NAME

SYNOPSIS

DESCRIPTION

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

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

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.

    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.

-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.

    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.

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

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

tcpflow -e scan_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 scan_md5 -o outdir -Fk host helios and \( hot or ace \)

BUGS

tcpflow currently does not understand IP fragments. Flows containing IP fragments will not be recorded correctly.

AUTHORS

The current version of this software is available at

An announcement mailing list for this program is at:

SEE ALSO