packages icon



 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



 NAME
      tcpflow - TCP flow recorder

 SYNOPSIS
      tcpflow [-chpsv] [-b max_bytes] [-d debug_level] [-f max_fds] [-i iface
      ] [-r file] [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.  A program like tcpdump(4) shows a
      summary 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 correctly 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   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
           -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   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.

      -h   Help.  Print usage information and exit.



                                    - 1 -     Formatted:  September 23, 2018






 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



      -i   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.

      -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.

      -r   Read from file.  Read packets from file, which was created using
           the -w option of tcpdump(1).  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.

      -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

      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.




                                    - 2 -     Formatted:  September 23, 2018






 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



      proto
           qualifiers restrict the match to a particular protocol.  Possible
           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 protocols
           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 identically 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



                                    - 3 -     Formatted:  September 23, 2018






 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



           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
           traffic, 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.




                                    - 4 -     Formatted:  September 23, 2018






 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



      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
           identification 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



                                    - 5 -     Formatted:  September 23, 2018






 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



           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



                                    - 6 -     Formatted:  September 23, 2018






 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



           unfragmented datagrams and frag zero of fragmented datagrams.
           This check is implicitly applied to the tcp and udp index
           operations.  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
           argument or as multiple arguments, whichever is more convenient.
           Generally, if the expression contains Shell metacharacters, it is
           easier to pass it as a single, quoted argument.  Multiple
           arguments are concatenated with spaces before being parsed.

 EXAMPLES
      The following part of the man 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 jelson@circlemud.org.  tcpflow currently
      does not understand IP fragments.  Flows containing IP fragments will
      not be recorded correctly.  tcpflow never frees state associated with



                                    - 7 -     Formatted:  September 23, 2018






 tcpflow(1)                     tcpflow 0.21                      tcpflow(1)
 tcpflow 0.21                                                   tcpflow 0.21

                                20 April 1999



      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
      listening to the Linux loopback interface, selective packet filtering
      is not possible; all TCP flows on the localhost interface will be
      recorded.

 AUTHOR
      Jeremy Elson <jelson@circlemud.org> The current version of this
      software is available at
           http://www.circlemud.org/~jelson/software/tcpflow

 SEE ALSO
      tcpdump(1), nit(4P), bpf(4), pcap(3)





































                                    - 8 -     Formatted:  September 23, 2018