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IEEE80211(9)	       FreeBSD Kernel Developer's Manual	  IEEE80211(9)

NAME
     IEEE80211 -- 802.11 network layer

SYNOPSIS
     #include <net80211/ieee80211_var.h>

     void
     ieee80211_ifattach(struct ieee80211com *ic,
	 const uint8_t macaddr[IEEE80211_ADDR_LEN]);

     void
     ieee80211_ifdetach(struct ieee80211com *ic);

DESCRIPTION
     IEEE 802.11 device	drivers	are written to use the infrastructure provided
     by	the IEEE80211 software layer.  This software provides a	support	frame-
     work for drivers that includes ifnet cloning, state management, and a
     user management API by which applications interact	with 802.11 devices.
     Most drivers depend on the	IEEE80211 layer	for protocol services but
     devices that off-load functionality may bypass the	layer to connect
     directly to the device (e.g. the ndis(4) emulation	support	does this).

     A IEEE80211 device	driver implements a virtual radio API that is exported
     to	users through network interfaces (aka vaps) that are cloned from the
     underlying	device.	 These interfaces have an operating mode (station,
     adhoc, hostap, wds, monitor, etc.)	 that is fixed for the lifetime	of the
     interface.	 Devices that can support multiple concurrent interfaces allow
     multiple vaps to be cloned.  This enables construction of interesting
     applications such as an AP	vap and	one or more WDS	vaps or	multiple AP
     vaps, each	with a different security model.  The IEEE80211	layer virtual-
     izes most 802.11 state and	coordinates vap	state changes including	sched-
     uling multiple vaps.  State that is not virtualized includes the current
     channel and WME/WMM parameters.  Protocol processing is typically handled
     entirely in the IEEE80211 layer with drivers responsible purely for mov-
     ing data between the host and device.  Similarly, IEEE80211 handles most
     ioctl(2) requests without entering	the driver; instead drivers are	noti-
     fied of state changes that	require	their involvement.

     The virtual radio interface defined by the	IEEE80211 layer	means that
     drivers must be structured	to follow specific rules.  Drivers that	sup-
     port only a single	interface at any time must still follow	these rules.

DATA STRUCTURES
     The virtual radio architecture splits state between a single per-device
     ieee80211com structure and	one or more ieee80211vap structures.  Drivers
     are expected to setup various shared state	in these structures at device
     attach and	during vap creation but	otherwise should treat them as read-
     only.  The	ieee80211com structure is allocated by the IEEE80211 layer as
     adjunct data to a device's	ifnet; it is accessed through the if_l2com
     structure member.	The ieee80211vap structure is allocated	by the driver
     in	the ``vap create'' method and should be	extended with any driver-pri-
     vate state.  This technique of giving the driver control to allocate data
     structures	is used	for other IEEE80211 data structures and	should be
     exploited to maintain driver-private state	together with public IEEE80211
     state.

     The other main data structures are	the station, or	node, table that
     tracks peers in the local BSS, and	the channel table that defines the
     current set of available radio channels.  Both tables are bound to	the
     ieee80211com structure and	shared by all vaps.  Long-lasting references
     to	a node are counted to guard against premature reclamation.  In partic-
     ular every	packet sent/received holds a node reference (either explicitly
     for transmit or implicitly	on receive).

     The ieee80211com and ieee80211vap structures also hold a collection of
     method pointers that drivers fill-in and/or override to take control of
     certain operations.  These	methods	are the	primary	way drivers are	bound
     to	the IEEE80211 layer and	are described below.

DRIVER ATTACH/DETACH
     Drivers attach to the IEEE80211 layer with	the ieee80211_ifattach() func-
     tion.  The	driver is expected to allocate and setup any device-private
     data structures before passing control.  The ieee80211com structure must
     be	pre-initialized	with state required to setup the IEEE80211 layer:

     ic_ifp	  Backpointer to the physical device's ifnet.

     ic_caps	  Device/driver	capabilities; see below	for a complete
		  description.

     ic_channels  Table	of channels the	device is capable of operating on.
		  This is initially provided by	the driver but may be changed
		  through calls	that change the	regulatory state.

     ic_nchan	  Number of entries in ic_channels.

     On	return from ieee80211_ifattach() the driver is expected	to override
     default callback functions	in the ieee80211com structure to register it's
     private routines.	Methods	marked with a ``*'' must be provided by	the
     driver.

     ic_vap_create*
		  Create a vap instance	of the specified type (operating
		  mode).  Any fixed BSSID and/or MAC address is	provided.
		  Drivers that support multi-bssid operation may honor the
		  requested BSSID or assign their own.

     ic_vap_delete*
		  Destroy a vap	instance created with ic_vap_create.

     ic_getradiocaps
		  Return the list of calibrated	channels for the radio.	 The
		  default method returns the current list of channels (space
		  permitting).

     ic_setregdomain
		  Process a request to change regulatory state.	 The routine
		  may reject a request or constrain changes (e.g. reduce
		  transmit power caps).	 The default method accepts all	pro-
		  posed	changes.

     ic_send_mgmt
		  Send an 802.11 management frame.  The	default	method fabri-
		  cates	the frame using	IEEE80211 state	and passes it to the
		  driver through the ic_raw_xmit method.

     ic_raw_xmit  Transmit a raw 802.11	frame.	The default method drops the
		  frame	and generates a	message	on the console.

     ic_updateslot
		  Update hardware state	after an 802.11	IFS slot time change.
		  There	is no default method; the pointer may be NULL in which
		  case it will not be used.

     ic_update_mcast
		  Update hardware for a	change in the multicast	packet filter.
		  The default method prints a console message.

     ic_update_promisc
		  Update hardware for a	change in the promiscuous mode set-
		  ting.	 The default method prints a console message.

     ic_newassoc  Update driver/device state for association to	a new AP (in
		  station mode)	or when	a new station associates (e.g. in AP
		  mode).  There	is no default method; the pointer may be NULL
		  in which case	it will	not be used.

     ic_node_alloc
		  Allocate and initialize a ieee80211_node structure.  This
		  method cannot	sleep.	The default method allocates zero'd
		  memory using malloc(9).  Drivers should override this	method
		  to allocate extended storage for their own needs.  Memory
		  allocated by the driver must be tagged with M_80211_NODE to
		  balance the memory allocation	statistics.

     ic_node_free
		  Reclaim storage of a node allocated by ic_node_alloc.	 Driv-
		  ers are expected to interpose	their own method to cleanup
		  private state	but must call through this method to allow
		  IEEE80211 to reclaim it's private state.

     ic_node_cleanup
		  Cleanup state	in a ieee80211_node created by ic_node_alloc.
		  This operation is distinguished from ic_node_free in that it
		  may be called	long before the	node is	actually reclaimed to
		  cleanup adjunct state.  This can happen, for example,	when a
		  node must not	be reclaimed due to references held by packets
		  in the transmit queue.  Drivers typically interpose
		  ic_node_cleanup instead of ic_node_free.

     ic_node_age  Age, and potentially reclaim,	resources associated with a
		  node.	 The default method ages frames	on the power-save
		  queue	(in AP mode) and pending frames	in the receive reorder
		  queues (for stations using A-MPDU).

     ic_node_drain
		  Reclaim all optional resources associated with a node.  This
		  call is used to free up resources when they are in short
		  supply.

     ic_node_getrssi
		  Return the Receive Signal Strength Indication	(RSSI) in .5
		  dBm units for	the specified node.  This interface returns a
		  subset of the	information returned by	ic_node_getsignal.
		  The default method calculates	a filtered average over	the
		  last ten samples passed in to	ieee80211_input(9) or
		  ieee80211_input_all(9).

     ic_node_getsignal
		  Return the RSSI and noise floor (in .5 dBm units) for	a sta-
		  tion.	 The default method calculates RSSI as described
		  above; the noise floor returned is the last value supplied
		  to ieee80211_input(9)	or ieee80211_input_all(9).

     ic_node_getmimoinfo
		  Return MIMO radio state for a	station	in support of the
		  IEEE80211_IOC_STA_INFO ioctl request.	 The default method
		  returns nothing.

     ic_scan_start*
		  Prepare driver/hardware state	for scanning.  This callback
		  is done in a sleepable context.

     ic_scan_end*
		  Restore driver/hardware state	after scanning completes.
		  This callback	is done	in a sleepable context.

     ic_set_channel*
		  Set the current radio	channel	using ic_curchan.  This	call-
		  back is done in a sleepable context.

     ic_scan_curchan
		  Start	scanning on a channel.	This method is called immedi-
		  ately	after each channel change and must initiate the	work
		  to scan a channel and	schedule a timer to advance to the
		  next channel in the scan list.  This callback	is done	in a
		  sleepable context.  The default method handles active	scan
		  work (e.g. sending ProbeRequest frames), and schedules a
		  call to ieee80211_scan_next(9) according to the maximum
		  dwell	time for the channel.  Drivers that off-load scan work
		  to firmware typically	use this method	to trigger per-channel
		  scan activity.

     ic_scan_mindwell
		  Handle reaching the minimum dwell time on a channel when
		  scanning.  This event	is triggered when one or more stations
		  have been found on a channel and the minimum dwell time has
		  been reached.	 This callback is done in a sleepable context.
		  The default method signals the scan machinery	to advance to
		  the next channel as soon as possible.	 Drivers can use this
		  method to preempt further work (e.g. if scanning is handled
		  by firmware) or ignore the request to	force maximum dwell
		  time on a channel.

     ic_recv_action
		  Process a received Action frame.  The	default	method points
		  to ieee80211_recv_action(9) which provides a mechanism for
		  setting up handlers for each Action frame class.

     ic_send_action
		  Transmit an Action frame.  The default method	points to
		  ieee80211_send_action(9) which provides a mechanism for set-
		  ting up handlers for each Action frame class.

     ic_ampdu_enable
		  Check	if transmit A-MPDU should be enabled for the specified
		  station and AC.  The default method checks a per-AC traffic
		  rate against a per-vap threshold to decide if	A-MPDU should
		  be enabled.  This method also	rate-limits ADDBA requests so
		  that requests	are not	made too frequently when a receiver
		  has limited resources.

     ic_addba_request
		  Request A-MPDU transmit aggregation.	The default method
		  sets up local	state and issues an ADDBA Request Action
		  frame.  Drivers may interpose	this method if they need to
		  setup	private	state for handling transmit A-MPDU.

     ic_addb_response
		  Process a received ADDBA Response Action frame and setup
		  resources as needed for doing	transmit A-MPDU.

     ic_addb_stop
		  Shutdown an A-MPDU transmit stream for the specified station
		  and AC.  The default method reclaims local state after send-
		  ing a	DelBA Action frame.

     ic_bar_response
		  Process a response to	a transmitted BAR control frame.

     ic_ampdu_rx_start
		  Prepare to receive A-MPDU data from the specified station
		  for the TID.

     ic_ampdu_rx_stop
		  Terminate receipt of A-MPDU data from	the specified station
		  for the TID.

     Once the IEEE80211	layer is attached to a driver there are	two more steps
     typically done to complete	the work:

     1.	  Setup	``radiotap support'' for capturing raw 802.11 packets that
	  pass through the device.  This is done with a	call to
	  ieee80211_radiotap_attach(9).

     2.	  Do any final device setup like enabling interrupts.

     State is torn down	and reclaimed with a call to ieee80211_ifdetach().
     Note this call may	result in multiple callbacks into the driver so	it
     should be done before any critical	driver state is	reclaimed.  On return
     from ieee80211_ifdetach() all associated vaps and ifnet structures	are
     reclaimed or inaccessible to user applications so it is safe to teardown
     driver state without worry	about being re-entered.	 The driver is respon-
     sible for calling if_free(9) on the ifnet it allocated for	the physical
     device.

DRIVER CAPABILITIES
     Driver/device capabilities	are specified using several sets of flags in
     the ieee80211com structure.  General capabilities are specified by
     ic_caps.  Hardware	cryptographic capabilities are specified by
     ic_cryptocaps.  802.11n capabilities, if any, are specified by ic_htcaps.
     The IEEE80211 layer propagates a subset of	these capabilities to each vap
     through the equivalent fields: iv_caps, iv_cryptocaps, and	iv_htcaps.
     The following general capabilities	are defined:

     IEEE80211_C_STA	    Device is capable of operating in station (aka In-
			    frastructure) mode.

     IEEE80211_C_8023ENCAP  Device requires 802.3-encapsulated frames be
			    passed for transmit.  By default IEEE80211 will
			    encapsulate	all outbound frames as 802.11 frames
			    (without a PLCP header).

     IEEE80211_C_FF	    Device supports Atheros Fast-Frames.

     IEEE80211_C_TURBOP	    Device supports Atheros Dynamic Turbo mode.

     IEEE80211_C_IBSS	    Device is capable of operating in adhoc/IBSS mode.

     IEEE80211_C_PMGT	    Device supports dynamic power-management (aka
			    power save)	in station mode.

     IEEE80211_C_HOSTAP	    Device is capable of operating as an Access	Point
			    in Infrastructure mode.

     IEEE80211_C_AHDEMO	    Device is capable of operating in Adhoc Demo mode.
			    In this mode the device is used purely to
			    send/receive raw 802.11 frames.

     IEEE80211_C_SWRETRY    Device supports software retry of transmitted
			    frames.

     IEEE80211_C_TXPMGT	    Device support dynamic transmit power changes on
			    transmitted	frames;	also known as Transmit Power
			    Control (TPC).

     IEEE80211_C_SHSLOT	    Device supports short slot time operation (for
			    802.11g).

     IEEE80211_C_SHPREAMBLE
			    Device supports short preamble operation (for
			    802.11g).

     IEEE80211_C_MONITOR    Device is capable of operating in monitor mode.

     IEEE80211_C_DFS	    Device supports radar detection and/or DFS.	 DFS
			    protocol support can be handled by IEEE80211 but
			    the	device must be capable of detecting radar
			    events.

     IEEE80211_C_MBSS	    Device is capable of operating in MeshBSS (MBSS)
			    mode (as defined by	802.11s	Draft 3.0).

     IEEE80211_C_WPA1	    Device supports WPA1 operation.

     IEEE80211_C_WPA2	    Device supports WPA2/802.11i operation.

     IEEE80211_C_BURST	    Device supports frame bursting.

     IEEE80211_C_WME	    Device supports WME/WMM operation (at the moment
			    this is mostly support for sending and receiving
			    QoS	frames with EDCF).

     IEEE80211_C_WDS	    Device supports transmit/receive of	4-address
			    frames.

     IEEE80211_C_BGSCAN	    Device supports background scanning.

     IEEE80211_C_TXFRAG	    Device supports transmit of	fragmented 802.11
			    frames.

     IEEE80211_C_TDMA	    Device is capable of operating in TDMA mode.

     The follow	general	crypto capabilities are	defined.  In general IEEE80211
     will fall-back to software	support	when a device is not capable of	hard-
     ware acceleration of a cipher.  This can be done on a per-key basis.
     IEEE80211 can also	handle software	Michael	calculation combined with
     hardware AES acceleration.

     IEEE80211_CRYPTO_WEP   Device supports hardware WEP cipher.

     IEEE80211_CRYPTO_TKIP  Device supports hardware TKIP cipher.

     IEEE80211_CRYPTO_AES_OCB
			    Device supports hardware AES-OCB cipher.

     IEEE80211_CRYPTO_AES_CCM
			    Device supports hardware AES-CCM cipher.

     IEEE80211_CRYPTO_TKIPMIC
			    Device supports hardware Michael for use with
			    TKIP.

     IEEE80211_CRYPTO_CKIP  Devices supports hardware CKIP cipher.

     The follow	general	802.11n	capabilities are defined.  The first capabili-
     ties are defined exactly as they appear in	the 802.11n specification.
     Capabilities beginning with IEEE80211_HTC_AMPDU are used solely by	the
     IEEE80211 layer.

     IEEE80211_HTCAP_CHWIDTH40
			    Device supports 20/40 channel width	operation.

     IEEE80211_HTCAP_SMPS_DYNAMIC
			    Device supports dynamic SM power save operation.

     IEEE80211_HTCAP_SMPS_ENA
			    Device supports static SM power save operation.

     IEEE80211_HTCAP_GREENFIELD
			    Device supports Greenfield preamble.

     IEEE80211_HTCAP_SHORTGI20
			    Device supports Short Guard	Interval on 20MHz
			    channels.

     IEEE80211_HTCAP_SHORTGI40
			    Device supports Short Guard	Interval on 40MHz
			    channels.

     IEEE80211_HTCAP_TXSTBC
			    Device supports Space Time Block Convolution
			    (STBC) for transmit.

     IEEE80211_HTCAP_RXSTBC_1STREAM
			    Device supports 1 spatial stream for STBC receive.

     IEEE80211_HTCAP_RXSTBC_2STREAM
			    Device supports 1-2	spatial	streams	for STBC
			    receive.

     IEEE80211_HTCAP_RXSTBC_3STREAM
			    Device supports 1-3	spatial	streams	for STBC
			    receive.

     IEEE80211_HTCAP_MAXAMSDU_7935
			    Device supports A-MSDU frames up to	7935 octets.

     IEEE80211_HTCAP_MAXAMSDU_3839
			    Device supports A-MSDU frames up to	3839 octets.

     IEEE80211_HTCAP_DSSSCCK40
			    Device supports use	of DSSS/CCK on 40MHz channels.

     IEEE80211_HTCAP_PSMP   Device supports PSMP.

     IEEE80211_HTCAP_40INTOLERANT
			    Device is intolerant of 40MHz wide channel use.

     IEEE80211_HTCAP_LSIGTXOPPROT
			    Device supports L-SIG TXOP protection.

     IEEE80211_HTC_AMPDU    Device supports A-MPDU aggregation.	 Note that any
			    802.11n compliant device must support A-MPDU
			    receive so this implicitly means support for
			    transmit of	A-MPDU frames.

     IEEE80211_HTC_AMSDU    Device supports A-MSDU aggregation.	 Note that any
			    802.11n compliant device must support A-MSDU
			    receive so this implicitly means support for
			    transmit of	A-MSDU frames.

     IEEE80211_HTC_HT	    Device supports High Throughput (HT) operation.
			    This capability must be set	to enable 802.11n
			    functionality in IEEE80211.

     IEEE80211_HTC_SMPS	    Device supports MIMO Power Save operation.

     IEEE80211_HTC_RIFS	    Device supports Reduced Inter Frame	Spacing
			    (RIFS).

SEE ALSO
     ioctl(2), ndis(4),	ieee80211_amrr(9), ieee80211_beacon(9),
     ieee80211_bmiss(9), ieee80211_crypto(9), ieee80211_ddb(9),
     ieee80211_input(9), ieee80211_node(9), ieee80211_output(9),
     ieee80211_proto(9), ieee80211_radiotap(9),	ieee80211_regdomain(9),
     ieee80211_scan(9),	ieee80211_vap(9), ifnet(9), malloc(9)

FreeBSD	10.1			April 28, 2010			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | DATA STRUCTURES | DRIVER ATTACH/DETACH | DRIVER CAPABILITIES | SEE ALSO

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