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 _PUBLIC_ int close_low_fd(int fd)
  25 {
  26 #ifndef VALGRIND
  27         int ret, dev_null;
  28
  29         dev_null = open("/dev/null", O_RDWR, 0);
  30
  31         if ((dev_null == -1) && (errno = ENFILE)) {
  32                 /*
  33                  * Try to free up an fd
  34                  */
  35                 ret = close(fd);
  36                 if (ret != 0) {
  37                         return errno;
  38                 }
  39         }
  40
  41         dev_null = open("/dev/null", O_RDWR, 0);
  42         if (dev_null == -1) {
  43                 dev_null = open("/dev/null", O_WRONLY, 0);
  44         }
  45         if (dev_null == -1) {
  46                 return errno;
  47         }
  48
  49         if (dev_null == fd) {
  50                 /*
  51                  * This can happen in the ENFILE case above
  52                  */
  53                 return 0;
  54         }
  55
  56         ret = dup2(dev_null, fd);
  57         if (ret == -1) {
  58                 int err = errno;
  59                 close(dev_null);
  60                 return err;
  61         }
  62         close(dev_null);
  63 #endif
  64         return 0;
  65 }