softflowd.8

根据网络原始数据生成NetFlow记录的软件。NetFlow是Cisco提出的流技术

.\" $Id: softflowd.8,v 1.17 2006/02/11 11:27:38 djm Exp $
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.\" Copyright (c) 2002 Damien Miller.  All rights reserved.
.\" Portions Copyright (c) 2001 Kevin Steves.  All rights reserved.
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.Dd October 14, 2002
.Dt SOFTFLOWD 8
.Os
.Sh NAME
.Nm softflowd
.Nd Traffic flow monitoring
.Sh SYNOPSIS
.Nm softflowd
.Op Fl 6dDh
.Op Fl i Ar interface
.Op Fl r Ar pcap_file
.Op Fl t Ar timeout_name=seconds
.Op Fl m Ar max_flows
.Op Fl n Ar host:port
.Op Fl p Ar pidfile
.Op Fl c Ar ctl_sock
.Op Fl L Ar hoplimit
.Op Fl T Ar track_level
.Op bpf_program
.Sh DESCRIPTION
.Nm
is a software implementation of a flow-based network traffic monitor. 
.Nm
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. 
.Pp
The intended use of
.Nm 
is as a software implementation of Cisco's NetFlow(tm) traffic account
system.
.Nm 
supports data export using versions 1, 5 or 9 of the NetFlow protocol. 
.Nm 
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.
.Pp
Network traffic may be obtained by listening on a promiscuous network
interface or by reading stored
.Xr pcap 3
files, such as those written by 
.Xr tcpdump 8 .
Traffic may be filtered with an optional
.Xr bpf 4
program, specified on the command-line as
.Ar bpf_prog .
.Nm
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). 
.Pp
.Nm
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 2Gb or if the number of flows being tracked exceeds 
.Ar max_flows
(default: 8192).
In this last case, flows are expired oldest-first. 
.Pp
Upon expiry, the flow information is accumulated into statistics which may
be viewed using 
.Xr softflowctl 8 .
If the 
.Fl n
option has been specified the flow informaion 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
.Ar host
and
.Ar port .
The host may represent a unicast host or a multicast group.
.Pp
The command-line options are as follows:
.Bl -tag -width Ds
.It Fl n Ar host:port
Specify the 
.Ar host
and 
.Ar 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 
.Xr services 5
or a numeric port.
.It Fl i Ar interface
Specify a network interface on which to listen for traffic.
Either the 
.Fl i
or the
.Fl r 
options must be specified.
.It Fl r Ar pcap_file
Specify that
.Nm
should read from a 
.Xr pcap 3
packet capture (such as one created with the 
.Fl w
option of 
.Xr tcpdump 8 )
file rather than a network interface. 
.Nm
processes the whole capture file and only expires flows when 
.Ar max_flows
is exceeded. In this mode, 
.Nm
will not fork and will automatically print summary statistics before 
exiting.
.It Fl p Ar pidfile
Specify an alternate location to store the process-id when in daemon mode.
Default is 
.Pa /var/run/softflowd.pid
.It Fl c Ar ctlsock
Specify an alternate location for the remote control socket in daemon mode.
Default is 
.Pa /var/run/softflowd.pid
.It Fl m Ar max_flows
Specifies the maximum number of flow 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.
.It Fl t Ar timeout_name=time
Set the timeout names
.Ar timeout_name
to 
.Ar time 
Refer to the 
.Sx Timeouts
section for the valid timeout names and their meanings.
The 
.Ar time
parameter may be specified using one of the formats explained in the 
.Sx Time Formats
section below.
.It Fl d
Specify that 
.Nm
should not fork and daemonise itself.
.It Fl 6
Forces
.Nm
To track IPv6 flows even if the NetFlow export protocol does not support
reporting them.
This is useful for debugging and statistics gathering only.
.It Fl D
Places
.Nm
in a debugging mode.
This implies the 
.Fl d
and
.Fl 6
flags and turns on additional debugging output.
.It Fl h
Displays commandline usage information.
.It Fl L Ar hoplimit
Sets the IPv4 TTL or the IPv6 hop limit to
.Ar hoplimit .
.Nm
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).
.It Fl T Ar track_level
Specifies what flow elements
.Nm
should be used to define a flow.
.Ar track_level
may be one of:
.Dq full
(track everything in the flow, the default),
.Dq proto
(track source and destination addresses and protocol), or
.Dq 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
.Nm
will place on the system at the cost of some detail.
.El
.Pp
Any further commandline arguments will be concatenated together and 
applied as a 
.Xr bpf 4
packet filter.
This filter will cause 
.Nm
to ignore the specified traffic.
.Ss Timeouts
.Pp
.Nm
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 
.Fl t 
option) and their meanings are:
.Bl -tag -width Ds
.It Ar general
This is the general timeout applied to all traffic unless overridden by 
one of the other timeouts.
.It Ar tcp
This is the general TCP timeout, applied to open TCP connections.
.It Ar tcp.rst
This timeout is applied to a TCP connection when a RST packet has been 
sent by one or both endpoints.
.It Ar tcp.fin
This timeout is applied to a TCP connection when a FIN packet has been
sent by both endpoints.
.It Ar udp
This is the general UDP timeout, applied to all UDP connections.
.It Ar maxlife
This is the maximum lifetime that a flow may exist for.
All flows 
are forcibly expired when they pass
.Ar maxlife
seconds.
To disable this feature, specify a 
.Ar maxlife
of 0.
.It Ar expint
Specify the interval between expiry checks.
Increase this to group more flows into a NetFlow packet.
To disable this feature, specify a 
.Ar expint
of 0.
.El
.Pp
Flows may also be expired if there are not enough flow entries to hold them
or if their traffic exceeds 2Gb in either direction. 
.Xr softflowctl 8
may be used to print information on the average lifetimes of flows and 
the reasons for their expiry.
.Ss Time Formats
.Pp
.Nm
command-line arguments that specify time
may be expressed using a sequence of the form:
.Sm off
.Ar time Op Ar qualifier ,
.Sm on
where
.Ar time
is a positive integer value and
.Ar qualifier
is one of the following:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It Cm <none>
seconds
.It Cm s | Cm S
seconds
.It Cm m | Cm M
minutes
.It Cm h | Cm H
hours
.It Cm d | Cm D
days
.It Cm w | Cm W
weeks
.El
.Pp
Each member of the sequence is added together to calculate
the total time value.
.Pp
Time format examples:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It 600
600 seconds (10 minutes)
.It 10m
10 minutes
.It 1h30m
1 hour 30 minutes (90 minutes)
.El
.Ss Run-time Control
.Pp
A daemonised
.Nm
instance may be controlled using the 
.Xr 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, upon 
receipt of a 
.Dv SIGTERM
or 
.DV SIGINT
.Nm
will cause 
.Nm
to exit, after expiring all flows (and thus sending flow export packets 
if 
.Fl -n 
was specified on the commandline).
If you do not want to export flows upon shutdown, clear them first with
.Xr softflowctl 8 .

.Sh EXAMPLES
.Bl -tag -width Ds
.It softflowd -i fxp0
This commandlie will cause 
.Nm
to listen on interface \fBfxp0\fP and
to run in statistics gathering mode only (i.e no NetFlow data export).
.It softflowd -i fxp0 -n10.1.0.2:4432
This commandlie will cause
.Nm
to listen on interface \fBfxp0\fP and
to export NetFlow v.5 datagrams on flow expiry to a flow collector running
on \fB10.1.0.2\fP port \fB4432\fP.
.It softflowd -v 5 -i fxp0 -n10.1.0.2:4432 -m 65536 -t udp=1m30s
This commandline increases the number of concurrent flows that 
.Nm
will track to \fB65536\fP and increases the timeout for UDP flows to 
90 seconds.
.It softflowd -v 9 -i fxp0 -n224.0.1.20:4432 -L 64
This commandline 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.
.It softflowd -i fxp0 -p /var/run/sfd.pid.fxp0 -c /var/run/sfd.ctl.fxp0
This commandline specifies alternate locations for the control socket
and pid file.
Similar commandlines are useful when running multiple 
instances of 
.Nm
on a single machine.
.El
.Sh FILES
.Bl -tag -width Ds
.It Pa /var/run/softflowd.pid
This file stores the process-id when
.Nm
is in daemon mode.
This location may be overridden using the 
.Fl p
command-line option.
.It Pa /var/run/softflowd.ctl
This is the remote control socket. 
.Nm 
listens on this socket for commands from 
.Xr softflowctl 8 . This location may be overridden using the 
.Fl c
command-line option.
.El
.Sh BUGS
Currently
.Nm
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.
.Sh AUTHORS
Damien Miller <[e-mail]>
.Sh SEE ALSO
.Xr softflowctl 8 ,
.Xr tcpdump 8 ,
.Xr pcap 3 ,
.Xr bpf 4
.Bd -literal
http://www.cisco.com/univercd/cc/td/doc/product/rtrmgmt/nfc/nfc_3_0/nfc_ug/nfcform.htm