usr/src/lib/libshare/common/issubdir.c

   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, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 /*
  31  * University Copyright- Copyright (c) 1982, 1986, 1988
  32  * The Regents of the University of California
  33  * All Rights Reserved
  34  *
  35  * University Acknowledgment- Portions of this document are derived from
  36  * software developed by the University of California, Berkeley, and its
  37  * contributors.
  38  */
  39
  40 #pragma ident   "%Z%%M% %I%     %E% SMI"
  41
  42 /*
  43  * Subdirectory detection: needed by exportfs and rpc.mountd.
  44  * The above programs call issubdir() frequently, so we make
  45  * it fast by caching the results of stat().
  46  */
  47 #include <sys/types.h>
  48 #include <sys/param.h>
  49 #include <sys/stat.h>
  50 #include <string.h>
  51
  52 #define MAXSTATS MAXPATHLEN/2   /* maximum number of stat()'s to save */
  53
  54 #define inoeq(ino1, ino2)       ((ino1) == (ino2))
  55 #define deveq(dev1, dev2)       ((dev1) == (dev2))
  56
  57 /*
  58  * dir1 is a subdirectory of dir2 within the same filesystem if
  59  *     (a) dir1 is identical to dir2
  60  *     (b) dir1's parent is dir2
  61  */
  62 int
  63 issubdir(dir1, dir2)
  64         char *dir1;
  65         char *dir2;
  66 {
  67         struct stat st;
  68         struct stat parent_st;
  69         char *p;
  70         int index;
  71
  72         static dev_t child_dev;
  73         static dev_t child_rdev;
  74         static ino_t child_ino[MAXSTATS];
  75         static int valid;
  76         static char childdir[MAXPATHLEN];
  77         static char child_fstype[_ST_FSTYPSZ];
  78
  79         /*
  80          * Get parent directory info
  81          */
  82         if (stat(dir2, &parent_st) < 0) {
  83                 return (0);
  84         }
  85
  86         if (strcmp(childdir, dir1) != 0) {
  87                 /*
  88                  * Not in cache: get child directory info
  89                  */
  90                 p = strcpy(childdir, dir1) + strlen(dir1);
  91                 index = 0;
  92                 valid = 0;
  93                 for (;;) {
  94                         if (stat(childdir, &st) < 0) {
  95                                 childdir[0] = 0;        /* invalidate cache */
  96                                 return (0);
  97                         }
  98                         if (index == 0) {
  99                                 child_dev = st.st_dev;
 100                                 child_rdev = st.st_rdev;
 101                                 (void) strncpy(child_fstype, st.st_fstype,
 102                                                 sizeof (child_fstype));
 103                         }
 104                         if (index > 0 &&
 105                             (child_dev != st.st_dev ||
 106                                 inoeq(child_ino[index - 1], st.st_ino))) {
 107                                 /*
 108                                  * Hit root: done
 109                                  */
 110                                 break;
 111                         }
 112                         child_ino[index++] = st.st_ino;
 113                         if (S_ISDIR(st.st_mode)) {
 114                                 p = strcpy(p, "/..") + 3;
 115                         } else {
 116                                 p = strrchr(childdir, '/');
 117                                 if (p == NULL) {
 118                                         p = strcpy(childdir, ".") + 1;
 119                                 } else {
 120                                         while (((p - 1) > childdir) &&
 121                                                 *(p - 1) == '/') {
 122                                                 p--;
 123                                         }
 124                                         *p = '\0';
 125                                 }
 126                         }
 127                 }
 128                 valid = index;
 129                 (void) strcpy(childdir, dir1);
 130         }
 131
 132         /*
 133          * Perform the test
 134          */
 135         if (!deveq(parent_st.st_dev, child_dev)) {
 136                 return (0);
 137         }
 138
 139         /*
 140          * Check rdev also in case of lofs
 141          */
 142         if (((strcmp(parent_st.st_fstype, "lofs") == 0)) &&
 143                 (strcmp(child_fstype, "lofs") == 0)) {
 144                 if (!deveq(parent_st.st_rdev, child_rdev)) {
 145                         return (0);
 146                 }
 147         }
 148
 149         for (index = 0; index < valid; index++) {
 150                 if (inoeq(child_ino[index], parent_st.st_ino)) {
 151                         return (1);
 152                 }
 153         }
 154         return (0);
 155 }