#!/usr/bin/ruby

require 'optparse'

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

def show_help(parser, code=0, io=STDOUT)
  program_name = File.basename($0, '.*')
  io.puts "Usage: #{program_name} [options]"
  io.puts parser.summarize
  exit(code)
end
ARGV.options do |opts|
        opts.on_tail("-h", "--help" , "Display this help screen")                { show_help(opts) }
        opts.parse!
end
show_help(ARGV.options, 1, STDERR) if ARGV.length > 0

unless File.executable?('/sbin/ip')
	puts "/sbin/ip is not executable"
	exit NAGIOS_STATUS[:UNKNOWN]
end

ip_output = nil
IO.popen("-") do |f|
	unless f  # child
		begin
			exec('/sbin/ip', 'route', 'show', '0.0.0.0/0')
		rescue => e
			puts "Cannot exec ip: "+e.message
			exit 1
		end
	end
	ip_output = f.readlines
end

if $? != 0
	puts "Child exited with non-zero exit code(%d): %s"%[$? >> 8, ip_output]
else
	if ip_output.length > 0
		puts "OK: %s" % [ip_output.join(' ')]
		exit NAGIOS_STATUS[:OK]
	else
		puts "CRITICAL: no default route found."
		exit NAGIOS_STATUS[:CRITICAL]
	end
end