#!/usr/bin/env python

# Authors:  Jiri Jaburek  <jjaburek@redhat.com>

#

# Description: Daemonization backend for rlDaemonize

#

# Copyright (c) 2012 Red Hat, Inc. All rights reserved. This copyrighted

# material is made available to anyone wishing to use, modify, copy, or

# redistribute it subject to the terms and conditions of the GNU General

# Public License v.2.

#

# This program is distributed in the hope that it will be useful, but WITHOUT

# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License

# for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

import os, sys

from pwd import getpwnam

from grp import getgrnam

from optparse import OptionParser

from shlex import shlex

def file_write(filename, content):

    fd = open(filename, 'w')

    fd.write(content + '\n')

    fd.close()

def close_all_fds():

    try:

        maxfd = os.sysconf('SC_OPEN_MAX')  # same as _SC_OPEN_MAX in C

    except:

        maxfd = 1024

    for fd in range(0, maxfd):

        try:

            os.close(fd)

        except OSError:

            pass

# daemonize `command' (list) with arguments,

# optionally change argv[0] to `alias',

#            write child pid to file named `pidfile',

#            fully daemonize or just background (fork) - `true_daemon',

#            change effective+real user/group to `su' (list, user and group)

#            (when true_daemon=True) redirect stdin/out/err to filenames

#              specified in ioredir vector (list),

def daemonize(command, alias=None, pidfile=None, true_daemon=True, su=None, ioredir=None):

    if not alias:

        alias = command[0]

    if not true_daemon:

        pid = os.fork()

        if (pid != 0):

            # parent, write pidfile and _exit,

            # avoiding possible double cleanups/flushes

            if pidfile:

                file_write(pidfile, str(pid))

            os._exit(0)

        else:

           # child, simply execute

           os.execvp(command[0],[alias]+command[1:])

    else:

        pid = os.fork()

        if (pid != 0):

            # parent, just exit, since final pid depends on the second fork

            os._exit(0)

        else:

            os.setsid()

            pid = os.fork()

            if (pid != 0):

                # parent of the second child

                if pidfile:

                    file_write(pidfile, str(pid))

                os._exit(0)

            else:

                # second child, real daemon!

                os.chdir('/')

                # change real and effective uid/gid of a process

                if su:

                    uid = getpwnam(su[0]).pw_uid

                    gid = getgrnam(su[1]).gr_gid

                    os.setgroups([])

                    os.setregid(gid, gid)

                    os.setreuid(uid, uid)

                # pre-create possible in/out files with default umask,

                # with original stderr (in case of errors), but with new uid/gid

                if ioredir:

                    os.open(ioredir[0], os.O_RDWR)

                    os.open(ioredir[1], os.O_RDWR | os.O_CREAT | os.O_TRUNC, 0666)

                    os.open(ioredir[2], os.O_RDWR | os.O_CREAT | os.O_TRUNC, 0666)

                os.umask(0)

                close_all_fds()

                if ioredir:

                    for ioport in ioredir:

                        os.open(ioport, os.O_RDWR)

                else:

                    os.open(os.devnull, os.O_RDWR)

                    os.dup2(0,1)

                    os.dup2(0,2)

                # execute

                os.execvp(command[0],[alias]+command[1:])

# argument parsing

def error(msg):

    print >> sys.stderr, "error: " + str(msg)

    sys.exit(1)

parser = OptionParser(usage='%prog [options] COMMAND')

parser.add_option('--alias', action='store', type='string', metavar='NAME',

                  dest='alias', help='specify custom argv[0]')

parser.add_option('--background', action='store_true',

                  dest='background', help='background (fork) only, nothing else')

parser.add_option('--su', action='store', type='string', metavar='USER:GROUP',

                  dest='su', help='run daemon under another user')

parser.add_option('--ioredir', action='store', type='string', metavar='IN,OUT,ERR',

                  dest='ioredir', help='redirect std{in,out,err} of the daemon to files')

parser.add_option('--pidfile', action='store', type='string', metavar='FILE',

                  dest='pidfile', help='write daemon pid to a file')

(opts, args) = parser.parse_args()

# additional parsing

if opts.su:

    su = opts.su.split(':')

else:

    su = None

if opts.ioredir:

    ioredir = opts.ioredir.split(',')

else:

    ioredir = None

# sanity checks

if not args:

    error("no COMMAND specified")

if len(args) > 1:

    error("COMMAND can be only one argument, quote it")

if opts.su:

    if len(su) != 2:

        error("wrong --su argument specification")

    for i in su:

        if not i:

            error("wrong --su argument specification")

if opts.ioredir:

    if len(ioredir) != 3:

        error("wrong --ioredir argument specification")

    for i in ioredir:

        if not i:

            error("wrong --ioredir argument specification")

# shell-expand the COMMAND into list

lex = shlex(args[0])

lex.whitespace_split = True

args = list(lex)

# input parsing finished

daemonize(args, alias=opts.alias, pidfile=opts.pidfile,

          true_daemon=(not opts.background), su=su, ioredir=ioredir)