#!/usr/bin/ruby

# Copyright 2006, 2012 Peter Palfrader
#           2012  Uli Martens
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

require 'ipaddr'
require 'resolv'
require 'optparse'
require 'yaml'

NAGIOS_STATUS = { :OK => 0, :WARNING => 1, :CRITICAL => 2, :UNKNOWN => -1 };
@verbose = 0;
@additional_nameservers = []
@check_soa_nameservers = true;

def show_help(parser, code=0, io=STDOUT)
  program_name = File.basename($0, '.*')
  io.puts "Usage: #{program_name} [options] <domainname> [<domainname> ...]"
  io.puts parser.summarize
  exit(code)
end
ARGV.options do |opts|
        opts.on_tail("-h", "--help" , "Display this help screen")                               { show_help(opts) }
        opts.on("-v", "--verbose"   , String, "Be verbose")                                     { @verbose += 1 }
        opts.on("-a", "--add=HOST"  , String, "Also check SOA on <nameserver>")                 { |val| @additional_nameservers << val }
        opts.on("-n", "--no-soa-ns" , String, "Don't query SOA record for list of nameservers") { @check_soa_nameservers = false }
        opts.parse!
end
show_help(ARGV.options, 1, STDERR) if ARGV.length == 0

if @additional_nameservers.count <= 1 and not @check_soa_nameservers
	program_name = File.basename($0, '.*')
	STDERR.puts "#{program_name}: Only know about #{@additional_nameservers.count} nameserver(s) and --no-soa-ns specified.  I want at least two."
	exit(1)
end

warnings = []
oks = []

def resolve_ns(dns, domain, nameserver)
	puts "Getting A record for nameserver #{nameserver} for #{domain}" if @verbose > 0
	arecords = dns.getresources(nameserver, Resolv::DNS::Resource::IN::A)
	warnings << "Nameserver #{nameserver} for #{domain} has #{arecords.length} A records" if arecords.length != 1
	addresses = arecords.map { |a| a.address.to_s }
	puts "Addresses for nameserver #{nameserver} for #{domain}: #{addresses.join(', ')}" if @verbose > 0
	return addresses
end

dns = Resolv::DNS.new
ARGV.each{ |domain|
	serial = []
	nameserver_addresses = {}
	if @check_soa_nameservers
		nameservers = dns.getresources(domain, Resolv::DNS::Resource::IN::NS)
		nameservernames = nameservers.collect{ |ns| ns.name.to_s }
		nameservernames.each do |nameserver|
			addrs = resolve_ns(dns, domain, nameserver)
			warnings << "Duplicate nameserver #{nameserver} for #{domain}" if nameserver_addresses[nameserver]
			nameserver_addresses[nameserver] = addrs
		end
	end
	@additional_nameservers.each do |ns|
		begin
			ipa = IPAddr.new(ns)  # check if it's an address
			addrs = [ns]
		rescue ArgumentError
			addrs = resolve_ns(dns, domain, ns)
		end
		warnings << "Duplicate nameserver #{ns} for #{domain}" if nameserver_addresses[ns]
		nameserver_addresses[ns] = addrs
	end

	nameserver_addresses.each_pair do |nameserver, addrs|
		puts "Testing nameserver #{nameserver} for #{domain}" if @verbose > 0
		addrs.each do |a|
			puts " Nameserver #{nameserver} is at #{a}" if @verbose > 0
			begin
				resolver = Resolv::DNS.new({:nameserver => a})
				soas = resolver.getresources(domain, Resolv::DNS::Resource::IN::SOA)
			rescue SystemCallError => e
				warnings << "Could not resolve #{domain} on #{nameserver}: #{e.message}"
			else
				resolver.close
				warnings << "Nameserver #{nameserver} for #{domain} returns #{soas.length} SOAs" if soas.length != 1
				soas.each do |soa|
					puts " Nameserver #{nameserver} returns serial #{soa.serial} for #{domain}" if @verbose > 0
					serial << soa.serial unless serial.include? soa.serial
				end
			end
		end
	end
	case serial.length
		when 0
			warnings << "Found no serials for #{domain}"
		when 1
			oks << "#{domain} is at #{serial.first}"
		else
			warnings << "Nameservers disagree on serials for #{domain}: found #{serial.join(', ')}" if serial.length != 1
	end
}
dns.close

if warnings.length > 0
	puts warnings.join('; ')
	exit NAGIOS_STATUS[:WARNING]
else
	puts oks.join('; ')
	exit NAGIOS_STATUS[:OK]
end