aboutsummaryrefslogtreecommitdiffstats
path: root/wiretap/etherpeek.c
blob: 9da771ae030c7359fd2d654b178e3012b7601179 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
/* etherpeek.c
 * Routines for opening EtherPeek (and TokenPeek?) files
 * Copyright (c) 2001, Daniel Thompson <d.thompson@gmx.net>
 *
 * $Id: etherpeek.c,v 1.26 2004/01/25 21:55:13 guy Exp $
 *
 * Wiretap Library
 * Copyright (c) 1998 by Gilbert Ramirez <gram@alumni.rice.edu>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <errno.h>
#include <string.h>
#include "wtap-int.h"
#include "file_wrappers.h"
#include "buffer.h"
#include "etherpeek.h"
/* CREDITS
 *
 * This file decoder could not have been writen without examining how
 * tcptrace (http://www.tcptrace.org/) handles EtherPeek files.
 */

/* master header */
typedef struct etherpeek_master_header {
	guint8  version;
	guint8  status;
} etherpeek_master_header_t;
#define ETHERPEEK_MASTER_HDR_SIZE 2

/* secondary header (V5,V6,V7) */
typedef struct etherpeek_v567_header {
	guint32 filelength;
	guint32 numPackets;
	guint32 timeDate;
	guint32 timeStart;
	guint32 timeStop;
	guint32 mediaType;  /* Media Type Ethernet=0 Token Ring = 1 */
	guint32 physMedium; /* Physical Medium native=0 802.1=1 */
	guint32 appVers;    /* App Version Number Maj.Min.Bug.Build */
	guint32 linkSpeed;  /* Link Speed Bits/sec */
	guint32 reserved[3];
} etherpeek_v567_header_t;
#define ETHERPEEK_V567_HDR_SIZE 48

/* full header */
typedef struct etherpeek_header {
	etherpeek_master_header_t master;
	union {
		etherpeek_v567_header_t v567;
	} secondary;
} etherpeek_header_t;

/*
 * Packet header (V5, V6).
 *
 * NOTE: the time stamp, although it's a 32-bit number, is only aligned
 * on a 16-bit boundary.  (Does this date back to 68K Macs?  The 68000
 * only required 16-bit alignment of 32-bit quantities, as did the 68010,
 * and the 68020/68030/68040 required no alignment.)
 *
 * As such, we cannot declare this as a C structure, as compilers on
 * most platforms will put 2 bytes of padding before the time stamp to
 * align it on a 32-bit boundary.
 *
 * So, instead, we #define numbers as the offsets of the fields.
 */
#define ETHERPEEK_V56_LENGTH_OFFSET		0
#define ETHERPEEK_V56_SLICE_LENGTH_OFFSET	2
#define ETHERPEEK_V56_FLAGS_OFFSET		4
#define ETHERPEEK_V56_STATUS_OFFSET		5
#define ETHERPEEK_V56_TIMESTAMP_OFFSET		6
#define ETHERPEEK_V56_DESTNUM_OFFSET		10
#define ETHERPEEK_V56_SRCNUM_OFFSET		12
#define ETHERPEEK_V56_PROTONUM_OFFSET		14
#define ETHERPEEK_V56_PROTOSTR_OFFSET		16
#define ETHERPEEK_V56_FILTERNUM_OFFSET		24
#define ETHERPEEK_V56_PKT_SIZE			26

/* 64-bit time in micro seconds from the (Mac) epoch */
typedef struct etherpeek_utime {
	guint32 upper;
	guint32 lower;
} etherpeek_utime;

/*
 * Packet header (V7).
 *
 * This doesn't have the same alignment problem, but we do it with
 * #defines anyway.
 */
#define ETHERPEEK_V7_PROTONUM_OFFSET		0
#define ETHERPEEK_V7_LENGTH_OFFSET		2
#define ETHERPEEK_V7_SLICE_LENGTH_OFFSET	4
#define ETHERPEEK_V7_FLAGS_OFFSET		6
#define ETHERPEEK_V7_STATUS_OFFSET		7
#define ETHERPEEK_V7_TIMESTAMP_UPPER_OFFSET	8
#define ETHERPEEK_V7_TIMESTAMP_LOWER_OFFSET	12
#define ETHERPEEK_V7_PKT_SIZE			16

/*
 * AiroPeek radio information, at the beginning of every packet.
 */
typedef struct {
	guint8	data_rate;
	guint8	channel;
	guint8	signal_level;
	guint8	unused;
} airopeek_radio_hdr_t;

typedef struct etherpeek_encap_lookup {
	guint16 protoNum;
	int     encap;
} etherpeek_encap_lookup_t;

static const unsigned int mac2unix = 2082844800u;
static const etherpeek_encap_lookup_t etherpeek_encap[] = {
	{ 1400, WTAP_ENCAP_ETHERNET }
};
#define NUM_ETHERPEEK_ENCAPS \
	(sizeof (etherpeek_encap) / sizeof (etherpeek_encap[0]))

static gboolean etherpeek_read_v7(wtap *wth, int *err, gchar **err_info,
    long *data_offset);
static gboolean etherpeek_seek_read_v7(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int length,
    int *err, gchar **err_info);
static gboolean etherpeek_read_v56(wtap *wth, int *err, gchar **err_info,
    long *data_offset);
static gboolean etherpeek_seek_read_v56(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int length,
    int *err, gchar **err_info);
static void etherpeek_close(wtap *wth);

int etherpeek_open(wtap *wth, int *err, gchar **err_info _U_)
{
	etherpeek_header_t ep_hdr;
	struct timeval reference_time;
	int file_encap;

	/* EtherPeek files do not start with a magic value large enough
	 * to be unique; hence we use the following algorithm to determine
	 * the type of an unknown file:
	 *  - populate the master header and reject file if there is no match
	 *  - populate the secondary header and check that the reserved space
	 *      is zero, and check some other fields; this isn't perfect,
	 *	and we may have to add more checks at some point.
	 */
	g_assert(sizeof(ep_hdr.master) == ETHERPEEK_MASTER_HDR_SIZE);
	wtap_file_read_unknown_bytes(
		&ep_hdr.master, sizeof(ep_hdr.master), wth->fh, err);
	wth->data_offset += sizeof(ep_hdr.master);

	/*
	 * It appears that EtherHelp (a free application from WildPackets
	 * that did blind capture, saving to a file, so that you could
	 * give the resulting file to somebody with EtherPeek) saved
	 * captures in EtherPeek format except that it ORed the 0x80
	 * bit on in the version number.
	 *
	 * We therefore strip off the 0x80 bit in the version number.
	 * Perhaps there's some reason to care whether the capture
	 * came from EtherHelp; if we discover one, we should check
	 * that bit.
	 */
	ep_hdr.master.version &= ~0x80;

	/* switch on the file version */
	switch (ep_hdr.master.version) {

	case 5:
	case 6:
	case 7:
		/* get the secondary header */
		g_assert(sizeof(ep_hdr.secondary.v567) ==
		        ETHERPEEK_V567_HDR_SIZE);
		wtap_file_read_unknown_bytes(
			&ep_hdr.secondary.v567,
			sizeof(ep_hdr.secondary.v567), wth->fh, err);
		wth->data_offset += sizeof(ep_hdr.secondary.v567);

		if ((0 != ep_hdr.secondary.v567.reserved[0]) ||
		    (0 != ep_hdr.secondary.v567.reserved[1]) ||
		    (0 != ep_hdr.secondary.v567.reserved[2])) {
			/* still unknown */
			return 0;
		}

		/*
		 * Check the mediaType and physMedium fields.
		 * We assume it's not an EtherPeek/TokenPeek/AiroPeek
		 * file if these aren't values we know, rather than
		 * reporting them as invalid *Peek files, as, given
		 * the lack of a magic number, we need all the checks
		 * we can get.
		 */
		ep_hdr.secondary.v567.mediaType =
		    g_ntohl(ep_hdr.secondary.v567.mediaType);
		ep_hdr.secondary.v567.physMedium =
		    g_ntohl(ep_hdr.secondary.v567.physMedium);

		switch (ep_hdr.secondary.v567.physMedium) {

		case 0:
			/*
			 * "Native" format, presumably meaning
			 * Ethernet or Token Ring.
			 */
			switch (ep_hdr.secondary.v567.mediaType) {

			case 0:
				file_encap = WTAP_ENCAP_ETHERNET;
				break;

			case 1:
				file_encap = WTAP_ENCAP_TOKEN_RING;
				break;

			default:
				/*
				 * Assume this isn't a *Peek file.
				 */
				return 0;
			}
			break;

		case 1:
			switch (ep_hdr.secondary.v567.mediaType) {

			case 0:
				/*
				 * 802.11, with a private header giving
				 * some radio information.  Presumably
				 * this is from AiroPeek.
				 *
				 * We supply the private header as
				 * the WTAP_ENCAP_IEEE_802_11_WITH_RADIO
				 * pseudo-header, rather than as frame
				 * data.
				 */
				file_encap = WTAP_ENCAP_IEEE_802_11_WITH_RADIO;
				break;

			default:
				/*
				 * Assume this isn't a *Peek file.
				 */
				return 0;
			}
			break;

		default:
			/*
			 * Assume this isn't a *Peek file.
			 */
			return 0;
		}


		/*
		 * Assume this is a V5, V6 or V7 *Peek file, and byte
		 * swap the rest of the fields in the secondary header.
		 *
		 * XXX - we could check the file length if the file were
		 * uncompressed, but it might be compressed.
		 */
		ep_hdr.secondary.v567.filelength =
		    g_ntohl(ep_hdr.secondary.v567.filelength);
		ep_hdr.secondary.v567.numPackets =
		    g_ntohl(ep_hdr.secondary.v567.numPackets);
		ep_hdr.secondary.v567.timeDate =
		    g_ntohl(ep_hdr.secondary.v567.timeDate);
		ep_hdr.secondary.v567.timeStart =
		    g_ntohl(ep_hdr.secondary.v567.timeStart);
		ep_hdr.secondary.v567.timeStop =
		    g_ntohl(ep_hdr.secondary.v567.timeStop);
		ep_hdr.secondary.v567.appVers =
		    g_ntohl(ep_hdr.secondary.v567.appVers);
		ep_hdr.secondary.v567.linkSpeed =
		    g_ntohl(ep_hdr.secondary.v567.linkSpeed);

		/* Get the reference time as a "struct timeval" */
		reference_time.tv_sec  =
		    ep_hdr.secondary.v567.timeDate - mac2unix;
		reference_time.tv_usec = 0;
		break;

	default:
		/*
		 * Assume this isn't a *Peek file.
		 */
		return 0;
	}

	/*
	 * This is an EtherPeek (or TokenPeek or AiroPeek?) file.
	 *
	 * At this point we have recognised the file type and have populated
	 * the whole ep_hdr structure in host byte order.
	 */
	wth->capture.etherpeek = g_malloc(sizeof(etherpeek_t));
	wth->capture.etherpeek->reference_time = reference_time;
	wth->subtype_close = etherpeek_close;
	switch (ep_hdr.master.version) {

	case 5:
	case 6:
		wth->file_type = WTAP_FILE_ETHERPEEK_V56;
		/*
		 * XXX - can we get the file encapsulation from the
		 * header in the same way we do for V7 files?
		 */
		wth->file_encap = WTAP_ENCAP_PER_PACKET;
		wth->subtype_read = etherpeek_read_v56;
		wth->subtype_seek_read = etherpeek_seek_read_v56;
		break;

	case 7:
		wth->file_type = WTAP_FILE_ETHERPEEK_V7;
		wth->file_encap = file_encap;
		wth->subtype_read = etherpeek_read_v7;
		wth->subtype_seek_read = etherpeek_seek_read_v7;
		break;

	default:
		/* this is impossible */
		g_assert_not_reached();
	}

	wth->snapshot_length   = 0; /* not available in header */

	return 1;
}

static void etherpeek_close(wtap *wth)
{
	g_free(wth->capture.etherpeek);
}

static gboolean etherpeek_read_v7(wtap *wth, int *err, gchar **err_info,
    long *data_offset)
{
	guchar ep_pkt[ETHERPEEK_V7_PKT_SIZE];
	guint16 protoNum;
	guint16 length;
	guint16 sliceLength;
	guint8  flags;
	guint8  status;
	etherpeek_utime timestamp;
	double  t;
	airopeek_radio_hdr_t radio_hdr;

	*data_offset = wth->data_offset;

	wtap_file_read_expected_bytes(ep_pkt, sizeof(ep_pkt), wth->fh, err);
	wth->data_offset += sizeof(ep_pkt);

	/* Extract the fields from the packet */
	protoNum = pntohs(&ep_pkt[ETHERPEEK_V7_PROTONUM_OFFSET]);
	length = pntohs(&ep_pkt[ETHERPEEK_V7_LENGTH_OFFSET]);
	sliceLength = pntohs(&ep_pkt[ETHERPEEK_V7_SLICE_LENGTH_OFFSET]);
	flags = ep_pkt[ETHERPEEK_V7_FLAGS_OFFSET];
	status = ep_pkt[ETHERPEEK_V7_STATUS_OFFSET];
	timestamp.upper = pntohl(&ep_pkt[ETHERPEEK_V7_TIMESTAMP_UPPER_OFFSET]);
	timestamp.lower = pntohl(&ep_pkt[ETHERPEEK_V7_TIMESTAMP_LOWER_OFFSET]);

	/* force sliceLength to be the actual length of the packet */
	if (0 == sliceLength) {
		sliceLength = length;
	}

	/* fill in packet header length values before slicelength may be
	   adjusted */
	wth->phdr.len    = length;
	wth->phdr.caplen = sliceLength;

	if (sliceLength % 2) /* packets are padded to an even length */
		sliceLength++;

	switch (wth->file_encap) {

	case WTAP_ENCAP_IEEE_802_11_WITH_RADIO:
		/*
		 * The first 4 bytes of the packet data are radio
		 * information (including a reserved byte).
		 */
		if (sliceLength < 4) {
			/*
			 * We don't *have* 4 bytes of packet data.
			 */
			*err = WTAP_ERR_BAD_RECORD;
			*err_info = g_strdup("etherpeek: packet not long enough for 802.11 radio header");
			return FALSE;
		}
		wtap_file_read_expected_bytes(&radio_hdr, 4, wth->fh, err);

		/*
		 * We don't treat the radio information as packet data.
		 */
		sliceLength -= 4;
		wth->phdr.len -= 4;
		wth->phdr.caplen -= 4;
		wth->data_offset += 4;

		wth->pseudo_header.ieee_802_11.channel = radio_hdr.channel;
		wth->pseudo_header.ieee_802_11.data_rate = radio_hdr.data_rate;
		wth->pseudo_header.ieee_802_11.signal_level = radio_hdr.signal_level;
		break;

	case WTAP_ENCAP_ETHERNET:
		/* XXX - it appears that if the low-order bit of
		   "status" is 0, there's an FCS in this frame,
		   and if it's 1, there's 4 bytes of 0. */
		wth->pseudo_header.eth.fcs_len = (status & 0x01) ? 0 : 4;
		break;
	}

	/* read the frame data */
	buffer_assure_space(wth->frame_buffer, sliceLength);
	wtap_file_read_expected_bytes(buffer_start_ptr(wth->frame_buffer),
	                              sliceLength, wth->fh, err);
	wth->data_offset += sliceLength;

	/* fill in packet header values */
	t =  (double) timestamp.lower +
	     (double) timestamp.upper * 4294967296.0;
	t -= (double) mac2unix * 1000000.0;
	wth->phdr.ts.tv_sec  = (time_t)  (t/1000000.0);
	wth->phdr.ts.tv_usec = (guint32) (t - (double) wth->phdr.ts.tv_sec *
	                                               1000000.0);

	if (wth->file_encap == WTAP_ENCAP_IEEE_802_11_WITH_RADIO) {
		/*
		 * The last 4 bytes appear to be random data - the length
		 * might include the FCS - so we reduce the length by 4.
		 *
		 * Or maybe this is just the same kind of random 4 bytes
		 * of junk at the end you get in Wireless Sniffer
		 * captures.
		 */
		 wth->phdr.len -= 4;
		 wth->phdr.caplen -= 4;
	}

	wth->phdr.pkt_encap = wth->file_encap;
	return TRUE;
}

static gboolean
etherpeek_seek_read_v7(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int length,
    int *err, gchar **err_info)
{
	guchar ep_pkt[ETHERPEEK_V7_PKT_SIZE];
	guint8  status;
	airopeek_radio_hdr_t radio_hdr;

	if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
		return FALSE;

	/* Read the packet header. */
	wtap_file_read_expected_bytes(ep_pkt, sizeof(ep_pkt), wth->random_fh,
	    err);
	status = ep_pkt[ETHERPEEK_V7_STATUS_OFFSET];

	switch (wth->file_encap) {

	case WTAP_ENCAP_IEEE_802_11_WITH_RADIO:
		/*
		 * The first 4 bytes of the packet data are radio
		 * information (including a reserved byte).
		 */
		if (length < 4) {
			/*
			 * We don't *have* 4 bytes of packet data.
			 */
			*err = WTAP_ERR_BAD_RECORD;
			*err_info = g_strdup("etherpeek: packet not long enough for 802.11 radio header");
			return FALSE;
		}
		wtap_file_read_expected_bytes(&radio_hdr, 4, wth->random_fh,
		    err);

		pseudo_header->ieee_802_11.channel = radio_hdr.channel;
		pseudo_header->ieee_802_11.data_rate = radio_hdr.data_rate;
		pseudo_header->ieee_802_11.signal_level = radio_hdr.signal_level;
		break;

	case WTAP_ENCAP_ETHERNET:
		/* XXX - it appears that if the low-order bit of
		   "status" is 0, there's an FCS in this frame,
		   and if it's 1, there's 4 bytes of 0. */
		pseudo_header->eth.fcs_len = (status & 0x01) ? 0 : 4;
		break;
	}

	/*
	 * XXX - should "errno" be set in "wtap_file_read_expected_bytes()"?
	 */
	errno = WTAP_ERR_CANT_READ;
	wtap_file_read_expected_bytes(pd, length, wth->random_fh, err);
	return TRUE;
}

static gboolean etherpeek_read_v56(wtap *wth, int *err, gchar **err_info _U_,
    long *data_offset)
{
	guchar ep_pkt[ETHERPEEK_V56_PKT_SIZE];
	guint16 length;
	guint16 sliceLength;
	guint8  flags;
	guint8  status;
	guint32 timestamp;
	guint16 destNum;
	guint16 srcNum;
	guint16 protoNum;
	char    protoStr[8];
	unsigned int i;

	/*
	 * XXX - in order to figure out whether this packet is an
	 * Ethernet packet or not, we have to look at the packet
	 * header, so we have to remember the address of the header,
	 * not the address of the data, for random access.
	 *
	 * If we can determine that from the file header, rather than
	 * the packet header, we can remember the offset of the data,
	 * and not have the seek_read routine read the header.
	 */
	*data_offset = wth->data_offset;

	wtap_file_read_expected_bytes(ep_pkt, sizeof(ep_pkt), wth->fh, err);
	wth->data_offset += sizeof(ep_pkt);

	/* Extract the fields from the packet */
	length = pntohs(&ep_pkt[ETHERPEEK_V56_LENGTH_OFFSET]);
	sliceLength = pntohs(&ep_pkt[ETHERPEEK_V56_SLICE_LENGTH_OFFSET]);
	flags = ep_pkt[ETHERPEEK_V56_FLAGS_OFFSET];
	status = ep_pkt[ETHERPEEK_V56_STATUS_OFFSET];
	timestamp = pntohl(&ep_pkt[ETHERPEEK_V56_TIMESTAMP_OFFSET]);
	destNum = pntohs(&ep_pkt[ETHERPEEK_V56_DESTNUM_OFFSET]);
	srcNum = pntohs(&ep_pkt[ETHERPEEK_V56_SRCNUM_OFFSET]);
	protoNum = pntohs(&ep_pkt[ETHERPEEK_V56_PROTONUM_OFFSET]);
	memcpy(protoStr, &ep_pkt[ETHERPEEK_V56_PROTOSTR_OFFSET],
	    sizeof protoStr);

	/*
	 * XXX - is the captured packet data padded to a multiple
	 * of 2 bytes?
	 */

	/* force sliceLength to be the actual length of the packet */
	if (0 == sliceLength) {
		sliceLength = length;
	}

	/* read the frame data */
	buffer_assure_space(wth->frame_buffer, sliceLength);
	wtap_file_read_expected_bytes(buffer_start_ptr(wth->frame_buffer),
	                              sliceLength, wth->fh, err);
	wth->data_offset += sliceLength;

	/* fill in packet header values */
	wth->phdr.len        = length;
	wth->phdr.caplen     = sliceLength;
	/* timestamp is in milliseconds since reference_time */
	wth->phdr.ts.tv_sec  = wth->capture.etherpeek->reference_time.tv_sec
	    + (timestamp / 1000);
	wth->phdr.ts.tv_usec = 1000 * (timestamp % 1000);

	wth->phdr.pkt_encap = WTAP_ENCAP_UNKNOWN;
	for (i=0; i<NUM_ETHERPEEK_ENCAPS; i++) {
		if (etherpeek_encap[i].protoNum == protoNum) {
			wth->phdr.pkt_encap = etherpeek_encap[i].encap;
		}
	}

	switch (wth->phdr.pkt_encap) {

	case WTAP_ENCAP_ETHERNET:
		/* We assume there's no FCS in this frame. */
		wth->pseudo_header.eth.fcs_len = 0;
		break;
	}
	return TRUE;
}

static gboolean
etherpeek_seek_read_v56(wtap *wth, long seek_off,
    union wtap_pseudo_header *pseudo_header, guchar *pd, int length,
    int *err, gchar **err_info _U_)
{
	guchar ep_pkt[ETHERPEEK_V56_PKT_SIZE];
	int pkt_encap;
	guint16 protoNum;
	unsigned int i;

	if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
		return FALSE;

	wtap_file_read_expected_bytes(ep_pkt, sizeof(ep_pkt), wth->random_fh,
	    err);

	protoNum = pntohs(&ep_pkt[ETHERPEEK_V56_PROTONUM_OFFSET]);
	pkt_encap = WTAP_ENCAP_UNKNOWN;
	for (i=0; i<NUM_ETHERPEEK_ENCAPS; i++) {
		if (etherpeek_encap[i].protoNum == protoNum) {
			pkt_encap = etherpeek_encap[i].encap;
		}
	}

	switch (pkt_encap) {

	case WTAP_ENCAP_ETHERNET:
		/* We assume there's no FCS in this frame. */
		pseudo_header->eth.fcs_len = 0;
		break;
	}

	/*
	 * XXX - should "errno" be set in "wtap_file_read_expected_bytes()"?
	 */
	errno = WTAP_ERR_CANT_READ;
	wtap_file_read_expected_bytes(pd, length, wth->random_fh, err);
	return TRUE;
}