usr/src/lib/libc/port/gen/daemon.c

   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
  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 }