// Copyright(c) 2017-2020, Intel Corporation

//

// 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 Corporation  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 THE COPYRIGHT OWNER  OR 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

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/*

 * daemonize.c : routine to become a system daemon process.

 */

#include <stdlib.h>

#include <string.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <unistd.h>

#include <fcntl.h>

#include <signal.h>

int daemonize(void (*hndlr)(int, siginfo_t *, void *), mode_t mask, const char *dir)

{

	pid_t pid;

	pid_t sid;

	int res;

	int fd;

	struct sigaction sa;

	pid = fork();

	if (pid < 0) // fork() failed.

		return errno;

	// 1) Orphan the child process so that it runs in the background.

	if (pid > 0)

		exit(0);

	// 2) Become leader of a new session and process group leader of new process

	// group. The process is now detached from its controlling terminal.

	sid = setsid();

	if (sid < 0)

		return errno;

	// 3) Establish signal handler.

	memset(&sa, 0, sizeof(sa));

	sa.sa_flags     = SA_SIGINFO | SA_RESETHAND;

	sa.sa_sigaction = hndlr;

	res = sigaction(SIGINT, &sa, NULL);

	if (res < 0)

		return errno;

	res = sigaction(SIGTERM, &sa, NULL);

	if (res < 0)

		return errno;

	// 4) Orphan the child again - the session leading process terminates.

	// (only session leaders can request TTY).

	pid = fork();

	if (pid < 0) // fork() failed.

		return errno;

	if (pid > 0)

		exit(0);

	// 5) Set new file mode mask.

	umask(mask);

	// 6) change directory

	res = chdir(dir);

	if (res < 0)

		return errno;

	// 7) Close all open file descriptors

	fd = sysconf(_SC_OPEN_MAX);

	while (fd >= 0)

		close(fd--);

	return 0;

}