Manpage of stakrate
Section: User Commands (1)
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stak - Statistical Traffic Analysis Kit
stakextract [-i <interface>] [-p <prefix>] [-s <snarflen>] [-l] [-X <expression> [-0 <c>]] [-f <filtering expression>] [-a] [-P <pattern>] <regular expression>
is a part of the Statistical Traffic Analysis Kit (STAK), which is a set of
utilities designed to help an administrator to figure out what is happening in
his network at the moment.
extracts strings from packets. Such a capability is useful to monitor protocols
that use plain text, like the HTTP, SMTP or Jabber protocols. The utility breaks
convention: no reports are generated, the extracted strings are being outputted as
soon as they are catched.
accepts parameters in a standard, short
There are several options concerning the
common for the all
utilities - these options have been described in the
The remaining options, described in the
REGULAR EXPRESSION EXTRACTOR MODE
are stakextract-specific and do not apply to other
uses regular expressions
to match strings in packets. Before doing the actual analysis, the
user has to invent a regular expression 'catching' packets and
string he or she wishes to monitor. For instance, to see what
WWW sites are being visited at the moment, one could use an expression
Like in the
strings are used to delimit the actual string that is to be extracted. In
addition to the standard regular expressions, special sequences are permitted
to mark a CR (\r), LF (\n), TAB (\t) or to specify any character by its
hexadecimal code (\xNN).
# stakextract -i eth5 'Host: \([^\r\n]+\)\r\n'
The output can be formatted in a sense, by specyfing an output-formatting
string with the
option. Like in
again, the special sequences \1, \2, \3, etc. are replaced with the corresponding
bracket content in the expression:
# stakextract -i eth5 'MAIL FROM: \([^\r\n]+\)\r' -P '\1 tries to send a message'
<email@example.com> tries to send a message
<QNXIRRKSWX@chez.com> tries to send a message
<firstname.lastname@example.org> tries to send a message
<email@example.com> tries to send a message
Additionally, you can specify the
option to see the source and destination addresses of the packet the string was
- -0 c
Replace every NUL character (ASCII 0) with c before doing regular expression
based matching. Ignored if the
option was not specified. The default is '@'.
- -f f
BPF filter expression to use. Using this option causes
to ignore any packets not matching the specified BPF filter expression. For
a detailed description of BPF filter expressions syntax, consult the
- -h -?
dumps a short help on available command-line options and quits, regardless
of other options.
- -i I
Bind to interface I. The default is 'eth0', which of course will cause a failure on
systems other than Linux. Make sure you specify the datalink prefix (see -p)
when you order stak to bind to an interface of an uncommon type.
Make stdout line-buffered. This option is useful when reports are redirected
(eg. using shell redirection) to a file.
- -p N
Datalink layer header prefix length. Every (or at least almost every) known datalink
layer protocol prefixes a packet with its own header - which has to be stripped
before the actual data essential for stak (the IP protocol header) can be read.
is able to determine automatically how many bytes to skip only for the most common
datalink layer protocols (Ethernet, FDDI, TokenRing, loopback, PPP) - in other cases
the prefix length
must be specified using this option. It is EXTREMELY IMPORTANT to set the right value
might print completely irrevelant reports and output invalid IP addresses. The default
is autosense, or if that fails - 14 bytes, which is the length of an
- -s N
Capture at least N bytes. For performance reasons,
does not acquire the whole packet from network, it just reads and processes first N
bytes. The default is 64 bytes, which might be not enough if you are using complicated BPF
expressions or filtering the packets using a regular expression. In such cases, it is
good to set the capture length to MTU on the interface. The value is automatically increased
to at least 1500 (which is the default MTU for an Ethernet interface) if one of -x, -E or -T
options is used. This option does NOT affect statistical data (amount of bytes, per-second byte rate)
collected by stak - the accounted packet size is always the 'real' one.
Print exact values. Normally,
uses SI prefixes (like k - kilo, M - mega, G - giga, T - tera) to make
the printed numeric values more attractive for a human being. The -v option
disables this feature, causing
to print exact values.
Regular expression-based filtering. This option will cause
to ignore packets that DO NOT match specified regular expression. Before
any tests, NUL characters occuring in a packet are replaced with
an other character, as specified in the -0 option (the default is '@').
manual for a detailed description of POSIX regular expressions.
In addition to standard regex syntax, you may use the
\r (CR), \n (LF), \t (TAB), \\ (\)
and \xNN (hex NN) special sequences.
REGULAR EXPRESSION EXTRACTOR MODE
- -P <string>
Output formatting string. Instead of just printing the extracted strings, this string
is outputted, and the special sequences it may contain: \1, \2, \3, etc. are replaced
with the contents of corresponding groups in the extracting expression.
Enables outputting source and destination IP addresses of the packet the strings
were extracted from.
Mateusz Golicz <firstname.lastname@example.org>
Feel free to send comments, suggestions, bug reports, etc. The
author is not a native english speaker, and is aware of the fact that his english is far from
perfect. Because of that, reports on grammar or vocabulary mistakes in this manual are also welcome.
The asynchronous DNS resolver part was taken from
- a very handy traceroute replacement by Matt Kimball.
Copyright 2003 - 2004 Mateusz Golicz. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, Version 2,
as published by the Free Software Foundation. A copy of this license is
distributed with this software in the file "COPYING".
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. Read the
file "COPYING" for more details.
- GENERIC OPTIONS
- REGULAR EXPRESSION EXTRACTOR MODE
- SEE ALSO
This document was created by
using the manual pages.
Time: 14:58:55 GMT, March 21, 2004