#!/usr/bin/perl -w
# nagios: -epn
# the above line makes nagios run the script as a separately.
# rather than as part of nagios.
use POSIX;
use lib "/usr/lib/nagios/plugins";
use utils qw(%ERRORS);

sub fail_usage {
  if (scalar @_) {
    print "$0: error: \n";
    map { print "   $_\n"; } @_;
  }
  print "$0: Usage: \n";
  print "$0 [<options>] <server> [<server> [<server>]] \n";
  print "$0 [<options>] [-s <server> [-s <server> [-s <server>]]] \n";
  print "    options:  \n";
  print "      [-v [-v [-v]]] (verbose) \n";
  print "      [-t  <secs>] (wait this number of seconds)   \n";
  print "      [-f] (fuzzy - ok if one or more of the designated servers answer)   \n";
  print "      [-F] (force (default) - all the designated servers must answer)   \n";
  print " \n";
  exit 3 ;
}

my $verbose = 0;
my %servers=();
my $opt = "-t 5";
my $time = 5;
my $force=1;

## for some reason I can't test for empty ARGs in the while loop
@ARGV = grep {!/^\s*$/} @ARGV;

# examine commandline args
while ($ARGV=$ARGV[0]) {
  my $myarg = $ARGV;
  if ($ARGV eq '-s') {
    shift @ARGV;
    if (!($ARGV = $ARGV[0])) { fail_usage ("$myarg needs an argument"); }
    if ($ARGV =~ /^-/) { fail_usage ("$myarg must be followed by an argument"); }
    if (!defined($servers{$ARGV})) { $servers{$ARGV}=1; }
  }
  elsif ($ARGV eq '-t') {
    shift @ARGV;
    if (!($ARGV = $ARGV[0])) { fail_usage ("$myarg needs an argument"); }
    if ($ARGV =~ /^-/) { fail_usage ("$myarg must be followed by an argument"); }
    if ($ARGV !~ /^(\d+)$/) { fail_usage ("$myarg must be followed by an number"); }
    $time = $1;
    $opt = "-t $time";
  }
  elsif ($ARGV eq '-f' ) { $force=0; }
  elsif ($ARGV eq '-F' ) { $force=1; }
  elsif ($ARGV eq '-h' or $ARGV eq '--help' ) { fail_usage ; }
  elsif ($ARGV =~ /^-/ ) { fail_usage " invalid option ($ARGV)"; }
  elsif ($ARGV =~ /^\d+\.\d+\.\d+\.\d+$/)
    # servers should be ip addresses.  I'm not doing detailed checks for this.
    { if (!defined($servers{$ARGV})) { $servers{$ARGV}=1; } }
  else { last; }
  shift @ARGV;
}

if (scalar @ARGV) { fail_usage "didn't understand arguments: (".join (" ",@ARGV).")"; }  
my $serversn = scalar keys %servers;

if ($verbose > 2) {
  print "verbosity=($verbose)\n";
  print "servers = ($serversn)\n";
  if ($serversn) { for my $i (keys %servers) { print "server ($i)\n"; } }
}

if (!$serversn) { fail_usage "no servers"; }
my $responses=0;
my $responders="";
my @check_dhcp = qx{/usr/lib/nagios/plugins/check_dhcp -v $opt};
foreach my $value (@check_dhcp) {
  if ($value =~ /Added offer from server \@ /i){
    $value =~ m/(\d+\.\d+\.\d+\.\d+)/i;
    my $host = $1;
    # we find a server in our list
    if (defined($servers{$host})) { $responses++; $responders.="$host "; }
    else {
      # we find a rogue DHCP server.  Danger Will Robinson!
      print "SERVICE STATUS:CRITICAL: Rogue DHCP service running on $host";
      exit $ERRORS{'CRITICAL'}
    }
  }
}
if ($responses == $serversn) {
  # we saw all the servers in our list.  All is good.
  print "SERVICE STATUS:OK: $responses of $serversn Expected Responses to DHCP Broadcast";
  exit $ERRORS{'OK'};
}

if ($responses == 0) {
  # we found no DHCP responses.
  print "SERVICE STATUS:CRITICAL: no DHCP service responded";
  exit $ERRORS{'CRITICAL'}
}

# we found less DHCP servers than we should have. Oh Nos!
$responders =~ s/ $//;
if ($force == 1) {
  print "SERVICE STATUS:WARNING: $responses of $serversn Responses to DHCP Broadcast. Only ($responders) responded. ";
  exit $ERRORS{'WARNING'};
}
else {
  print "SERVICE STATUS:OK: $responses of $serversn Responses to DHCP Broadcast. Only ($responders) responded. ";
  exit $ERRORS{'OK'};
}