editcap - Edit and/or translate the format of capture files
editcap [
-a <frame:comment> ]
[
-A <start time> ] [
-B <stop time> ] [
-c <packets per file> ] [
-C [offset:]<choplen> ] [
-E <error probability> ] [
-F <file format> ] [
-i <seconds per file> ] [
-o <change offset> ] [
-L ] [
-r ] [
-s <snaplen> ] [
-S <strict time adjustment> ]
[
-t <time adjustment> ] [
-T <encapsulation type> ] [
-V ] [
--inject-secrets <secrets type>,<file> ]
[
--discard-all-secrets ] [
--capture-comment <comment> ] [
--discard-capture-comment ]
infile outfile
[
packet#[-
packet#] ... ]
editcap -d -D <dup window>
-w <dup time window> [
-V ] [
-I <bytes to ignore> ] [
--skip-radiotap-header ]
infile outfile
editcap -h|--help
editcap -v|--version
Editcap is a program that reads some or all of the captured packets from
the
infile, optionally converts them in various ways and writes the
resulting packets to the capture
outfile (or outfiles).
By default, it reads all packets from the
infile and writes them to the
outfile in pcapng file format. Use '-' for
infile or
outfile to read from standard input or write to standard output,
respectively.
The
-A and
-B option allow you to limit the time range from which
packets are read from the
infile.
An optional list of packet numbers can be specified on the command tail;
individual packet numbers separated by whitespace and/or ranges of packet
numbers can be specified as
start-
end, referring to all packets
from
start to
end. By default the selected packets with those
numbers will
not be written to the capture file. If the
-r flag
is specified, the whole packet selection is reversed; in that case
only
the selected packets will be written to the capture file.
Editcap can also be used to remove duplicate packets. Several different
options (
-d,
-D and
-w) are used to control the packet
window or relative time window to be used for duplicate comparison.
Editcap can be used to assign comment strings to frame numbers.
Editcap is able to detect, read and write the same capture files that are
supported by
Wireshark. The input file doesn’t need a specific
filename extension; the file format and an optional gzip, zstd or lz4
compression will be automatically detected. Near the beginning of the
DESCRIPTION section of
wireshark(1) or
<
https://www.wireshark.org/docs/man-pages/wireshark.html> is a detailed
description of the way
Wireshark handles this, which is the same way
Editcap handles this.
Editcap can write the file in several output formats. The
-F flag
can be used to specify the format in which to write the capture file;
editcap -F provides a list of the available output formats.
-a <framenum:comment>
For the specified frame number, assign the given comment string. Can be repeated
for multiple frames. Quotes should be used with comment strings that include
spaces.
-A <start time>
Reads only the packets whose timestamp is on or after <start time>. The
time may be given either in ISO 8601 format or in Unix epoch timestamp format.
ISO 8601 format is either
YYYY-MM-DD HH:MM:SS[.nnnnnnnnn][Z|±hh:mm]
or
YYYY-MM-DDTHH:MM:SS[.nnnnnnnnn][Z|±hh:mm]
The fractional seconds are optional, as is the time zone offset from UTC (in
which case local time is assumed).
Unix epoch format is in seconds since the Unix epoch and nanoseconds, with
either a period or a comma separating the seconds and nanoseconds. The
nanoseconds are optional. The Unix epoch is 1970-01-01 00:00:00 UTC, so this
format is not local time.
-B <stop time>
Reads only the packets whose timestamp is before <stop time>. The time may
be given either in ISO 8601 format or in Unix epoch timestamp format.
ISO 8601 format is either
YYYY-MM-DD HH:MM:SS[.nnnnnnnnn][Z|±hh:mm]
or
YYYY-MM-DDTHH:MM:SS[.nnnnnnnnn][Z|±hh:mm]
The fractional seconds are optional, as is the time zone offset from UTC (in
which case local time is assumed).
Unix epoch format is in seconds since the Unix epoch and nanoseconds, with
either a period or a comma separating the seconds and nanoseconds. The
nanoseconds are optional. The Unix epoch is 1970-01-01 00:00:00 UTC, so this
format is not local time.
-c <packets per file>
Splits the packet output to different files based on uniform packet counts with
a maximum of <packets per file> each.
Each output file will be created with an infix _nnnnn[_YYYYmmddHHMMSS] inserted
before the file extension (which may be null) of
outfile. The infix
consists of the ordinal number of the output file, starting with 00000,
followed by the timestamp of its first packet. The timestamp is omitted if the
input file does not contain timestamp information.
After the specified number of packets is written to the output file, the next
output file is opened. The default is to use a single output file. This option
conflicts with
-i.
-C [offset:]<choplen>
Sets the chop length to use when writing the packet data. Each packet is chopped
by <choplen> bytes of data. Positive values chop at the packet beginning
while negative values chop at the packet end.
If an optional offset precedes the <choplen>, then the bytes chopped will
be offset from that value. Positive offsets are from the packet beginning,
while negative offsets are from the packet end.
This is useful for chopping headers for decapsulation of an entire capture,
removing tunneling headers, or in the rare case that the conversion between
two file formats leaves some random bytes at the end of each packet. Another
use is for removing vlan tags.
Note
This option can be used more than once, effectively allowing you to chop
bytes from up to two different areas of a packet in a single pass provided that
you specify at least one chop length as a positive value and at least one as a
negative value. All positive chop lengths are added together as are all
negative chop lengths.
-d
Attempts to remove duplicate packets. The length and MD5 hash of the current
packet are compared to the previous four (4) packets. If a match is found, the
current packet is skipped. This option is equivalent to using the option
-D
5.
-D <dup window>
Attempts to remove duplicate packets. The length and MD5 hash of the current
packet are compared to the previous <dup window> - 1 packets. If a match
is found, the current packet is skipped.
The use of the option
-D 0 combined with the
-V option is useful
in that each packet’s Packet number, Len and MD5 Hash will be printed
to standard error. This verbose output (specifically the MD5 hash strings) can
be useful in scripts to identify duplicate packets across trace files.
The <dup window> is specified as an integer value between 0 and 1000000
(inclusive).
Note
Specifying large <dup window> values with large tracefiles can
result in very long processing times for
editcap.
-E <error probability>
Sets the probability that bytes in the output file are randomly changed.
Editcap uses that probability (between 0.0 and 1.0 inclusive) to apply
errors to each data byte in the file. For instance, a probability of 0.02
means that each byte has a 2% chance of having an error.
This option is meant to be used for fuzz-testing protocol dissectors.
-F <file format>
Sets the file format of the output capture file.
Editcap can write the
file in several formats,
editcap -F provides a list of the available
output formats. The default is the
pcapng format.
-h|--help
Prints the version and options and exits.
-i <seconds per file>
Splits the packet output to different files based on uniform time intervals
using a maximum interval of <seconds per file> each. Floating point
values (e.g. 0.5) are allowed.
Each output file will be created with an infix _nnnnn[_YYYYmmddHHMMSS] inserted
before the file extension (which may be null) of
outfile. The infix
consists of the ordinal number of the output file, starting with 00000,
followed by the timestamp of its first packet. The timestamp is omitted if the
input file does not contain timestamp information.
After packets for the specified time interval are written to the output file,
the next output file is opened. The default is to use a single output file.
This option conflicts with
-c.
-I <bytes to ignore>
Ignore the specified number of bytes at the beginning of the frame during MD5
hash calculation, unless the frame is too short, then the full frame is used.
Useful to remove duplicated packets taken on several routers (different mac
addresses for example) e.g. -I 26 in case of Ether/IP will ignore ether(14)
and IP header(20 - 4(src ip) - 4(dst ip)). The default value is 0.
-L
Adjust the original frame length accordingly when chopping and/or snapping (in
addition to the captured length, which is always adjusted regardless of
whether
-L is specified or not). See also
-C <choplen> and
-s <snaplen>.
-o <change offset>
When used in conjunction with -E, skip some bytes from the beginning of the
packet from being changed. In this way some headers don’t get changed,
and the fuzzer is more focused on a smaller part of the packet. Keeping a part
of the packet fixed the same dissector is triggered, that make the fuzzing
more precise.
-r
Reverse the packet selection. Causes the packets whose packet numbers are
specified on the command line to be written to the output capture file,
instead of discarding them.
-s <snaplen>
Sets the snapshot length to use when writing the data. If the
-s flag is
used to specify a snapshot length, packets in the input file with more
captured data than the specified snapshot length will have only the amount of
data specified by the snapshot length written to the output file.
This may be useful if the program that is to read the output file cannot handle
packets larger than a certain size (for example, the versions of snoop in
Solaris 2.5.1 and Solaris 2.6 appear to reject Ethernet packets larger than
the standard Ethernet MTU, making them incapable of handling gigabit Ethernet
captures if jumbo packets were used).
--seed <seed>
When used in conjunction with -E, set the seed for the pseudo-random number
generator. This is useful for recreating a particular sequence of
errors.
--skip-radiotap-header
Skip the radiotap header of each frame when checking for packet duplicates. This
is useful when processing a capture created by combining outputs of multiple
capture devices on the same channel in the vicinity of each other.
-S <strict time adjustment>
Time adjust selected packets to ensure strict chronological order.
The <strict time adjustment> value represents relative seconds specified
as
seconds[
.fractional seconds].
As the capture file is processed each packet’s absolute time is
possibly adjusted to be equal to or greater than the previous
packet’s absolute timestamp depending on the <strict time
adjustment> value.
If <strict time adjustment> value is 0 or greater (e.g. 0.000001) then
only packets with a timestamp less than the previous packet will
adjusted. The adjusted timestamp value will be set to be equal to the
timestamp value of the previous packet plus the value of the <strict time
adjustment> value. A <strict time adjustment> value of 0 will adjust
the minimum number of timestamp values necessary to ensure that the resulting
capture file is in strict chronological order.
If <strict time adjustment> value is specified as a negative value, then
the timestamp values of
all packets will be adjusted to be equal to the
timestamp value of the previous packet plus the absolute value of the
<strict time adjustment> value. A <strict time adjustment> value
of -0 will result in all packets having the timestamp value of the first
packet.
This feature is useful when the trace file has an occasional packet with a
negative delta time relative to the previous packet.
-t <time adjustment>
Sets the time adjustment to use on selected packets. If the
-t flag is
used to specify a time adjustment, the specified adjustment will be applied to
all selected packets in the capture file. The adjustment is specified as
seconds[
.fractional seconds]. For example,
-t 3600
advances the timestamp on selected packets by one hour while
-t -0.5
reduces the timestamp on selected packets by one-half second.
This feature is useful when synchronizing dumps collected on different machines
where the time difference between the two machines is known or can be
estimated.
-T <encapsulation type>
Sets the packet encapsulation type of the output capture file. If the
-T
flag is used to specify an encapsulation type, the encapsulation type of the
output capture file will be forced to the specified type.
editcap -T
provides a list of the available types. The default type is the one
appropriate to the encapsulation type of the input capture file.
Note: this merely forces the encapsulation type of the output file to be the
specified type; the packet headers of the packets will not be translated from
the encapsulation type of the input capture file to the specified
encapsulation type (for example, it will not translate an Ethernet capture to
an FDDI capture if an Ethernet capture is read and '
-T fddi' is
specified). If you need to remove/add headers from/to a packet, you will need
od(1)/
text2pcap(1).
-v|--version
Print the version and exit.
-V
Causes
editcap to print verbose messages while it’s working.
Use of
-V with the de-duplication switches of
-d,
-D or
-w will cause all MD5 hashes to be printed whether the packet is
skipped or not.
-w <dup time window>
Attempts to remove duplicate packets. The current packet’s arrival time
is compared with up to 1000000 previous packets. If the packet’s
relative arrival time is
less than or equal to the <dup time
window> of a previous packet and the packet length and MD5 hash of the
current packet are the same then the packet to skipped. The duplicate
comparison test stops when the current packet’s relative arrival time
is greater than <dup time window>.
The <dup time window> is specified as
seconds[
.fractional
seconds].
The [.fractional seconds] component can be specified to nine (9) decimal places
(billionths of a second) but most typical trace files have resolution to six
(6) decimal places (millionths of a second).
Note
Specifying large <dup time window> values with large tracefiles can
result in very long processing times for
editcap.
Note
The
-w option assumes that the packets are in chronological order.
If the packets are NOT in chronological order then the
-w duplication
removal option may not identify some duplicates.
--inject-secrets <secrets type>,<file>
--discard-all-secrets
Discard all decryption secrets from the input file when writing the output file.
Does not discard secrets added by
--inject-secrets in the same command
line.
--capture-comment <comment>
Adds the given comment to the output file, if supported by the output file
format. New comments will be added
after any comments present in the
input file unless
--discard-capture-comment is also specified.
This option may be specified multiple times. Note that Wireshark currently only
displays the first comment of a capture file.
--discard-capture-comment
Discard all capture file comments from the input file when writing the output
file. Does not discard comments added by
--capture-comment in the same
command line.
--log-level <level>
Set the active log level. Supported levels in
lowest to highest order are "noisy", "debug",
"info", "message", "warning",
"critical", and "error". Messages at each level and higher
will be printed, for example "warning" prints "warning",
"critical", and "error" messages and "noisy"
prints all messages. Levels are case insensitive.
--log-fatal <level>
Abort the program if any messages are logged
at the specified level or higher. For example, "warning" aborts on
any "warning", "critical", or "error"
messages.
--log-domains <list>
Only print messages for the specified log
domains, e.g. "GUI,Epan,sshdump". List of domains must be
comma-separated.
--log-debug <list>
Force the specified domains to log at the
"debug" level. List of domains must be comma-separated.
--log-noisy <list>
Force the specified domains to log at the
"noisy" level. List of domains must be comma-separated.
--log-file <path>
Write log messages and stderr output to the
specified file.
To see more detailed description of the options use:
To shrink the capture file by truncating the packets at 64 bytes and writing it
as Sun snoop file use:
editcap -s 64 -F snoop capture.pcapng shortcapture.snoop
To delete packet 1000 from the capture file use:
editcap capture.pcapng sans1000.pcapng 1000
To limit a capture file to packets from number 200 to 750 (inclusive) use:
editcap -r capture.pcapng small.pcapng 200-750
To get all packets from number 1-500 (inclusive) use:
editcap -r capture.pcapng first500.pcapng 1-500
or
editcap capture.pcapng first500.pcapng 501-9999999
To exclude packets 1, 5, 10 to 20 and 30 to 40 from the new file use:
editcap capture.pcapng exclude.pcapng 1 5 10-20 30-40
To select just packets 1, 5, 10 to 20 and 30 to 40 for the new file use:
editcap -r capture.pcapng select.pcapng 1 5 10-20 30-40
To remove duplicate packets seen within the prior four frames use:
editcap -d capture.pcapng dedup.pcapng
To remove duplicate packets seen within the prior four frames while skipping
radiotap headers use:
editcap -d --skip-radiotap-header capture.pcapng dedup.pcapng
To remove duplicate packets seen within the prior 100 frames use:
editcap -D 101 capture.pcapng dedup.pcapng
To remove duplicate packets seen
equal to or less than 1/10th of a
second:
editcap -w 0.1 capture.pcapng dedup.pcapng
To display the MD5 hash for all of the packets (and NOT generate any real output
file):
editcap -V -D 0 capture.pcapng /dev/null
or on Windows systems
editcap -V -D 0 capture.pcapng NUL
To advance the timestamps of each packet forward by 3.0827 seconds:
editcap -t 3.0827 capture.pcapng adjusted.pcapng
To ensure all timestamps are in strict chronological order:
editcap -S 0 capture.pcapng adjusted.pcapng
To introduce 5% random errors in a capture file use:
editcap -E 0.05 capture.pcapng capture_error.pcapng
To remove vlan tags from all packets within an Ethernet-encapsulated capture
file, use:
editcap -L -C 12:4 capture_vlan.pcapng capture_no_vlan.pcapng
To chop both the 10 byte and 20 byte regions from the following 75 byte packet
in a single pass, use any of the 8 possible methods provided below:
<--------------------------- 75 ---------------------------->
+---+-------+-----------+---------------+-------------------+
| 5 | 10 | 15 | 20 | 25 |
+---+-------+-----------+---------------+-------------------+
1) editcap -C 5:10 -C -25:-20 capture.pcapng chopped.pcapng
2) editcap -C 5:10 -C 50:-20 capture.pcapng chopped.pcapng
3) editcap -C -70:10 -C -25:-20 capture.pcapng chopped.pcapng
4) editcap -C -70:10 -C 50:-20 capture.pcapng chopped.pcapng
5) editcap -C 30:20 -C -60:-10 capture.pcapng chopped.pcapng
6) editcap -C 30:20 -C 15:-10 capture.pcapng chopped.pcapng
7) editcap -C -45:20 -C -60:-10 capture.pcapng chopped.pcapng
8) editcap -C -45:20 -C 15:-10 capture.pcapng chopped.pcapng
To add comment strings to the first 2 input frames, use:
editcap -a "1:1st frame" -a 2:Second capture.pcapng capture-comments.pcapng
pcap(3),
wireshark(1),
tshark(1),
mergecap(1),
dumpcap(1),
capinfos(1),
text2pcap(1),
reordercap(1),
od(1),
pcap-filter(7) or
tcpdump(8)
This is the manual page for
Editcap 4.0.11.
Editcap is part of the
Wireshark distribution. The latest version of
Wireshark can be
found at
<
https://www.wireshark.org>.
HTML versions of the Wireshark project man pages are available at
<
https://www.wireshark.org/docs/man-pages>.
Original Author
Richard Sharpe <sharpe[AT]ns.aus.com>
Contributors
Guy Harris <guy[AT]alum.mit.edu>
Ulf Lamping <ulf.lamping[AT]web.de>