xref: /illumos-gate/usr/src/lib/libc/port/gen/daemon.c (revision 48bbca816818409505a6e214d0911fda44e622e3)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  * Copyright (c) 2016 by Delphix. All rights reserved.
26  */
27 
28 #include "lint.h"
29 #include "file64.h"
30 #include "mtlib.h"
31 
32 #include <stdio.h>
33 #include <stdlib.h>
34 #include <unistd.h>
35 #include <fcntl.h>
36 
37 #include "stdiom.h"
38 
39 /*
40  * Use fork/setsid/fork to go into background and permanently remove
41  * controlling terminal.
42  */
43 int
daemon(int nochdir,int noclose)44 daemon(int nochdir, int noclose)
45 {
46 	int retv, fd;
47 
48 	/*
49 	 * By the first fork+setsid, we disconnect from our current controlling
50 	 * terminal and become a session group leader.
51 	 */
52 	retv = fork();
53 	if (retv == -1)
54 		return (-1);
55 	if (retv != 0)
56 		_exit(EXIT_SUCCESS);
57 	if (setsid() == -1)
58 		return (-1);
59 	/*
60 	 * By forking again without calling setsid again, we make certain
61 	 * that we are not the session group leader and can never reacquire
62 	 * a controlling terminal.
63 	 */
64 	retv = fork();
65 	if (retv == -1)
66 		return (-1);
67 	if (retv != 0)
68 		_exit(EXIT_SUCCESS);
69 
70 	if (nochdir == 0)
71 		(void) chdir("/");
72 
73 	if (noclose == 0) {
74 		/*
75 		 * Missing the PRIV_FILE_READ privilege may be one of the
76 		 * reasons that prevent the opening of /dev/null to succeed.
77 		 */
78 		if ((fd = open("/dev/null", O_RDWR)) == -1)
79 			return (-1);
80 
81 		/*
82 		 * Also, if any of the descriptor redirects fails we should
83 		 * return with error to signal to the caller that its request
84 		 * cannot be fulfilled properly. It is up to the caller to
85 		 * do the cleanup.
86 		 */
87 		if ((fd != STDIN_FILENO) && (dup2(fd, STDIN_FILENO) < 0)) {
88 			(void) close(fd);
89 			return (-1);
90 		}
91 		if ((fd != STDOUT_FILENO) && (dup2(fd, STDOUT_FILENO) < 0)) {
92 			(void) close(fd);
93 			return (-1);
94 		}
95 		if ((fd != STDERR_FILENO) && (dup2(fd, STDERR_FILENO) < 0)) {
96 			(void) close(fd);
97 			return (-1);
98 		}
99 
100 		if (fd > STDERR_FILENO)
101 			(void) close(fd);
102 	}
103 	return (0);
104 }
105