The Tcpdump Group git mirrors - libpcap/blob - savefile.c

   1 /*
   2  * Copyright (c) 1993, 1994, 1995, 1996, 1997
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that: (1) source code distributions
   7  * retain the above copyright notice and this paragraph in its entirety, (2)
   8  * distributions including binary code include the above copyright notice and
   9  * this paragraph in its entirety in the documentation or other materials
  10  * provided with the distribution, and (3) all advertising materials mentioning
  11  * features or use of this software display the following acknowledgement:
  12  * ``This product includes software developed by the University of California,
  13  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14  * the University nor the names of its contributors may be used to endorse
  15  * or promote products derived from this software without specific prior
  16  * written permission.
  17  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20  *
  21  * savefile.c - supports offline use of tcpdump
  22  *      Extraction/creation by Jeffrey Mogul, DECWRL
  23  *      Modified by Steve McCanne, LBL.
  24  *
  25  * Used to save the received packet headers, after filtering, to
  26  * a file, and then read them later.
  27  * The first record in the file contains saved values for the machine
  28  * dependent values so we can print the dump file on any architecture.
  29  */
  30
  31 #ifdef HAVE_CONFIG_H
  32 #include <config.h>
  33 #endif
  34
  35 #include <pcap-types.h>
  36 #ifdef _WIN32
  37 #include <io.h>
  38 #include <fcntl.h>
  39 #endif /* _WIN32 */
  40
  41 #include <errno.h>
  42 #include <memory.h>
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46 #include <limits.h> /* for INT_MAX */
  47
  48 #include "pcap-int.h"
  49
  50 #ifdef HAVE_OS_PROTO_H
  51 #include "os-proto.h"
  52 #endif
  53
  54 #include "sf-pcap.h"
  55 #include "sf-pcapng.h"
  56 #include "pcap-common.h"
  57 #include "charconv.h"
  58
  59 #ifdef _WIN32
  60 /*
  61  * This isn't exported on Windows, because it would only work if both
  62  * WinPcap/Npcap and the code using it were to use the Universal CRT; otherwise,
  63  * a FILE structure in WinPcap/Npcap and a FILE structure in the code using it
  64  * could be different if they're using different versions of the C runtime.
  65  *
  66  * Instead, pcap/pcap.h defines it as a macro that wraps the hopen version,
  67  * with the wrapper calling _fileno() and _get_osfhandle() themselves,
  68  * so that it convert the appropriate CRT version's FILE structure to
  69  * a HANDLE (which is OS-defined, not CRT-defined, and is part of the Win32
  70  * and Win64 ABIs).
  71  */
  72 static pcap_t *pcap_fopen_offline_with_tstamp_precision(FILE *, u_int, char *);
  73 #endif
  74
  75 /*
  76  * Setting O_BINARY on DOS/Windows is a bit tricky
  77  */
  78 #if defined(_WIN32)
  79   #define SET_BINMODE(f)  _setmode(_fileno(f), _O_BINARY)
  80 #elif defined(MSDOS)
  81   #if defined(__HIGHC__)
  82   #define SET_BINMODE(f)  setmode(f, O_BINARY)
  83   #else
  84   #define SET_BINMODE(f)  setmode(fileno(f), O_BINARY)
  85   #endif
  86 #endif
  87
  88 #ifdef _WI32
  89 /*
  90  * XXX - TEMPORARY TO FIGURE OUT WHY WE'RE NOT GETTING WARNINGS ABOUT
  91  * ASSIGNMENT OF A POINTER TO CONST CHAR VALUE TO A POINTER TO CHAR
  92  * VARIABLE.
  93  */
  94 LPCSTR PacketGetLPCSTR(void);
  95 const char *PacketGetConstCharStar(void);
  96
  97 LPCSTR
  98 PacketGetLPCSTR(void)
  99 {
 100         return "LPCSTR";
 101 }
 102
 103 const char *
 104 PacketGetConstCharStar(void)
 105 {
 106         return "const char *";
 107 }
 108 #endif
 109
 110 static int
 111 sf_getnonblock(pcap_t *p _U_)
 112 {
 113         /*
 114          * This is a savefile, not a live capture file, so never say
 115          * it's in non-blocking mode.
 116          */
 117         return (0);
 118 }
 119
 120 static int
 121 sf_setnonblock(pcap_t *p, int nonblock _U_)
 122 {
 123         /*
 124          * This is a savefile, not a live capture file, so reject
 125          * requests to put it in non-blocking mode.  (If it's a
 126          * pipe, it could be put in non-blocking mode, but that
 127          * would significantly complicate the code to read packets,
 128          * as it would have to handle reading partial packets and
 129          * keeping the state of the read.)
 130          */
 131         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 132             "Savefiles cannot be put into non-blocking mode");
 133         return (-1);
 134 }
 135
 136 static int
 137 sf_stats(pcap_t *p, struct pcap_stat *ps _U_)
 138 {
 139         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 140             "Statistics aren't available from savefiles");
 141         return (-1);
 142 }
 143
 144 #ifdef _WIN32
 145 static struct pcap_stat *
 146 sf_stats_ex(pcap_t *p, int *size _U_)
 147 {
 148         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 149             "Statistics aren't available from savefiles");
 150         return (NULL);
 151 }
 152
 153 static int
 154 sf_setbuff(pcap_t *p, int dim _U_)
 155 {
 156         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 157             "The kernel buffer size cannot be set while reading from a file");
 158         return (-1);
 159 }
 160
 161 static int
 162 sf_setmode(pcap_t *p, int mode _U_)
 163 {
 164         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 165             "impossible to set mode while reading from a file");
 166         return (-1);
 167 }
 168
 169 static int
 170 sf_setmintocopy(pcap_t *p, int size _U_)
 171 {
 172         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 173             "The mintocopy parameter cannot be set while reading from a file");
 174         return (-1);
 175 }
 176
 177 static HANDLE
 178 sf_getevent(pcap_t *pcap)
 179 {
 180         (void)snprintf(pcap->errbuf, sizeof(pcap->errbuf),
 181             "The read event cannot be retrieved while reading from a file");
 182         return (INVALID_HANDLE_VALUE);
 183 }
 184
 185 static int
 186 sf_oid_get_request(pcap_t *p, bpf_u_int32 oid _U_, void *data _U_,
 187     size_t *lenp _U_)
 188 {
 189         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 190             "An OID get request cannot be performed on a file");
 191         return (PCAP_ERROR);
 192 }
 193
 194 static int
 195 sf_oid_set_request(pcap_t *p, bpf_u_int32 oid _U_, const void *data _U_,
 196     size_t *lenp _U_)
 197 {
 198         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 199             "An OID set request cannot be performed on a file");
 200         return (PCAP_ERROR);
 201 }
 202
 203 static u_int
 204 sf_sendqueue_transmit(pcap_t *p, pcap_send_queue *queue _U_, int sync _U_)
 205 {
 206         pcap_strlcpy(p->errbuf, "Sending packets isn't supported on savefiles",
 207             PCAP_ERRBUF_SIZE);
 208         return (0);
 209 }
 210
 211 static int
 212 sf_setuserbuffer(pcap_t *p, int size _U_)
 213 {
 214         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 215             "The user buffer cannot be set when reading from a file");
 216         return (-1);
 217 }
 218
 219 static int
 220 sf_live_dump(pcap_t *p, char *filename _U_, int maxsize _U_, int maxpacks _U_)
 221 {
 222         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 223             "Live packet dumping cannot be performed when reading from a file");
 224         return (-1);
 225 }
 226
 227 static int
 228 sf_live_dump_ended(pcap_t *p, int sync _U_)
 229 {
 230         snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
 231             "Live packet dumping cannot be performed on a pcap_open_dead pcap_t");
 232         return (-1);
 233 }
 234
 235 static PAirpcapHandle
 236 sf_get_airpcap_handle(pcap_t *pcap _U_)
 237 {
 238         return (NULL);
 239 }
 240 #endif
 241
 242 static int
 243 sf_inject(pcap_t *p, const void *buf _U_, int size _U_)
 244 {
 245         pcap_strlcpy(p->errbuf, "Sending packets isn't supported on savefiles",
 246             PCAP_ERRBUF_SIZE);
 247         return (-1);
 248 }
 249
 250 /*
 251  * Set direction flag: Which packets do we accept on a forwarding
 252  * single device? IN, OUT or both?
 253  */
 254 static int
 255 sf_setdirection(pcap_t *p, pcap_direction_t d _U_)
 256 {
 257         snprintf(p->errbuf, sizeof(p->errbuf),
 258             "Setting direction is not supported on savefiles");
 259         return (-1);
 260 }
 261
 262 void
 263 sf_cleanup(pcap_t *p)
 264 {
 265         if (p->rfile != stdin)
 266                 (void)fclose(p->rfile);
 267         if (p->buffer != NULL)
 268                 free(p->buffer);
 269         pcap_freecode(&p->fcode);
 270 }
 271
 272 #ifdef _WIN32
 273 /*
 274  * Wrapper for fopen() and _wfopen().
 275  *
 276  * If we're in UTF-8 mode, map the pathname from UTF-8 to UTF-16LE and
 277  * call _wfopen().
 278  *
 279  * If we're not, just use fopen(); that'll treat it as being in the
 280  * local code page.
 281  */
 282 FILE *
 283 charset_fopen(const char *path, const char *mode)
 284 {
 285         wchar_t *utf16_path;
 286 #define MAX_MODE_LEN    16
 287         wchar_t utf16_mode[MAX_MODE_LEN+1];
 288         int i;
 289         char c;
 290         FILE *fp;
 291         int save_errno;
 292
 293         if (pcap_utf_8_mode) {
 294                 /*
 295                  * Map from UTF-8 to UTF-16LE.
 296                  * Fail if there are invalid characters in the input
 297                  * string, rather than converting them to REPLACEMENT
 298                  * CHARACTER; the latter is appropriate for strings
 299                  * to be displayed to the user, but for file names
 300                  * you just want the attempt to open the file to fail.
 301                  */
 302                 utf16_path = cp_to_utf_16le(CP_UTF8, path,
 303                     MB_ERR_INVALID_CHARS);
 304                 if (utf16_path == NULL) {
 305                         /*
 306                          * Error.  Assume errno has been set.
 307                          *
 308                          * XXX - what about Windows errors?
 309                          */
 310                         return (NULL);
 311                 }
 312
 313                 /*
 314                  * Now convert the mode to UTF-16LE as well.
 315                  * We assume the mode is ASCII, and that
 316                  * it's short, so that's easy.
 317                  */
 318                 for (i = 0; (c = *mode) != '\0'; i++, mode++) {
 319                         if (c > 0x7F) {
 320                                 /* Not an ASCII character; fail with EINVAL. */
 321                                 free(utf16_path);
 322                                 errno = EINVAL;
 323                                 return (NULL);
 324                         }
 325                         if (i >= MAX_MODE_LEN) {
 326                                 /* The mode string is longer than we allow. */
 327                                 free(utf16_path);
 328                                 errno = EINVAL;
 329                                 return (NULL);
 330                         }
 331                         utf16_mode[i] = c;
 332                 }
 333                 utf16_mode[i] = '\0';
 334
 335                 /*
 336                  * OK, we have UTF-16LE strings; hand them to
 337                  * _wfopen().
 338                  */
 339                 fp = _wfopen(utf16_path, utf16_mode);
 340
 341                 /*
 342                  * Make sure freeing the UTF-16LE string doesn't
 343                  * overwrite the error code we got from _wfopen().
 344                  */
 345                 save_errno = errno;
 346                 free(utf16_path);
 347                 errno = save_errno;
 348
 349                 return (fp);
 350         } else {
 351                 /*
 352                  * This takes strings in the local code page as an
 353                  * argument.
 354                  */
 355                 return (fopen(path, mode));
 356         }
 357 }
 358 #endif
 359
 360 pcap_t *
 361 pcap_open_offline_with_tstamp_precision(const char *fname, u_int precision,
 362                                         char *errbuf)
 363 {
 364         FILE *fp;
 365         pcap_t *p;
 366
 367         if (fname == NULL) {
 368                 snprintf(errbuf, PCAP_ERRBUF_SIZE,
 369                     "A null pointer was supplied as the file name");
 370                 return (NULL);
 371         }
 372         if (fname[0] == '-' && fname[1] == '\0')
 373         {
 374                 fp = stdin;
 375                 if (stdin == NULL) {
 376                         snprintf(errbuf, PCAP_ERRBUF_SIZE,
 377                             "The standard input is not open");
 378                         return (NULL);
 379                 }
 380 #if defined(_WIN32) || defined(MSDOS)
 381                 /*
 382                  * We're reading from the standard input, so put it in binary
 383                  * mode, as savefiles are binary files.
 384                  */
 385                 SET_BINMODE(fp);
 386 #endif
 387         }
 388         else {
 389                 /*
 390                  * Use charset_fopen(); on Windows, it tests whether we're
 391                  * in "local code page" or "UTF-8" mode, and treats the
 392                  * pathname appropriately, and on other platforms, it just
 393                  * wraps fopen().
 394                  *
 395                  * "b" is supported as of C90, so *all* UN*Xes should
 396                  * support it, even though it does nothing.  For MS-DOS,
 397                  * we again need it.
 398                  */
 399                 fp = charset_fopen(fname, "rb");
 400                 if (fp == NULL) {
 401                         pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
 402                             errno, "%s", fname);
 403                         return (NULL);
 404                 }
 405         }
 406         p = pcap_fopen_offline_with_tstamp_precision(fp, precision, errbuf);
 407         if (p == NULL) {
 408                 if (fp != stdin)
 409                         fclose(fp);
 410         }
 411         return (p);
 412 }
 413
 414 pcap_t *
 415 pcap_open_offline(const char *fname, char *errbuf)
 416 {
 417         return (pcap_open_offline_with_tstamp_precision(fname,
 418             PCAP_TSTAMP_PRECISION_MICRO, errbuf));
 419 }
 420
 421 #ifdef _WIN32
 422 pcap_t* pcap_hopen_offline_with_tstamp_precision(intptr_t osfd, u_int precision,
 423     char *errbuf)
 424 {
 425         int fd;
 426         FILE *file;
 427
 428         fd = _open_osfhandle(osfd, _O_RDONLY);
 429         if ( fd < 0 )
 430         {
 431                 pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
 432                     errno, "_open_osfhandle");
 433                 return NULL;
 434         }
 435
 436         file = _fdopen(fd, "rb");
 437         if ( file == NULL )
 438         {
 439                 pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
 440                     errno, "_fdopen");
 441                 _close(fd);
 442                 return NULL;
 443         }
 444
 445         return pcap_fopen_offline_with_tstamp_precision(file, precision,
 446             errbuf);
 447 }
 448
 449 pcap_t* pcap_hopen_offline(intptr_t osfd, char *errbuf)
 450 {
 451         return pcap_hopen_offline_with_tstamp_precision(osfd,
 452             PCAP_TSTAMP_PRECISION_MICRO, errbuf);
 453 }
 454 #endif
 455
 456 /*
 457  * Given a link-layer header type and snapshot length, return a
 458  * snapshot length to use when reading the file; it's guaranteed
 459  * to be > 0 and <= INT_MAX.
 460  *
 461  * XXX - the only reason why we limit it to <= INT_MAX is so that
 462  * it fits in p->snapshot, and the only reason that p->snapshot is
 463  * signed is that pcap_snapshot() returns an int, not an unsigned int.
 464  */
 465 bpf_u_int32
 466 pcap_adjust_snapshot(bpf_u_int32 linktype, bpf_u_int32 snaplen)
 467 {
 468         if (snaplen == 0 || snaplen > INT_MAX) {
 469                 /*
 470                  * Bogus snapshot length; use the maximum for this
 471                  * link-layer type as a fallback.
 472                  *
 473                  * XXX - we don't clamp snapshot lengths that are
 474                  * <= INT_MAX but > max_snaplen_for_dlt(linktype),
 475                  * so a capture file could cause us to allocate
 476                  * a Really Big Buffer.
 477                  */
 478                 snaplen = max_snaplen_for_dlt(linktype);
 479         }
 480         return snaplen;
 481 }
 482
 483 static pcap_t *(*check_headers[])(const uint8_t *, FILE *, u_int, char *, int *) = {
 484         pcap_check_header,
 485         pcap_ng_check_header
 486 };
 487
 488 #define N_FILE_TYPES    (sizeof check_headers / sizeof check_headers[0])
 489
 490 #ifdef _WIN32
 491 static
 492 #endif
 493 pcap_t *
 494 pcap_fopen_offline_with_tstamp_precision(FILE *fp, u_int precision,
 495     char *errbuf)
 496 {
 497         register pcap_t *p;
 498         uint8_t magic[4];
 499         size_t amt_read;
 500         u_int i;
 501         int err;
 502
 503         /*
 504          * Fail if we were passed a NULL fp.
 505          *
 506          * That shouldn't happen if we're opening with a path name, but
 507          * it could happen if buggy code is opening with a FILE * and
 508          * didn't bother to make sure the FILE * isn't null.
 509          */
 510         if (fp == NULL) {
 511                 snprintf(errbuf, PCAP_ERRBUF_SIZE,
 512                     "Null FILE * pointer provided to savefile open routine");
 513                 return (NULL);
 514         }
 515
 516         /*
 517          * Read the first 4 bytes of the file; the network analyzer dump
 518          * file formats we support (pcap and pcapng), and several other
 519          * formats we might support in the future (such as snoop, DOS and
 520          * Windows Sniffer, and Microsoft Network Monitor) all have magic
 521          * numbers that are unique in their first 4 bytes.
 522          */
 523         amt_read = fread(&magic, 1, sizeof(magic), fp);
 524         if (amt_read != sizeof(magic)) {
 525                 if (ferror(fp)) {
 526                         pcap_fmt_errmsg_for_errno(errbuf, PCAP_ERRBUF_SIZE,
 527                             errno, "error reading dump file");
 528                 } else {
 529                         snprintf(errbuf, PCAP_ERRBUF_SIZE,
 530                             "truncated dump file; tried to read %zu file header bytes, only got %zu",
 531                             sizeof(magic), amt_read);
 532                 }
 533                 return (NULL);
 534         }
 535
 536         /*
 537          * Try all file types.
 538          */
 539         for (i = 0; i < N_FILE_TYPES; i++) {
 540                 p = (*check_headers[i])(magic, fp, precision, errbuf, &err);
 541                 if (p != NULL) {
 542                         /* Yup, that's it. */
 543                         goto found;
 544                 }
 545                 if (err) {
 546                         /*
 547                          * Error trying to read the header.
 548                          */
 549                         return (NULL);
 550                 }
 551         }
 552
 553         /*
 554          * Well, who knows what this mess is....
 555          */
 556         snprintf(errbuf, PCAP_ERRBUF_SIZE, "unknown file format");
 557         return (NULL);
 558
 559 found:
 560         p->rfile = fp;
 561
 562         /* Padding only needed for live capture fcode */
 563         p->fddipad = 0;
 564
 565 #if !defined(_WIN32) && !defined(MSDOS)
 566         /*
 567          * You can do "select()" and "poll()" on plain files on most
 568          * platforms, and should be able to do so on pipes.
 569          *
 570          * You can't do "select()" on anything other than sockets in
 571          * Windows, so, on Win32 systems, we don't have "selectable_fd".
 572          */
 573         p->selectable_fd = fileno(fp);
 574 #endif
 575
 576         p->read_op = pcap_offline_read;
 577         p->inject_op = sf_inject;
 578         p->setfilter_op = install_bpf_program;
 579         p->setdirection_op = sf_setdirection;
 580         p->set_datalink_op = NULL;      /* we don't support munging link-layer headers */
 581         p->getnonblock_op = sf_getnonblock;
 582         p->setnonblock_op = sf_setnonblock;
 583         p->stats_op = sf_stats;
 584 #ifdef _WIN32
 585         p->stats_ex_op = sf_stats_ex;
 586         p->setbuff_op = sf_setbuff;
 587         p->setmode_op = sf_setmode;
 588         p->setmintocopy_op = sf_setmintocopy;
 589         p->getevent_op = sf_getevent;
 590         p->oid_get_request_op = sf_oid_get_request;
 591         p->oid_set_request_op = sf_oid_set_request;
 592         p->sendqueue_transmit_op = sf_sendqueue_transmit;
 593         p->setuserbuffer_op = sf_setuserbuffer;
 594         p->live_dump_op = sf_live_dump;
 595         p->live_dump_ended_op = sf_live_dump_ended;
 596         p->get_airpcap_handle_op = sf_get_airpcap_handle;
 597 #endif
 598
 599         /*
 600          * For offline captures, the standard one-shot callback can
 601          * be used for pcap_next()/pcap_next_ex().
 602          */
 603         p->oneshot_callback = pcap_oneshot;
 604
 605         /*
 606          * Default breakloop operation.
 607          */
 608         p->breakloop_op = pcap_breakloop_common;
 609
 610         /*
 611          * Savefiles never require special BPF code generation.
 612          */
 613         p->bpf_codegen_flags = 0;
 614
 615         p->activated = 1;
 616
 617         return (p);
 618 }
 619
 620 /*
 621  * This isn't needed on Windows; we #define pcap_fopen_offline() as
 622  * a wrapper around pcap_hopen_offline(), and we don't call it from
 623  * inside this file, so it's unused.
 624  */
 625 #ifndef _WIN32
 626 pcap_t *
 627 pcap_fopen_offline(FILE *fp, char *errbuf)
 628 {
 629         return (pcap_fopen_offline_with_tstamp_precision(fp,
 630             PCAP_TSTAMP_PRECISION_MICRO, errbuf));
 631 }
 632 #endif
 633
 634 /*
 635  * Read packets from a capture file, and call the callback for each
 636  * packet.
 637  * If cnt > 0, return after 'cnt' packets, otherwise continue until eof.
 638  */
 639 int
 640 pcap_offline_read(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
 641 {
 642         struct bpf_insn *fcode;
 643         int status = 0;
 644         int n = 0;
 645         u_char *data;
 646
 647         while (status == 0) {
 648                 struct pcap_pkthdr h;
 649
 650                 /*
 651                  * Has "pcap_breakloop()" been called?
 652                  * If so, return immediately - if we haven't read any
 653                  * packets, clear the flag and return -2 to indicate
 654                  * that we were told to break out of the loop, otherwise
 655                  * leave the flag set, so that the *next* call will break
 656                  * out of the loop without having read any packets, and
 657                  * return the number of packets we've processed so far.
 658                  */
 659                 if (p->break_loop) {
 660                         if (n == 0) {
 661                                 p->break_loop = 0;
 662                                 return (-2);
 663                         } else
 664                                 return (n);
 665                 }
 666
 667                 status = p->next_packet_op(p, &h, &data);
 668                 if (status) {
 669                         if (status == 1)
 670                                 return (0);
 671                         return (status);
 672                 }
 673
 674                 if ((fcode = p->fcode.bf_insns) == NULL ||
 675                     pcap_filter(fcode, data, h.len, h.caplen)) {
 676                         (*callback)(user, &h, data);
 677                         if (++n >= cnt && cnt > 0)
 678                                 break;
 679                 }
 680         }
 681         /*XXX this breaks semantics tcpslice expects */
 682         return (n);
 683 }