xref: /titanic_41/usr/src/lib/libc/port/gen/daemon.c (revision a8c92b49f4e8de856d9e4775e15e4fa90a687664)
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  */
26 
27 #include "lint.h"
28 #include "file64.h"
29 #include "mtlib.h"
30 
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <unistd.h>
34 #include <fcntl.h>
35 
36 #include "stdiom.h"
37 
38 /*
39  * Use fork/setsid/fork to go into background and permanently remove
40  * controlling terminal.
41  */
42 int
43 daemon(int nochdir, int noclose)
44 {
45 	int retv, fd;
46 
47 	/*
48 	 * By the first fork+setsid, we disconnect from our current controlling
49 	 * terminal and become a session group leader.
50 	 */
51 	retv = fork();
52 	if (retv == -1)
53 		return (-1);
54 	if (retv != 0)
55 		_exit(EXIT_SUCCESS);
56 	if (setsid() == -1)
57 		return (-1);
58 	/*
59 	 * By forking again without calling setsid again, we make certain
60 	 * that we are not the session group leader and can never reacquire
61 	 * a controlling terminal.
62 	 */
63 	retv = fork();
64 	if (retv == -1)
65 		return (-1);
66 	if (retv != 0)
67 		_exit(EXIT_SUCCESS);
68 
69 	if (nochdir == 0)
70 		(void) chdir("/");
71 
72 	if (noclose == 0) {
73 		/*
74 		 * Missing the PRIV_FILE_READ privilege may be one of the
75 		 * reasons that prevent the opening of /dev/null to succeed.
76 		 */
77 		if ((fd = open("/dev/null", O_RDWR)) == -1)
78 			return (-1);
79 
80 		/*
81 		 * Also, if any of the descriptor redirects fails we should
82 		 * return with error to signal to the caller that his request
83 		 * cannot be fulfilled properly. It is up to the caller to
84 		 * do the cleanup.
85 		 */
86 		if ((fd != STDIN_FILENO) && (dup2(fd, STDIN_FILENO) < 0)) {
87 			(void) close(fd);
88 			return (-1);
89 		}
90 		if ((fd != STDOUT_FILENO) && (dup2(fd, STDOUT_FILENO) < 0)) {
91 			(void) close(fd);
92 			return (-1);
93 		}
94 		if ((fd != STDERR_FILENO) && (dup2(fd, STDERR_FILENO) < 0)) {
95 			(void) close(fd);
96 			return (-1);
97 		}
98 
99 		if (fd > STDERR_FILENO)
100 			(void) close(fd);
101 	}
102 	return (0);
103 }
104