tcpflow(1)tcpflow 1.3.0 tcpflow(1)NAMEtcpflow - TCP flow recorder
SYNOPSIStcpflow [-BcCehPpsv] [-b max_bytes] [-d debug_level] [-f max_fds]
[-i iface] [-r file1.pcap] [-R file0.pcap] [-m minskip] [-X file.xml]
[-F[outputformat]] [-T[filenameetemplate]] [expression]
DESCRIPTIONtcpflow is a program that captures data transmitted as part of TCP con‐
nections (flows), and stores the data in a way that is convenient for
protocol analysis or debugging. A program like tcpdump(4) shows a sum‐
mary of packets seen on the wire, but usually doesn't store the data
that's actually being transmitted. In contrast, tcpflow reconstructs
the actual data streams and stores each flow in a separate file for
later analysis. tcpflow understands TCP sequence numbers and will cor‐
rectly reconstruct data streams regardless of retransmissions or out-
of-order delivery.
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.
OPTIONS-B Force binary output even when printing to console with -C or -c.
-b Max bytes per flow. Capture no more than max_bytes bytes per
flow. Any data captured for a flow beyond max_bytes from the
first byte captured will be discarded. The default is to store
an unlimited number of bytes per flow.
-c Console print. Print the contents of packets to stdout as they
are received, without storing any captured data to files
(implies
-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 -e When outputting to the console each flow will be
output in different colors (blue for client to server flows, red
for server to client flows, green for undecided flows). -s ).
-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.
-F[format]
Specifies format for output filenames. Format specifiers: t
prepends each filename with a Unix timestamp. T prepends each
filename with an ISO-8601 timestamp. c appends each filename
with a connection counter.
-FM Include MD5 of each flow in the DFXML output.
-FX Suppresses file output entirely (DFXML file is still produced).
-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. %a 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 con‐
nection count. %% prints a "%".
-AH 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 file
-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 oper‐
ating 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.
-h Help. Print usage information and exit.
-i Interface name. Capture packets from the network interface
named iface. If no interface is specified with -i , a reason‐
able default will be used by libpcap automatically.
-m min_size
Forces a new connection output file when there is a skip in the
TCP session of min_size bytes or more.
-P No purge. Normally tcpflow removes connections from the hash ta‐
ble 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 net‐
work interface into promiscuous mode before capturing packets.
The -p option tells tcpflow not to put the interface into pro‐
miscuous mode. Note that it might already be in promiscuous
mode for some other reason.
-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 as of tcpflow version 1.2.7. 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 filen.pcap
should be processed with -rfilen.pcap, while file(n-1).pcap
should be processed with -Rfile(n-1).pcap.
-s Strip non-printables. Convert all non-printable characters to
the "." character before printing packets to the console or
storing them to a file.
-v Verbose operation. Verbosely describe tcpflow's operation.
Equivalent to -d 10 .
FILTERING EXPRESSIONS
The expression specified on the command-line specifies which packets
should be captured. Because tcpflow uses the the libpcap library,
tcpflow has the same powerful filtering language available as programs
such as tcpdump(1).
The following part of the man page is excerpted from the tcpdump man
page.
expression selects which packets will be dumped. If no expression is
given, all packets on the net will be dumped. Otherwise, only packets
for which expression is `true' will be dumped.
The expression consists of one or more primitives. Primitives usually
consist of an id (name or number) preceded by one or more qualifiers.
There are three different kinds of qualifier:
type qualifiers say what kind of thing the id name or number refers
to. Possible types are host, net and port. E.g., `host foo',
`net 128.3', `port 20'. If there is no type qualifier, host is
assumed.
dir qualifiers specify a particular transfer direction to and/or
from id. Possible directions are src, dst, src or dst and src
and dst. E.g., `src foo', `dst net 128.3', `src or dst port
ftp-data'. If there is no dir qualifier, src or dst is assumed.
For `null' link layers (i.e. point to point protocols such as
slip) the inbound and outbound qualifiers can be used to specify
a desired direction.
proto qualifiers restrict the match to a particular protocol. Possi‐
ble protos are: ether, fddi, ip, arp, rarp, decnet, lat, sca,
moprc, mopdl, tcp and udp. E.g., `ether src foo', `arp net
128.3', `tcp port 21'. If there is no proto qualifier, all pro‐
tocols consistent with the type are assumed. E.g., `src foo'
means `(ip or arp or rarp) src foo' (except the latter is not
legal syntax), `net bar' means `(ip or arp or rarp) net bar' and
`port 53' means `(tcp or udp) port 53'.
[`fddi' is actually an alias for `ether'; the parser treats them iden‐
tically as meaning ``the data link level used on the specified network
interface.'' FDDI headers contain Ethernet-like source and destination
addresses, and often contain Ethernet-like packet types, so you can
filter on these FDDI fields just as with the analogous Ethernet fields.
FDDI headers also contain other fields, but you cannot name them
explicitly in a filter expression.]
In addition to the above, there are some special `primitive' keywords
that don't follow the pattern: gateway, broadcast, less, greater and
arithmetic expressions. All of these are described below.
More complex filter expressions are built up by using the words and, or
and not to combine primitives. E.g., `host foo and not port ftp and
not port ftp-data'. To save typing, identical qualifier lists can be
omitted. E.g., `tcp dst port ftp or ftp-data or domain' is exactly the
same as `tcp dst port ftp or tcp dst port ftp-data or tcp dst port
domain'.
Allowable primitives are:
dst host host
True if the IP destination field of the packet is host, which
may be either an address or a name.
src host host
True if the IP source field of the packet is host.
host host
True if either the IP source or destination of the packet is
host. Any of the above host expressions can be prepended with
the keywords, ip, arp, or rarp as in:
ip host host
which is equivalent to:
ether proto \ip and host host
If host is a name with multiple IP addresses, each address will
be checked for a match.
ether dst ehost
True if the ethernet destination address is ehost. Ehost may be
either a name from /etc/ethers or a number (see ethers(3N) for
numeric format).
ether src ehost
True if the ethernet source address is ehost.
ether host ehost
True if either the ethernet source or destination address is
ehost.
gateway host
True if the packet used host as a gateway. I.e., the ethernet
source or destination address was host but neither the IP source
nor the IP destination was host. Host must be a name and must
be found in both /etc/hosts and /etc/ethers. (An equivalent
expression is
ether host ehost and not host host
which can be used with either names or numbers for host /
ehost.)
dst net net
True if the IP destination address of the packet has a network
number of net. Net may be either a name from /etc/networks or a
network number (see networks(5) for details).
src net net
True if the IP source address of the packet has a network number
of net.
net net
True if either the IP source or destination address of the
packet has a network number of net.
net net mask mask
True if the IP address matches net with the specific netmask.
May be qualified with src or dst.
net net/len
True if the IP address matches net a netmask len bits wide. May
be qualified with src or dst.
dst port port
True if the packet is ip/tcp or ip/udp and has a destination
port value of port. The port can be a number or a name used in
/etc/services (see tcp(4P) and udp(4P)). If a name is used,
both the port number and protocol are checked. If a number or
ambiguous name is used, only the port number is checked (e.g.,
dst port 513 will print both tcp/login traffic and udp/who traf‐
fic, and port domain will print both tcp/domain and udp/domain
traffic).
src port port
True if the packet has a source port value of port.
port port
True if either the source or destination port of the packet is
port. Any of the above port expressions can be prepended with
the keywords, tcp or udp, as in:
tcp src port port
which matches only tcp packets whose source port is port.
less length
True if the packet has a length less than or equal to length.
This is equivalent to:
len <= length.
greater length
True if the packet has a length greater than or equal to length.
This is equivalent to:
len >= length.
ip proto protocol
True if the packet is an ip packet (see ip(4P)) of protocol type
protocol. Protocol can be a number or one of the names icmp,
igrp, udp, nd, or tcp. Note that the identifiers tcp, udp, and
icmp are also keywords and must be escaped via backslash (\),
which is \\ in the C-shell.
ether broadcast
True if the packet is an ethernet broadcast packet. The ether
keyword is optional.
ip broadcast
True if the packet is an IP broadcast packet. It checks for
both the all-zeroes and all-ones broadcast conventions, and
looks up the local subnet mask.
ether multicast
True if the packet is an ethernet multicast packet. The ether
keyword is optional. This is shorthand for `ether[0] & 1 != 0'.
ip multicast
True if the packet is an IP multicast packet.
ether proto protocol
True if the packet is of ether type protocol. Protocol can be a
number or a name like ip, arp, or rarp. Note these identifiers
are also keywords and must be escaped via backslash (\). [In
the case of FDDI (e.g., `fddi protocol arp'), the protocol iden‐
tification comes from the 802.2 Logical Link Control (LLC)
header, which is usually layered on top of the FDDI header.
Tcpdump assumes, when filtering on the protocol identifier, that
all FDDI packets include an LLC header, and that the LLC header
is in so-called SNAP format.]
decnet src host
True if the DECNET source address is host, which may be an
address of the form ``10.123'', or a DECNET host name. [DECNET
host name support is only available on Ultrix systems that are
configured to run DECNET.]
decnet dst host
True if the DECNET destination address is host.
decnet host host
True if either the DECNET source or destination address is host.
ip, arp, rarp, decnet
Abbreviations for:
ether proto p
where p is one of the above protocols.
lat, moprc, mopdl
Abbreviations for:
ether proto p
where p is one of the above protocols. Note that tcpdump does
not currently know how to parse these protocols.
tcp, udp, icmp
Abbreviations for:
ip proto p
where p is one of the above protocols.
expr relop expr
True if the relation holds, where relop is one of >, <, >=, <=,
=, !=, and expr is an arithmetic expression composed of integer
constants (expressed in standard C syntax), the normal binary
operators [+, -, *, /, &, |], a length operator, and special
packet data accessors. To access data inside the packet, use
the following syntax:
proto [ expr : size ]
Proto is one of ether, fddi, ip, arp, rarp, tcp, udp, or icmp,
and indicates the protocol layer for the index operation. The
byte offset, relative to the indicated protocol layer, is given
by expr. Size is optional and indicates the number of bytes in
the field of interest; it can be either one, two, or four, and
defaults to one. The length operator, indicated by the keyword
len, gives the length of the packet.
For example, `ether[0] & 1 != 0' catches all multicast traffic.
The expression `ip[0] & 0xf != 5' catches all IP packets with
options. The expression `ip[6:2] & 0x1fff = 0' catches only
unfragmented datagrams and frag zero of fragmented datagrams.
This check is implicitly applied to the tcp and udp index opera‐
tions. For instance, tcp[0] always means the first byte of the
TCP header, and never means the first byte of an intervening
fragment.
Primitives may be combined using:
A parenthesized group of primitives and operators (parentheses
are special to the Shell and must be escaped).
Negation (`!' or `not').
Concatenation (`&&' or `and').
Alternation (`||' or `or').
Negation has highest precedence. Alternation and concatenation have
equal precedence and associate left to right. Note that explicit and
tokens, not juxtaposition, are now required for concatenation.
If an identifier is given without a keyword, the most recent keyword is
assumed. For example,
not host vs and ace
is short for
not host vs and host ace
which should not be confused with
not ( host vs or ace )
Expression arguments can be passed to tcpdump as either a single argu‐
ment or as multiple arguments, whichever is more convenient. Gener‐
ally, if the expression contains Shell metacharacters, it is easier to
pass it as a single, quoted argument. Multiple arguments are concate‐
nated with spaces before being parsed.
EXAMPLES
The following part of the man page is excerpted from the tcpdump man
page.
To record all packets arriving at or departing from sundown:
tcpflow host sundown
To record traffic between helios and either hot or ace:
tcpflow host helios and \( hot or ace \)
To record traffic between ace and any host except helios:
tcpflow host ace and not helios
To record all traffic between local hosts and hosts at Berkeley:
tcpflow net ucb-ether
To record all ftp traffic through internet gateway snup: (note that the
expression is quoted to prevent the shell from (mis-)interpreting the
parentheses):
tcpflow 'gateway snup and (port ftp or ftp-data)'
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.
tcpflow never frees state associated with flows that it records, so
will grow large if used to capture a very large number of flows (e.g.,
on the order of 100,000 flows or more).
There appears to be a bug in the way that Linux delivers packets to
libpcap when using the loopback interface ("localhost"). When listen‐
ing to the Linux loopback interface, selective packet filtering is not
possible; all TCP flows on the localhost interface will be recorded.
AUTHORS
Originally by Jeremy Elson <jelson@circlemud.org>. Substantially modi‐
fied and maintained by Simson L. Garfinkel <simsong@acm.org>.
The current version of this software is available at
http://www.afflib.org/
An announcement mailing list for this program is at:
http://groups.google.com/group/tcpflow-users
SEE ALSOtcpdump(1), nit(4P), bpf(4), pcap(3)tcpflow 1.3.0 15 Jan 2011 tcpflow(1)
