port/gen/closefrom.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#pragma weak _closefrom = closefrom
#pragma weak _fdwalk = fdwalk

#include "lint.h"
#include <ctype.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <dirent.h>
#include <limits.h>
#include <errno.h>
#include <alloca.h>
#include <sys/resource.h>

/* Initial size of the open file descriptor array */
#define FDS_SZ  (1024 * sizeof (int))

/*
 * Iterate over all open file descriptors, calling 'func' on each one.
 * Terminate the iteration when 'func' returns non-zero or when all
 * open file descriptors have been processed.  Return the value of
 * the last non-zero return from 'func' or zero.
 */
int
fdwalk(int (*func)(void *, int), void *cd)
{
    int err = errno;
    int rv = 0;
    int max_fds = INT_MAX;
    struct rlimit rl;
    DIR *dirp;
    struct dirent64 *dp;
    int *fds;
    size_t fds_sz;
    int nfds;
    int i;

    nfds = 0;
    fds = alloca(FDS_SZ);
    fds_sz = FDS_SZ;
    if ((dirp = opendir("/proc/self/fd")) != NULL) {
        /*
         * Collect all of the open file descriptors and close
         * the directory before calling 'func' on any of them.
         */
        while ((dp = readdir64(dirp)) != NULL) {
            /* skip '.', '..' and the opendir() fd */
            if (!isdigit(dp->d_name[0]) ||
                (i = atoi(dp->d_name)) == dirp->dd_fd)
                continue;
            if (fds_sz <= nfds * sizeof (int)) {
                fds = memcpy(alloca(fds_sz * 2), fds, fds_sz);
                fds_sz *= 2;
            }
            fds[nfds++] = i;
        }
        (void) closedir(dirp);
    } else {
        /*
         * We could not open the /proc file descriptor directory.
         * We have to do it the hard way.
         */
        if (getrlimit(RLIMIT_NOFILE, &rl) == 0)
            max_fds = (rl.rlim_max == RLIM_INFINITY)?
                INT_MAX : rl.rlim_max;
        for (i = 0; i < max_fds; i++) {
            if (fcntl(i, F_GETFD) < 0)
                continue;
            if (fds_sz <= nfds * sizeof (int)) {
                fds = memcpy(alloca(fds_sz * 2), fds, fds_sz);
                fds_sz *= 2;
            }
            fds[nfds++] = i;
        }
    }

    /*
     * Restore the original value of errno so that
     * the caller sees only the value of errno set
     * by the callback function.
     */
    errno = err;

    /*
     * Perform the callbacks on all of the open files.
     */
    for (i = 0; i < nfds; i++)
        if ((rv = func(cd, fds[i])) != 0)
            break;

    return (rv);
}

/*
 * Call-back function for closefrom(), below.
 */
static int
void_close(void *lowp, int fd)
{
    if (fd >= *(int *)lowp)
        (void) close(fd);
    return (0);
}

/*
 * Close all open file descriptors greater than or equal to lowfd.
 */
void
closefrom(int lowfd)
{
    int low = (lowfd < 0)? 0 : lowfd;

    /*
     * Close lowfd right away as a hedge against failing
     * to open the /proc file descriptor directory due
     * all file descriptors being currently used up.
     */
    (void) close(low++);
    (void) fdwalk(void_close, &low);
}