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openwrt/docs/wireless.tex
Andy Boyett 91f7c80407 wireless.tex: update docs to reflect txpower move 
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2009-01-31 16:15:18 +00:00

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The WiFi settings are configured in the file \texttt{/etc/config/wireless}
(currently supported on Broadcom, Atheros and mac80211). When booting the router for the first time
it should detect your card and create a sample configuration file. By default '\texttt{option network lan}' is
commented. This prevents unsecured sharing of the network over the wireless interface.
Each wireless driver has its own configuration script in \texttt{/lib/wifi/driver\_name.sh} which handles
driver specific options and configurations. This script is also calling driver specific binaries like wlc for
Broadcom, or hostapd and wpa\_supplicant for atheros.
The reason for using such architecture, is that it abstracts the driver configuration.
\paragraph{Generic Broadcom wireless config:}
\begin{Verbatim}
config wifi-device "wl0"
option type "broadcom"
option channel "5"
config wifi-iface
option device "wl0"
# option network lan
option mode "ap"
option ssid "OpenWrt"
option hidden "0"
option encryption "none"
\end{Verbatim}
\paragraph{Generic Atheros wireless config:}
\begin{Verbatim}
config wifi-device "wifi0"
option type "atheros"
option channel "5"
option hwmode "11g"
config wifi-iface
option device "wifi0"
# option network lan
option mode "ap"
option ssid "OpenWrt"
option hidden "0"
option encryption "none"
\end{Verbatim}
\paragraph{Generic mac80211 wireless config:}
\begin{Verbatim}
config wifi-device "wifi0"
option type "mac80211"
option channel "5"
config wifi-iface
option device "wlan0"
# option network lan
option mode "ap"
option ssid "OpenWrt"
option hidden "0"
option encryption "none"
\end{Verbatim}
\paragraph{Generic multi-radio Atheros wireless config:}
\begin{Verbatim}
config wifi-device wifi0
option type atheros
option channel 1
config wifi-iface
option device wifi0
# option network lan
option mode ap
option ssid OpenWrt_private
option hidden 0
option encryption none
config wifi-device wifi1
option type atheros
option channel 11
config wifi-iface
option device wifi1
# option network lan
option mode ap
option ssid OpenWrt_public
option hidden 1
option encryption none
\end{Verbatim}
There are two types of config sections in this file. The '\texttt{wifi-device}' refers to
the physical wifi interface and '\texttt{wifi-iface}' configures a virtual interface on top
of that (if supported by the driver).
A full outline of the wireless configuration file with description of each field:
\begin{Verbatim}
config wifi-device wifi device name
option type broadcom, atheros, mac80211
option country us, uk, fr, de, etc.
option channel 1-14
option maxassoc 1-128 (broadcom only)
option distance 1-n
option hwmode 11b, 11g, 11a, 11bg (atheros, mac80211)
option rxantenna 0,1,2 (atheros, broadcom)
option txantenna 0,1,2 (atheros, broadcom)
option txpower transmission power in dBm
config wifi-iface
option network the interface you want wifi to bridge with
option device wifi0, wifi1, wifi2, wifiN
option mode ap, sta, adhoc, monitor, or wds
option txpower (deprecated) transmission power in dBm
option ssid ssid name
option bssid bssid address
option encryption none, wep, psk, psk2, wpa, wpa2
option key encryption key
option key1 key 1
option key2 key 2
option key3 key 3
option key4 key 4
option server ip address
option port port
option hidden 0,1
option isolate 0,1
\end{Verbatim}
\paragraph{Options for the \texttt{wifi-device}:}
\begin{itemize}
\item \texttt{type} \\
The driver to use for this interface.
\item \texttt{country} \\
The country code used to determine the regulatory settings.
\item \texttt{channel} \\
The wifi channel (e.g. 1-14, depending on your country setting).
\item \texttt{maxassoc} \\
Optional: Maximum number of associated clients. This feature is supported only on the broadcom chipset.
\item \texttt{distance} \\
Optional: Distance between the ap and the furthest client in meters. This feature is supported only on the atheros chipset.
\item \texttt{mode} \\
The frequency band (\texttt{b}, \texttt{g}, \texttt{bg}, \texttt{a}). This feature is only supported on the atheros chipset.
\item \texttt{diversity} \\
Optional: Enable diversity for the Wi-Fi device. This feature is supported only on the atheros chipset.
\item \texttt{rxantenna} \\
Optional: Antenna identifier (0, 1 or 2) for reception. This feature is supported by atheros and some broadcom chipsets.
\item \texttt{txantenna} \\
Optional: Antenna identifier (0, 1 or 2) for emission. This feature is supported by atheros and some broadcom chipsets.
\item \texttt{txpower}
Set the transmission power to be used. The amount is specified in dBm.
\end{itemize}
\paragraph{Options for the \texttt{wifi-iface}:}
\begin{itemize}
\item \texttt{network} \\
Selects the interface section from \texttt{/etc/config/network} to be
used with this interface
\item \texttt{device} \\
Set the wifi device name.
\item \texttt{mode} \\
Operating mode:
\begin{itemize}
\item \texttt{ap} \\
Access point mode
\item \texttt{sta} \\
Client mode
\item \texttt{adhoc} \\
Ad-Hoc mode
\item \texttt{monitor} \\
Monitor mode
\item \texttt{wds} \\
WDS point-to-point link
\end{itemize}
\item \texttt{ssid}
Set the SSID to be used on the wifi device.
\item \texttt{bssid}
Set the BSSID address to be used for wds to set the mac address of the other wds unit.
\item \texttt{txpower}
(Deprecated, set in wifi-device) Set the transmission power to be used. The amount is specified in dBm.
\item \texttt{encryption} \\
Encryption setting. Accepts the following values:
\begin{itemize}
\item \texttt{none}
\item \texttt{wep}
\item \texttt{psk}, \texttt{psk2} \\
WPA(2) Pre-shared Key
\item \texttt{wpa}, \texttt{wpa2} \\
WPA(2) RADIUS
\end{itemize}
\item \texttt{key, key1, key2, key3, key4} (wep, wpa and psk) \\
WEP key, WPA key (PSK mode) or the RADIUS shared secret (WPA RADIUS mode)
\item \texttt{server} (wpa) \\
The RADIUS server ip address
\item \texttt{port} (wpa) \\
The RADIUS server port (defaults to 1812)
\item \texttt{hidden} \\
0 broadcasts the ssid; 1 disables broadcasting of the ssid
\item \texttt{isolate} \\
Optional: Isolation is a mode usually set on hotspots that limits the clients to communicate only with the AP and not with other wireless clients.
0 disables ap isolation (default); 1 enables ap isolation.
\end{itemize}
\paragraph{Wireless Distribution System}
WDS is a non-standard mode which will be working between two Broadcom devices for instance
but not between a Broadcom and Atheros device.
\subparagraph{Unencrypted WDS connections}
This configuration example shows you how to setup unencrypted WDS connections.
We assume that the peer configured as below as the BSSID ca:fe:ba:be:00:01
and the remote WDS endpoint ca:fe:ba:be:00:02 (option bssid field).
\begin{Verbatim}
config wifi-device "wl0"
option type "broadcom"
option channel "5"
config wifi-iface
option device "wl0"
option network lan
option mode "ap"
option ssid "OpenWrt"
option hidden "0"
option encryption "none"
config wifi-iface
option device "wl0"
option network lan
option mode wds
option ssid "OpenWrt WDS"
option bssid "ca:fe:ba:be:00:02"
\end{Verbatim}
\subparagraph{Encrypted WDS connections}
It is also possible to encrypt WDS connections. \texttt{psk}, \texttt{psk2} and
\texttt{psk+psk2} modes are supported. Configuration below is an example
configuration using Pre-Shared-Keys with AES algorithm.
\begin{Verbatim}
config wifi-device wl0
option type broadcom
option channel 5
config wifi-iface
option device "wl0"
option network lan
option mode ap
option ssid "OpenWrt"
option encryption psk2
option key "<key for clients>"
config wifi-iface
option device "wl0"
option network lan
option mode wds
option bssid ca:fe:ba:be:00:02
option ssid "OpenWrt WDS"
option encryption psk2
option key "<psk for WDS>"
\end{Verbatim}
\paragraph{802.1x configurations}
OpenWrt supports both 802.1x client and Access Point
configurations. 802.1x client is only working with
Atheros or mac80211 drivers. Configuration only
supports EAP types TLS, TTLS or PEAP.
\subparagraph{EAP-TLS}
\begin{Verbatim}
config wifi-iface
option device "ath0"
option network lan
option ssid OpenWrt
option eap_type tls
option ca_cert "/etc/config/certs/ca.crt"
option priv_key "/etc/config/certs/priv.crt"
option priv_key_pwd "PKCS#12 passphrase"
\end{Verbatim}
\subparagraph{EAP-PEAP}
\begin{Verbatim}
config wifi-iface
option device "ath0"
option network lan
option ssid OpenWrt
option eap_type peap
option ca_cert "/etc/config/certs/ca.crt"
option auth MSCHAPV2
option identity username
option password password
\end{Verbatim}
\paragraph{Limitations:}
There are certain limitations when combining modes.
Only the following mode combinations are supported:
\begin{itemize}
\item \textbf{Broadcom}: \\
\begin{itemize}
\item 1x \texttt{sta}, 0-3x \texttt{ap}
\item 1-4x \texttt{ap}
\item 1x \texttt{adhoc}
\item 1x \texttt{monitor}
\end{itemize}
WDS links can only be used in pure AP mode and cannot use WEP (except when sharing the
settings with the master interface, which is done automatically).
\item \textbf{Atheros}: \\
\begin{itemize}
\item 1x \texttt{sta}, 0-Nx \texttt{ap}
\item 1-Nx \texttt{ap}
\item 1x \texttt{adhoc}
\end{itemize}
N is the maximum number of VAPs that the module allows, it defaults to 4, but can be
changed by loading the module with the maxvaps=N parameter.
\end{itemize}
\paragraph{Adding a new driver configuration}
Since we currently only support thread different wireless drivers : Broadcom, Atheros and mac80211,
you might be interested in adding support for another driver like Ralink RT2x00,
Texas Instruments ACX100/111.
The driver specific script should be placed in \texttt{/lib/wifi/<driver>.sh} and has to
include several functions providing :
\begin{itemize}
\item detection of the driver presence
\item enabling/disabling the wifi interface(s)
\item configuration reading and setting
\item third-party programs calling (nas, supplicant)
\end{itemize}
Each driver script should append the driver to a global DRIVERS variable :
\begin{Verbatim}
append DRIVERS "driver name"
\end{Verbatim}
\subparagraph{\texttt{scan\_<driver>}}
This function will parse the \texttt{/etc/config/wireless} and make sure there
are no configuration incompatibilities, like enabling hidden SSIDS with ad-hoc mode
for instance. This can be more complex if your driver supports a lof of configuration
options. It does not change the state of the interface.
Example:
\begin{Verbatim}
scan_dummy() {
local device="$1"
config_get vifs "$device" vifs
for vif in $vifs; do
# check config consistency for wifi-iface sections
done
# check mode combination
}
\end{Verbatim}
\subparagraph{\texttt{enable\_<driver>}}
This function will bring up the wifi device and optionally create application specific
configuration files, e.g. for the WPA authenticator or supplicant.
Example:
\begin{Verbatim}
enable_dummy() {
local device="$1"
config_get vifs "$device" vifs
for vif in $vifs; do
# bring up virtual interface belonging to
# the wifi-device "$device"
done
}
\end{Verbatim}
\subparagraph{\texttt{disable\_<driver>}}
This function will bring down the wifi device and all its virtual interfaces (if supported).
Example:
\begin{Verbatim}
disable_dummy() {
local device="$1"
# bring down virtual interfaces belonging to
# "$device" regardless of whether they are
# configured or not. Don't rely on the vifs
# variable at this point
}
\end{Verbatim}
\subparagraph{\texttt{detect\_<driver>}}
This function looks for interfaces that are usable with the driver. Template config sections
for new devices should be written to stdout. Must check for already existing config sections
belonging to the interfaces before creating new templates.
Example:
\begin{Verbatim}
detect_dummy() {
[ wifi-device = "$(config_get dummydev type)" ] && return 0
cat <<EOF
config wifi-device dummydev
option type dummy
# REMOVE THIS LINE TO ENABLE WIFI:
option disabled 1
config wifi-iface
option device dummydev
option mode ap
option ssid OpenWrt
EOF
}
\end{Verbatim}
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