#! /usr/bin/perl -w

my $ALARMED = 0;

$SIG{ALRM} = sub { ++$ALARMED; };

use POSIX qw(mktime);

# Work out ticket expiry

# Valid starting     Expires            Service principal
# 11/17/11 10:34:23  11/17/11 20:34:23  krbtgt/CALVAEDI.COM@CALVAEDI.COM
# 	renew until 11/18/11 10:34:23
# 11/17/11 10:34:23  11/17/11 20:34:23  nfs/olympic.calvaedi.com@CALVAEDI.COM
# 	renew until 11/18/11 10:34:23
# 11/17/11 11:24:24  11/17/11 20:34:23  host/olympic.calvaedi.com@CALVAEDI.COM
# 	renew until 11/18/11 10:34:23

# Eurgh - non localised, US format dates.

sub expiry {
	local *KLIST;
	open KLIST, "/usr/bin/klist | " or return;
	my $expiry;
	while (<KLIST>) {
		if (m((\d+)/(\d+)/(\d+) (\d+):(\d+):(\d+)  krbtgt)) {
			$expiry = mktime ($6, $5, $4, $2, $1 - 1, 100 +  $3);
			last;
		}
	}

	$expiry;
}


for (;;) {
	my $sleepytime = 60;

	my $expiry = expiry ();
	
	if (defined $expiry) {
		my $left = $expiry - time;
		if ($left <= 0) {
			# Ticket expired, zap it.  Potential race with
			# new ticket creation.
			print "Destroy expired ticket\n";
			system "/usr/bin/kdestroy";
		}
		else {
			$sleepytime = $left;
		}
	}

	if ($ALARMED) {
		$ALARMED = 0;
		next;
	}

	# If machine freezes during this sleap how long will
	# it sleep for?
	print "Sleeping for $sleepytime seconds\n";
	sleep $sleepytime;
}