1                 : /*
       2                 :  * closefrom.c - closefrom() replacement
       3                 :  * $Id: closefrom.c 1329 2006-05-09 19:29:45Z remi $
       4                 :  */
       5                 : 
       6                 : /***********************************************************************
       7                 :  *  Copyright © 2006 Rémi Denis-Courmont.                              *
       8                 :  *  This program is free software; you can redistribute and/or modify  *
       9                 :  *  it under the terms of the GNU General Public License as published  *
      10                 :  *  by the Free Software Foundation; version 2 of the license.         *
      11                 :  *                                                                     *
      12                 :  *  This program is distributed in the hope that it will be useful,    *
      13                 :  *  but WITHOUT ANY WARRANTY; without even the implied warranty of     *
      14                 :  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.               *
      15                 :  *  See the GNU General Public License for more details.               *
      16                 :  *                                                                     *
      17                 :  *  You should have received a copy of the GNU General Public License  *
      18                 :  *  along with this program; if not, you can get it from:              *
      19                 :  *  http://www.gnu.org/copyleft/gpl.html                               *
      20                 :  ***********************************************************************/
      21                 : 
      22                 : #ifdef HAVE_CONFIG_H
      23                 : # include <config.h>
      24                 : #endif
      25                 : 
      26                 : #include <sys/types.h>
      27                 : #include <sys/time.h> /* for <sys/resource.h> */
      28                 : #include <sys/resource.h> /* getrlimit() */
      29                 : #include <unistd.h>
      30                 : #include <errno.h> /* errno */
      31                 : #include <sys/select.h> /* FD_SETSIZE */
      32                 : 
      33                 : /**
      34                 :  * BSD closefrom() replacement.
      35                 :  *
      36                 :  * We don't handle EINTR error properly;
      37                 :  * this replacement is obviously not atomic.
      38                 :  */
      39                 : extern int closefrom (int fd)
      40               0 : {
      41                 :         struct rlimit lim;
      42               0 :         unsigned found = 0;
      43                 :         int saved_errno;
      44                 : 
      45               0 :         if (getrlimit (RLIMIT_NOFILE, &lim))
      46               0 :                 return -1;
      47                 : 
      48               0 :         saved_errno = errno;
      49                 : 
      50                 :         /*
      51                 :          * Make sure closefrom() does not take ages if the file number limit
      52                 :          * is very big. closefrom() is not supposed to setrlimit(), but it is
      53                 :          * not standard, neither common (Darwin, Linux don't have it at the
      54                 :          * moment, and IIRC, FreeBSD and NetBSD neither).
      55                 :          *
      56                 :          * Rather than put some completely arbitrary limit, we use FD_SETSIZE.
      57                 :          * As such we can warranty that subsequent FD_SET() won't overflow.
      58                 :          * Miredo has a O(1) open file descriptors number behavior anyway. If
      59                 :          * you want to use this in another project, you should first consider
      60                 :          * using BSD kqueue/Linux epoll or a portable wrapper of these
      61                 :          * scalable I/O polling calls, and *THEN* use a higher limit here
      62                 :          * instead of FD_SETSIZE.
      63                 :          *
      64                 :          * Mac OS X returns (2^31 - 1) as its limit, and closefrom() is way
      65                 :          * too long (and intensive) in this case. Linux usually returns 1024,
      66                 :          * though root can raise the limit to 1048576.
      67                 :          */
      68               0 :         if (lim.rlim_max > FD_SETSIZE)
      69                 :         {
      70               0 :                 if (lim.rlim_cur > FD_SETSIZE)
      71               0 :                         lim.rlim_cur = FD_SETSIZE;
      72               0 :                 lim.rlim_max = FD_SETSIZE;
      73               0 :                 setrlimit (RLIMIT_NOFILE, &lim);
      74                 :         }
      75                 : 
      76               0 :         while ((unsigned)fd < lim.rlim_max)
      77               0 :                 if (close (fd++) == 0)
      78               0 :                         found++;
      79                 : 
      80               0 :         if (found == 0)
      81                 :         {
      82               0 :                 errno = EBADF;
      83               0 :                 return -1;
      84                 :         }
      85               0 :         errno = saved_errno;
      86               0 :         return 0;
      87                 : }