#!/usr/bin/perl -w

use Fcntl qw(LOCK_EX LOCK_NB);
use strict;

open( LOCK, ">>/tmp/SecureMail.lock" ) or die("Cannot open lock file: $!");
flock( LOCK, LOCK_EX | LOCK_NB ) or die("Another SecureMail session is already running - exiting");

my $SSHCMD = "ssh -a -C -N -o 'BatchMode=yes' -L 1430:mail.improbable.org:143 -L2525:mail2.qwknetllc.com:25 improbable.org";

chdir("/");    # No problems with $PWD disappearing

open( STDOUT, "|-", "logger -t SecureMail" );
open( STDERR, ">&STDOUT" );
# Disable buffering for our input and output streams:
select(STDERR); $| = 1;
select(STDOUT); $| = 1;

# Double-fork to avoid leaving a zombie process:
unless ( fork() ) {
		unless ( fork() ) {
				sleep 1 until getppid() == 1;

				while ( 1 == 1 ) {
						kill_old_tunnels();

						start_tunnel();

						print "Sleeping before restarting SSH tunnel...\n";
						sleep(3);
				}
		}
}

sub kill_old_tunnels {
		open( PS, "-|", "/bin/ps wwwwax -o pid,command" ) or die("Couldn't start ps: $!");
		while (<PS>) {
				if (m/^(\d+) $SSHCMD/i) {
						print "Killing old ssh tunnel[$1]\n";
						kill($1);
				}
		}
		close(PS);
}

sub start_tunnel {
		print "Starting SSH tunnel using '$SSHCMD'\n";

		open( TUNNEL, "-|", $SSHCMD ) or die("Couldn't start tunnel: $!");
		while (<TUNNEL>) {
				print $_;
		}
		close(TUNNEL);
}