check_wan_ip_ddwrt

#!/usr/bin/env perl 

use strict;
use warnings;

# load the libwww module
use LWP::Simple;

# load the Getopt::Long module for cli arguments
use Getopt::Long;

# load the Pod::Usage module for automatic documentation
use Pod::Usage;

#-------------------------------------------------------------------------------
# GLOBAL VARIABLES
#-------------------------------------------------------------------------------
my $hostname    = undef;    # this has to be a cli argument
my $response    = undef;
my $help        = undef;
my $wan_ip      = undef;
my $expected_ip = undef;

#-------------------------------------------------------------------------------
# process cli arguments
#-------------------------------------------------------------------------------
Getopt::Long::Configure( "no_ignore_case", "bundling" );
GetOptions(
    'H|hostname=s'  => \$hostname,
    'h|help|?'      => \$help,
    'i|ipaddress=s' => \$expected_ip,
);

# if help chosen, display it
pod2usage( -verbose => 2, -noperldoc => 1, ) if $help;

# if no -H specified, show usage
pod2usage() unless $hostname and $expected_ip;

# fetch the site
my $html = get "http://$hostname";

# if fetch is successful, process html
if ( defined $html ) {
    _get_wan_ip();
    if ( $wan_ip eq $expected_ip ) {
        print "OK: our WAN ip is $wan_ip and we expected $expected_ip\n";
        exit 0;
    }
    else {
        print
"WARNING: our WAN ip has changed. We expected $expected_ip but got $wan_ip\n";
        exit 1;
    }
}
else {
    print "WARNING: Something went wrong fetching it.\n";
    exit 1;
}


#===  FUNCTION  ================================================================
#         NAME: _get_wan_ip
#      PURPOSE: get WAN ip of dd-wrt router
#   PARAMETERS: none
#      RETURNS: wan ip address
#  DESCRIPTION: 
#       THROWS: 
#     COMMENTS: the wan ip is in this html code:
#               <span id="wan_ipaddr">ipv4 address</span>
#               so we we need the span tag with an wan_ipaddr id attribute
#     SEE ALSO: n/a
#===============================================================================
sub _get_wan_ip {

    # parse the html $response file
    use HTML::TreeBuilder;
    my $tree = HTML::TreeBuilder->new_from_content($html);

    if ( my $div = $tree->look_down( _tag => "span", id => "wan_ipaddr" ) ) {

        $wan_ip = $div->as_text();
        return $wan_ip;
    }

    # if we do not find the wan_ipaddr attr end with unknown
    else {
        print "UNKNOWN: something went wrong while parsing the html code\n";
        exit 3;
    }
}

#%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
#  Application Documentation
#%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

=head1 NAME

check_wan_ip_ddwrt - check WAN ip address of dd-wrt broadband routers

=head1 VERSION

This documentation refers to <check_wan_ip_ddwrt> version 0.1

=head1 USAGE

check_wan_ip_ddwrt -H host -i ip.add.re.ss

=head1 REQUIRED ARGUMENTS

-H|--hostname
host name or LAN ip address of our dd-wrt router;

-i|--ipaddress
expected ip address we want to check.

=head1 OPTIONS

-H|--hostname
host name or LAN ip address of our dd-wrt router;

-i|--ipaddress
expected ip address we want to check.

-h|--help
this text;

=head1 DESCRIPTION

Nagios check to monitor if the WAN ip address our dd-wrt router gets from our
internet provider is the one we expect it to be. I need to know this to modify
a DNS A record accordingly because I do not have a fixed ip address.

The check retrieves the info web site from the router and parses it to
retrieve its WAN ip.

=head1 DIAGNOSTICS

This check can fail because of network problems (no connectivity to the
router) or because the router does not have a WAN ip address (internet
provider problem).

=head1 CONFIGURATION AND ENVIRONMENT

Place the plugin in the plugin directory of the nagios server (usually,
/usr/local/nagios/libexec/), make the nagios user its owner and change the
permissions to 775.

=head1 DEPENDENCIES

This plugin requires the LWP::Simple and HTML::TreeBuilder modules.

On a recent Redhat based system you can install it like this:
# yum install perl-HTML-Tree

On a debian based system the package is called libhtml-tree-perl and you
use apt-get so:

# apt-get install libhtml-tree-perl

On other flavours of unix, check your package manager documentation or use
something like perlbrew with cpanminus.

=head1 INCOMPATIBILITIES

None known yet.

=head1 BUGS AND LIMITATIONS

Plenty, patches welcome :-)

=head1 AUTHOR

<Natxo Asenjo>  (<natxo@asenjo.nl_removethis>)

=head1 LICENCE AND COPYRIGHT

This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself. See perldoc perlartistic.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

=cut