wlan —
generic
802.11 link-layer support
device wlan
The
wlan module provides generic code to support
802.11 drivers. Where a device does not directly support 802.11 functionality
this layer fills in. The
wlan module is required
by all native 802.11 drivers as well as the
ndis(4) support.
wlan supports multi-mode devices capable of
operating in both 2.4GHz and 5GHz bands and supports numerous 802.11
standards: 802.11a, 802.11b, 802.11g, 802.11n, and 802.11s (Draft 3.0). The
WPA, 802.11i, and 802.1x security protocols are supported through a
combination of in-kernel code and user-mode applications. The WME/WMM
multi-media protocols are supported entirely within the
wlan module but require a suitably capable
hardware device. Likewise the 802.11h specification is supported only by
suitably capable devices.
Drivers provide 802.11 functionality through
wlan
interfaces that are created at runtime using interface cloning. This is done
with the
ifconfig(8)
create command or using the
wlans_IFX variable in
rc.conf(5). Some drivers support the creation of
multiple
wlan interfaces that share the same
underlying device; this is the way by which ``multi-bss support'' is provided
but it can also be used to create WDS links and other interesting
applications.
There are several types of
wlan interfaces that may
be created:
- sta
- A client station in an infrastructure bss (i.e. one that
associates to an access point).
- hostap
- An access point in an infrastructure bss.
- mesh
- A mesh station in an MBSS network.
- adhoc
- A station in an IBSS network.
- ahdemo
- A station operating in ``adhoc demo mode''. This is
essentially an IBSS station that does not use management frames (e.g. no
beacons are transmitted). An ahdemo interface
is especially useful for applications that want to transmit and receive
raw 802.11 packets.
- monitor
- An interface used exclusively for capturing 802.11 frames.
In particular this specified to have read-only properties which enables it
to be operated on frequencies where one would otherwise not be
allowed.
- wds
- A station that passes 4-address 802.11 traffic for the
purpose of tunneling traffic over a wireless link. Typically this station
would share the same MAC address as a hostap
interface. It may be possible to create wds
interfaces without a companion hostap
interface but that is not guaranteed; one may need to create a
hostap interface that does not send beacon
frames before wds interfaces may be
created.
Note that an interface's type cannot be changed once it is created.
wlan defines several mechanisms by which plugin
modules may be used to extend its functionality. Cryptographic support such as
WEP, TKIP, and AES-CCMP are implemented as standalone modules (if not
statically configured into a system) that register with
wlan. Similarly there is an authenticator
framework for defining 802.11 authentication services and a framework for
integrating access control mechanisms specific to the 802.11 protocol.
If the
IEEE80211_DEBUG option is included in
the kernel configuration, debugging controls are available using:
sysctl net.wlan.X.debug=mask
where
X is the number of the
wlan instance and mask is a bit-or of control
bits that determine which debugging messages to enable. For example,
sysctl net.wlan.0.debug=0x00200000
enables debugging messages related to scanning for an access point, adhoc
neighbor, or an unoccupied channel when operation as an access point. The
wlandebug(8) tool provides a more user-friendly
mechanism for doing the same thing. Note that
sysctl net.wlan.debug=mask
defines the initial value of the debugging flags for each cloned
wlan interface; this is useful to enable debug
messages during interface creation.
The module name of
wlan was used to be compatible
with
NetBSD.
Mesh stations follow the 802.11s Draft 3.0 specification which is not ratified
and subject to change. Be aware that this specification is incompatible with
earlier drafts. Stations implementing earlier drafts (e.g., Linux) may be
incompatible.
an(4),
ath(4),
bwi(4),
bwn(4),
ipw(4),
iwi(4),
iwm(4),
iwn(4),
malo(4),
mwl(4),
netintro(4),
otus(4),
ral(4),
rsu(4),
rtwn(4),
rum(4),
run(4),
uath(4),
upgt(4),
ural(4),
urtw(4),
wi(4),
wlan_acl(4),
wlan_ccmp(4),
wlan_tkip(4),
wlan_wep(4),
wlan_xauth(4),
wpi(4),
zyd(4)
More information can be found in the IEEE 802.11 Standards.
The
wlan driver first appeared in
FreeBSD 5.0.
Atsushi Onoe is the author of original
NetBSD software
from which this work began.
Sam Leffler
brought the code into
FreeBSD and then rewrote it to
support multi-mode devices, 802.11g, 802.11n, WPA/802.11i, WME, multi-bss, and
add the extensible frameworks for cryptographic, authentication, and access
control plugins. This manual page was written by
Tom Rhodes
<
[email protected]>.