#!/usr/bin/perl

# Copyright 2014 Jan Pazdziora

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#     http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

use strict;

use warnings FATAL => 'all';

use IO::Socket::UNIX ();

use Socket ();

use POSIX ();

sub daemonize {

	open(STDERR, '>>', '/var/log/systemctl-socket-daemon.log')        || die "can't write log: $!";

	open(STDOUT, '>&STDERR')     || die "can't write stdout to log: $!";

	chdir("/")                      || die "can't chdir to /: $!";

	open(STDIN,  '<', '/dev/null')     || die "can't read /dev/null: $!";

	defined(my $pid = fork())       || die "can't fork: $!";

	exit if $pid;                   # non-zero now means I am the parent

	(POSIX::setsid() != -1)                || die "Can't start a new session: $!";

}

my ($socket_path, $socket_mode, $service) = @ARGV;

if (not defined $socket_path or not defined $service) {

	die "Usage: $0 /path/to/unix/socket mode service-to-run\n";

}

if (-e $socket_path) {

	warn "Path [$socket_path] already exists, removing\n";

	unlink $socket_path;

}

my $service_data = `/bin/systemctl show $service 2>&1;;

if ($?) {

	die "Failed to find service [$service]:\n$service_data";

}

my $socket = new IO::Socket::UNIX(

	Type => Socket::SOCK_STREAM,

	Local => $socket_path,

	Listen => Socket::SOMAXCONN

) or die "socket: $!\n";

chmod oct($socket_mode), $socket_path;

daemonize();

while (1) {

	next unless my $connection = $socket->accept;

	my $pid = fork();

	if ($pid == 0) {

		*STDIN = $connection;

		*STDOUT = $connection;

		exec '/bin/systemctl', 'start', $service;

		die "exec should have never reached here\n";

	}

}