/*
 * 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.
 */

/*
 * 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(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) strlcpy(childdir, dir1, MAXPATHLEN);
        }

        /*
         * 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);
}