[darkstat] / darkstat.8

.\"
.\" darkstat 3
.\" Copyright 2001-2009, Emil Mikulic.
.\"
.\" You may use, modify and redistribute this file under the terms of the
.\" GNU General Public License version 2. (see COPYING.GPL)
.\"
.TH darkstat 8 "September 2008" "darkstat 3"
.SH NAME
darkstat \- network statistics gatherer
.\"
.SH SYNOPSIS
.B darkstat
[
.BI \-i " interface"
] [
.BI \-r " file"
] [
.BI \-\-pppoe
] [
.BI \-\-verbose
] [
.BI \-\-no\-daemon
] [
.BI \-\-no\-promisc
] [
.BI \-\-no\-dns
] [
.BI \-\-no\-macs
] [
.BI \-p " port"
] [
.BI \-b " bindaddr"
] [
.BI \-f " filter"
] [
.BI \-l " network/netmask"
] [
.BI \-\-chroot " dir"
] [
.BI \-\-user " username"
] [
.BI \-\-daylog " filename"
] [
.BI \-\-import " filename"
] [
.BI \-\-export " filename"
] [
.BI \-\-pidfile " filename"
] [
.BI \-\-hosts\-max " count"
] [
.BI \-\-hosts\-keep " count"
] [
.BI \-\-ports\-max " count"
] [
.BI \-\-ports\-keep " count"
] [
.BI \-\-highest\-port " port"
] [
.BI \-\-hexdump
]
.\"
.SH DESCRIPTION
.I darkstat
is a packet sniffer that runs as a background process on
a cable/DSL router, gathers all sorts of statistics about network usage,
and serves them over HTTP.

All settings are passed on the commandline.
.\"
.SH OPTIONS
.\"
.TP
.BI \-i " interface"
Capture traffic on the specified network interface.
This is the only mandatory commandline argument.
.\"
.TP
.BI \-r " file"
Instead of capturing live traffic, read it from a
.BR pcap (3)
capture file.
This is only useful for development and benchmarking.
The
.BI \-r
and
.BI \-i
arguments are mutually exclusive.
.\"
.TP
.BI \-\-pppoe
Don't use this.
.RS

Instead, capture on the tunnel interface that your PPPoE software
provides, for example \fBtun0\fR on \fIFreeBSD\fR, \fBpppoe0\fR on
\fIOpenBSD\fR or \fINetBSD\fR.

If you really must, you can capture on an Ethernet interface and pass
this argument to have \fIdarkstat\fR decode PPPoE frames and ignore
everything else.
Make sure you also specify your local address with the \fB\-l\fR
argument.
.RE
.\"
.TP
.BI \-\-verbose
Print debugging messages to the terminal.
.\"
.TP
.BI \-\-no\-daemon
Do not detach from the controlling terminal;
stay in the foreground.
.\"
.TP
.BI \-\-no\-promisc
Do not use promiscuous mode to capture.
Note that an interface may already be in promiscuous mode.
If this is a problem, use an appropriate
.BR bpf (4)
filter.
.\"
.TP
.BI \-\-no\-dns
Do not resolve IPs to host names.
This can significantly reduce memory footprint on small systems
as an extra process is created for DNS resolving.
.\"
.TP
.BI \-\-no\-macs
Do not display MAC addresses in hosts table.
.\"
.TP
.BI \-p " port"
Bind the web interface to the specified port.
The default is 667.
.\"
.TP
.BI \-b " bindaddr"
Bind the web interface to the specified address.
The default is to listen on all interfaces.
.\"
.TP
.BI \-f " filter"
Use the specified filter expression when capturing traffic.
The filter syntax is beyond the scope of this manual page;
please refer to the
.BR tcpdump (1)
documentation.
.\"
.TP
.BI \-l " network/netmask"
Define a "local network" according to the network and netmask addresses.
All traffic entering or leaving this network will be graphed, as opposed
to the default behaviour of only graphing traffic to and from the local
host.
.RS

The rule is that if \fBip_addr & netmask == network\fR,
then that address is considered local.
See the usage example below.
.RE
.\"
.TP
.BI \-\-chroot " dir"
Force \fIdarkstat\fR to \fBchroot()\fR into the specified directory.
Without this argument, a default directory will be used, which is
determined at build time.
Usually \fI/var/empty\fR or \fI/var/lib/empty\fR.
.RS

For security reasons, this directory should be empty, and the user that
\fIdarkstat\fR is running as should not have write access to it.

However, if you wish to use \fB\-\-daylog\fR or \fB\-\-export\fR,
\fIdarkstat\fR will need write access to the chroot.
If you are uncomfortable with the security implications, don't
use any functionality that requires write access.
.RE
.\"
.TP
.BI \-\-user " username"
Force \fIdarkstat\fR to drop privileges to the \fBuid\fR and \fBgid\fR of
the specified user.
Without this argument, a default value will be used, which is set at
build time.
Usually \fBnobody\fR.
.RS

For security reasons, this should not be \fBroot\fR.
.RE
.\"
.TP
.BI \-\-daylog " filename"
.RS
Log daily traffic statistics into the named file, relative to the
chroot directory.
If you wish to use \fB\-\-daylog\fR, you must first specify a
\fB\-\-chroot\fR directory, and it must be writeable by the
\fIdarkstat\fR user.
A writeable chroot has security implications; if you are uncomfortable
with this, do not use the \fB\-\-daylog\fR functionality.

If the daylog argument is not specified, no logging is performed.

The daylog format is:

localtime|time_t|bytes_in|bytes_out|pkts_in|pkts_outs

Lines starting with a # are comments stating when logging started and
stopped.
.RE
.\"
.TP
.BI \-\-import " filename"
Upon starting, import a \fIdarkstat\fR database from the named file,
relative to the chroot directory.
If you wish to use \fB\-\-import\fR, you must first specify a
\fB\-\-chroot\fR directory.
If the import is unsuccessful, \fIdarkstat\fR will start with an empty
database.
.\"
.TP
.BI \-\-export " filename"
On shutdown, and upon receiving SIGUSR1, export the in-memory database
to the named file, relative to the chroot directory.
If you wish to use \fB\-\-export\fR, you must first specify a
\fB\-\-chroot\fR directory, and it must be writeable by the
\fIdarkstat\fR user.
A writeable chroot has security implications - if you are uncomfortable
with this, do not use the \fB\-\-export\fR functionality.
.\"
.TP
.BI \-\-pidfile " filename"
.RS
Creates a file containing the process ID of \fIdarkstat\fR.
This file will be unlinked upon clean shutdown.
As with all pidfiles, if \fIdarkstat\fR dies uncleanly, a stale pidfile
can be left over.

For example, start \fIdarkstat\fR with:
.IP
darkstat \-i fxp0 \-\-chroot /var/run/darkstat \-\-pidfile darkstat.pid
.PP
And stop with:
.IP
kill `cat /var/run/darkstat/darkstat.pid`
.PP
By default,
.BR kill (1)
will send SIGTERM, which will cause \fIdarkstat\fR to shut down cleanly.
.RE
.\"
.TP
.BI \-\-hosts\-max " count"
The maximum number of hosts that will be kept in the hosts table.
This is used to limit how much accounting data will be kept in memory.
The number of
.BI \-\-hosts\-max
must be greater than
.BI \-\-hosts\-keep
.\"
.TP
.BI \-\-hosts\-keep " count"
When the hosts table hits
.BI \-\-hosts\-max
and traffic is seen from a new host, we clean out the hosts table,
keeping only the top
.BI \-\-hosts\-keep
number of hosts, sorted by total traffic.
.\"
.TP
.BI \-\-ports\-max " count"
The maximum number of ports that will be tracked for each host.
This is used to limit how much accounting data will be kept in memory.
The number of
.BI \-\-ports\-max
must be greater than
.BI \-\-ports\-keep
.\"
.TP
.BI \-\-ports\-keep " count"
When a ports table fills up, this many ports are kept and the rest are
discarded.
.\"
.TP
.BI \-\-highest\-port " port"
Ports that are numerically higher than this will not appear in the
per-host ports tables, although their traffic will still be accounted
for.
This can be used to hide ephemeral ports.
By default, all ports are tracked.
.\"
.TP
.BI \-\-hexdump
Show hex dumps of received traffic.
This is only for debugging, and implies \-\-verbose and \-\-no\-daemon.
.\"
.\" --------------------------------------------------------------------
.SH USAGE EXAMPLES
To gather statistics on the
.I fxp0
interface:
.IP
darkstat \-i fxp0
.PP
.\"
We want to account for traffic on the Internet-facing interface,
but only serve web pages to our private local network where we have the
IP address 192.168.0.1:
.IP
darkstat \-i fxp0 \-b 192.168.0.1
.PP
.\"
We want to serve web pages on the standard HTTP port:
.IP
darkstat \-i fxp0 \-p 80
.PP
.\"
We are on Optus (cable) and don't want to account for the constant ARP
traffic we are receiving:
.IP
darkstat \-i fxp0 \-f "not arp"
.PP
.\"
We only want to account for SSH traffic:
.IP
darkstat \-i fxp0 \-f "port 22"
.PP
.\"
We don't want to account for network internal traffic:
.IP
darkstat \-i fxp0 \-f "not (src net 192.168.0 and dst net 192.168.0)"
.PP
.\"
(For a full reference on filter syntax, refer to the
.BR tcpdump (1)
manpage)
.PP
.\"
We have a network consisting of a gateway server (192.168.1.1) and a few
workstations (192.168.1.2, 192.168.1.3, etc.) and we want to graph all
traffic entering and leaving the local network, not just the gateway
server (which is running \fIdarkstat\fR):
.IP
darkstat \-i fxp0 \-l 192.168.1.0/255.255.255.0
.PP
.\"
We want to specify the local IP of the gateway manually because it
cannot be automatically detected, e.g. \fB\-\-pppoe\fR is in use.
Note the /32 netmask:
.IP
darkstat \-i fxp0 \-\-pppoe \-l 192.168.1.1/255.255.255.255
.\"
.SH SIGNALS
To shut
.I darkstat
down cleanly, send a SIGTERM or SIGINT signal to the
.I darkstat
parent process.
.PP
Sending the SIGUSR1 signal will cause \fIdarkstat\fR to empty out its
in-memory database.
If an \fB\-\-export\fR file was set, it will first save the database to
file.
.PP
.\"
.SH FREQUENTLY ASKED QUESTIONS
.SS How many bytes does each bar on the graph represent?
Hover your mouse cursor over a bar and you should get a tooltip
saying exactly how many bytes in and out the bar represents.
.\"
.SS Why aren't there labels / tics / a scale on the graphs?
Because implementing them is hard.
And doing so \fIcorrectly\fR, and in a way that works across all
browsers, looks pretty much impossible.

I might attempt it some day.
In the meantime, patches would be gladly accepted.
.\"
.SS Why are the graphs blank?  All the bars are zero.
The graphs only show traffic in/out of the local host, which is
determined by getting the IP address of the interface you're sniffing
on.

You can use the \fB\-l\fR argument to override the local address for
accounting purposes.
You can also use it to do accounting for a whole subnet by specifying
an appropriate netmask.
.\"
.SH SEE ALSO
.BR tcpdump (1)
.\"
.SH HISTORY
.I darkstat
was written in 2001, largely as a result of a certain Australian
cable Internet provider introducing a 3GB monthly traffic limit.
.\"
.SH AUTHORS
Emil Mikulic and others. (see the AUTHORS and THANKS files)
.\"
.SH WEBSITE
http://dmr.ath.cx/net/darkstat/