 'net/https'
require 'json'

RedirectDomain = '[SUBDOMAIN.EXAMPLE.COM]'
APIKey = '[LINODE API KEY]'
PublicIPURL = 'http://icanhazip.com/'
APIURL = 'https://api.linode.com/?api_key=%s&api_action=%s'

def execute(action, params)
	url = APIURL % [APIKey, action]
	param_strings = params.map { |param, value| "#{param}=#{URI.escape(value)}" }
	url << '&' << param_strings * '&'
	uri = URI.parse(url)
	
	http = Net::HTTP.new(uri.host, uri.port)
	http.use_ssl = true
	http.verify_mode = OpenSSL::SSL::VERIFY_NONE
	
	request = Net::HTTP::Get.new(uri.request_uri)
	response = http.request(request)
	JSON.parse(response.body)
end

# Figure out the subdomain
subdomain_name = RedirectDomain.split('.')[0]
domain_name = RedirectDomain.split('.')[1..2] * '.'

# Get the public IP
public_ip = Net::HTTP.get(URI(PublicIPURL)).chomp

# First find the domain ID

response = execute('domain.list', {})

response['DATA'].each do |domain|
	if domain['DOMAIN'].downcase == domain_name.downcase
		@domain_id = domain['DOMAINID'].to_s
		break
	end
end

raise "Domain #{domain_name} not found" unless @domain_id

# Now get the resource ID, and create it if not already there

response = execute('domain.resource.list', { :DomainID => @domain_id })

response['DATA'].each do |resource|
	if resource['TYPE'].downcase == 'a' and resource['NAME'].downcase == subdomain_name.downcase
		@resource_id = resource['RESOURCEID'].to_s
		@old_ip = resource['TARGET']
		break
	end
end

if @resource_id
	if @old_ip == public_ip
		puts "Subdomain '#{subdomain_name}' found, no update needed"
	else
		puts "Subdomain '#{subdomain_name}' found, updating..."
		response = execute('domain.resource.update', { :DomainID => @domain_id, :ResourceID => @resource_id, :Target => public_ip })
	end
else
	puts "Subdomain '#{subdomain_name}' not found, creating..."
	response = execute('domain.resource.create', { :DomainID => @domain_id, :Type => 'A', :Name => subdomain_name, :Target => public_ip })
end

puts "Updated #{RedirectDomain} to #{public_ip}"