usr.sbin/hostapd/hostapd.8

.\" $OpenBSD: hostapd.8,v 1.18 2012/08/15 19:25:41 jmc Exp $
.\"
.\" Copyright (c) 2004, 2005 Reyk Floeter <reyk@openbsd.org>
.\"
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.Dd $Mdocdate: August 15 2012 $
.Dt HOSTAPD 8
.Os
.Sh NAME
.Nm hostapd
.Nd Host Access Point daemon
.Sh SYNOPSIS
.Nm hostapd
.Op Fl dv
.Op Fl D Ar macro Ns = Ns Ar value
.Op Fl f Ar file
.Sh DESCRIPTION
.Nm
is a daemon which allows communication between different 802.11
wireless access points running in
.Em Host AP
mode.
.Pp
.Nm
implements the Inter Access Point Protocol (IAPP).
Its purpose is to exchange station association updates between access
points in large wireless networks.
IAPP has been designed to speed up roaming between different access
points in the same Extended Service Set (ESS).
IAPP is described in the IEEE 802.11f standard.
.Pp
.Nm
additionally allows the monitoring and logging of station associations on a
non-hostap host which is receiving IAPP messages.
.Pp
.Nm
uses two network interfaces on startup specified in the configuration file
.Xr hostapd.conf 5 .
The first interface is used to access the Host AP,
which is a wireless interface running in Host AP mode.
Host AP mode can be enabled using
.Xr ifconfig 8 .
The second interface is used to communicate with other
.Nm
in the same broadcast domain or multicast group.
Usually a wired interface is used to communicate with other
.Nm .
.Pp
.Nm
broadcasts an
.Em ADD.notify
IAPP message when a new station is associated to the Host AP.
When
.Nm
receives an ADD.notify message it tells the Host AP
to remove the specified station.
.Pp
.Nm
may also handle dynamic roaming of IP addresses and routes in
addition to the standard IAPP ADD.notify behaviour.
See the section called
.Sx IP Roaming
in
.Xr hostapd.conf 5
for details.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl D Ar macro Ns = Ns Ar value
Define
.Ar macro
to be set to
.Ar value
on the command line.
Overrides the definition of
.Ar macro
in the configuration file.
.It Fl d
Do not daemonize and log to
.Em stderr .
.It Fl f Ar file
Use
.Ar file
as the configuration file, instead of the default
.Pa /etc/hostapd.conf .
.It Fl v
Produce more verbose output.
.El
.Sh FILES
.Bl -tag -width "/etc/hostapd.confXXX" -compact
.It Pa /etc/hostapd.conf
default
.Nm
configuration file
.El
.Sh SEE ALSO
.Xr hostapd.conf 5 ,
.Xr ifconfig 8
.Rs
.%R IEEE 802.11f
.%T Inter Access Point Protocol
.%D March 2001
.Re
.Sh HISTORY
The
.Nm
program first appeared at the 21st Chaos Communication Congress
.Pq Lk http://www.ccc.de/congress/2004/
and later in
.Ox 3.8 .
.Sh AUTHORS
The
.Nm
program was written by
.An Reyk Floeter Aq reyk@openbsd.org .
.Sh CAVEATS
.Nm
depends on drivers using the net80211
kernel wireless layer with support of Host AP mode.
For traditional reasons,
the
.Xr wi 4
driver still uses its own Host AP code in
.Fn if_wi_hostap ,
which is not supported by
.Nm .
.Pp
The IEEE 802.11 WLAN protocol lacks authentication of management
frames and is vulnerable to various Denial-of-Service and
Man-in-the-Middle attacks.
That should be considered when implementing wireless networks
with
.Nm .