wireshark/doc/editcap.pod

=head1 NAME

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

=head1 SYNOPSYS

B<editcap>
S<[ B<-c> E<lt>packets per fileE<gt> ]>
S<[ B<-C> E<lt>choplenE<gt> ]>
S<[ B<-E> E<lt>error probabilityE<gt> ]>
S<[ B<-F> E<lt>file formatE<gt> ]>
S<[ B<-A> E<lt>start timeE<gt> ]>
S<[ B<-B> E<lt>stop timeE<gt> ]>
S<[ B<-h> ]>
S<[ B<-r> ]>
S<[ B<-s> E<lt>snaplenE<gt> ]>
S<[ B<-t> E<lt>time adjustmentE<gt> ]>
S<[ B<-T> E<lt>encapsulation typeE<gt> ]>
S<[ B<-v> ]>
I<infile>
I<outfile>
S<[ I<packet#>[-I<packet#>] ... ]>

B<editcap>
S< B<-d> > |
S< B<-D> E<lt>dup windowE<gt> > |
S< B<-w> E<lt>dup time windowE<gt> >
S<[ B<-v> ]>
I<infile>
I<outfile>

=head1 DESCRIPTION

B<Editcap> is a program that reads some or all of the captured packets from the 
I<infile>, optionally converts them in various ways and writes the 
resulting packets to the capture I<outfile> (or outfiles). 

By default, it reads all packets from the I<infile> and writes them to the 
I<outfile> in libpcap file format.

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 I<start>-I<end>, referring to all packets from
I<start> to I<end>.  By default the selected packets with those numbers will
I<not> be written to the capture file.  If the B<-r> flag is specified, the
whole packet selection is reversed; in that case I<only> the selected packets
will be written to the capture file.

B<Editcap> can also be used to remove duplicate packets.  Several different
options (B<-d>, B<-D> and B<-w>) are used to control the packet window
or relative time window to be used for duplicate comparison.

B<Editcap> is able to detect, read and write the same capture files that 
are supported by B<Wireshark>.
The input file doesn't need a specific filename extension; the file 
format and an optional gzip compression will be automatically detected.
Near the beginning of the DESCRIPTION section of wireshark(1) or
L<http://www.wireshark.org/docs/man-pages/wireshark.html>
is a detailed description of the way B<Wireshark> handles this, which is
the same way B<Editcap> handles this.

B<Editcap> can write the file in several output formats. The B<-F>
flag can be used to specify the format in which to write the capture
file, B<editcap -F> provides a list of the available output formats.

=head1 OPTIONS

=over 4

=item -c  E<lt>packets per fileE<gt>

Sets the maximum number of packets per output file. Each output file will 
be created with a suffix -nnnnn, starting with 00000. If the specified 
number of packets are written to the output file, the next output file is 
opened. The default is to use a single output file.

=item -C  E<lt>choplenE<gt>

Sets the chop length to use when writing the packet data.
Each packet is chopped at the packet end by a few <choplen> bytes of data.

This is useful in the rare case that the conversion between two file 
formats leaves some random bytes at the end of each packet.

=item -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 B<-D 5>.

=item -D  E<lt>dup windowE<gt>

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 B<-D 0> combined with the B<-v> option is useful
in that each packet's Packet number, Len and MD5 Hash will be printed
to standard out.  This verbose output (specifically the MD5 hash strings)
can be useful in scripts to identify duplicate packets across trace
files.

The <dup window> is specifed 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 B<editcap>.

=item -w  E<lt>dup time windowE<gt>

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 I<less than> 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 specifed as I<seconds>[I<.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 B<editcap>.

NOTE: The B<-w> option assumes that the packets are in chronological order.  
If the packets are NOT in chronological order then the B<-w> duplication 
removal option may not identify some duplicates.

=item -E  E<lt>error probabilityE<gt>

Sets the probabilty that bytes in the output file are randomly changed.
B<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.

=item -F  E<lt>file formatE<gt>

Sets the file format of the output capture file.
B<Editcap> can write the file in several formats, B<editcap -F> 
provides a list of the available output formats. The default
is the B<libpcap> format.

=item -A  E<lt>start timeE<gt>

Saves only the packets whose timestamp is on or after start time.
The time is given in the following format YYYY-MM-DD HH:MM:SS

=item -B  E<lt>stop timeE<gt>

Saves only the packets whose timestamp is on or before stop time.
The time is given in the following format YYYY-MM-DD HH:MM:SS

=item -h

Prints the version and options and exits.

=item -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.

=item -s  E<lt>snaplenE<gt>

Sets the snapshot length to use when writing the data.
If the B<-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).

=item -t  E<lt>time adjustmentE<gt>

Sets the time adjustment to use on selected packets.
If the B<-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 [-]I<seconds>[I<.fractional seconds>].
For example, B<-t> 3600 advances the timestamp on selected packets by one
hour while B<-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.

=item -T  E<lt>encapsulation typeE<gt>

Sets the packet encapsulation type of the output capture file.
If the B<-T> flag is used to specify an encapsulation type, the
encapsulation type of the output capture file will be forced to the
specified type. 
B<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 'B<-T
fddi>' is specified). If you need to remove/add headers from/to a
packet, you will need od(1)/text2pcap(1).

=item -v

Causes B<editcap> to print verbose messages while it's working.

Use of B<-v> with the de-duplication switches of B<-d>, B<-D> or B<-w>
will cause all MD5 hashes to be printed whether the packet is skipped
or not.

=back

=head1 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.pcap shortcapture.snoop

To delete packet 1000 from the capture file use:

    editcap capture.pcap sans1000.pcap 1000

To limit a capture file to packets from number 200 to 750 (inclusive) use:

    editcap -r capture.pcap small.pcap 200-750

To get all packets from number 1-500 (inclusive) use:

    editcap -r capture.pcap first500.pcap 1-500

or

    editcap capture.pcap first500.pcap 501-9999999

To exclude packets 1, 5, 10 to 20 and 30 to 40 from the new file use:

    editcap capture.pcap exclude.pcap 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.pcap select.pcap 1 5 10-20 30-40

To remove duplicate packets seen within the prior four frames use:

    editcap -d capture.pcap dedup.pcap

To remove duplicate packets seen within the prior 100 frames use:

    editcap -D 101 capture.pcap dedup.pcap

To remove duplicate packets seen I<less than> 1/10th of a second:

    editcap -w 0.1 capture.pcap dedup.pcap

To remove duplicate packets seen I<equal to or less than> 1/10th of a second:

    editcap -w 0.1 capture.pcap dedup.pcap

To display the MD5 hash for all of the packets (and NOT generate any
real output file):

    editcap -v -D 0 capture.pcap /dev/null

or on Windows systems

    editcap -v -D 0 capture.pcap NUL

To introduce 5% random errors in a capture file use:

=over 4

  editcap -E 0.05 capture.pcap capture_error.pcap

=back

=head1 SEE ALSO

tcpdump(8), pcap(3), wireshark(1), tshark(1), mergecap(1), dumpcap(1),
capinfos(1), text2pcap(1), od(1)

=head1 NOTES

B<Editcap> is part of the B<Wireshark> distribution.  The latest version
of B<Wireshark> can be found at L<http://www.wireshark.org>.

HTML versions of the Wireshark project man pages are available at:
L<http://www.wireshark.org/docs/man-pages>.

=head1 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>