EDITCAP(1)                                                          EDITCAP(1)

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

SYNOPSIS
       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 ]
       [ --discard-packet-comments ] infile outfile [ packet#[-packet#] ... ]

       editcap -d -D <dup window> -w <dup time window> [ -V ]
       [ -I <bytes to ignore> ] [ --skip-radiotap-header ] [ --set-unused ]
       infile outfile

       editcap -h|--help

       editcap -v|--version

DESCRIPTION
       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.

OPTIONS
       -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
           Print the version number and options and exit.

       -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 full version information 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>

           Inserts the contents of <file> into a Decryption Secrets Block
           (DSB) within the pcapng output file. This enables decryption
           without requiring additional configuration in protocol preferences.

           The file format is described by <secrets type> which can be one of:

           tls  TLS Key Log as described at
           <https://developer.mozilla.org/NSS_Key_Log_Format>
           wg   WireGuard Key Log, see
           <https://gitlab.com/wireshark/wireshark/-/wikis/WireGuard#key-log-format>

           This option may be specified multiple times. The available options
           for <secrets type> can be listed with --inject-secrets help.

       --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.

       --set-unused

           Set the unused bytes (if any) to zero in SLL link type. Useful when
           when checking for duplicates.  As the unused bytes can be anything.
           When the packet traverses the device stack for bonded interfaces on
           Linux for example.

       --discard-packet-comments

           Discard all packet comments from the input file when writing the
           output file. Does not discard comments added by -a in the same
           command line.

DIAGNOSTIC OPTIONS
       --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. Can
           be negated with "!" as the first character (inverts the match).

       --log-debug <list>
           Force the specified domains to log at the "debug" level.  List of
           domains must be comma-separated. Can be negated with "!" as the
           first character (inverts the match).

       --log-noisy <list>
           Force the specified domains to log at the "noisy" level.  List of
           domains must be comma-separated. Can be negated with "!" as the
           first character (inverts the match).

       --log-fatal-domains <list>
           Abort the program if any messages are logged for the specified log
           domains.  List of domains must be comma-separated.

       --log-file <path>
           Write log messages and stderr output to the specified file.

EXAMPLES
       To see more detailed description of the options use:

           editcap -h

       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

SEE ALSO
       pcap(3), wireshark(1), tshark(1), mergecap(1), dumpcap(1), capinfos(1),
       text2pcap(1), reordercap(1), od(1), pcap-filter(7) or tcpdump(8)

NOTES
       This is the manual page for Editcap 4.2.4.  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>.

AUTHORS
       Original Author
       Richard Sharpe <sharpe[AT]ns.aus.com>

       Contributors
       Guy Harris <guy[AT]alum.mit.edu>
       Ulf Lamping <ulf.lamping[AT]web.de>

                                  2024-04-06                        EDITCAP(1)