/*******************************************************************************
 * Copyright (C) 2004-2008 Intel Corp. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  - Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 *  - Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 *  - Neither the name of Intel Corp. nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL Intel Corp. OR THE CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *******************************************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef DAEMON

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cerrno>
#include <csignal>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <syslog.h>
#include <pwd.h>

#include "daemonize.h"

static RETSIGTYPE child_handler(int signum)
{
	switch (signum) {
	case SIGALRM:
		exit(EXIT_FAILURE);
		break;
	case SIGUSR1:
		exit(EXIT_SUCCESS);
		break;
	case SIGCHLD:
		exit(EXIT_FAILURE);
		break;
	}
}

void daemonize()
{
	pid_t pid, sid, parent;

	/* Drop user if there is one, and we were run as root */
	if (getuid() == 0 || geteuid() == 0) {
		struct passwd *pw = getpwnam(RUN_AS_USER);
		if (pw) {
			//syslog(LOG_NOTICE, "setting user to " RUN_AS_USER);
			setuid(pw->pw_uid);
		}
	}

	/* Trap signals that we expect to recieve */
	signal(SIGCHLD, child_handler);
	signal(SIGUSR1, child_handler);
	signal(SIGALRM, child_handler);

	/* Fork off the parent process */
	pid = fork();
	if (pid < 0) {
		syslog(LOG_ERR, "unable to fork daemon, code=%d (%s)",
		       errno, strerror(errno));
		exit(EXIT_FAILURE);
	}
	/* If we got a good PID, then we can exit the parent process. */
	if (pid > 0) {

		/* Wait for confirmation from the child via SIGTERM or SIGCHLD, or
		   for two seconds to elapse (SIGALRM).  pause() should not return. */
		alarm(2);
		pause();

		exit(EXIT_FAILURE);
	}

	/* At this point we are executing as the child process */
	parent = getppid();

	signal(SIGCHLD, SIG_DFL);
	signal(SIGUSR1, SIG_DFL);
	signal(SIGALRM, SIG_DFL);
	setTerminationHandler();

	/* Create a new SID for the child process */
	sid = setsid();
	if (sid < 0) {
		syslog(LOG_ERR,
		       "unable to create a new session, code %d (%s)",
		       errno, strerror(errno));
		exit(EXIT_FAILURE);
	}

	/* Change the current working directory.  This prevents the current
	   directory from being locked; hence not being able to remove it. */
	if ((chdir("/")) < 0) {
		syslog(LOG_ERR,
		       "unable to change directory to %s, code %d (%s)",
		       "/", errno, strerror(errno));
		exit(EXIT_FAILURE);
	}

	/* Redirect standard files to /dev/null */
	freopen("/dev/null", "r", stdin);
	freopen("/dev/null", "w", stdout);
	freopen("/dev/null", "w", stderr);

	/* Tell the parent process that we are A-okay */
	kill(parent, SIGUSR1);
}

#endif //DAEMON