1EDITCAP(1)              The Wireshark Network Analyzer              EDITCAP(1)
2
3
4

NAME

6       editcap - Edit and/or translate the format of capture files
7

SYNOPSIS

9       editcap [ -a <frame:comment> ] [ -A <start time> ] [ -B <stop time> ]
10       [ -c <packets per file> ] [ -C [offset:]<choplen> ]
11       [ -E <error probability> ] [ -F <file format> ] [ -h ]
12       [ -i <seconds per file> ] [ -o <change offset> ] [ -L ] [ -r ]
13       [ -s <snaplen> ] [ -S <strict time adjustment> ]
14       [ -t <time adjustment> ] [ -T <encapsulation type> ] [ -v ]
15       [ --inject-secrets <secrets type>,<file> ] [ --discard-all-secrets ]
16       infile outfile [ packet#[-packet#] ... ]
17
18       editcap  -d  |  -D <dup window>  |  -w <dup time window>  [ -v ]
19       [ -I <bytes to ignore> ] [ --skip-radiotap-header ] infile outfile
20
21       editcap [ -V ]
22

DESCRIPTION

24       Editcap is a program that reads some or all of the captured packets
25       from the infile, optionally converts them in various ways and writes
26       the resulting packets to the capture outfile (or outfiles).
27
28       By default, it reads all packets from the infile and writes them to the
29       outfile in pcapng file format.
30
31       An optional list of packet numbers can be specified on the command
32       tail; individual packet numbers separated by whitespace and/or ranges
33       of packet numbers can be specified as start-end, referring to all
34       packets from start to end.  By default the selected packets with those
35       numbers will not be written to the capture file.  If the -r flag is
36       specified, the whole packet selection is reversed; in that case only
37       the selected packets will be written to the capture file.
38
39       Editcap can also be used to remove duplicate packets.  Several
40       different options (-d, -D and -w) are used to control the packet window
41       or relative time window to be used for duplicate comparison.
42
43       Editcap can be used to assign comment strings to frame numbers.
44
45       Editcap is able to detect, read and write the same capture files that
46       are supported by Wireshark.  The input file doesn't need a specific
47       filename extension; the file format and an optional gzip compression
48       will be automatically detected.  Near the beginning of the DESCRIPTION
49       section of wireshark(1) or
50       <https://www.wireshark.org/docs/man-pages/wireshark.html> is a detailed
51       description of the way Wireshark handles this, which is the same way
52       Editcap handles this.
53
54       Editcap can write the file in several output formats. The -F flag can
55       be used to specify the format in which to write the capture file;
56       editcap -F provides a list of the available output formats.
57

OPTIONS

59       -a  <framenum:comment>
60           For the specificed frame number, assign the given comment string.
61           Can be repeated for multiple frames.  Quotes should be used with
62           comment strings that include spaces.
63
64       -A  <start time>
65           Saves only the packets whose timestamp is on or after start time.
66           The time is given in the following format YYYY-MM-DD HH:MM:SS
67
68       -B  <stop time>
69           Saves only the packets whose timestamp is before stop time.  The
70           time is given in the following format YYYY-MM-DD HH:MM:SS
71
72       -c  <packets per file>
73           Splits the packet output to different files based on uniform packet
74           counts with a maximum of <packets per file> each. Each output file
75           will be created with a suffix -nnnnn, starting with 00000. If the
76           specified number of packets is written to the output file, the next
77           output file is opened. The default is to use a single output file.
78
79       -C  [offset:]<choplen>
80           Sets the chop length to use when writing the packet data. Each
81           packet is chopped by <choplen> bytes of data. Positive values chop
82           at the packet beginning while negative values chop at the packet
83           end.
84
85           If an optional offset precedes the <choplen>, then the bytes
86           chopped will be offset from that value. Positive offsets are from
87           the packet beginning, while negative offsets are from the packet
88           end.
89
90           This is useful for chopping headers for decapsulation of an entire
91           capture, removing tunneling headers, or in the rare case that the
92           conversion between two file formats leaves some random bytes at the
93           end of each packet. Another use is for removing vlan tags.
94
95           NOTE: This option can be used more than once, effectively allowing
96           you to chop bytes from up to two different areas of a packet in a
97           single pass provided that you specify at least one chop length as a
98           positive value and at least one as a negative value.  All positive
99           chop lengths are added together as are all negative chop lengths.
100
101       -d  Attempts to remove duplicate packets.  The length and MD5 hash of
102           the current packet are compared to the previous four (4) packets.
103           If a match is found, the current packet is skipped.  This option is
104           equivalent to using the option -D 5.
105
106       -D  <dup window>
107           Attempts to remove duplicate packets.  The length and MD5 hash of
108           the current packet are compared to the previous <dup window> - 1
109           packets.  If a match is found, the current packet is skipped.
110
111           The use of the option -D 0 combined with the -v option is useful in
112           that each packet's Packet number, Len and MD5 Hash will be printed
113           to standard out.  This verbose output (specifically the MD5 hash
114           strings) can be useful in scripts to identify duplicate packets
115           across trace files.
116
117           The <dup window> is specified as an integer value between 0 and
118           1000000 (inclusive).
119
120           NOTE: Specifying large <dup window> values with large tracefiles
121           can result in very long processing times for editcap.
122
123       -E  <error probability>
124           Sets the probability that bytes in the output file are randomly
125           changed.  Editcap uses that probability (between 0.0 and 1.0
126           inclusive) to apply errors to each data byte in the file.  For
127           instance, a probability of 0.02 means that each byte has a 2%
128           chance of having an error.
129
130           This option is meant to be used for fuzz-testing protocol
131           dissectors.
132
133       -F  <file format>
134           Sets the file format of the output capture file.  Editcap can write
135           the file in several formats, editcap -F provides a list of the
136           available output formats. The default is the pcapng format.
137
138       -h  Prints the version and options and exits.
139
140       -i  <seconds per file>
141           Splits the packet output to different files based on uniform time
142           intervals using a maximum interval of <seconds per file> each. Each
143           output file will be created with a suffix -nnnnn, starting with
144           00000. If packets for the specified time interval are written to
145           the output file, the next output file is opened. The default is to
146           use a single output file.
147
148       -I  <bytes to ignore>
149           Ignore the specified number of bytes at the beginning of the frame
150           during MD5 hash calculation, unless the frame is too short, then
151           the full frame is used.  Useful to remove duplicated packets taken
152           on several routers (different mac addresses for example) e.g. -I 26
153           in case of Ether/IP will ignore ether(14) and IP header(20 - 4(src
154           ip) - 4(dst ip)).  The default value is 0.
155
156       -L  Adjust the original frame length accordingly when chopping and/or
157           snapping (in addition to the captured length, which is always
158           adjusted regardless of whether -L is specified or not).  See also
159           -C <choplen> and -s <snaplen>.
160
161       -o  <change offset>
162           When used in conjunction with -E, skip some bytes from the
163           beginning of the packet from being changed. In this way some
164           headers don't get changed, and the fuzzer is more focused on a
165           smaller part of the packet. Keeping a part of the packet fixed the
166           same dissector is triggered, that make the fuzzing more precise.
167
168       -r  Reverse the packet selection.  Causes the packets whose packet
169           numbers are specified on the command line to be written to the
170           output capture file, instead of discarding them.
171
172       -s  <snaplen>
173           Sets the snapshot length to use when writing the data.  If the -s
174           flag is used to specify a snapshot length, packets in the input
175           file with more captured data than the specified snapshot length
176           will have only the amount of data specified by the snapshot length
177           written to the output file.
178
179           This may be useful if the program that is to read the output file
180           cannot handle packets larger than a certain size (for example, the
181           versions of snoop in Solaris 2.5.1 and Solaris 2.6 appear to reject
182           Ethernet packets larger than the standard Ethernet MTU, making them
183           incapable of handling gigabit Ethernet captures if jumbo packets
184           were used).
185
186       --seed  <seed>
187           When used in conjunction with -E, set the seed for the pseudo-
188           random number generator.  This is useful for recreating a
189           particular sequence of errors.
190
191       --skip-radiotap-header
192           Skip the readiotap header of each frame when checking for packet
193           duplicates. This is useful when processing a caputure created by
194           combining outputs of multiple capture devices on the same channel
195           in the vicinity of each other.
196
197       -S  <strict time adjustment>
198           Time adjust selected packets to ensure strict chronological order.
199
200           The <strict time adjustment> value represents relative seconds
201           specified as [-]seconds[.fractional seconds].
202
203           As the capture file is processed each packet's absolute time is
204           possibly adjusted to be equal to or greater than the previous
205           packet's absolute timestamp depending on the <strict time
206           adjustment> value.
207
208           If <strict time adjustment> value is 0 or greater (e.g. 0.000001)
209           then only packets with a timestamp less than the previous packet
210           will adjusted.  The adjusted timestamp value will be set to be
211           equal to the timestamp value of the previous packet plus the value
212           of the <strict time adjustment> value.  A <strict time adjustment>
213           value of 0 will adjust the minimum number of timestamp values
214           necessary to ensure that the resulting capture file is in strict
215           chronological order.
216
217           If <strict time adjustment> value is specified as a negative value,
218           then the timestamp values of all packets will be adjusted to be
219           equal to the timestamp value of the previous packet plus the
220           absolute value of the <lt>strict time adjustment<gt> value. A
221           <strict time adjustment> value of -0 will result in all packets
222           having the timestamp value of the first packet.
223
224           This feature is useful when the trace file has an occasional packet
225           with a negative delta time relative to the previous packet.
226
227       -t  <time adjustment>
228           Sets the time adjustment to use on selected packets.  If the -t
229           flag is used to specify a time adjustment, the specified adjustment
230           will be applied to all selected packets in the capture file.  The
231           adjustment is specified as [-]seconds[.fractional seconds].  For
232           example, -t 3600 advances the timestamp on selected packets by one
233           hour while -t -0.5 reduces the timestamp on selected packets by
234           one-half second.
235
236           This feature is useful when synchronizing dumps collected on
237           different machines where the time difference between the two
238           machines is known or can be estimated.
239
240       -T  <encapsulation type>
241           Sets the packet encapsulation type of the output capture file.  If
242           the -T flag is used to specify an encapsulation type, the
243           encapsulation type of the output capture file will be forced to the
244           specified type.  editcap -T provides a list of the available types.
245           The default type is the one appropriate to the encapsulation type
246           of the input capture file.
247
248           Note: this merely forces the encapsulation type of the output file
249           to be the specified type; the packet headers of the packets will
250           not be translated from the encapsulation type of the input capture
251           file to the specified encapsulation type (for example, it will not
252           translate an Ethernet capture to an FDDI capture if an Ethernet
253           capture is read and '-T fddi' is specified). If you need to
254           remove/add headers from/to a packet, you will need
255           od(1)/text2pcap(1).
256
257       -v  Causes editcap to print verbose messages while it's working.
258
259           Use of -v with the de-duplication switches of -d, -D or -w will
260           cause all MD5 hashes to be printed whether the packet is skipped or
261           not.
262
263       -V  Print the version and exit.
264
265       -w  <dup time window>
266           Attempts to remove duplicate packets.  The current packet's arrival
267           time is compared with up to 1000000 previous packets.  If the
268           packet's relative arrival time is less than or equal to the <dup
269           time window> of a previous packet and the packet length and MD5
270           hash of the current packet are the same then the packet to skipped.
271           The duplicate comparison test stops when the current packet's
272           relative arrival time is greater than <dup time window>.
273
274           The <dup time window> is specified as seconds[.fractional seconds].
275
276           The [.fractional seconds] component can be specified to nine (9)
277           decimal places (billionths of a second) but most typical trace
278           files have resolution to six (6) decimal places (millionths of a
279           second).
280
281           NOTE: Specifying large <dup time window> values with large
282           tracefiles can result in very long processing times for editcap.
283
284           NOTE: The -w option assumes that the packets are in chronological
285           order.  If the packets are NOT in chronological order then the -w
286           duplication removal option may not identify some duplicates.
287
288       --inject-secrets <secrets type>,<file>
289           Inserts the contents of <file> into a Decryption Secrets Block
290           (DSB) within the pcapng output file. This enables decryption
291           without requiring additional configuration in protocol preferences.
292
293           The file format is described by <secrets type> which can be one of:
294
295           tls TLS Key Log as described at
296           <https://developer.mozilla.org/NSS_Key_Log_Format>
297
298           This option may be specified multiple times. The available options
299           for <secrets type> can be listed with --inject-secrets help.
300
301       --discard-all-secrets
302           Discard all decryption secrets from the input file when writing the
303           output file.  Does not discard secrets added by --inject-secrets in
304           the same command line.
305

EXAMPLES

307       To see more detailed description of the options use:
308
309           editcap -h
310
311       To shrink the capture file by truncating the packets at 64 bytes and
312       writing it as Sun snoop file use:
313
314           editcap -s 64 -F snoop capture.pcapng shortcapture.snoop
315
316       To delete packet 1000 from the capture file use:
317
318           editcap capture.pcapng sans1000.pcapng 1000
319
320       To limit a capture file to packets from number 200 to 750 (inclusive)
321       use:
322
323           editcap -r capture.pcapng small.pcapng 200-750
324
325       To get all packets from number 1-500 (inclusive) use:
326
327           editcap -r capture.pcapng first500.pcapng 1-500
328
329       or
330
331           editcap capture.pcapng first500.pcapng 501-9999999
332
333       To exclude packets 1, 5, 10 to 20 and 30 to 40 from the new file use:
334
335           editcap capture.pcapng exclude.pcapng 1 5 10-20 30-40
336
337       To select just packets 1, 5, 10 to 20 and 30 to 40 for the new file
338       use:
339
340           editcap -r capture.pcapng select.pcapng 1 5 10-20 30-40
341
342       To remove duplicate packets seen within the prior four frames use:
343
344           editcap -d capture.pcapng dedup.pcapng
345
346       To remove duplicate packets seen within the prior four frames while
347       skipping radiotap headers use:
348
349           editcap -d --skip-radiotap-header capture.pcapng dedup.pcapng
350
351       To remove duplicate packets seen within the prior 100 frames use:
352
353           editcap -D 101 capture.pcapng dedup.pcapng
354
355       To remove duplicate packets seen equal to or less than 1/10th of a
356       second:
357
358           editcap -w 0.1 capture.pcapng dedup.pcapng
359
360       To display the MD5 hash for all of the packets (and NOT generate any
361       real output file):
362
363           editcap -v -D 0 capture.pcapng /dev/null
364
365       or on Windows systems
366
367           editcap -v -D 0 capture.pcapng NUL
368
369       To advance the timestamps of each packet forward by 3.0827 seconds:
370
371           editcap -t 3.0827 capture.pcapng adjusted.pcapng
372
373       To ensure all timestamps are in strict chronological order:
374
375           editcap -S 0 capture.pcapng adjusted.pcapng
376
377       To introduce 5% random errors in a capture file use:
378
379           editcap -E 0.05 capture.pcapng capture_error.pcapng
380
381       To remove vlan tags from all packets within an Ethernet-encapsulated
382       capture file, use:
383
384           editcap -L -C 12:4 capture_vlan.pcapng capture_no_vlan.pcapng
385
386       To chop both the 10 byte and 20 byte regions from the following 75 byte
387       packet in a single pass, use any of the 8 possible methods provided
388       below:
389
390           <--------------------------- 75 ---------------------------->
391
392           +---+-------+-----------+---------------+-------------------+
393           | 5 |   10  |     15    |       20      |         25        |
394           +---+-------+-----------+---------------+-------------------+
395
396           1) editcap -C 5:10 -C -25:-20 capture.pcapng chopped.pcapng
397           2) editcap -C 5:10 -C 50:-20 capture.pcapng chopped.pcapng
398           3) editcap -C -70:10 -C -25:-20 capture.pcapng chopped.pcapng
399           4) editcap -C -70:10 -C 50:-20 capture.pcapng chopped.pcapng
400           5) editcap -C 30:20 -C -60:-10 capture.pcapng chopped.pcapng
401           6) editcap -C 30:20 -C 15:-10 capture.pcapng chopped.pcapng
402           7) editcap -C -45:20 -C -60:-10 capture.pcapng chopped.pcapng
403           8) editcap -C -45:20 -C 15:-10 capture.pcapng chopped.pcapng
404
405       To add comment strings to the first 2 input frames, use:
406
407           editcap -a "1:1st frame" -a 2:Second capture.pcapng capture-comments.pcapng
408

SEE ALSO

410       pcap(3), wireshark(1), tshark(1), mergecap(1), dumpcap(1), capinfos(1),
411       text2pcap(1), od(1), pcap-filter(7) or tcpdump(8)
412

NOTES

414       Editcap is part of the Wireshark distribution.  The latest version of
415       Wireshark can be found at <https://www.wireshark.org>.
416
417       HTML versions of the Wireshark project man pages are available at:
418       <https://www.wireshark.org/docs/man-pages>.
419

AUTHORS

421         Original Author
422         -------- ------
423         Richard Sharpe           <sharpe[AT]ns.aus.com>
424
425
426         Contributors
427         ------------
428         Guy Harris               <guy[AT]alum.mit.edu>
429         Ulf Lamping              <ulf.lamping[AT]web.de>
430
431
432
4333.0.1                             2019-04-08                        EDITCAP(1)
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