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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License (the "License").
      6  * You may not use this file except in compliance with the License.
      7  *
      8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      9  * or http://www.opensolaris.org/os/licensing.
     10  * See the License for the specific language governing permissions
     11  * and limitations under the License.
     12  *
     13  * When distributing Covered Code, include this CDDL HEADER in each
     14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     15  * If applicable, add the following below this CDDL HEADER, with the
     16  * fields enclosed by brackets "[]" replaced with your own identifying
     17  * information: Portions Copyright [yyyy] [name of copyright owner]
     18  *
     19  * CDDL HEADER END
     20  */
     21 
     22 /*
     23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     28 
     29 #pragma weak _closefrom = closefrom
     30 #pragma weak _fdwalk = fdwalk
     31 
     32 #include "lint.h"
     33 #include <ctype.h>
     34 #include <stdlib.h>
     35 #include <unistd.h>
     36 #include <string.h>
     37 #include <fcntl.h>
     38 #include <dirent.h>
     39 #include <limits.h>
     40 #include <errno.h>
     41 #include <alloca.h>
     42 #include <sys/resource.h>
     43 
     44 /* Initial size of the open file descriptor array */
     45 #define	FDS_SZ	(1024 * sizeof (int))
     46 
     47 /*
     48  * Iterate over all open file descriptors, calling 'func' on each one.
     49  * Terminate the iteration when 'func' returns non-zero or when all
     50  * open file descriptors have been processed.  Return the value of
     51  * the last non-zero return from 'func' or zero.
     52  */
     53 int
     54 fdwalk(int (*func)(void *, int), void *cd)
     55 {
     56 	int err = errno;
     57 	int rv = 0;
     58 	int max_fds = INT_MAX;
     59 	struct rlimit rl;
     60 	DIR *dirp;
     61 	struct dirent64 *dp;
     62 	int *fds;
     63 	size_t fds_sz;
     64 	int nfds;
     65 	int i;
     66 
     67 	nfds = 0;
     68 	fds = alloca(FDS_SZ);
     69 	fds_sz = FDS_SZ;
     70 	if ((dirp = opendir("/proc/self/fd")) != NULL) {
     71 		/*
     72 		 * Collect all of the open file descriptors and close
     73 		 * the directory before calling 'func' on any of them.
     74 		 */
     75 		while ((dp = readdir64(dirp)) != NULL) {
     76 			/* skip '.', '..' and the opendir() fd */
     77 			if (!isdigit(dp->d_name[0]) ||
     78 			    (i = atoi(dp->d_name)) == dirp->dd_fd)
     79 				continue;
     80 			if (fds_sz <= nfds * sizeof (int)) {
     81 				fds = memcpy(alloca(fds_sz * 2), fds, fds_sz);
     82 				fds_sz *= 2;
     83 			}
     84 			fds[nfds++] = i;
     85 		}
     86 		(void) closedir(dirp);
     87 	} else {
     88 		/*
     89 		 * We could not open the /proc file descriptor directory.
     90 		 * We have to do it the hard way.
     91 		 */
     92 		if (getrlimit(RLIMIT_NOFILE, &rl) == 0)
     93 			max_fds = (rl.rlim_max == RLIM_INFINITY)?
     94 			    INT_MAX : rl.rlim_max;
     95 		for (i = 0; i < max_fds; i++) {
     96 			if (fcntl(i, F_GETFD) < 0)
     97 				continue;
     98 			if (fds_sz <= nfds * sizeof (int)) {
     99 				fds = memcpy(alloca(fds_sz * 2), fds, fds_sz);
    100 				fds_sz *= 2;
    101 			}
    102 			fds[nfds++] = i;
    103 		}
    104 	}
    105 
    106 	/*
    107 	 * Restore the original value of errno so that
    108 	 * the caller sees only the value of errno set
    109 	 * by the callback function.
    110 	 */
    111 	errno = err;
    112 
    113 	/*
    114 	 * Perform the callbacks on all of the open files.
    115 	 */
    116 	for (i = 0; i < nfds; i++)
    117 		if ((rv = func(cd, fds[i])) != 0)
    118 			break;
    119 
    120 	return (rv);
    121 }
    122 
    123 /*
    124  * Call-back function for closefrom(), below.
    125  */
    126 static int
    127 void_close(void *lowp, int fd)
    128 {
    129 	if (fd >= *(int *)lowp)
    130 		(void) close(fd);
    131 	return (0);
    132 }
    133 
    134 /*
    135  * Close all open file descriptors greater than or equal to lowfd.
    136  */
    137 void
    138 closefrom(int lowfd)
    139 {
    140 	int low = (lowfd < 0)? 0 : lowfd;
    141 
    142 	/*
    143 	 * Close lowfd right away as a hedge against failing
    144 	 * to open the /proc file descriptor directory due
    145 	 * all file descriptors being currently used up.
    146 	 */
    147 	(void) close(low++);
    148 	(void) fdwalk(void_close, &low);
    149 }
    150