server/background.c

   1 /* nbdkit
   2  * Copyright (C) 2019 Red Hat Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdarg.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40 #include <fcntl.h>
  41
  42 #include "internal.h"
  43
  44 /* True if we forked into the background (used to control log messages). */
  45 bool forked_into_background;
  46
  47 /* Run as a background process.  If foreground is set (ie. -f or
  48  * equivalent) then this does nothing.  Otherwise it forks into the
  49  * background and sets forked_into_background.
  50  */
  51 void
  52 fork_into_background (void)
  53 {
  54   pid_t pid;
  55
  56   if (foreground)
  57     return;
  58
  59   pid = fork ();
  60   if (pid == -1) {
  61     perror ("fork");
  62     exit (EXIT_FAILURE);
  63   }
  64
  65   if (pid > 0)                  /* Parent process exits. */
  66     exit (EXIT_SUCCESS);
  67
  68 #pragma GCC diagnostic push
  69 #pragma GCC diagnostic ignored "-Wunused-result"
  70   chdir ("/");
  71 #pragma GCC diagnostic pop
  72
  73   /* Close stdin/stdout and redirect to /dev/null. */
  74   close (0);
  75   close (1);
  76   open ("/dev/null", O_RDONLY);
  77   open ("/dev/null", O_WRONLY);
  78
  79   /* If not verbose, set stderr to the same as stdout as well. */
  80   if (!verbose)
  81     dup2 (1, 2);
  82
  83   forked_into_background = true;
  84   debug ("forked into background (new pid = %d)", getpid ());
  85 }