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opendir.c revision 1.20 
      1 /*	$NetBSD: opendir.c,v 1.20 2000/01/22 22:19:11 mycroft Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1983, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)opendir.c	8.7 (Berkeley) 12/10/94";
     40 #else
     41 __RCSID("$NetBSD: opendir.c,v 1.20 2000/01/22 22:19:11 mycroft Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include "namespace.h"
     46 #include <sys/param.h>
     47 #include <sys/mount.h>
     48 #include <sys/stat.h>
     49 
     50 #include <assert.h>
     51 #include <dirent.h>
     52 #include <errno.h>
     53 #include <fcntl.h>
     54 #include <stdlib.h>
     55 #include <string.h>
     56 #include <unistd.h>
     57 
     58 #ifdef __weak_alias
     59 __weak_alias(opendir,_opendir)
     60 #endif
     61 
     62 /*
     63  * Open a directory.
     64  */
     65 DIR *
     66 opendir(name)
     67 	const char *name;
     68 {
     69 
     70 	_DIAGASSERT(name != NULL);
     71 
     72 	return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
     73 }
     74 
     75 DIR *
     76 __opendir2(name, flags)
     77 	const char *name;
     78 	int flags;
     79 {
     80 	DIR *dirp;
     81 	int fd;
     82 	struct stat sb;
     83 	int pagesz;
     84 	int incr;
     85 	int unionstack, nfsdir;
     86 	struct statfs sfb;
     87 
     88 	_DIAGASSERT(name != NULL);
     89 
     90 	if ((fd = open(name, O_RDONLY | O_NONBLOCK)) == -1)
     91 		return (NULL);
     92 	if (fstat(fd, &sb) || !S_ISDIR(sb.st_mode)) {
     93 		errno = ENOTDIR;
     94 		close(fd);
     95 		return (NULL);
     96 	}
     97 	if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
     98 	    (dirp = (DIR *)malloc(sizeof(DIR))) == NULL) {
     99 		close(fd);
    100 		return (NULL);
    101 	}
    102 
    103 	/*
    104 	 * If the machine's page size is an exact multiple of DIRBLKSIZ,
    105 	 * use a buffer that is cluster boundary aligned.
    106 	 * Hopefully this can be a big win someday by allowing page trades
    107 	 * to user space to be done by getdirentries()
    108 	 */
    109 	if (((pagesz = getpagesize()) % DIRBLKSIZ) == 0)
    110 		incr = pagesz;
    111 	else
    112 		incr = DIRBLKSIZ;
    113 
    114 	/*
    115 	 * Determine whether this directory is the top of a union stack.
    116 	 */
    117 
    118 	if (fstatfs(fd, &sfb) < 0) {
    119 		free(dirp);
    120 		close(fd);
    121 		return (NULL);
    122 	}
    123 
    124 	if (flags & DTF_NODUP)
    125 		unionstack = !(strncmp(sfb.f_fstypename, MOUNT_UNION,
    126 		    MFSNAMELEN)) || (sfb.f_flags & MNT_UNION);
    127 	else
    128 		unionstack = 0;
    129 
    130 	nfsdir = !(strncmp(sfb.f_fstypename, MOUNT_NFS, MFSNAMELEN));
    131 
    132 	if (unionstack || nfsdir) {
    133 		size_t len;
    134 		size_t space;
    135 		char *buf;
    136 		char *ddptr;
    137 		char *ddeptr;
    138 		int n;
    139 		struct dirent **dpv;
    140 
    141 		/*
    142 		 * The strategy here for directories on top of a union stack
    143 		 * is to read all the directory entries into a buffer, sort
    144 		 * the buffer, and remove duplicate entries by setting the
    145 		 * inode number to zero.
    146 		 *
    147 		 * For directories on an NFS mounted filesystem, we try
    148 	 	 * to get a consistent snapshot by trying until we have
    149 		 * successfully read all of the directory without errors
    150 		 * (i.e. 'bad cookie' errors from the server because
    151 		 * the directory was modified). These errors should not
    152 		 * happen often, but need to be dealt with.
    153 		 */
    154 retry:
    155 		len = 0;
    156 		space = 0;
    157 		buf = 0;
    158 		ddptr = 0;
    159 
    160 		do {
    161 			/*
    162 			 * Always make at least DIRBLKSIZ bytes
    163 			 * available to getdirentries
    164 			 */
    165 			if (space < DIRBLKSIZ) {
    166 				space += incr;
    167 				len += incr;
    168 				buf = realloc(buf, len);
    169 				if (buf == NULL) {
    170 					free(dirp);
    171 					close(fd);
    172 					return (NULL);
    173 				}
    174 				ddptr = buf + (len - space);
    175 			}
    176 
    177 			dirp->dd_seek = lseek(fd, (off_t)0, SEEK_CUR);
    178 			n = getdents(fd, ddptr, space);
    179 			/*
    180 			 * For NFS: EINVAL means a bad cookie error
    181 			 * from the server. Keep trying to get a
    182 			 * consistent view, in this case this means
    183 			 * starting all over again.
    184 			 */
    185 			if (n == -1 && errno == EINVAL && nfsdir) {
    186 				free(buf);
    187 				lseek(fd, (off_t)0, SEEK_SET);
    188 				goto retry;
    189 			}
    190 			if (n > 0) {
    191 				ddptr += n;
    192 				space -= n;
    193 			}
    194 		} while (n > 0);
    195 
    196 		ddeptr = ddptr;
    197 		flags |= __DTF_READALL;
    198 
    199 		/*
    200 		 * Re-open the directory.
    201 		 * This has the effect of rewinding back to the
    202 		 * top of the union stack and is needed by
    203 		 * programs which plan to fchdir to a descriptor
    204 		 * which has also been read -- see fts.c.
    205 		 */
    206 		if (flags & DTF_REWIND) {
    207 			(void) close(fd);
    208 			if ((fd = open(name, O_RDONLY)) == -1) {
    209 				free(buf);
    210 				free(dirp);
    211 				return (NULL);
    212 			}
    213 		}
    214 
    215 		/*
    216 		 * There is now a buffer full of (possibly) duplicate
    217 		 * names.
    218 		 */
    219 		dirp->dd_buf = buf;
    220 
    221 		/*
    222 		 * Go round this loop twice...
    223 		 *
    224 		 * Scan through the buffer, counting entries.
    225 		 * On the second pass, save pointers to each one.
    226 		 * Then sort the pointers and remove duplicate names.
    227 		 */
    228 		if (!nfsdir) {
    229 			for (dpv = 0;;) {
    230 				for (n = 0, ddptr = buf; ddptr < ddeptr;) {
    231 					struct dirent *dp;
    232 
    233 					dp = (struct dirent *)(void *)ddptr;
    234 					if ((long)dp & 03)
    235 						break;
    236 					/*
    237 					 * d_reclen is unsigned,
    238 					 * so no need to compare <= 0
    239 					 */
    240 					if (dp->d_reclen > (ddeptr + 1 - ddptr))
    241 						break;
    242 					ddptr += dp->d_reclen;
    243 					if (dp->d_fileno) {
    244 						if (dpv)
    245 							dpv[n] = dp;
    246 						n++;
    247 					}
    248 				}
    249 
    250 				if (dpv) {
    251 					struct dirent *xp;
    252 
    253 					/*
    254 					 * This sort must be stable.
    255 					 */
    256 					mergesort(dpv, (size_t)n, sizeof(*dpv),
    257 					    alphasort);
    258 
    259 					dpv[n] = NULL;
    260 					xp = NULL;
    261 
    262 					/*
    263 					 * Scan through the buffer in sort
    264 					 * order, zapping the inode number
    265 					 * of any duplicate names.
    266 					 */
    267 					for (n = 0; dpv[n]; n++) {
    268 						struct dirent *dp = dpv[n];
    269 
    270 						if ((xp == NULL) ||
    271 						    strcmp(dp->d_name,
    272 						      xp->d_name))
    273 							xp = dp;
    274 						else
    275 							dp->d_fileno = 0;
    276 						if (dp->d_type == DT_WHT &&
    277 						    (flags & DTF_HIDEW))
    278 							dp->d_fileno = 0;
    279 					}
    280 
    281 					free(dpv);
    282 					break;
    283 				} else {
    284 					dpv = malloc((n+1) * sizeof(struct dirent *));
    285 					if (dpv == NULL)
    286 						break;
    287 				}
    288 			}
    289 		}
    290 
    291 		dirp->dd_len = len;
    292 		dirp->dd_size = ddptr - dirp->dd_buf;
    293 	} else {
    294 		dirp->dd_len = incr;
    295 		dirp->dd_buf = malloc((size_t)dirp->dd_len);
    296 		if (dirp->dd_buf == NULL) {
    297 			free(dirp);
    298 			close (fd);
    299 			return (NULL);
    300 		}
    301 		dirp->dd_seek = 0;
    302 		flags &= ~DTF_REWIND;
    303 	}
    304 
    305 	dirp->dd_loc = 0;
    306 	dirp->dd_fd = fd;
    307 	dirp->dd_flags = flags;
    308 
    309 	/*
    310 	 * Set up seek point for rewinddir.
    311 	 */
    312 	dirp->dd_rewind = telldir(dirp);
    313 
    314 	return (dirp);
    315 }
    316