libshare/common/issubdir.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

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

/*
 * Subdirectory detection: needed by exportfs and rpc.mountd.
 * The above programs call issubdir() frequently, so we make
 * it fast by caching the results of stat().
 */
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <string.h>

#define MAXSTATS MAXPATHLEN/2   /* maximum number of stat()'s to save */

#define inoeq(ino1, ino2)   ((ino1) == (ino2))
#define deveq(dev1, dev2)   ((dev1) == (dev2))

/*
 * dir1 is a subdirectory of dir2 within the same filesystem if
 *     (a) dir1 is identical to dir2
 *     (b) dir1's parent is dir2
 */
int
issubdir(dir1, dir2)
    char *dir1;
    char *dir2;
{
    struct stat st;
    struct stat parent_st;
    char *p;
    int index;

    static dev_t child_dev;
    static dev_t child_rdev;
    static ino_t child_ino[MAXSTATS];
    static int valid;
    static char childdir[MAXPATHLEN];
    static char child_fstype[_ST_FSTYPSZ];

    /*
     * Get parent directory info
     */
    if (stat(dir2, &parent_st) < 0) {
        return (0);
    }

    if (strcmp(childdir, dir1) != 0) {
        /*
         * Not in cache: get child directory info
         */
        p = strcpy(childdir, dir1) + strlen(dir1);
        index = 0;
        valid = 0;
        for (;;) {
            if (stat(childdir, &st) < 0) {
                childdir[0] = 0;    /* invalidate cache */
                return (0);
            }
            if (index == 0) {
                child_dev = st.st_dev;
                child_rdev = st.st_rdev;
                (void) strncpy(child_fstype, st.st_fstype,
                        sizeof (child_fstype));
            }
            if (index > 0 &&
                (child_dev != st.st_dev ||
                inoeq(child_ino[index - 1], st.st_ino))) {
                /*
                 * Hit root: done
                 */
                break;
            }
            child_ino[index++] = st.st_ino;
            if (S_ISDIR(st.st_mode)) {
                p = strcpy(p, "/..") + 3;
            } else {
                p = strrchr(childdir, '/');
                if (p == NULL) {
                    p = strcpy(childdir, ".") + 1;
                } else {
                    while (((p - 1) > childdir) &&
                        *(p - 1) == '/') {
                        p--;
                    }
                    *p = '\0';
                }
            }
        }
        valid = index;
        (void) strcpy(childdir, dir1);
    }

    /*
     * Perform the test
     */
    if (!deveq(parent_st.st_dev, child_dev)) {
        return (0);
    }

    /*
     * Check rdev also in case of lofs
     */
    if (((strcmp(parent_st.st_fstype, "lofs") == 0)) &&
        (strcmp(child_fstype, "lofs") == 0)) {
        if (!deveq(parent_st.st_rdev, child_rdev)) {
            return (0);
        }
    }

    for (index = 0; index < valid; index++) {
        if (inoeq(child_ino[index], parent_st.st_ino)) {
            return (1);
        }
    }
    return (0);
}