#!/usr/bin/perl -w
use strict;
use IO::Socket;

# Debian: apt-get install libtime-hires-perl
# RHEL:   yum install perl-Time-HiRes
use Time::HiRes qw( gettimeofday tv_interval);

# Should come with Perl
use Term::ANSIColor qw(:constants);

my (@god, @dammit);
sub usage {
 print "$0 <ip/host> <port>\n";
 exit(1);
}
&usage unless defined ($ARGV[1]);
my $ip = $ARGV[0];
my $port = $ARGV[1];
my @ips;
if ($ip =~ /[a-zA-Z]+/) {
 @ips = gethostbyname("$ip") or die BLINK BOLD RED "Can't resolve $ip", RESET . "\n";
 @ips = map { inet_ntoa($_) } @ips[4 .. $#ips];
 for (@ips) {
  &check($_,$port);
 }
}
else {
 &check($ip,$port);
}

sub check {
 our $h = $_[0];
 our $p = $_[1];
 our $message;
 sub timeout {
  print "UDP OpenVPN connection " . BLINK BOLD RED "timed out", RESET . " on $h:$p\n";
  close($message);
 }
 eval {
  local $SIG{ALRM} = sub { &timeout; };
  alarm 3;
  my $now = [gettimeofday()];
  my $message = IO::Socket::INET->new(Proto=>"udp",PeerPort=>"$p",PeerAddr=>"$h") or die "$@";
  $message->send("\x38\x40\x80\x2a\xfa\xdb\x9b\x67\x95\x00\x00\x00\x00\x00");
  my ($datagram,$flags);
  $message->recv($datagram,26,$flags);
  if (length($datagram) == 26) {
   my $andagain = tv_interval($now)*1000;
   my $ms = sprintf("%d", $andagain);
   print "UDP OpenVPN is " . BOLD GREEN "UP", RESET . " on $h:$p and responded in $ms ms\n";
  }
  else {
   print "UDP OpenVPN is " . BLINK BOLD RED "DOWN", RESET . " on $h:$p\n";
  }
  alarm 0;
 }
}