#!/usr/bin/perl

use strict;

if (($ARGV[0] ne "v4") and ($ARGV[0] ne "v6")) {
	print "Usage: $0 v4|v6\n";
	exit 1;
};
# Check for IPV6 requ.
my $ipver = "v4";
if ($ARGV[0] eq "v6") {
  require Net::INET6Glue::INET_is_INET6;
  $ipver = "v6";
};

my $previp = '';

# DNS record types:
my %drts = (
		'v4' =>	'A',
		'v6' =>	'AAAA',
	);

# Checkip url
my $checkurl = 'http://www.example.com.gr/myip';
# Updateip url
my $updateurl = 'http://www.example.com/ddnsset.pl?';
# FQDN to set:
my $fqdn = 'myhost'; 
# History filenames:
my %iphist = (
		'v4' =>	'/tmp/dynipsethistv4.txt',
		'v6' =>	'/tmp/dynipsethistv6.txt',
	);

# Load history:
if (-e $iphist{$ipver}) {
	open (HI, "<", $iphist{$ipver}) or die "Failed to open " . $iphist{$ipver} . " for reading: $!.\n";
	$previp = <HI>;
	close HI;
}; 

# Create a user agent object
use LWP::UserAgent;
my $ua = LWP::UserAgent->new;
$ua->agent("dynipset/0.1 ");

# Create a request
my $req = HTTP::Request->new(GET => $checkurl);

# Pass request to the user agent and get a response back
my $res = $ua->request($req);

# Check the outcome of the response
if ($res->is_success) {
	my $newip = $res->content;
	#print "DEBUG: My new IP is $newip ($ipver) \n";
	if ($previp eq $newip) {
		# Do nothing.
		#print "DEBUG: IP not changed.\n";
		exit 0;
	} else {
		# Set ip: 
		my $dbrec = "$fqdn|" . $drts{$ipver} . "|$newip";
		my $rc = &setDNS($dbrec);
		if ($rc) {
			print "SET: $fqdn " . $drts{$ipver} . " $newip\n";
		} else {
			print "ERROR: setDNS failed ($fqdn|$newip)!\n";
			exit 1;
		};
		# Save new ip to history:
		open (HI, ">", $iphist{$ipver}) or die "Failed to open " . $iphist{$ipver} . " for writing: $!.\n";
		print HI $newip;
		close HI;
		exit 0;
	};	
} else {
	print "ERROR: checkip request failed: " . $res->status_line, "\n";
	exit 1;
};

exit 0;

sub setDNS {
	my ($dbrec, $rest) = @_; 
	use Crypt::CBC;
	use MIME::Base64 qw(encode_base64url decode_base64url);

	my $cipher = Crypt::CBC->new( 	-key    => 'a pass phrase',
					-cipher => 'Blowfish',
					-keysize => 56
			);
	my $ciphertext = $cipher->encrypt($dbrec);
 	my $encoded = encode_base64url($ciphertext);
	#print "DEBUG: $encoded\n";
	my $url = "$updateurl$encoded";
	my $ua = LWP::UserAgent->new;
	$ua->agent("dynipset/0.1 ");

	# Create a request
	my $req = HTTP::Request->new(GET => $url);

	# Pass request to the user agent and get a response back
	my $res = $ua->request($req);
	if ($res->is_success) {
		return 1;
	} else {
		print "ERROR: updateip request failed: " . $res->status_line, "\n";
		return 0;
	};
};