SPF record の ip4 部分を再帰的に取り出す

spfaddr.rb

#! /usr/bin/env ruby
#****************************************************************************
#
# Usage: spfaddr.rb <domain>
#
#        spfaddr.rb _spf.google.com
#
#****************************************************************************
require 'dnsruby'

def spfaddr(domain)
  res = Dnsruby::Resolver.new
  res.nameservers = ['8.8.8.8', '8.8.4.4']
  ret = res.query(domain, Dnsruby::Types.TXT)
  ret.each_answer do |a|
    if a.data.match('v=spf')
      a.data.split(/\s+/).each do |atom|
        if atom.gsub!(/^ip4:/, '')
          puts atom
        elsif atom.gsub!(/^include:/, '')
          spfaddr(atom)
        end
      end
    end
  end
end

spfaddr(ARGV[0])