Provided by: tcpflow_1.6.1-3_amd64 
NAME
tcpflow - TCP flow recorder
SYNOPSIS
tcpflow [-aBcCDIpsZ] [-b max_bytes] [-d debug_level] [-[eE] scanner] [-f max_fds]
[-F[ctTXMkmg]] [-h|--help] [-i iface] [-l file1.pcap file2.pcap...] [-L semlock]
[-m min_bytes] [-o outdir] [-r file1.pcap] [-R file0.pcap] [-S name=value]
[-T[filename template]] [-U|--relinquish-privileges username] [-v|--verbose]
[-V|--version] [-w file] [-x scanner] [-X file.xml] [-z|--chroot directory] [expression]
DESCRIPTION
tcpflow is a program that captures data transmitted as part of TCP connections (flows),
and stores the data in a way that is convenient for protocol analysis or debugging.
Rather than showing packet-by-packet information, tcpflow reconstructs the actual data
streams and stores each flow in a separate file for later analysis. tcpflow understands
TCP sequence numbers and will correctly reconstruct data streams regardless of
retransmissions or out-of-order delivery. tcpflow provides control over filenames for
automatic binning of connections by protocol, IP address or connection number, and has a
sophisticated plug-in system for decompressing compressed HTTP connections, undoing MIME
encoding, or calling user-provided programs for post-processing.
By default tcpflow stores all captured data in files that have names of the form:
192.168.101.102.02345-010.011.012.013.45103
...where the contents of the above file would be data transmitted from host
192.168.101.102 port 2345, to host 10.11.12.13 port 45103.
If you want to simply process a few hundred thousand packets and see what you have, try
this:
tcpflow -a -o outdir -Fk -r packets.pcap
This will cause tcpflow to perform (-a) all processing, store the output in a directory
called outdir, bin the output in directories of 1000 connections each, and read its input
from the file packets.pcap. More sophisticated processing is possible, of course.
OPTIONS
-a Enable all processing. Same as -e all.
-B Force binary output even when printing to console with -C or -c.
-b max_bytes
Specifies the maximum size of a captured flow. Any bytes beyond max_bytes from the
first byte captured will be discarded. The default is to store an unlimited number
of bytes per flow. Note: before version 1.4, tcpflow could only store a maximum of
4GiB per flow.
-c Console print. Print the contents of packets to stdout as they are received,
without storing any captured data to files (implies -s).
-C Console print without the packet source and destination details being printed.
Print the contents of packets to stdout as they are received, without storing any
captured data to files (implies -s).
-D Console output should be in hex.
-d Debug level. Set the level of debugging messages printed to stderr to debug_level.
Higher numbers produce more messages. -d 0 causes completely silent operation. -d
1 , the default, produces minimal status messages. -d 10 produces verbose output
equivalent to -v . Numbers higher than 10 can produce a large amount of debugging
information useful only to developers.
-E name
Disable all scanners and then enable scanner name
-e name
Enable scanner name.
-e all Enables all scanners. Same as -a
-e http
Perform HTTP post-processing ("After" processing). If the output file is
208.111.153.175.00080-192.168.001.064.37314,
Then the post-processing will create the files:
208.111.153.175.00080-192.168.001.064.37314-HTTP
208.111.153.175.00080-192.168.001.064.37314-HTTPBODY
If the HTTPBODY was compressed with GZIP, you may get a third file as well:
208.111.153.175.00080-192.168.001.064.37314-HTTPBODY-GZIP
Additional information about these streams, such as their MD5 hash value, is also
written to the DFXML report file.
-e python -S py_path=path -S py_module=module -S py_function=foo
Post-process TCP payload by an external python function.
The python function must take a single string parameter. The python function can
return a string (else the function does must not return). The returned string (if
any) is written in the DFXML report file inside the XML tag
<scan_python_result>...</scan_python_result>. A sample python script is available
within the tcpflow source code in directory python/plugins.
Example:
tcpflow -r my.cap -e python -S py_path=python/plugins -S py_module=samplePlugin -S py_function=sampleFunction
-F[format]
Specifies format for output filenames.
Format specifiers:
c Appends the connection counter to ALL filenames.
t Prepends each filename with a Unix timestamp (seconds since epoch).
T Prepends each filename with an ISO-8601 timestamp.
X Do not output any files (other than the DFXML report file).
-FM Include MD5 of each flow in the DFXML report file.
-FX Suppresses file output entirely, DFXML report file is still produced.
-Fk bin output in 1K directories
-Fm bin output in 1M directories (2 levels)
-Fg bin output in 1G directories (3 levels)
-fmax_fds
Max file descriptors used. Limit the number of file descriptors used by tcpflow to
max_fds. Higher numbers use more system resources, but usually perform better. If
the underlying operating system supports the setrlimit() system call, the OS will
be asked to enforce the requested limit. The default is for tcpflow to use the
maximum number of file descriptors allowed by the OS. The -v option will report
how many file descriptors tcpflow is using.
-g Output flow information to console in multiple colors. (Blue for client to server
flows, red for server to client flows, green for undecided flows.) Note: This
option was different from tcpflow 1.3 (-e) and 1.4.4 (-J).
-h --help
Help. Print usage information and exit.
-hh More help. Print more usage information and exit.
-i iface
Interface name. Capture packets from the network interface named iface. If no
interface is specified with -i , a reasonable default will be used by libpcap
automatically.
-I Store the reception timestamps (of TCP packets) in a companion file *.findx.
Therefore each flow will have two files: (1) the usual file containing payload
bytes and (2) the text file containing the corresponding timestamps. This last
file *.findx has three columns using the pipe '|' as separator:
byte-index|timestamp|length
The byte-index column is the postion within the file containing the payload bytes.
The timestamp column represents the number of seconds since epoch as a floating
point number. The precision is the microsecond but may also be the nanosecond in a
future tcpflow version. The length column is the number of successive bytes
concerned by timestamp and can include several TCP frames (TCP packets). The
extension findx may become from the fact that the timestamps are frame indexed.
-L semlock_name
Specifies that semlock_name should be used as a Unix semaphore to prevent two
different copies of tcpflow running in two different processes but outputting to
the same standard output from printing on top of each other. This is an application
of Unix named semaphores; bet you have never seen one before.
-l Treat the following arguments as filenames with an assumed -r command before each
one. This allows you to read a lot of files at once with shell globbing. For
example, to process all of the pcap files in the current directory, use this:
tcpflow -o out -a -l *.pcap
-m min_size
Forces a new connection output file when there is a skip in the TCP session of
min_size bytes or more.
-o outdir
Specifies the output directory where the transcript files will be written.
-P No purge. Normally tcpflow removes connections from the hash table after the
connection is closed with a FIN. This conserves memory but takes additional CPU
time. Selecting this option causes the std::tr1:unordered_map to grow without
bounds, as tcpflow did prior to version 1.1. That makes tcpflow run faster if there
are less than 10 million connections, but can lead to out-of-memory errors.
-p No promiscuous mode. Normally, tcpflow attempts to put the network interface into
promiscuous mode before capturing packets. The -p option tells tcpflow not to put
the interface into promiscuous mode. Note that it might already be in promiscuous
mode for some other reason.
-q Quiet mode --- don't print warnings. Currently the only warning that tcpflow prints
is a warning when more than 10,000 files are created that the user should have
provided the -Fk, -Fm, or -Fg options. We might have other warnings in the future.
--relinquish-privileges=username
When tcpflow is run as root, this option changes the user ID and group ID to write
files owned by username. The group ID is the first one from the username groups
list. This operation is performed just after opening the capture device or just
after opening the first input PCAP file. This option does not support multi root-
only readable input files as the root privileges are dropped after opening the
first file (e.g. -r root-only-access.pcap -R root-only.pcap -l root-only*.pcap).
This option has the same behaviour as the tcpdump(1) option having the same name
--relinquish-privileges
-r Read from file. Read packets from file, which was created using the -w option of
tcpdump(1). This option may be repeated any number of times. Standard input is
used if file is "-". Note that for this option to be useful, tcpdump's -s option
should be used to set the snaplen to the MTU of the interface (e.g., 1500) while
capturing packets.
-R Read from a file, but only to complete TCP flows. This option is used when tcpflow
is used to process a series of files that are captured over time. For each time
period n, file file(n).pcap should be processed with -R file(n).pcap, while
file(n-1).pcap should be processed with -r file(n-1).pcap.
-Sname=value
Sets a name parameter to be equal to value for a plug-in. Use -hh to find out all
of the settable parameters.
-s Strip non-printables. Convert all non-printable characters to the "." character
before printing packets to the console or storing them to a file.
-T[format]
Specifies an arbitrary template for filenames.
%A expands to source IP address.
%a expands to source IP port.
%B expands to destination IP address.
%b expands to destination IP port.
%T expands to timestamp in ISO8601 format.
%t expands to timestamp in Unix time_t format.
%V expands to "--" if a VLAN is present.
%v expands to the VLAN number if a VLAN is present.
%C expands to "c" if the connection count>0.
%c expands to the connection count if the connection count>0.
%# always expands to the connection count.
%N (connection_number ) % 1000
%K (connection_number / 1000) % 1000
%M (connection_number / 1000000) % 1000
%G (connection_number / 1000000000) % 1000
%% prints a "%".
When the option -T is used, tcpflow ignores options -Fk, -Fm and -Fg.
However, the option -T handles '/' within the filename template patern to create
sub-directories. For example the following line will create a directory tree
out/IP-src/port-src/IP-dst/port-dst.
tcpflow -r packets.pcap -o out -T %A/%a/%B/%b/%c%N.flow
-V --version
Print the version number and exit.
-v --verbose
Verbose operation. Verbosely describe tcpflow's operation. Equivalent to -d 10.
-w filename.pcap
Write packets that were not processed to filename.pcap. Typically this will be UDP
packets.
-X filename.xml
Write a DFXML report to filename.xml. The file contains a record of every tcp
connection, how the tcpflow program was compiled, and the computer on which tcpflow
was run. By default tcpflow writes the DFXML report in file report.xml.
-Z Don't decompress gzip-compressed streams. -K Retain per flow isolated pcap
structure.
expression
selects which packets will be captured. If no expression is given, all packets on
the net will be captured. Otherwise, only packets for which expression is `true'
will be captured.
For the expression syntax, see pcap-filter(7).
The expression argument can be passed to tcpflow as either a single Shell argument,
or as multiple Shell arguments, whichever is more convenient. Generally, if the
expression contains Shell metacharacters, such as backslashes used to escape
protocol names, it is easier to pass it as a single, quoted argument rather than to
escape the Shell metacharacters. Multiple arguments are concatenated with spaces
before being parsed.
DFXML report
The DFXML report is the XML file written by tcpflow to provide tcpflow build details,
command line arguments and information about processed flows.
By default the DFXML file is named report.xml. But this filename can be changed using
command line option -X.
DFXML file respects the DFXML schema defined by project https://github.com/dfxml-working-
group/dfxml_schema.
Moreover tcpflow adds two extra XML tags, as illustrated by the following example:
<tcpflow startime='2017-07-22T00:12:21.962782Z' endtime='2017-07-22T00:12:22.097591Z'
family='2' mac_daddr='40:3d:78:57:ed:d4' mac_saddr='00:c5:42:d2:cb:f2'
src_ipn='141.134.34.12' dst_ipn='192.168.0.40' srcport='80' dstport='38797'
packets='4' len='677' caplen='611' />
<tcpflow:result scanner="python" path="python/plugins" module="samplePlugin"
function="sampleFunction">bla bla bla</tcpflow:result>
The first XML tag <tcpflow> provide information about the captured flow. This tag should
be renamed <tcpflow:cap> in a future version in order to conform better to DFXML schema.
The second XML tag <tcpflow:result> collects processing results. For the moment, only the
scanner python uses this feature.
The XML attributes of <tcpflow> are:
• startime Reception time of first packet
• endtime Reception time of last packet
• family
• mac_daddr Destination MAC address of first packet (printed if any)
• mac_saddr Source MAC address of first packet (printed if any)
• src_ipn IP source
• dst_ipn IP destination
• srcport TCP port source
• dstport TCP port destination
• packets Nummber of packets
• out_of_order_count Number of times tcpflow has replaced missing payload by zeros in
the flow file, for example when capture does not contain the TCP session begin
(printed if any)
• violations Number of protocol violations (printed if any)
• len Sum of un-truncated length of all packet data (including headers, see
https://stackoverflow.com/q/1491660)
• caplen Sum of captured bytes of all packet data (including headers, printed if
different from len)
The XML attributes of <tcpflow:result> are:
• scanner Name of the scanner
• path Directory of the scanner module (printed if relevant)
• module Module name (printed if relevant, used to indicate the python script)
• function Function name (printed if relevant, used to indicate the function within
the python module)
EXAMPLES
To record all packets arriving at or departing from sundown and extract all of the HTTP
attachments:
tcpflow -e http -o outdir host sundown
To record traffic between helios and either hot or ace and bin the results into 1000 files
per directory and calculate the MD5 of each flow:
tcpflow -X report.xml -e md5 -o outdir -Fk host helios and \( hot or ace \)
BUGS
Please send bug reports to simsong@acm.org.
tcpflow currently does not understand IP fragments. Flows containing IP fragments will
not be recorded correctly.
AUTHORS
Originally by Jeremy Elson <jelson@circlemud.org>. Substantially modified and maintained
by Simson L. Garfinkel <simsong@acm.org>. Network visualization code by Michael Shick
<mike@shick.in>
The current version of this software is available at
http://digitalcorpora.org/downloads/tcpflow/
An announcement mailing list for this program is at:
http://groups.google.com/group/tcpflow-users
SEE ALSO
tcpdump(1), nit(4P), bpf(4), pcap(3), pcap-savefile(5), pcap-filter(7)