lib/util/close_low_fd.c

   1 /*
   2  * Unix SMB/CIFS implementation.
   3  * Samba utility functions
   4  * Copyright (C) Volker Lendecke 2014
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "replace.h"
  21 #include "system/filesys.h"
  22 #include "close_low_fd.h"
  23
  24 #ifdef HAVE_VALGRIND_VALGRIND_H
  25 #include <valgrind/valgrind.h>
  26 #elif defined(HAVE_VALGRIND_H)
  27 #include <valgrind.h>
  28 #else
  29 #define RUNNING_ON_VALGRIND 0
  30 #endif
  31
  32 _PUBLIC_ int close_low_fd(int fd)
  33 {
  34         int ret, dev_null;
  35
  36         if (RUNNING_ON_VALGRIND) {
  37                 return 0;
  38         }
  39
  40         dev_null = open("/dev/null", O_RDWR, 0);
  41
  42         if ((dev_null == -1) && (errno == ENFILE)) {
  43                 /*
  44                  * Try to free up an fd
  45                  */
  46                 ret = close(fd);
  47                 if (ret != 0) {
  48                         return errno;
  49                 }
  50
  51                 dev_null = open("/dev/null", O_RDWR, 0);
  52         }
  53
  54         if (dev_null == -1) {
  55                 dev_null = open("/dev/null", O_WRONLY, 0);
  56         }
  57         if (dev_null == -1) {
  58                 return errno;
  59         }
  60
  61         if (dev_null == fd) {
  62                 /*
  63                  * This can happen in the ENFILE case above
  64                  */
  65                 return 0;
  66         }
  67
  68         ret = dup2(dev_null, fd);
  69         if (ret == -1) {
  70                 int err = errno;
  71                 close(dev_null);
  72                 return err;
  73         }
  74         close(dev_null);
  75         return 0;
  76 }