file_subs.c revision 1.8
1/* $NetBSD: file_subs.c,v 1.8 1997/10/19 13:02:43 mycroft 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 1.8 1997/10/19 13:02:43 mycroft 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 __P((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 83#if __STDC__ 84int 85file_creat(ARCHD *arcn) 86#else 87int 88file_creat(arcn) 89 ARCHD *arcn; 90#endif 91{ 92 int fd = -1; 93 mode_t file_mode; 94 int oerrno; 95 96 /* 97 * assume file doesn't exist, so just try to create it, most times this 98 * works. We have to take special handling when the file does exist. To 99 * detect this, we use O_EXCL. For example when trying to create a 100 * file and a character device or fifo exists with the same name, we 101 * can accidently open the device by mistake (or block waiting to open) 102 * If we find that the open has failed, then figure spend the effore to 103 * figure out why. This strategy was found to have better average 104 * performance in common use than checking the file (and the path) 105 * first with lstat. 106 */ 107 file_mode = arcn->sb.st_mode & FILEBITS; 108 if ((fd = open(arcn->name, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL, 109 file_mode)) >= 0) 110 return(fd); 111 112 /* 113 * the file seems to exist. First we try to get rid of it (found to be 114 * the second most common failure when traced). If this fails, only 115 * then we go to the expense to check and create the path to the file 116 */ 117 if (unlnk_exist(arcn->name, arcn->type) != 0) 118 return(-1); 119 120 for (;;) { 121 /* 122 * try to open it again, if this fails, check all the nodes in 123 * the path and give it a final try. if chk_path() finds that 124 * it cannot fix anything, we will skip the last attempt 125 */ 126 if ((fd = open(arcn->name, O_WRONLY | O_CREAT | O_TRUNC, 127 file_mode)) >= 0) 128 break; 129 oerrno = errno; 130 if (chk_path(arcn->name,arcn->sb.st_uid,arcn->sb.st_gid) < 0) { 131 syswarn(1, oerrno, "Unable to create %s", arcn->name); 132 return(-1); 133 } 134 } 135 return(fd); 136} 137 138/* 139 * file_close() 140 * Close file descriptor to a file just created by pax. Sets modes, 141 * ownership and times as required. 142 * Return: 143 * 0 for success, -1 for failure 144 */ 145 146#if __STDC__ 147void 148file_close(ARCHD *arcn, int fd) 149#else 150void 151file_close(arcn, fd) 152 ARCHD *arcn; 153 int fd; 154#endif 155{ 156 int res = 0; 157 158 if (fd < 0) 159 return; 160 if (close(fd) < 0) 161 syswarn(0, errno, "Unable to close file descriptor on %s", 162 arcn->name); 163 164 /* 165 * set owner/groups first as this may strip off mode bits we want 166 * then set file permission modes. Then set file access and 167 * modification times. 168 */ 169 if (pids) 170 res = set_ids(arcn->name, arcn->sb.st_uid, arcn->sb.st_gid); 171 172 /* 173 * IMPORTANT SECURITY NOTE: 174 * if not preserving mode or we cannot set uid/gid, then PROHIBIT 175 * set uid/gid bits 176 */ 177 if (!pmode || res) 178 arcn->sb.st_mode &= ~(SETBITS); 179 if (pmode) 180 set_pmode(arcn->name, arcn->sb.st_mode); 181 if (patime || pmtime) 182 set_ftime(arcn->name, arcn->sb.st_mtime, arcn->sb.st_atime, 0); 183} 184 185/* 186 * lnk_creat() 187 * Create a hard link to arcn->ln_name from arcn->name. arcn->ln_name 188 * must exist; 189 * Return: 190 * 0 if ok, -1 otherwise 191 */ 192 193#if __STDC__ 194int 195lnk_creat(ARCHD *arcn) 196#else 197int 198lnk_creat(arcn) 199 ARCHD *arcn; 200#endif 201{ 202 struct stat sb; 203 204 /* 205 * we may be running as root, so we have to be sure that link target 206 * is not a directory, so we lstat and check 207 */ 208 if (lstat(arcn->ln_name, &sb) < 0) { 209 syswarn(1,errno,"Unable to link to %s from %s", arcn->ln_name, 210 arcn->name); 211 return(-1); 212 } 213 214 if (S_ISDIR(sb.st_mode)) { 215 tty_warn(1, "A hard link to the directory %s is not allowed", 216 arcn->ln_name); 217 return(-1); 218 } 219 220 return(mk_link(arcn->ln_name, &sb, arcn->name, 0)); 221} 222 223/* 224 * cross_lnk() 225 * Create a hard link to arcn->org_name from arcn->name. Only used in copy 226 * with the -l flag. No warning or error if this does not succeed (we will 227 * then just create the file) 228 * Return: 229 * 1 if copy() should try to create this file node 230 * 0 if cross_lnk() ok, -1 for fatal flaw (like linking to self). 231 */ 232 233#if __STDC__ 234int 235cross_lnk(ARCHD *arcn) 236#else 237int 238cross_lnk(arcn) 239 ARCHD *arcn; 240#endif 241{ 242 /* 243 * try to make a link to orginal file (-l flag in copy mode). make sure 244 * we do not try to link to directories in case we are running as root 245 * (and it might succeed). 246 */ 247 if (arcn->type == PAX_DIR) 248 return(1); 249 return(mk_link(arcn->org_name, &(arcn->sb), arcn->name, 1)); 250} 251 252/* 253 * chk_same() 254 * In copy mode if we are not trying to make hard links between the src 255 * and destinations, make sure we are not going to overwrite ourselves by 256 * accident. This slows things down a little, but we have to protect all 257 * those people who make typing errors. 258 * Return: 259 * 1 the target does not exist, go ahead and copy 260 * 0 skip it file exists (-k) or may be the same as source file 261 */ 262 263#if __STDC__ 264int 265chk_same(ARCHD *arcn) 266#else 267int 268chk_same(arcn) 269 ARCHD *arcn; 270#endif 271{ 272 struct stat sb; 273 274 /* 275 * if file does not exist, return. if file exists and -k, skip it 276 * quietly 277 */ 278 if (lstat(arcn->name, &sb) < 0) 279 return(1); 280 if (kflag) 281 return(0); 282 283 /* 284 * better make sure the user does not have src == dest by mistake 285 */ 286 if ((arcn->sb.st_dev == sb.st_dev) && (arcn->sb.st_ino == sb.st_ino)) { 287 tty_warn(1, "Unable to copy %s, file would overwrite itself", 288 arcn->name); 289 return(0); 290 } 291 return(1); 292} 293 294/* 295 * mk_link() 296 * try to make a hard link between two files. if ign set, we do not 297 * complain. 298 * Return: 299 * 0 if successful (or we are done with this file but no error, such as 300 * finding the from file exists and the user has set -k). 301 * 1 when ign was set to indicates we could not make the link but we 302 * should try to copy/extract the file as that might work (and is an 303 * allowed option). -1 an error occurred. 304 */ 305 306#if __STDC__ 307static int 308mk_link(char *to, struct stat *to_sb, char *from, 309 int ign) 310#else 311static int 312mk_link(to, to_sb, from, ign) 313 char *to; 314 struct stat *to_sb; 315 char *from; 316 int ign; 317#endif 318{ 319 struct stat sb; 320 int oerrno; 321 322 /* 323 * if from file exists, it has to be unlinked to make the link. If the 324 * file exists and -k is set, skip it quietly 325 */ 326 if (lstat(from, &sb) == 0) { 327 if (kflag) 328 return(0); 329 330 /* 331 * make sure it is not the same file, protect the user 332 */ 333 if ((to_sb->st_dev==sb.st_dev)&&(to_sb->st_ino == sb.st_ino)) { 334 tty_warn(1, "Unable to link file %s to itself", to); 335 return(-1);; 336 } 337 338 /* 339 * try to get rid of the file, based on the type 340 */ 341 if (S_ISDIR(sb.st_mode)) { 342 if (rmdir(from) < 0) { 343 syswarn(1, errno, "Unable to remove %s", from); 344 return(-1); 345 } 346 } else if (unlink(from) < 0) { 347 if (!ign) { 348 syswarn(1, errno, "Unable to remove %s", from); 349 return(-1); 350 } 351 return(1); 352 } 353 } 354 355 /* 356 * from file is gone (or did not exist), try to make the hard link. 357 * if it fails, check the path and try it again (if chk_path() says to 358 * try again) 359 */ 360 for (;;) { 361 if (link(to, from) == 0) 362 break; 363 oerrno = errno; 364 if (chk_path(from, to_sb->st_uid, to_sb->st_gid) == 0) 365 continue; 366 if (!ign) { 367 syswarn(1, oerrno, "Could not link to %s from %s", to, 368 from); 369 return(-1); 370 } 371 return(1); 372 } 373 374 /* 375 * all right the link was made 376 */ 377 return(0); 378} 379 380/* 381 * node_creat() 382 * create an entry in the file system (other than a file or hard link). 383 * If successful, sets uid/gid modes and times as required. 384 * Return: 385 * 0 if ok, -1 otherwise 386 */ 387 388#if __STDC__ 389int 390node_creat(ARCHD *arcn) 391#else 392int 393node_creat(arcn) 394 ARCHD *arcn; 395#endif 396{ 397 int res; 398 int ign = 0; 399 int oerrno; 400 int pass = 0; 401 mode_t file_mode; 402 struct stat sb; 403 404 /* 405 * create node based on type, if that fails try to unlink the node and 406 * try again. finally check the path and try again. As noted in the 407 * file and link creation routines, this method seems to exhibit the 408 * best performance in general use workloads. 409 */ 410 file_mode = arcn->sb.st_mode & FILEBITS; 411 412 for (;;) { 413 switch(arcn->type) { 414 case PAX_DIR: 415 res = mkdir(arcn->name, file_mode); 416 if (ign) 417 res = 0; 418 break; 419 case PAX_CHR: 420 file_mode |= S_IFCHR; 421 res = mknod(arcn->name, file_mode, arcn->sb.st_rdev); 422 break; 423 case PAX_BLK: 424 file_mode |= S_IFBLK; 425 res = mknod(arcn->name, file_mode, arcn->sb.st_rdev); 426 break; 427 case PAX_FIF: 428 res = mkfifo(arcn->name, file_mode); 429 break; 430 case PAX_SCK: 431 /* 432 * Skip sockets, operation has no meaning under BSD 433 */ 434 tty_warn(0, 435 "%s skipped. Sockets cannot be copied or extracted", 436 arcn->name); 437 return(-1); 438 case PAX_SLK: 439 res = symlink(arcn->ln_name, arcn->name); 440 break; 441 case PAX_CTG: 442 case PAX_HLK: 443 case PAX_HRG: 444 case PAX_REG: 445 default: 446 /* 447 * we should never get here 448 */ 449 tty_warn(0, "%s has an unknown file type, skipping", 450 arcn->name); 451 return(-1); 452 } 453 454 /* 455 * if we were able to create the node break out of the loop, 456 * otherwise try to unlink the node and try again. if that 457 * fails check the full path and try a final time. 458 */ 459 if (res == 0) 460 break; 461 462 /* 463 * we failed to make the node 464 */ 465 oerrno = errno; 466 if ((ign = unlnk_exist(arcn->name, arcn->type)) < 0) 467 return(-1); 468 469 if (++pass <= 1) 470 continue; 471 472 if (chk_path(arcn->name,arcn->sb.st_uid,arcn->sb.st_gid) < 0) { 473 syswarn(1, oerrno, "Could not create: %s", arcn->name); 474 return(-1); 475 } 476 } 477 478 /* 479 * we were able to create the node. set uid/gid, modes and times 480 */ 481 if (pids) 482 res = set_ids(arcn->name, arcn->sb.st_uid, arcn->sb.st_gid); 483 else 484 res = 0; 485 486 /* 487 * IMPORTANT SECURITY NOTE: 488 * if not preserving mode or we cannot set uid/gid, then PROHIBIT any 489 * set uid/gid bits 490 */ 491 if (!pmode || res) 492 arcn->sb.st_mode &= ~(SETBITS); 493 if (pmode) 494 set_pmode(arcn->name, arcn->sb.st_mode); 495 496 if (arcn->type == PAX_DIR) { 497 /* 498 * Dirs must be processed again at end of extract to set times 499 * and modes to agree with those stored in the archive. However 500 * to allow extract to continue, we may have to also set owner 501 * rights. This allows nodes in the archive that are children 502 * of this directory to be extracted without failure. Both time 503 * and modes will be fixed after the entire archive is read and 504 * before pax exits. 505 */ 506 if (access(arcn->name, R_OK | W_OK | X_OK) < 0) { 507 if (lstat(arcn->name, &sb) < 0) { 508 syswarn(0, errno,"Could not access %s (stat)", 509 arcn->name); 510 set_pmode(arcn->name,file_mode | S_IRWXU); 511 } else { 512 /* 513 * We have to add rights to the dir, so we make 514 * sure to restore the mode. The mode must be 515 * restored AS CREATED and not as stored if 516 * pmode is not set. 517 */ 518 set_pmode(arcn->name, 519 ((sb.st_mode & FILEBITS) | S_IRWXU)); 520 if (!pmode) 521 arcn->sb.st_mode = sb.st_mode; 522 } 523 524 /* 525 * we have to force the mode to what was set here, 526 * since we changed it from the default as created. 527 */ 528 add_dir(arcn->name, arcn->nlen, &(arcn->sb), 1); 529 } else if (pmode || patime || pmtime) 530 add_dir(arcn->name, arcn->nlen, &(arcn->sb), 0); 531 } 532 533 if (patime || pmtime) 534 set_ftime(arcn->name, arcn->sb.st_mtime, arcn->sb.st_atime, 0); 535 return(0); 536} 537 538/* 539 * unlnk_exist() 540 * Remove node from file system with the specified name. We pass the type 541 * of the node that is going to replace it. When we try to create a 542 * directory and find that it already exists, we allow processing to 543 * continue as proper modes etc will always be set for it later on. 544 * Return: 545 * 0 is ok to proceed, no file with the specified name exists 546 * -1 we were unable to remove the node, or we should not remove it (-k) 547 * 1 we found a directory and we were going to create a directory. 548 */ 549 550#if __STDC__ 551int 552unlnk_exist(char *name, int type) 553#else 554int 555unlnk_exist(name, type) 556 char *name; 557 int type; 558#endif 559{ 560 struct stat sb; 561 562 /* 563 * the file does not exist, or -k we are done 564 */ 565 if (lstat(name, &sb) < 0) 566 return(0); 567 if (kflag) 568 return(-1); 569 570 if (S_ISDIR(sb.st_mode)) { 571 /* 572 * try to remove a directory, if it fails and we were going to 573 * create a directory anyway, tell the caller (return a 1) 574 */ 575 if (rmdir(name) < 0) { 576 if (type == PAX_DIR) 577 return(1); 578 syswarn(1,errno,"Unable to remove directory %s", name); 579 return(-1); 580 } 581 return(0); 582 } 583 584 /* 585 * try to get rid of all non-directory type nodes 586 */ 587 if (unlink(name) < 0) { 588 syswarn(1, errno, "Could not unlink %s", name); 589 return(-1); 590 } 591 return(0); 592} 593 594/* 595 * chk_path() 596 * We were trying to create some kind of node in the file system and it 597 * failed. chk_path() makes sure the path up to the node exists and is 598 * writeable. When we have to create a directory that is missing along the 599 * path somewhere, the directory we create will be set to the same 600 * uid/gid as the file has (when uid and gid are being preserved). 601 * NOTE: this routine is a real performance loss. It is only used as a 602 * last resort when trying to create entries in the file system. 603 * Return: 604 * -1 when it could find nothing it is allowed to fix. 605 * 0 otherwise 606 */ 607 608#if __STDC__ 609int 610chk_path( char *name, uid_t st_uid, gid_t st_gid) 611#else 612int 613chk_path(name, st_uid, st_gid) 614 char *name; 615 uid_t st_uid; 616 gid_t st_gid; 617#endif 618{ 619 char *spt = name; 620 struct stat sb; 621 int retval = -1; 622 623 /* 624 * watch out for paths with nodes stored directly in / (e.g. /bozo) 625 */ 626 if (*spt == '/') 627 ++spt; 628 629 for(;;) { 630 /* 631 * work foward from the first / and check each part of the path 632 */ 633 spt = strchr(spt, '/'); 634 if (spt == NULL) 635 break; 636 *spt = '\0'; 637 638 /* 639 * if it exists we assume it is a directory, it is not within 640 * the spec (at least it seems to read that way) to alter the 641 * file system for nodes NOT EXPLICITLY stored on the archive. 642 * If that assumption is changed, you would test the node here 643 * and figure out how to get rid of it (probably like some 644 * recursive unlink()) or fix up the directory permissions if 645 * required (do an access()). 646 */ 647 if (lstat(name, &sb) == 0) { 648 *(spt++) = '/'; 649 continue; 650 } 651 652 /* 653 * the path fails at this point, see if we can create the 654 * needed directory and continue on 655 */ 656 if (mkdir(name, S_IRWXU | S_IRWXG | S_IRWXO) < 0) { 657 *spt = '/'; 658 retval = -1; 659 break; 660 } 661 662 /* 663 * we were able to create the directory. We will tell the 664 * caller that we found something to fix, and it is ok to try 665 * and create the node again. 666 */ 667 retval = 0; 668 if (pids) 669 (void)set_ids(name, st_uid, st_gid); 670 671 /* 672 * make sure the user doen't have some strange umask that 673 * causes this newly created directory to be unusable. We fix 674 * the modes and restore them back to the creation default at 675 * the end of pax 676 */ 677 if ((access(name, R_OK | W_OK | X_OK) < 0) && 678 (lstat(name, &sb) == 0)) { 679 set_pmode(name, ((sb.st_mode & FILEBITS) | S_IRWXU)); 680 add_dir(name, spt - name, &sb, 1); 681 } 682 *(spt++) = '/'; 683 continue; 684 } 685 return(retval); 686} 687 688/* 689 * set_ftime() 690 * Set the access time and modification time for a named file. If frc is 691 * non-zero we force these times to be set even if the the user did not 692 * request access and/or modification time preservation (this is also 693 * used by -t to reset access times). 694 * When ign is zero, only those times the user has asked for are set, the 695 * other ones are left alone. We do not assume the un-documented feature 696 * of many utimes() implementations that consider a 0 time value as a do 697 * not set request. 698 */ 699 700#if __STDC__ 701void 702set_ftime(char *fnm, time_t mtime, time_t atime, int frc) 703#else 704void 705set_ftime(fnm, mtime, atime, frc) 706 char *fnm; 707 time_t mtime; 708 time_t atime; 709 int frc; 710#endif 711{ 712 struct timeval tv[2]; 713 struct stat sb; 714 715 tv[0].tv_sec = (long)atime; 716 tv[0].tv_usec = 0; 717 tv[1].tv_sec = (long)mtime; 718 tv[1].tv_usec = 0; 719 if (!frc && (!patime || !pmtime)) { 720 /* 721 * if we are not forcing, only set those times the user wants 722 * set. We get the current values of the times if we need them. 723 */ 724 if (lstat(fnm, &sb) == 0) { 725 if (!patime) 726 TIMESPEC_TO_TIMEVAL(&tv[0], &sb.st_atimespec); 727 if (!pmtime) 728 TIMESPEC_TO_TIMEVAL(&tv[1], &sb.st_mtimespec); 729 } else 730 syswarn(0,errno,"Unable to obtain file stats %s", fnm); 731 } 732 733 /* 734 * set the times 735 */ 736 if (lutimes(fnm, tv) < 0) 737 syswarn(1, errno, "Access/modification time set failed on: %s", 738 fnm); 739 return; 740} 741 742/* 743 * set_ids() 744 * set the uid and gid of a file system node 745 * Return: 746 * 0 when set, -1 on failure 747 */ 748 749#if __STDC__ 750int 751set_ids(char *fnm, uid_t uid, gid_t gid) 752#else 753int 754set_ids(fnm, uid, gid) 755 char *fnm; 756 uid_t uid; 757 gid_t gid; 758#endif 759{ 760 if (lchown(fnm, uid, gid) < 0) { 761 syswarn(1, errno, "Unable to set file uid/gid of %s", fnm); 762 return(-1); 763 } 764 return(0); 765} 766 767/* 768 * set_pmode() 769 * Set file access mode 770 */ 771 772#if __STDC__ 773void 774set_pmode(char *fnm, mode_t mode) 775#else 776void 777set_pmode(fnm, mode) 778 char *fnm; 779 mode_t mode; 780#endif 781{ 782 mode &= ABITS; 783 if (lchmod(fnm, mode) < 0) 784 syswarn(1, errno, "Could not set permissions on %s", fnm); 785 return; 786} 787 788/* 789 * file_write() 790 * Write/copy a file (during copy or archive extract). This routine knows 791 * how to copy files with lseek holes in it. (Which are read as file 792 * blocks containing all 0's but do not have any file blocks associated 793 * with the data). Typical examples of these are files created by dbm 794 * variants (.pag files). While the file size of these files are huge, the 795 * actual storage is quite small (the files are sparse). The problem is 796 * the holes read as all zeros so are probably stored on the archive that 797 * way (there is no way to determine if the file block is really a hole, 798 * we only know that a file block of all zero's can be a hole). 799 * At this writing, no major archive format knows how to archive files 800 * with holes. However, on extraction (or during copy, -rw) we have to 801 * deal with these files. Without detecting the holes, the files can 802 * consume a lot of file space if just written to disk. This replacement 803 * for write when passed the basic allocation size of a file system block, 804 * uses lseek whenever it detects the input data is all 0 within that 805 * file block. In more detail, the strategy is as follows: 806 * While the input is all zero keep doing an lseek. Keep track of when we 807 * pass over file block boundries. Only write when we hit a non zero 808 * input. once we have written a file block, we continue to write it to 809 * the end (we stop looking at the input). When we reach the start of the 810 * next file block, start checking for zero blocks again. Working on file 811 * block boundries significantly reduces the overhead when copying files 812 * that are NOT very sparse. This overhead (when compared to a write) is 813 * almost below the measurement resolution on many systems. Without it, 814 * files with holes cannot be safely copied. It does has a side effect as 815 * it can put holes into files that did not have them before, but that is 816 * not a problem since the file contents are unchanged (in fact it saves 817 * file space). (Except on paging files for diskless clients. But since we 818 * cannot determine one of those file from here, we ignore them). If this 819 * ever ends up on a system where CTG files are supported and the holes 820 * are not desired, just do a conditional test in those routines that 821 * call file_write() and have it call write() instead. BEFORE CLOSING THE 822 * FILE, make sure to call file_flush() when the last write finishes with 823 * an empty block. A lot of file systems will not create an lseek hole at 824 * the end. In this case we drop a single 0 at the end to force the 825 * trailing 0's in the file. 826 * ---Parameters--- 827 * rem: how many bytes left in this file system block 828 * isempt: have we written to the file block yet (is it empty) 829 * sz: basic file block allocation size 830 * cnt: number of bytes on this write 831 * str: buffer to write 832 * Return: 833 * number of bytes written, -1 on write (or lseek) error. 834 */ 835 836#if __STDC__ 837int 838file_write(int fd, char *str, int cnt, int *rem, int *isempt, int sz, 839 char *name) 840#else 841int 842file_write(fd, str, cnt, rem, isempt, sz, name) 843 int fd; 844 char *str; 845 int cnt; 846 int *rem; 847 int *isempt; 848 int sz; 849 char *name; 850#endif 851{ 852 char *pt; 853 char *end; 854 int wcnt; 855 char *st = str; 856 857 /* 858 * while we have data to process 859 */ 860 while (cnt) { 861 if (!*rem) { 862 /* 863 * We are now at the start of file system block again 864 * (or what we think one is...). start looking for 865 * empty blocks again 866 */ 867 *isempt = 1; 868 *rem = sz; 869 } 870 871 /* 872 * only examine up to the end of the current file block or 873 * remaining characters to write, whatever is smaller 874 */ 875 wcnt = MIN(cnt, *rem); 876 cnt -= wcnt; 877 *rem -= wcnt; 878 if (*isempt) { 879 /* 880 * have not written to this block yet, so we keep 881 * looking for zero's 882 */ 883 pt = st; 884 end = st + wcnt; 885 886 /* 887 * look for a zero filled buffer 888 */ 889 while ((pt < end) && (*pt == '\0')) 890 ++pt; 891 892 if (pt == end) { 893 /* 894 * skip, buf is empty so far 895 */ 896 if (lseek(fd, (off_t)wcnt, SEEK_CUR) < 0) { 897 syswarn(1,errno,"File seek on %s", 898 name); 899 return(-1); 900 } 901 st = pt; 902 continue; 903 } 904 /* 905 * drat, the buf is not zero filled 906 */ 907 *isempt = 0; 908 } 909 910 /* 911 * have non-zero data in this file system block, have to write 912 */ 913 if (write(fd, st, wcnt) != wcnt) { 914 syswarn(1, errno, "Failed write to file %s", name); 915 return(-1); 916 } 917 st += wcnt; 918 } 919 return(st - str); 920} 921 922/* 923 * file_flush() 924 * when the last file block in a file is zero, many file systems will not 925 * let us create a hole at the end. To get the last block with zeros, we 926 * write the last BYTE with a zero (back up one byte and write a zero). 927 */ 928 929#if __STDC__ 930void 931file_flush(int fd, char *fname, int isempt) 932#else 933void 934file_flush(fd, fname, isempt) 935 int fd; 936 char *fname; 937 int isempt; 938#endif 939{ 940 static char blnk[] = "\0"; 941 942 /* 943 * silly test, but make sure we are only called when the last block is 944 * filled with all zeros. 945 */ 946 if (!isempt) 947 return; 948 949 /* 950 * move back one byte and write a zero 951 */ 952 if (lseek(fd, (off_t)-1, SEEK_CUR) < 0) { 953 syswarn(1, errno, "Failed seek on file %s", fname); 954 return; 955 } 956 957 if (write(fd, blnk, 1) < 0) 958 syswarn(1, errno, "Failed write to file %s", fname); 959 return; 960} 961 962/* 963 * rdfile_close() 964 * close a file we have beed reading (to copy or archive). If we have to 965 * reset access time (tflag) do so (the times are stored in arcn). 966 */ 967 968#if __STDC__ 969void 970rdfile_close(ARCHD *arcn, int *fd) 971#else 972void 973rdfile_close(arcn, fd) 974 ARCHD *arcn; 975 int *fd; 976#endif 977{ 978 /* 979 * make sure the file is open 980 */ 981 if (*fd < 0) 982 return; 983 984 (void)close(*fd); 985 *fd = -1; 986 if (!tflag) 987 return; 988 989 /* 990 * user wants last access time reset 991 */ 992 set_ftime(arcn->org_name, arcn->sb.st_mtime, arcn->sb.st_atime, 1); 993 return; 994} 995 996/* 997 * set_crc() 998 * read a file to calculate its crc. This is a real drag. Archive formats 999 * that have this, end up reading the file twice (we have to write the 1000 * header WITH the crc before writing the file contents. Oh well... 1001 * Return: 1002 * 0 if was able to calculate the crc, -1 otherwise 1003 */ 1004 1005#if __STDC__ 1006int 1007set_crc(ARCHD *arcn, int fd) 1008#else 1009int 1010set_crc(arcn, fd) 1011 ARCHD *arcn; 1012 int fd; 1013#endif 1014{ 1015 int i; 1016 int res; 1017 off_t cpcnt = 0L; 1018 u_long size; 1019 unsigned long crc = 0L; 1020 char tbuf[FILEBLK]; 1021 struct stat sb; 1022 1023 if (fd < 0) { 1024 /* 1025 * hmm, no fd, should never happen. well no crc then. 1026 */ 1027 arcn->crc = 0L; 1028 return(0); 1029 } 1030 1031 if ((size = (u_long)arcn->sb.st_blksize) > (u_long)sizeof(tbuf)) 1032 size = (u_long)sizeof(tbuf); 1033 1034 /* 1035 * read all the bytes we think that there are in the file. If the user 1036 * is trying to archive an active file, forget this file. 1037 */ 1038 for(;;) { 1039 if ((res = read(fd, tbuf, size)) <= 0) 1040 break; 1041 cpcnt += res; 1042 for (i = 0; i < res; ++i) 1043 crc += (tbuf[i] & 0xff); 1044 } 1045 1046 /* 1047 * safety check. we want to avoid archiving files that are active as 1048 * they can create inconsistant archive copies. 1049 */ 1050 if (cpcnt != arcn->sb.st_size) 1051 tty_warn(1, "File changed size %s", arcn->org_name); 1052 else if (fstat(fd, &sb) < 0) 1053 syswarn(1, errno, "Failed stat on %s", arcn->org_name); 1054 else if (arcn->sb.st_mtime != sb.st_mtime) 1055 tty_warn(1, "File %s was modified during read", arcn->org_name); 1056 else if (lseek(fd, (off_t)0L, SEEK_SET) < 0) 1057 syswarn(1, errno, "File rewind failed on: %s", arcn->org_name); 1058 else { 1059 arcn->crc = crc; 1060 return(0); 1061 } 1062 return(-1); 1063} 1064