file_subs.c revision 1.21
1/* $NetBSD: file_subs.c,v 1.21 2002/01/29 10:20:28 tv Exp $ */ 2 3/*- 4 * Copyright (c) 1992 Keith Muller. 5 * Copyright (c) 1992, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * Keith Muller of the University of California, San Diego. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the University of 22 * California, Berkeley and its contributors. 23 * 4. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 */ 39 40#include <sys/cdefs.h> 41#ifndef lint 42#if 0 43static char sccsid[] = "@(#)file_subs.c 8.1 (Berkeley) 5/31/93"; 44#else 45__RCSID("$NetBSD: file_subs.c,v 1.21 2002/01/29 10:20:28 tv Exp $"); 46#endif 47#endif /* not lint */ 48 49#include <sys/types.h> 50#include <sys/time.h> 51#include <sys/stat.h> 52#include <unistd.h> 53#include <sys/param.h> 54#include <fcntl.h> 55#include <string.h> 56#include <stdio.h> 57#include <ctype.h> 58#include <errno.h> 59#include <sys/uio.h> 60#include <stdlib.h> 61#include "pax.h" 62#include "extern.h" 63 64static int 65mk_link(char *,struct stat *,char *, int); 66 67/* 68 * routines that deal with file operations such as: creating, removing; 69 * and setting access modes, uid/gid and times of files 70 */ 71 72#define FILEBITS (S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO) 73#define SETBITS (S_ISUID | S_ISGID) 74#define ABITS (FILEBITS | SETBITS) 75 76/* 77 * file_creat() 78 * Create and open a file. 79 * Return: 80 * file descriptor or -1 for failure 81 */ 82 83int 84file_creat(ARCHD *arcn) 85{ 86 int fd = -1; 87 mode_t file_mode; 88 int oerrno; 89 90 /* 91 * assume file doesn't exist, so just try to create it, most times this 92 * works. We have to take special handling when the file does exist. To 93 * detect this, we use O_EXCL. For example when trying to create a 94 * file and a character device or fifo exists with the same name, we 95 * can accidently open the device by mistake (or block waiting to open) 96 * If we find that the open has failed, then figure spend the effort to 97 * figure out why. This strategy was found to have better average 98 * performance in common use than checking the file (and the path) 99 * first with lstat. 100 */ 101 file_mode = arcn->sb.st_mode & FILEBITS; 102 if ((fd = open(arcn->name, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL, 103 file_mode)) >= 0) 104 return(fd); 105 106 /* 107 * the file seems to exist. First we try to get rid of it (found to be 108 * the second most common failure when traced). If this fails, only 109 * then we go to the expense to check and create the path to the file 110 */ 111 if (unlnk_exist(arcn->name, arcn->type) != 0) 112 return(-1); 113 114 for (;;) { 115 /* 116 * try to open it again, if this fails, check all the nodes in 117 * the path and give it a final try. if chk_path() finds that 118 * it cannot fix anything, we will skip the last attempt 119 */ 120 if ((fd = open(arcn->name, O_WRONLY | O_CREAT | O_TRUNC, 121 file_mode)) >= 0) 122 break; 123 oerrno = errno; 124 if (chk_path(arcn->name,arcn->sb.st_uid,arcn->sb.st_gid) < 0) { 125 syswarn(1, oerrno, "Unable to create %s", arcn->name); 126 return(-1); 127 } 128 } 129 return(fd); 130} 131 132/* 133 * file_close() 134 * Close file descriptor to a file just created by pax. Sets modes, 135 * ownership and times as required. 136 * Return: 137 * 0 for success, -1 for failure 138 */ 139 140void 141file_close(ARCHD *arcn, int fd) 142{ 143 int res = 0; 144 145 if (fd < 0) 146 return; 147 if (close(fd) < 0) 148 syswarn(0, errno, "Unable to close file descriptor on %s", 149 arcn->name); 150 151 /* 152 * set owner/groups first as this may strip off mode bits we want 153 * then set file permission modes. Then set file access and 154 * modification times. 155 */ 156 if (pids) 157 res = set_ids(arcn->name, arcn->sb.st_uid, arcn->sb.st_gid); 158 159 /* 160 * IMPORTANT SECURITY NOTE: 161 * if not preserving mode or we cannot set uid/gid, then PROHIBIT 162 * set uid/gid bits 163 */ 164 if (!pmode || res) 165 arcn->sb.st_mode &= ~(SETBITS); 166 if (pmode) 167 set_pmode(arcn->name, arcn->sb.st_mode); 168 if (patime || pmtime) 169 set_ftime(arcn->name, arcn->sb.st_mtime, arcn->sb.st_atime, 0); 170#if HAVE_STRUCT_STAT_ST_FLAGS 171 if (pfflags && arcn->type != PAX_SLK) 172 set_chflags(arcn->name, arcn->sb.st_flags); 173#endif 174} 175 176/* 177 * lnk_creat() 178 * Create a hard link to arcn->ln_name from arcn->name. arcn->ln_name 179 * must exist; 180 * Return: 181 * 0 if ok, -1 otherwise 182 */ 183 184int 185lnk_creat(ARCHD *arcn) 186{ 187 struct stat sb; 188 189 /* 190 * we may be running as root, so we have to be sure that link target 191 * is not a directory, so we lstat and check 192 */ 193 if (lstat(arcn->ln_name, &sb) < 0) { 194 syswarn(1,errno,"Unable to link to %s from %s", arcn->ln_name, 195 arcn->name); 196 return(-1); 197 } 198 199 if (S_ISDIR(sb.st_mode)) { 200 tty_warn(1, "A hard link to the directory %s is not allowed", 201 arcn->ln_name); 202 return(-1); 203 } 204 205 return(mk_link(arcn->ln_name, &sb, arcn->name, 0)); 206} 207 208/* 209 * cross_lnk() 210 * Create a hard link to arcn->org_name from arcn->name. Only used in copy 211 * with the -l flag. No warning or error if this does not succeed (we will 212 * then just create the file) 213 * Return: 214 * 1 if copy() should try to create this file node 215 * 0 if cross_lnk() ok, -1 for fatal flaw (like linking to self). 216 */ 217 218int 219cross_lnk(ARCHD *arcn) 220{ 221 /* 222 * try to make a link to original file (-l flag in copy mode). make 223 * sure we do not try to link to directories in case we are running as 224 * root (and it might succeed). 225 */ 226 if (arcn->type == PAX_DIR) 227 return(1); 228 return(mk_link(arcn->org_name, &(arcn->sb), arcn->name, 1)); 229} 230 231/* 232 * chk_same() 233 * In copy mode if we are not trying to make hard links between the src 234 * and destinations, make sure we are not going to overwrite ourselves by 235 * accident. This slows things down a little, but we have to protect all 236 * those people who make typing errors. 237 * Return: 238 * 1 the target does not exist, go ahead and copy 239 * 0 skip it file exists (-k) or may be the same as source file 240 */ 241 242int 243chk_same(ARCHD *arcn) 244{ 245 struct stat sb; 246 247 /* 248 * if file does not exist, return. if file exists and -k, skip it 249 * quietly 250 */ 251 if (lstat(arcn->name, &sb) < 0) 252 return(1); 253 if (kflag) 254 return(0); 255 256 /* 257 * better make sure the user does not have src == dest by mistake 258 */ 259 if ((arcn->sb.st_dev == sb.st_dev) && (arcn->sb.st_ino == sb.st_ino)) { 260 tty_warn(1, "Unable to copy %s, file would overwrite itself", 261 arcn->name); 262 return(0); 263 } 264 return(1); 265} 266 267/* 268 * mk_link() 269 * try to make a hard link between two files. if ign set, we do not 270 * complain. 271 * Return: 272 * 0 if successful (or we are done with this file but no error, such as 273 * finding the from file exists and the user has set -k). 274 * 1 when ign was set to indicates we could not make the link but we 275 * should try to copy/extract the file as that might work (and is an 276 * allowed option). -1 an error occurred. 277 */ 278 279static int 280mk_link(char *to, struct stat *to_sb, char *from, int ign) 281{ 282 struct stat sb; 283 int oerrno; 284 285 /* 286 * if from file exists, it has to be unlinked to make the link. If the 287 * file exists and -k is set, skip it quietly 288 */ 289 if (lstat(from, &sb) == 0) { 290 if (kflag) 291 return(0); 292 293 /* 294 * make sure it is not the same file, protect the user 295 */ 296 if ((to_sb->st_dev==sb.st_dev)&&(to_sb->st_ino == sb.st_ino)) { 297 tty_warn(1, "Unable to link file %s to itself", to); 298 return(-1);; 299 } 300 301 /* 302 * try to get rid of the file, based on the type 303 */ 304 if (S_ISDIR(sb.st_mode)) { 305 if (rmdir(from) < 0) { 306 syswarn(1, errno, "Unable to remove %s", from); 307 return(-1); 308 } 309 } else if (unlink(from) < 0) { 310 if (!ign) { 311 syswarn(1, errno, "Unable to remove %s", from); 312 return(-1); 313 } 314 return(1); 315 } 316 } 317 318 /* 319 * from file is gone (or did not exist), try to make the hard link. 320 * if it fails, check the path and try it again (if chk_path() says to 321 * try again) 322 */ 323 for (;;) { 324 if (link(to, from) == 0) 325 break; 326 oerrno = errno; 327 if (chk_path(from, to_sb->st_uid, to_sb->st_gid) == 0) 328 continue; 329 if (!ign) { 330 syswarn(1, oerrno, "Could not link to %s from %s", to, 331 from); 332 return(-1); 333 } 334 return(1); 335 } 336 337 /* 338 * all right the link was made 339 */ 340 return(0); 341} 342 343/* 344 * node_creat() 345 * create an entry in the file system (other than a file or hard link). 346 * If successful, sets uid/gid modes and times as required. 347 * Return: 348 * 0 if ok, -1 otherwise 349 */ 350 351int 352node_creat(ARCHD *arcn) 353{ 354 int res; 355 int ign = 0; 356 int oerrno; 357 int pass = 0; 358 mode_t file_mode; 359 struct stat sb; 360 361 /* 362 * create node based on type, if that fails try to unlink the node and 363 * try again. finally check the path and try again. As noted in the 364 * file and link creation routines, this method seems to exhibit the 365 * best performance in general use workloads. 366 */ 367 file_mode = arcn->sb.st_mode & FILEBITS; 368 369 for (;;) { 370 switch(arcn->type) { 371 case PAX_DIR: 372 res = mkdir(arcn->name, file_mode); 373 if (ign) 374 res = 0; 375 break; 376 case PAX_CHR: 377 file_mode |= S_IFCHR; 378 res = mknod(arcn->name, file_mode, arcn->sb.st_rdev); 379 break; 380 case PAX_BLK: 381 file_mode |= S_IFBLK; 382 res = mknod(arcn->name, file_mode, arcn->sb.st_rdev); 383 break; 384 case PAX_FIF: 385 res = mkfifo(arcn->name, file_mode); 386 break; 387 case PAX_SCK: 388 /* 389 * Skip sockets, operation has no meaning under BSD 390 */ 391 tty_warn(0, 392 "%s skipped. Sockets cannot be copied or extracted", 393 arcn->name); 394 return(-1); 395 case PAX_SLK: 396 res = symlink(arcn->ln_name, arcn->name); 397 break; 398 case PAX_CTG: 399 case PAX_HLK: 400 case PAX_HRG: 401 case PAX_REG: 402 default: 403 /* 404 * we should never get here 405 */ 406 tty_warn(0, "%s has an unknown file type, skipping", 407 arcn->name); 408 return(-1); 409 } 410 411 /* 412 * if we were able to create the node break out of the loop, 413 * otherwise try to unlink the node and try again. if that 414 * fails check the full path and try a final time. 415 */ 416 if (res == 0) 417 break; 418 419 /* 420 * we failed to make the node 421 */ 422 oerrno = errno; 423 if ((ign = unlnk_exist(arcn->name, arcn->type)) < 0) 424 return(-1); 425 426 if (++pass <= 1) 427 continue; 428 429 if (chk_path(arcn->name,arcn->sb.st_uid,arcn->sb.st_gid) < 0) { 430 syswarn(1, oerrno, "Could not create: %s", arcn->name); 431 return(-1); 432 } 433 } 434 435 /* 436 * we were able to create the node. set uid/gid, modes and times 437 */ 438#if HAVE_LCHOWN 439 if (pids) 440#else 441 if (pids && arcn->type != PAX_SLK) 442#endif 443 res = set_ids(arcn->name, arcn->sb.st_uid, arcn->sb.st_gid); 444 else 445 res = 0; 446 447 /* 448 * IMPORTANT SECURITY NOTE: 449 * if not preserving mode or we cannot set uid/gid, then PROHIBIT any 450 * set uid/gid bits 451 */ 452 if (!pmode || res) 453 arcn->sb.st_mode &= ~(SETBITS); 454#if HAVE_LCHMOD 455 if (pmode) 456#else 457 if (pmode && arcn->type != PAX_SLK) 458#endif 459 set_pmode(arcn->name, arcn->sb.st_mode); 460 461 if (arcn->type == PAX_DIR) { 462 /* 463 * Dirs must be processed again at end of extract to set times 464 * and modes to agree with those stored in the archive. However 465 * to allow extract to continue, we may have to also set owner 466 * rights. This allows nodes in the archive that are children 467 * of this directory to be extracted without failure. Both time 468 * and modes will be fixed after the entire archive is read and 469 * before pax exits. 470 */ 471 if (access(arcn->name, R_OK | W_OK | X_OK) < 0) { 472 if (lstat(arcn->name, &sb) < 0) { 473 syswarn(0, errno,"Could not access %s (stat)", 474 arcn->name); 475 set_pmode(arcn->name,file_mode | S_IRWXU); 476 } else { 477 /* 478 * We have to add rights to the dir, so we make 479 * sure to restore the mode. The mode must be 480 * restored AS CREATED and not as stored if 481 * pmode is not set. 482 */ 483 set_pmode(arcn->name, 484 ((sb.st_mode & FILEBITS) | S_IRWXU)); 485 if (!pmode) 486 arcn->sb.st_mode = sb.st_mode; 487 } 488 489 /* 490 * we have to force the mode to what was set here, 491 * since we changed it from the default as created. 492 */ 493 add_dir(arcn->name, arcn->nlen, &(arcn->sb), 1); 494 } else if (pmode || patime || pmtime) 495 add_dir(arcn->name, arcn->nlen, &(arcn->sb), 0); 496 } 497 498#if HAVE_LUTIMES 499 if (patime || pmtime) 500#else 501 if ((patime || pmtime) && arcn->type != PAX_SLK) 502#endif 503 set_ftime(arcn->name, arcn->sb.st_mtime, arcn->sb.st_atime, 0); 504 505#if HAVE_STRUCT_STAT_ST_FLAGS 506 if (pfflags && arcn->type != PAX_SLK) 507 set_chflags(arcn->name, arcn->sb.st_flags); 508#endif 509 return(0); 510} 511 512/* 513 * unlnk_exist() 514 * Remove node from file system with the specified name. We pass the type 515 * of the node that is going to replace it. When we try to create a 516 * directory and find that it already exists, we allow processing to 517 * continue as proper modes etc will always be set for it later on. 518 * Return: 519 * 0 is ok to proceed, no file with the specified name exists 520 * -1 we were unable to remove the node, or we should not remove it (-k) 521 * 1 we found a directory and we were going to create a directory. 522 */ 523 524int 525unlnk_exist(char *name, int type) 526{ 527 struct stat sb; 528 529 /* 530 * the file does not exist, or -k we are done 531 */ 532 if (lstat(name, &sb) < 0) 533 return(0); 534 if (kflag) 535 return(-1); 536 537 if (S_ISDIR(sb.st_mode)) { 538 /* 539 * try to remove a directory, if it fails and we were going to 540 * create a directory anyway, tell the caller (return a 1) 541 */ 542 if (rmdir(name) < 0) { 543 if (type == PAX_DIR) 544 return(1); 545 syswarn(1,errno,"Unable to remove directory %s", name); 546 return(-1); 547 } 548 return(0); 549 } 550 551 /* 552 * try to get rid of all non-directory type nodes 553 */ 554 if (unlink(name) < 0) { 555 syswarn(1, errno, "Could not unlink %s", name); 556 return(-1); 557 } 558 return(0); 559} 560 561/* 562 * chk_path() 563 * We were trying to create some kind of node in the file system and it 564 * failed. chk_path() makes sure the path up to the node exists and is 565 * writeable. When we have to create a directory that is missing along the 566 * path somewhere, the directory we create will be set to the same 567 * uid/gid as the file has (when uid and gid are being preserved). 568 * NOTE: this routine is a real performance loss. It is only used as a 569 * last resort when trying to create entries in the file system. 570 * Return: 571 * -1 when it could find nothing it is allowed to fix. 572 * 0 otherwise 573 */ 574 575int 576chk_path( char *name, uid_t st_uid, gid_t st_gid) 577{ 578 char *spt = name; 579 struct stat sb; 580 int retval = -1; 581 582 /* 583 * watch out for paths with nodes stored directly in / (e.g. /bozo) 584 */ 585 if (*spt == '/') 586 ++spt; 587 588 for(;;) { 589 /* 590 * work forward from the first / and check each part of 591 * the path 592 */ 593 spt = strchr(spt, '/'); 594 if (spt == NULL) 595 break; 596 *spt = '\0'; 597 598 /* 599 * if it exists we assume it is a directory, it is not within 600 * the spec (at least it seems to read that way) to alter the 601 * file system for nodes NOT EXPLICITLY stored on the archive. 602 * If that assumption is changed, you would test the node here 603 * and figure out how to get rid of it (probably like some 604 * recursive unlink()) or fix up the directory permissions if 605 * required (do an access()). 606 */ 607 if (lstat(name, &sb) == 0) { 608 *(spt++) = '/'; 609 continue; 610 } 611 612 /* 613 * the path fails at this point, see if we can create the 614 * needed directory and continue on 615 */ 616 if (mkdir(name, S_IRWXU | S_IRWXG | S_IRWXO) < 0) { 617 *spt = '/'; 618 retval = -1; 619 break; 620 } 621 622 /* 623 * we were able to create the directory. We will tell the 624 * caller that we found something to fix, and it is ok to try 625 * and create the node again. 626 */ 627 retval = 0; 628 if (pids) 629 (void)set_ids(name, st_uid, st_gid); 630 631 /* 632 * make sure the user doen't have some strange umask that 633 * causes this newly created directory to be unusable. We fix 634 * the modes and restore them back to the creation default at 635 * the end of pax 636 */ 637 if ((access(name, R_OK | W_OK | X_OK) < 0) && 638 (lstat(name, &sb) == 0)) { 639 set_pmode(name, ((sb.st_mode & FILEBITS) | S_IRWXU)); 640 add_dir(name, spt - name, &sb, 1); 641 } 642 *(spt++) = '/'; 643 continue; 644 } 645 return(retval); 646} 647 648/* 649 * set_ftime() 650 * Set the access time and modification time for a named file. If frc 651 * is non-zero we force these times to be set even if the user did not 652 * request access and/or modification time preservation (this is also 653 * used by -t to reset access times). 654 * When ign is zero, only those times the user has asked for are set, the 655 * other ones are left alone. We do not assume the un-documented feature 656 * of many utimes() implementations that consider a 0 time value as a do 657 * not set request. 658 */ 659 660void 661set_ftime(char *fnm, time_t mtime, time_t atime, int frc) 662{ 663 struct timeval tv[2]; 664 struct stat sb; 665 666 tv[0].tv_sec = (long)atime; 667 tv[0].tv_usec = 0; 668 tv[1].tv_sec = (long)mtime; 669 tv[1].tv_usec = 0; 670 if (!frc && (!patime || !pmtime)) { 671 /* 672 * if we are not forcing, only set those times the user wants 673 * set. We get the current values of the times if we need them. 674 */ 675 if (lstat(fnm, &sb) == 0) { 676#ifdef BSD4_4 677 if (!patime) 678 TIMESPEC_TO_TIMEVAL(&tv[0], &sb.st_atimespec); 679 if (!pmtime) 680 TIMESPEC_TO_TIMEVAL(&tv[1], &sb.st_mtimespec); 681#else 682 if (!patime) 683 tv[0].tv_sec = sb.st_atime; 684 if (!pmtime) 685 tv[1].tv_sec = sb.st_mtime; 686#endif 687 } else 688 syswarn(0,errno,"Unable to obtain file stats %s", fnm); 689 } 690 691 /* 692 * set the times 693 */ 694#if HAVE_LUTIMES 695 if (lutimes(fnm, tv)) 696#else 697 if (utimes(fnm, tv)) 698#endif 699 syswarn(1, errno, "Access/modification time set failed on: %s", 700 fnm); 701 return; 702} 703 704/* 705 * set_ids() 706 * set the uid and gid of a file system node 707 * Return: 708 * 0 when set, -1 on failure 709 */ 710 711int 712set_ids(char *fnm, uid_t uid, gid_t gid) 713{ 714#if HAVE_LCHOWN 715 if (lchown(fnm, uid, gid)) 716#else 717 if (chown(fnm, uid, gid)) 718#endif 719 { 720 syswarn(1, errno, "Unable to set file uid/gid of %s", fnm); 721 return(-1); 722 } 723 return(0); 724} 725 726/* 727 * set_pmode() 728 * Set file access mode 729 */ 730 731void 732set_pmode(char *fnm, mode_t mode) 733{ 734 mode &= ABITS; 735#if HAVE_LCHMOD 736 if (lchmod(fnm, mode)) 737#else 738 if (chmod(fnm, mode)) 739#endif 740 syswarn(1, errno, "Could not set permissions on %s", fnm); 741 return; 742} 743 744/* 745 * set_chflags() 746 * Set 4.4BSD file flags 747 */ 748void 749set_chflags(char *fnm, u_int32_t flags) 750{ 751 752#if 0 753 if (chflags(fnm, flags) < 0 && errno != EOPNOTSUPP) 754 syswarn(1, errno, "Could not set file flags on %s", fnm); 755#endif 756 return; 757} 758 759/* 760 * file_write() 761 * Write/copy a file (during copy or archive extract). This routine knows 762 * how to copy files with lseek holes in it. (Which are read as file 763 * blocks containing all 0's but do not have any file blocks associated 764 * with the data). Typical examples of these are files created by dbm 765 * variants (.pag files). While the file size of these files are huge, the 766 * actual storage is quite small (the files are sparse). The problem is 767 * the holes read as all zeros so are probably stored on the archive that 768 * way (there is no way to determine if the file block is really a hole, 769 * we only know that a file block of all zero's can be a hole). 770 * At this writing, no major archive format knows how to archive files 771 * with holes. However, on extraction (or during copy, -rw) we have to 772 * deal with these files. Without detecting the holes, the files can 773 * consume a lot of file space if just written to disk. This replacement 774 * for write when passed the basic allocation size of a file system block, 775 * uses lseek whenever it detects the input data is all 0 within that 776 * file block. In more detail, the strategy is as follows: 777 * While the input is all zero keep doing an lseek. Keep track of when we 778 * pass over file block boundaries. Only write when we hit a non zero 779 * input. once we have written a file block, we continue to write it to 780 * the end (we stop looking at the input). When we reach the start of the 781 * next file block, start checking for zero blocks again. Working on file 782 * block boundaries significantly reduces the overhead when copying files 783 * that are NOT very sparse. This overhead (when compared to a write) is 784 * almost below the measurement resolution on many systems. Without it, 785 * files with holes cannot be safely copied. It does has a side effect as 786 * it can put holes into files that did not have them before, but that is 787 * not a problem since the file contents are unchanged (in fact it saves 788 * file space). (Except on paging files for diskless clients. But since we 789 * cannot determine one of those file from here, we ignore them). If this 790 * ever ends up on a system where CTG files are supported and the holes 791 * are not desired, just do a conditional test in those routines that 792 * call file_write() and have it call write() instead. BEFORE CLOSING THE 793 * FILE, make sure to call file_flush() when the last write finishes with 794 * an empty block. A lot of file systems will not create an lseek hole at 795 * the end. In this case we drop a single 0 at the end to force the 796 * trailing 0's in the file. 797 * ---Parameters--- 798 * rem: how many bytes left in this file system block 799 * isempt: have we written to the file block yet (is it empty) 800 * sz: basic file block allocation size 801 * cnt: number of bytes on this write 802 * str: buffer to write 803 * Return: 804 * number of bytes written, -1 on write (or lseek) error. 805 */ 806 807int 808file_write(int fd, char *str, int cnt, int *rem, int *isempt, int sz, 809 char *name) 810{ 811 char *pt; 812 char *end; 813 int wcnt; 814 char *st = str; 815 816 /* 817 * while we have data to process 818 */ 819 while (cnt) { 820 if (!*rem) { 821 /* 822 * We are now at the start of file system block again 823 * (or what we think one is...). start looking for 824 * empty blocks again 825 */ 826 *isempt = 1; 827 *rem = sz; 828 } 829 830 /* 831 * only examine up to the end of the current file block or 832 * remaining characters to write, whatever is smaller 833 */ 834 wcnt = MIN(cnt, *rem); 835 cnt -= wcnt; 836 *rem -= wcnt; 837 if (*isempt) { 838 /* 839 * have not written to this block yet, so we keep 840 * looking for zero's 841 */ 842 pt = st; 843 end = st + wcnt; 844 845 /* 846 * look for a zero filled buffer 847 */ 848 while ((pt < end) && (*pt == '\0')) 849 ++pt; 850 851 if (pt == end) { 852 /* 853 * skip, buf is empty so far 854 */ 855 if (fd > -1 && 856 lseek(fd, (off_t)wcnt, SEEK_CUR) < 0) { 857 syswarn(1,errno,"File seek on %s", 858 name); 859 return(-1); 860 } 861 st = pt; 862 continue; 863 } 864 /* 865 * drat, the buf is not zero filled 866 */ 867 *isempt = 0; 868 } 869 870 /* 871 * have non-zero data in this file system block, have to write 872 */ 873 if (fd == -1) { 874 /* GNU hack */ 875 if (gnu_hack_string) 876 err(1, "WARNING! Major Internal Error! GNU hack Failing!"); 877 gnu_hack_string = malloc(wcnt + 1); 878 if (gnu_hack_string == NULL) { 879 tty_warn(1, "Out of memory"); 880 return(-1); 881 } 882 strncpy(gnu_hack_string, st, wcnt); 883 gnu_hack_string[wcnt] = 0; 884 } else if (xwrite(fd, st, wcnt) != wcnt) { 885 syswarn(1, errno, "Failed write to file %s", name); 886 return(-1); 887 } 888 st += wcnt; 889 } 890 return(st - str); 891} 892 893/* 894 * file_flush() 895 * when the last file block in a file is zero, many file systems will not 896 * let us create a hole at the end. To get the last block with zeros, we 897 * write the last BYTE with a zero (back up one byte and write a zero). 898 */ 899 900void 901file_flush(int fd, char *fname, int isempt) 902{ 903 static char blnk[] = "\0"; 904 905 /* 906 * silly test, but make sure we are only called when the last block is 907 * filled with all zeros. 908 */ 909 if (!isempt) 910 return; 911 912 /* 913 * move back one byte and write a zero 914 */ 915 if (lseek(fd, (off_t)-1, SEEK_CUR) < 0) { 916 syswarn(1, errno, "Failed seek on file %s", fname); 917 return; 918 } 919 920 if (write_with_restart(fd, blnk, 1) < 0) 921 syswarn(1, errno, "Failed write to file %s", fname); 922 return; 923} 924 925/* 926 * rdfile_close() 927 * close a file we have been reading (to copy or archive). If we have to 928 * reset access time (tflag) do so (the times are stored in arcn). 929 */ 930 931void 932rdfile_close(ARCHD *arcn, int *fd) 933{ 934 /* 935 * make sure the file is open 936 */ 937 if (*fd < 0) 938 return; 939 940 (void)close(*fd); 941 *fd = -1; 942 if (!tflag) 943 return; 944 945 /* 946 * user wants last access time reset 947 */ 948 set_ftime(arcn->org_name, arcn->sb.st_mtime, arcn->sb.st_atime, 1); 949 return; 950} 951 952/* 953 * set_crc() 954 * read a file to calculate its crc. This is a real drag. Archive formats 955 * that have this, end up reading the file twice (we have to write the 956 * header WITH the crc before writing the file contents. Oh well... 957 * Return: 958 * 0 if was able to calculate the crc, -1 otherwise 959 */ 960 961int 962set_crc(ARCHD *arcn, int fd) 963{ 964 int i; 965 int res; 966 off_t cpcnt = 0L; 967 u_long size; 968 unsigned long crc = 0L; 969 char tbuf[FILEBLK]; 970 struct stat sb; 971 972 if (fd < 0) { 973 /* 974 * hmm, no fd, should never happen. well no crc then. 975 */ 976 arcn->crc = 0L; 977 return(0); 978 } 979 980 if ((size = (u_long)arcn->sb.st_blksize) > (u_long)sizeof(tbuf)) 981 size = (u_long)sizeof(tbuf); 982 983 /* 984 * read all the bytes we think that there are in the file. If the user 985 * is trying to archive an active file, forget this file. 986 */ 987 for(;;) { 988 if ((res = read(fd, tbuf, size)) <= 0) 989 break; 990 cpcnt += res; 991 for (i = 0; i < res; ++i) 992 crc += (tbuf[i] & 0xff); 993 } 994 995 /* 996 * safety check. we want to avoid archiving files that are active as 997 * they can create inconsistant archive copies. 998 */ 999 if (cpcnt != arcn->sb.st_size) 1000 tty_warn(1, "File changed size %s", arcn->org_name); 1001 else if (fstat(fd, &sb) < 0) 1002 syswarn(1, errno, "Failed stat on %s", arcn->org_name); 1003 else if (arcn->sb.st_mtime != sb.st_mtime) 1004 tty_warn(1, "File %s was modified during read", arcn->org_name); 1005 else if (lseek(fd, (off_t)0L, SEEK_SET) < 0) 1006 syswarn(1, errno, "File rewind failed on: %s", arcn->org_name); 1007 else { 1008 arcn->crc = crc; 1009 return(0); 1010 } 1011 return(-1); 1012} 1013