#!/usr/bin/perl
#
# check_trace plugin for nagios
# 
# This plugins checks whether a hostname resolves to the address you expect
# it to. It uses dig +trace to check the entire path, from the root
# nameservers to your domain
#
# See check_trace -h for usage information
# (c)2008 Dennis Kaarsemaker - Licensed under GNU GPL v3 or later

use strict;
use warnings;

sub print_help ();
sub _usage ();
sub in ($$);

use Getopt::Long;

use lib '/usr/lib/nagios/plugins';
use utils qw(%ERRORS $TIMEOUT &print_revision &usage);

our ($progname, $progversion);
my ($opt_h, $opt_A, $opt_V);
my ($verbose, $host, $address, @addresses, @found_addresses, $cnames);

$progname = "check_trace";
$progversion = "1.0";
$cnames = 5;


# Parse options
Getopt::Long::Configure('bundling');
GetOptions(
    "V"   => \$opt_V,   "version"   => \$opt_V,
    "h"   => \$opt_h,   "help"      => \$opt_h,
    "H=s" => \$host,    "hostname"  => \$host,
    "a=s" => \$address, "address"   => \$address,
    "A=s" => \$opt_A,   "addresses" => \$opt_A,
    "v"   => \$verbose, "verbose"   => \$verbose,
    "c"   => \$cnames,  "cnames"    => \$cnames,
);

if ($opt_h) { print_help(); exit $ERRORS{"OK"}; }
if ($opt_V) { print_revision($progname, $progversion); exit $ERRORS{"OK"}; } 
@addresses = ();
@addresses = split(/,/, $opt_A) if(defined($opt_A));
push(@addresses, $address);

usage(_usage) unless $host;
usage(_usage) unless $address;

# Trace the hostname
my $orig_host = $host;
$host .= '.' unless $host =~ /\.$/;
my @ns_trace = ();
my $cname_count = 0;

while($cname_count <= $cnames) {
    my $cname = undef;
    print "*** Searching $host\n" if $verbose;
    open(DIG, '-|', "dig +time=$TIMEOUT +trace $host");
    while(<DIG>) {
        print if $verbose;
        # ;; Received 427 bytes from 192.33.4.12#53(C.ROOT-SERVERS.NET) in 24 ms
        if(/^;; Received.*?\((.*?)\)./) {
            push(@ns_trace, $1);
        }
        # foo.example.com.  86400   IN  CNAME   bar.example.com.
        if(/$host\s+\d+\s+IN\s+CNAME\s+(.*)/) {
            $cname = sprintf('%s CNAME %s', $host, $1);
            $host = $1;
        }
        # bar.example.com. 300 IN  A   127.0.0.1
        if(/$host\s+\d+\s+IN\s+A\s+(.*)/) {
            push(@found_addresses, $1);
        }
    }
    last if not defined($cname);
    last if @found_addresses;
    push(@ns_trace, $cname);
    $cname_count++;
}

# So, did it work?
if($cname_count == $cnames) {
    print "Need to follow too many cnames (more than $cnames) to resolve address";
    exit($ERRORS{"CRITICAL"});
}

my @errors;
foreach my $address (@addresses) {
    if(!in(\@found_addresses, $address)) {
       push(@errors,"$orig_host did not resolve to $address");
    }
}
foreach my $address (@found_addresses) {
    if(!in(\@addresses, $address)) {
        push(@errors, "$orig_host resolved to unknonwn IP $address");
    }
}
if(@errors) {
    print join(', ', @errors);
    exit $ERRORS{"CRITICAL"};
}
print "$orig_host resolved to ".join(', ', @addresses)." via ".join(', ', @ns_trace);
exit $ERRORS{"OK"};

sub print_help() {
    print_revision($progname, $progversion);
    print "\n" .
    _usage .
    "\n" .
    "-H|--hostname hostname to resolve\n" .
    "-a|--address address it resolves to\n" .
    "-A|--addresses extra addresses it can resolve to (round robin)\n" .
    "-c|--cnames max. number of CNAME's to follow\n" .
    "\n" .
    "The plugin will use dig +trace to trace your hostname. It will\n" .
    "allso follow CNAME's unless the A answer came in baliwick\n";
}

sub _usage() {
    return "Usage:\n$progname -H hostname -a address [-A extra_addresses] -v\n" .
           "$progname -h|--help\n" .
           "$progname -V|--version\n"
}

sub in($$) {
    my $array_ref = shift;
    my $test = shift;

    foreach my $element (@{$array_ref}) {
        if ($test eq $element) {
            return 1;
        }
    }
    return 0;
}