#!/usr/bin/perl

=pod

=head1 NAME $RCSfile: checkdns,v $

Check DNS by attempting to call gethostbyname of a well known host.

=head1 VERSION

=over

=item Author

Andrew DeFaria <Andrew@ClearSCM.com>

=item Revision

$Revision: 1.6 $

=item Created:

Wed Aug 30 21:03:14 CDT 2006

=item Modified:

$Date: 2011/04/15 15:05:16 $

=back

=head1 SYNOPSIS

 Usage: checkdns [-u|sage] [-v|erbose] [-d|ebug]
                 [-s|leep <n>] [-l|ogpath <path>] 

 Where:
   -u|sage     Print this usage
   -v|erbose:  Verbose mode 
   -de|bug:    Emit debug information

   -h|ost:           Host to check (Default: google.com)
   -s|leep <n>:      Set sleep period to <n> minutes (Default: 15 minutes)
   -l|ogpath <path>: Put the log file in <path> (Default: /var/log)
   -da|emon:         Whether to go into daemon most (Default: yes)

=head1 DESCRIPTION

This script will look at the security logfile for attempted breakins and then 
use whois to report them to the upstream provider.

=cut

use strict;
use warnings;

use Getopt::Long;

use FindBin;

use lib "$FindBin::Bin/../lib";

use Logger;
use Utils;
use Display;

my $VERSION  = '$Revision: 1.6 $';
  ($VERSION) = ($VERSION =~ /\$Revision: (.*) /);

$0 = $FindBin::Script;

my ($log, $initial_sleep);

my %opts = (
  host        => 'google.com',
  sleep       => 15,
  logpath     => '/var/log',
  usage       => sub { Usage },
  verbose     => sub { set_verbose },
  debug       => sub { set_debug },
  daemon      => 1,
);

sub CheckDNS {
  my ($host) = @_;

  $? = 0;

  my @ipaddrs = gethostbyname $host;

  if (!@ipaddrs) {
    debug "Host: $host (ipaddrs empty)";

    # Cut down sleep time to monitor this outage more closely but do not go 
    # below once a minute.
    if ($opts{sleep} > 1) {
      $opts{sleep} -= $opts{sleep} / 2;
    } else {
      $opts{sleep} = 1;
    } # if

    return 1;
  } # if

  # Successful lookup - set $sleep to $initial_sleep
  $opts{sleep} = $initial_sleep;

  return;
} # CheckDNS

sub Shutdown {
  my $msg;

  my $errors = $log->errors;

  $log->msg("$errors errors encountered since starting") if $errors;
  $log->msg('Caught interrupt - shutting down');

  exit $errors;
} # Interrupt

# Main
GetOptions (
  \%opts,
  'usage',
  'verbose',
  'debug',
  'host=s',
  'sleep=i',
  'logpath=s',
  'daemon!',
) or Usage 'Invalid parameter';

$initial_sleep = $opts{sleep};

$SIG {INT}  =
$SIG {TERM} = \&Shutdown;

# Call sethostent so that gethostbyname is fresh everytime
sethostent (0);

$log = Logger->new (
  path        => $opts{logpath},
  timestamped => 'yes',
  append      => 'yes',
);

$log->msg (
  "Started $FindBin::Script $VERSION logging to $opts{logpath}/$FindBin::Script.log"
);

if ($opts{sleep} > 1) {
  $log->msg ("Polling DNS on host $opts{host} every $opts{sleep} minutes");
} else {
  $log->msg ("Polling DNS on host $opts{host} every minute");  
} # if

$opts{daemon} = 0 if get_debug;

EnterDaemonMode if $opts{daemon};

while () {
  my $status = CheckDNS $opts{host};

  if ($status) {
    $log->err ("Unable to resolve IP address for $opts{host}");
  } else {
    $log->msg ("Successfully resolved $opts{host}");
  } # if

  sleep $opts{sleep} * 60;
} # while

=pod

=head1 CONFIGURATION AND ENVIRONMENT

DEBUG: If set then $debug is set to this level.

VERBOSE: If set then $verbose is set to this level.

TRACE: If set then $trace is set to this level.

=head1 DEPENDENCIES

=head2 Perl Modules

L<FindBin>

L<Getopt::Long|Getopt::Long>

=head2 ClearSCM Perl Modules

=begin man 

 Display
 Logger
 Utils

=end man

=begin html

<blockquote>
<a href="http://clearscm.com/php/scm_man.php?file=lib/Display.pm">Display</a><br>
<a href="http://clearscm.com/php/scm_man.php?file=lib/Logger.pm">Logger</a><br>
<a href="http://clearscm.com/php/scm_man.php?file=lib/Utils.pm">Utils</a><br>
</blockquote>

=end html

=head1 BUGS AND LIMITATIONS

There are no known bugs in this script

Please report problems to Andrew DeFaria <Andrew@ClearSCM.com>.

=head1 LICENSE AND COPYRIGHT

Copyright (c) 2004, ClearSCM, Inc. All rights reserved.

=cut