1 /*
2 * closefrom.c - closefrom() replacement
3 */
4
5 /***********************************************************************
6 * Copyright © 2006 Rémi Denis-Courmont. *
7 * This program is free software; you can redistribute and/or modify *
8 * it under the terms of the GNU General Public License as published *
9 * by the Free Software Foundation; version 2 of the license, or (at *
10 * your option) any later version. *
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 */
closefrom(int fd)39 extern int closefrom (int fd)
40 {
41 struct rlimit lim;
42 unsigned found = 0;
43 int saved_errno;
44
45 if (getrlimit (RLIMIT_NOFILE, &lim))
46 return -1;
47
48 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 if (lim.rlim_max > FD_SETSIZE)
69 {
70 if (lim.rlim_cur > FD_SETSIZE)
71 lim.rlim_cur = FD_SETSIZE;
72 lim.rlim_max = FD_SETSIZE;
73 setrlimit (RLIMIT_NOFILE, &lim);
74 }
75
76 while ((unsigned)fd < lim.rlim_max)
77 if (close (fd++) == 0)
78 found++;
79
80 if (found == 0)
81 {
82 errno = EBADF;
83 return -1;
84 }
85 errno = saved_errno;
86 return 0;
87 }
88