OSX/libsecurity_utilities/lib/daemon.cpp

   1 /*
   2  * Copyright (c) 2000-2004,2011,2014 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 //
  26 // demon - support code for writing UNIXoid demons
  27 //
  28 #include <security_utilities/daemon.h>
  29 #include <security_utilities/logging.h>
  30 #include <security_utilities/debugging.h>
  31 #include <sys/types.h>
  32 #include <errno.h>
  33 #include <unistd.h>
  34 #include <fcntl.h>
  35
  36 namespace Security {
  37 namespace Daemon {
  38
  39 //
  40 // Daemonize this process, the UNIX way.
  41 //
  42 bool incarnate(bool doFork /*=true*/)
  43 {
  44         if (doFork) {
  45                 // fork with slight resilience
  46                 for (int forkTries = 1; forkTries <= 5; forkTries++) {
  47                         switch (fork()) {
  48                                 case 0:                 // child
  49                                                         // we are the daemon process (Har! Har!)
  50                                         break;
  51                                 case -1:                // parent: fork failed
  52                                         switch (errno) {
  53                                                 case EAGAIN:
  54                                                 case ENOMEM:
  55                                                         Syslog::warning("fork() short on resources (errno=%d); retrying", errno);
  56                                                         sleep(forkTries);
  57                                                         continue;
  58                                                 default:
  59                                                         Syslog::error("fork() failed (errno=%d)", errno);
  60                                                         return false;
  61                                         }
  62                                 default:                // parent
  63                                                         // @@@ we could close an assurance loop here, but we don't (yet?)
  64                                         exit(0);
  65                         }
  66                 }
  67                 // fork succeeded; we are the child; parent is terminating
  68         }
  69
  70         // create new session (the magic set-me-apart system call)
  71         setsid();
  72
  73         // redirect standard channels to /dev/null
  74         close(0);       // fail silently in case 0 is closed
  75         if (open("/dev/null", O_RDWR, 0) == 0) {        // /dev/null could be missing, I suppose...
  76                 dup2(0, 1);
  77                 dup2(0, 2);
  78         }
  79
  80         // ready to roll
  81         return true;
  82 }
  83
  84 } // end namespace Daemon
  85 } // end namespace Security