Monitor dns changes for hostname

Monitor DNS Changes for Hostname

#!/bin/env perl
use strict;
## Check to see if IP Address or CNAME has changed for a host
## If it has chagned, send message using mail function

require Net::DNS;
require MIME::Lite;

my %hostname = (
    'cdn.djtunez.net' => [ "ns1.lithiumfox.com", "ns1.lithiumfox.com"],
    );


for (keys %hostname){
    my $record; 
    my $res = Net::DNS::Resolver->new(
        nameservers => $hostname{$_},
        recurse     => 0,
        debug       => 0,
    );

    my $request = $res->query("$_");

    if ($request){
        foreach my $rr ($request->answer){
            if ($rr-> type eq "CNAME"){
                $record = $rr->cname;
            }
            elsif ($rr->type eq "A"){
                $record = $rr->address;
            }
        }
    }
    checkDifference($record,$_);
}

sub checkDifference {

    my ($record, $hostname) = @_;
    my $statepath = "/var/run/dnscheck";
    my $state = "$hostname.state";  

    open STATE, "<$statepath/$state" or die $!;
    while (<STATE>){
        chomp;
        my $sstate = $_;
        close STATE;
        if ($sstate ne $record){
            print "$hostname DNS record has changed from $sstate -> $record\n";
            my $msgbody = "$hostname DNS record has changed from $sstate -> $record\n";
            mail($msgbody, $hostname);
            open STATE, ">$statepath/$state" or die $!;
            print STATE $record;
            close STATE;
            }
        }
}


sub mail { 

    my ($msgbody, $hostname) = @_;
    my $subject = "$hostname DNS Record Changed!";
    my @mailto =  [ '[email protected]' ];

    my $msg = MIME::Lite->new(
        Subject => $subject,
        To  => @mailto,
        Type    => 'text/html',
        Data    => $msgbody,
    );
    $msg->send();
}