Ubuntu Manpage: softflowd — Traffic flow monitoring

NAME

     softflowd — Traffic flow monitoring

SYNOPSIS

     softflowd [-6dDh] [-L hoplimit] [-T track_level] [-c ctl_sock] [-i  [if_ndx:]interface]
               [-m max_flows] [-n host:port] [-p pidfile] [-r pcap_file]
               [-t timeout_name=seconds] [-v netflow_version] [-s sampling_rate] [bpf_expression]

DESCRIPTION

softflowd is a software implementation of a flow-based network traffic monitor. softflowd
reads network traffic and gathers information about active traffic flows. A "traffic flow"
is communication between two IP addresses or (if the overlying protocol is TCP or UDP)
address/port tuples.

The intended use of softflowd is as a software implementation of Cisco's NetFlow(tm) traffic
account system. softflowd supports data export using versions 1, 5 or 9 of the NetFlow
protocol. softflowd can also run in statistics-only mode, where it just collects summary
information. However, too few statistics are collected to make this mode really useful for
anything other than debugging.

Network traffic may be obtained by listening on a promiscuous network interface or by
reading stored pcap(3) files, such as those written by tcpdump(8). Traffic may be filtered
with an optional bpf(4) program, specified on the command-line as bpf_expression. softflowd
is IPv6 capable and will track IPv6 flows if the NetFlow export protocol supports it
(currently only NetFlow v.9 possesses an IPv6 export capability).

softflowd tries to track only active traffic flows. When the flow has been quiescent for a
period of time it is expired automatically. Flows may also be expired early if they
approach their traffic counts exceed 2 Gib or if the number of flows being tracked exceeds
max_flows (default: 8192). In this last case, flows are expired oldest-first.

Upon expiry, the flow information is accumulated into statistics which may be viewed using
softflowctl(8). If the -n option has been specified the flow information is formatted in a
UDP datagram which is compatible with versions 1, 5 or 9 of Cisco's NetFlow(tm) accounting
export format. These records are sent to the specified host and port. The host may
represent a unicast host or a multicast group.

The command-line options are as follows:

-n host:port
Specify the host and port that the accounting datagrams are to be sent to. The host
may be specified using a hostname or using a numeric IPv4 or IPv6 address. Numeric
IPv6 addresses should be encosed in square brackets to avoid ambiguity between the
address and the port. The destination port may be a portname listed in services(5)
or a numeric port.

-i [if_ndx:]interface
Specify a network interface on which to listen for traffic. Either the -i or the -r
options must be specified.

-r pcap_file
Specify that softflowd should read from a pcap(3) packet capture file (such as one
created with the -w option of tcpdump(8)) file rather than a network interface.
softflowd processes the whole capture file and only expires flows when max_flows is
exceeded. In this mode, softflowd will not fork and will automatically print
summary statistics before exiting.

-p pidfile
Specify an alternate location to store the process ID when in daemon mode. Default
is /var/run/softflowd.pid

-c ctlsock
Specify an alternate location for the remote control socket in daemon mode. Default
is /var/run/softflowd.ctl

-m max_flows
Specify the maximum number of flows to concurrently track. If this limit is
exceeded, the flows which have least recently seen traffic are forcibly expired. In
practice, the actual maximum may briefly exceed this limit by a small amount as
expiry processing happens less frequently than traffic collection. The default is
8192 flows, which corresponds to slightly less than 800k of working data.

-t timeout_name=time
Set the timeout names timeout_name to time. Refer to the Timeouts section for the
valid timeout names and their meanings. The time parameter may be specified using
one of the formats explained in the Time Formats section below.

-d Specify that softflowd should not fork and daemonise itself.

-6 Force softflowd to track IPv6 flows even if the NetFlow export protocol does not
support reporting them. This is useful for debugging and statistics gathering only.

-D Places softflowd in a debugging mode. This implies the -d and -6 flags and turns on
additional debugging output.

-h Display command-line usage information.

-L hoplimit
Set the IPv4 TTL or the IPv6 hop limit to hoplimit. softflowd will use the default
system TTL when exporting flows to a unicast host. When exporting to a multicast
group, the default TTL will be 1 (i.e. link-local).

-T track_level
Specify which flow elements softflowd should be used to define a flow. track_level
may be one of: “full” (track everything in the flow, the default), “proto” (track
source and destination addresses and protocol), or “ip” (only track source and
destination addresses). Selecting either of the latter options will produce flows
with less information in them (e.g. TCP/UDP ports will not be recorded). This will
cause flows to be consolidated, reducing the quantity of output and CPU load that
softflowd will place on the system at the cost of some detail being lost.

-v netflow_version
Specify which version of the NetFlow(tm) protocol softflowd should use for export of
the flow data. Supported versions are 1, 5 and 9. Default is version 5.

-s sampling_rate
Specify periodical sampling rate (denominator).

Any further command-line arguments will be concatenated together and applied as a bpf(4)
packet filter. This filter will cause softflowd to ignore the specified traffic.

Timeouts
softflowd will expire quiescent flows after user-configurable periods. The exact timeout
used depends on the nature of the flow. The various timeouts that may be set from the
command-line (using the -t option) and their meanings are:

general
This is the general timeout applied to all traffic unless overridden by one of the
other timeouts.

tcp This is the general TCP timeout, applied to open TCP connections.

tcp.rst
This timeout is applied to a TCP connection when a RST packet has been sent by one
or both endpoints.

tcp.fin
This timeout is applied to a TCP connection when a FIN packet has been sent by both
endpoints.

udp This is the general UDP timeout, applied to all UDP connections.

maxlife
This is the maximum lifetime that a flow may exist for. All flows are forcibly
expired when they pass maxlife seconds. To disable this feature, specify a maxlife
of 0.

expint Specify the interval between expiry checks. Increase this to group more flows into
a NetFlow packet. To disable this feature, specify a expint of 0.

Flows may also be expired if there are not enough flow entries to hold them or if their
traffic exceeds 2 Gib in either direction. softflowctl(8) may be used to print information
on the average lifetimes of flows and the reasons for their expiry.

Time Formats
softflowd command-line arguments that specify time may be expressed using a sequence of the
form: time[qualifier], where time is a positive integer value and qualifier is one of the
following:

Each member of the sequence is added together to calculate the total time value.

Time format examples:

600 600 seconds (10 minutes)
10m 10 minutes
1h30m 1 hour 30 minutes (90 minutes)

Run-time Control
A daemonised softflowd instance may be controlled using the softflowctl(8) command. This
interface allows one to shut down the daemon, force expiry of all tracked flows and extract
debugging and summary data. Also, receipt of a SIGTERM or SIGINT will cause softflowd to
exit, after expiring all flows (and thus sending flow export packets if -n was specified on
the command-line). If you do not want to export flows upon shutdown, clear them first with
softflowctl(8) or use softflowctl(8) 's “exit” command.

EXAMPLES

     softflowd -i fxp0
             This command-line will cause softflowd to listen on interface fxp0 and to run in
             statistics gathering mode only (i.e. no NetFlow data export).

     softflowd -i fxp0 -n 10.1.0.2:4432
             This command-line will cause softflowd to listen on interface fxp0 and to export
             NetFlow v.5 datagrams on flow expiry to a flow collector running on 10.1.0.2 port
             4432.

     softflowd -v 5 -i fxp0 -n 10.1.0.2:4432 -m 65536 -t udp=1m30s
             This command-line increases the number of concurrent flows that softflowd will track
             to 65536 and increases the timeout for UDP flows to 90 seconds.

     softflowd -v 9 -i fxp0 -n 224.0.1.20:4432 -L 64
             This command-line will export NetFlow v.9 flows to the multicast group 224.0.1.20.
             The export datagrams will have their TTL set to 64, so multicast receivers can be
             many hops away.

     softflowd -i fxp0 -p /var/run/sfd.pid.fxp0 -c /var/run/sfd.ctl.fxp0
             This command-line specifies alternate locations for the control socket and pid file.
             Similar command-lines are useful when running multiple instances of softflowd on a
             single machine.

FILES

     /var/run/softflowd.pid
             This file stores the process ID when softflowd is in daemon mode.  This location may
             be overridden using the -p command-line option.

     /var/run/softflowd.ctl
             This is the remote control socket.  softflowd listens on this socket for commands
             from softflowctl(8).  This location may be overridden using the -c command-line
             option.

BUGS

     Currently softflowd does not handle maliciously fragmented packets properly, i.e. packets
     fragemented such that the UDP or TCP header does not fit into the first fragment.  It will
     product correct traffic counts when presented with maliciously fragmented packets, but will
     not record TCP or UDP port information.

AUTHORS

     Damien Miller <djm@mindrot.org>