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