[802.11] Add support for 802.11 devices with software MAC layer

This is required for all modern 802.11 devices, and allows drivers
to be written for them with minimally more effort than is required
for a wired NIC.

Signed-off-by: Michael Brown <mcb30@etherboot.org>
Modified-by: Michael Brown <mcb30@etherboot.org>

src/Makefile

@@ -55,7 +55,7 @@ SRCDIRS		:=
 SRCDIRS		+= libgcc
 SRCDIRS		+= core
 SRCDIRS		+= proto
-SRCDIRS		+= net net/tcp net/udp net/infiniband
+SRCDIRS		+= net net/tcp net/udp net/infiniband net/80211
 SRCDIRS		+= image
 SRCDIRS		+= drivers/bus
 SRCDIRS		+= drivers/net

src/include/gpxe/errfile.h

@@ -148,6 +148,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define ERRFILE_ib_pathrec		( ERRFILE_NET | 0x001c0000 )
 #define ERRFILE_ib_mcast		( ERRFILE_NET | 0x001d0000 )
 #define ERRFILE_ib_cm			( ERRFILE_NET | 0x001e0000 )
+#define ERRFILE_net80211		( ERRFILE_NET | 0x001f0000 )
 
 #define ERRFILE_image		      ( ERRFILE_IMAGE | 0x00000000 )
 #define ERRFILE_elf		      ( ERRFILE_IMAGE | 0x00010000 )

src/include/gpxe/net80211.h

@@ -0,0 +1,983 @@
+#ifndef _GPXE_NET80211_H
+#define _GPXE_NET80211_H
+
+#include <gpxe/process.h>
+#include <gpxe/ieee80211.h>
+#include <gpxe/iobuf.h>
+#include <gpxe/netdevice.h>
+#include <gpxe/rc80211.h>
+
+/** @file
+ *
+ * The gPXE 802.11 MAC layer.
+ */
+
+/*
+ * Major things NOT YET supported:
+ * - any type of security
+ * - 802.11n
+ *
+ * Major things that probably will NEVER be supported, barring a
+ * compelling use case and/or corporate sponsorship:
+ * - QoS
+ * - 802.1X authentication ("WPA Enterprise")
+ * - Contention-free periods
+ * - "ad-hoc" networks (IBSS), monitor mode, host AP mode
+ * - hidden networks on the 5GHz band due to regulatory issues
+ * - spectrum management on the 5GHz band (TPC and DFS), as required
+ *   in some non-US regulatory domains
+ * - Clause 14 PHYs (Frequency-Hopping Spread Spectrum on 2.4GHz)
+ *   and Clause 16 PHYs (infrared) - I'm not aware of any real-world
+ *   use of these.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/* All 802.11 devices are handled using a generic "802.11 device"
+   net_device, with a link in its `priv' field to a net80211_device
+   which we use to handle 802.11-specific details. */
+
+
+/** @defgroup net80211_band RF bands on which an 802.11 device can transmit */
+/** @{ */
+
+/** The 2.4 GHz ISM band, unlicensed in most countries */
+#define NET80211_BAND_2GHZ	(1 << 0)
+/** The band from 4.9 GHz to 5.7 GHz, which tends to be more restricted */
+#define NET80211_BAND_5GHZ	(1 << 1)
+
+/** @} */
+
+
+/** @defgroup net80211_mode 802.11 operation modes supported by hardware */
+/** @{ */
+
+/** 802.11a: 54 Mbps operation using OFDM signaling on the 5GHz band */
+#define NET80211_MODE_A		(1 << 0)
+
+/** 802.11b: 1-11 Mbps operation using DSSS/CCK signaling on the 2.4GHz band */
+#define NET80211_MODE_B		(1 << 1)
+
+/** 802.11g: 54 Mbps operation using ERP/OFDM signaling on the 2.4GHz band */
+#define NET80211_MODE_G		(1 << 2)
+
+/** 802.11n: High-rate operation using MIMO technology on 2.4GHz or 5GHz */
+#define NET80211_MODE_N		(1 << 3)
+
+/** @} */
+
+
+/** @defgroup net80211_cfg Constants for the net80211 config callback */
+/** @{ */
+
+/** Channel choice (@c dev->channel) or regulatory parameters have changed */
+#define NET80211_CFG_CHANNEL	(1 << 0)
+
+/** Requested transmission rate (@c dev->rate) has changed */
+#define NET80211_CFG_RATE	(1 << 1)
+
+/** Association has been established with a new BSS (@c dev->bssid) */
+#define NET80211_CFG_ASSOC	(1 << 2)
+
+/** Low-level link parameters (short preamble, protection, etc) have changed */
+#define NET80211_CFG_PHY_PARAMS	(1 << 3)
+
+/** @} */
+
+
+/** An 802.11 security handshaking protocol */
+enum net80211_security_proto {
+	/** No security handshaking
+	 *
+	 * This might be used with an open network or with WEP, as
+	 * WEP does not have a cryptographic handshaking phase.
+	 */
+	NET80211_SECPROT_NONE = 0,
+
+	/** Pre-shared key handshaking
+	 *
+	 * This implements the "WPA Personal" handshake. 802.1X
+	 * authentication is not performed -- the user supplies a
+	 * pre-shared key directly -- but there is a 4-way handshake
+	 * between client and AP to verify that both have the same key
+	 * without revealing the contents of that key.
+	 */
+	NET80211_SECPROT_PSK = 1,
+
+	/** Full EAP 802.1X handshaking
+	 *
+	 * This implements the "WPA Enterprise" handshake, connecting
+	 * to an 802.1X authentication server to provide credentials
+	 * and receive a pairwise master key (PMK), which is then used
+	 * in the same 4-way handshake as the PSK method.
+	 */
+	NET80211_SECPROT_EAP = 2,
+};
+
+
+/** An 802.11 data encryption algorithm */
+enum net80211_crypto_alg {
+	/** No security, an "Open" network */
+	NET80211_CRYPT_NONE = 0,
+
+	/** Network protected with WEP (awful RC4-based system)
+	 *
+	 * WEP uses a naive application of RC4, with a monotonically
+	 * increasing initialization vector that is prepended to the
+	 * key to initialize the RC4 keystream. It is highly insecure
+	 * and can be completely cracked or subverted using automated,
+	 * robust, freely available tools (aircrack-ng) in minutes.
+	 *
+	 * 40-bit and 104-bit WEP are differentiated only by the size
+	 * of the key. They may be advertised as 64-bit and 128-bit,
+	 * counting the non-random IV as part of the key bits.
+	 */
+	NET80211_CRYPT_WEP = 1,
+
+	/** Network protected with TKIP (better RC4-based system)
+	 *
+	 * Usually known by its trade name of WPA (Wi-Fi Protected
+	 * Access), TKIP implements a message integrity code (MIC)
+	 * called Michael, a timestamp counter for replay prevention,
+	 * and a key mixing function that together remove almost all
+	 * the security problems with WEP. Countermeasures are
+	 * implemented to prevent high data-rate attacks.
+	 *
+	 * There exists one known attack on TKIP, that allows one to
+	 * send between 7 and 15 arbitrary short data packets on a
+	 * QoS-enabled network given about an hour of data
+	 * gathering. Since gPXE does not support QoS for 802.11
+	 * networks, this is not a threat to us. The only other method
+	 * is a brute-force passphrase attack.
+	 */
+	NET80211_CRYPT_TKIP = 2,
+
+	/** Network protected with CCMP (AES-based system)
+	 *
+	 * Often called WPA2 in commerce, or RSNA (Robust Security
+	 * Network Architecture) in the 802.11 standard, CCMP is
+	 * highly secure and does not have any known attack vectors.
+	 * Since it is based on a block cipher, the statistical
+	 * correlation and "chopchop" attacks used with great success
+	 * against WEP and minor success against TKIP fail.
+	 */
+	NET80211_CRYPT_CCMP = 3,
+};
+
+
+/** @defgroup net80211_state Bits for the 802.11 association state field */
+/** @{ */
+
+/** An error code indicating the failure mode, or 0 if successful */
+#define NET80211_STATUS_MASK    0x7F
+
+/** Whether the error code provided is a "reason" code, not a "status" code */
+#define NET80211_IS_REASON	0x80
+
+/** Whether we have found the network we will be associating with */
+#define NET80211_PROBED		(1 << 8)
+
+/** Whether we have successfully authenticated with the network
+ *
+ * This usually has nothing to do with actual security; it is a
+ * holdover from older 802.11 implementation ideas.
+ */
+#define NET80211_AUTHENTICATED  (1 << 9)
+
+/** Whether we have successfully associated with the network */
+#define NET80211_ASSOCIATED     (1 << 10)
+
+/** Whether we have completed security handshaking with the network
+ *
+ * Once this is set, we can send data packets. For that reason this
+ * bit is set even in cases where no security handshaking is
+ * required.
+ */
+#define NET80211_CRYPTO_SYNCED  (1 << 11)
+
+/** Whether the auto-association task is running */
+#define NET80211_WORKING        (1 << 12)
+
+/** Whether the auto-association task is waiting for a reply from the AP */
+#define NET80211_WAITING        (1 << 13)
+
+/** Whether the auto-association task should be suppressed
+ *
+ * This is set by the `iwlist' command so that it can open the device
+ * without starting another probe process that will interfere with its
+ * own.
+ */
+#define NET80211_NO_ASSOC	(1 << 14)
+
+/** Whether this association was performed using a broadcast SSID
+ *
+ * If the user opened this device without netX/ssid set, the device's
+ * SSID will be set to that of the network it chooses to associate
+ * with, but the netX/ssid setting will remain blank. If we don't
+ * remember that we started from no specified SSID, it will appear
+ * every time settings are updated (e.g. after DHCP) that we need to
+ * reassociate due to the difference between the set SSID and our own.
+ */
+#define NET80211_AUTO_SSID	(1 << 15)
+
+
+/** @} */
+
+
+/** @defgroup net80211_phy 802.11 physical layer flags */
+/** @{ */
+
+/** Whether to use RTS/CTS or CTS-to-self protection for transmissions
+ *
+ * Since the RTS or CTS is transmitted using 802.11b signaling, and
+ * includes a field indicating the amount of time that will be used by
+ * transmission of the following packet, this serves as an effective
+ * protection mechanism to avoid 802.11b clients interfering with
+ * 802.11g clients on mixed networks.
+ */
+#define NET80211_PHY_USE_PROTECTION      (1 << 1)
+
+/** Whether to use 802.11b short preamble operation
+ *
+ * Short-preamble operation can moderately increase throughput on
+ * 802.11b networks operating between 2Mbps and 11Mbps. It is
+ * irrelevant for 802.11g data rates, since they use a different
+ * modulation scheme.
+ */
+#define NET80211_PHY_USE_SHORT_PREAMBLE  (1 << 2)
+
+/** Whether to use 802.11g short slot operation
+ *
+ * This affects a low-level timing parameter of 802.11g transmissions.
+ */
+#define NET80211_PHY_USE_SHORT_SLOT      (1 << 3)
+
+/** @} */
+
+
+/** The maximum number of TX rates we allow to be configured simultaneously */
+#define NET80211_MAX_RATES	16
+
+/** The maximum number of channels we allow to be configured simultaneously */
+#define NET80211_MAX_CHANNELS	32
+
+/** Seconds we'll wait to get all fragments of a packet */
+#define NET80211_FRAG_TIMEOUT	2
+
+/** The number of fragments we can receive at once
+ *
+ * The 802.11 standard requires that this be at least 3.
+ */
+#define NET80211_NR_CONCURRENT_FRAGS 3
+
+/** Maximum TX power to allow (dBm), if we don't get a regulatory hint */
+#define NET80211_REG_TXPOWER	20
+
+
+struct net80211_device;
+
+/** Operations that must be implemented by an 802.11 driver */
+struct net80211_device_operations {
+	/** Open 802.11 device
+	 *
+	 * @v dev	802.11 device
+	 * @ret rc	Return status code
+	 *
+	 * This method should allocate RX I/O buffers and enable the
+	 * hardware to start transmitting and receiving packets on the
+	 * channels its net80211_register() call indicated it could
+	 * handle. It does not need to tune the antenna to receive
+	 * packets on any particular channel.
+	 */
+	int ( * open ) ( struct net80211_device *dev );
+
+	/** Close 802.11 network device
+	 *
+	 * @v dev	802.11 device
+	 *
+	 * This method should stop the flow of packets, and call
+	 * net80211_tx_complete() for any packets remaining in the
+	 * device's TX queue.
+	 */
+	void ( * close ) ( struct net80211_device *dev );
+
+	/** Transmit packet on 802.11 network device
+	 *
+	 * @v dev	802.11 device
+	 * @v iobuf	I/O buffer
+	 * @ret rc	Return status code
+	 *
+	 * This method should cause the hardware to initiate
+	 * transmission of the I/O buffer, using the channel and rate
+	 * most recently indicated by an appropriate call to the
+	 * @c config callback. The 802.11 layer guarantees that said
+	 * channel and rate will be the same as those currently
+	 * reflected in the fields of @a dev.
+	 *
+	 * If this method returns success, the I/O buffer remains
+	 * owned by the network layer's TX queue, and the driver must
+	 * eventually call net80211_tx_complete() to free the buffer
+	 * whether transmission succeeded or not. If this method
+	 * returns failure, it will be interpreted as "failure to
+	 * enqueue buffer" and the I/O buffer will be immediately
+	 * released.
+	 *
+	 * This method is guaranteed to be called only when the device
+	 * is open.
+	 */
+	int ( * transmit ) ( struct net80211_device *dev,
+			     struct io_buffer *iobuf );
+
+	/** Poll for completed and received packets
+	 *
+	 * @v dev	802.11 device
+	 *
+	 * This method should cause the hardware to check for
+	 * completed transmissions and received packets. Any received
+	 * packets should be delivered via net80211_rx(), and
+	 * completed transmissions should be indicated using
+	 * net80211_tx_complete().
+	 *
+	 * This method is guaranteed to be called only when the device
+	 * is open.
+	 */
+	void ( * poll ) ( struct net80211_device *dev );
+
+	/** Enable or disable interrupts
+	 *
+	 * @v dev	802.11 device
+	 * @v enable	If TRUE, interrupts should be enabled
+	 */
+	void ( * irq ) ( struct net80211_device *dev, int enable );
+
+	/** Update hardware state to match 802.11 layer state
+	 *
+	 * @v dev	802.11 device
+	 * @v changed	Set of flags indicating what may have changed
+	 * @ret rc	Return status code
+	 *
+	 * This method should cause the hardware state to be
+	 * reinitialized from the state indicated in fields of
+	 * net80211_device, in the areas indicated by bits set in
+	 * @a changed. If the hardware is unable to do so, this method
+	 * may return an appropriate error indication.
+	 *
+	 * This method is guaranteed to be called only when the device
+	 * is open.
+	 */
+	int ( * config ) ( struct net80211_device *dev, int changed );
+};
+
+/** An 802.11 RF channel. */
+struct net80211_channel
+{
+	/** The band with which this channel is associated */
+	u8 band;
+
+	/** A channel number interpreted according to the band
+	 *
+	 * The 2.4GHz band uses channel numbers from 1-13 at 5MHz
+	 * intervals such that channel 1 is 2407 MHz; channel 14,
+	 * legal for use only in Japan, is defined separately as 2484
+	 * MHz. Adjacent channels will overlap, since 802.11
+	 * transmissions use a 20 MHz (4-channel) bandwidth. Most
+	 * commonly, channels 1, 6, and 11 are used.
+	 *
+	 * The 5GHz band uses channel numbers derived directly from
+	 * the frequency; channel 0 is 5000 MHz, and channels are
+	 * always spaced 5 MHz apart. Channel numbers over 180 are
+	 * relative to 4GHz instead of 5GHz, but these are rarely
+	 * seen. Most channels are not legal for use.
+	 */
+	u8 channel_nr;
+
+	/** The center frequency for this channel
+	 *
+	 * Currently a bandwidth of 20 MHz is assumed.
+	 */
+	u16 center_freq;
+
+	/** Maximum allowable transmit power, in dBm
+	 *
+	 * This should be interpreted as EIRP, the power supplied to
+	 * an ideal isotropic antenna in order to achieve the same
+	 * average signal intensity as the real hardware at a
+	 * particular distance.
+	 *
+	 * Currently no provision is made for directional antennas.
+	 */
+	u8 maxpower;
+};
+
+/** Information on the capabilities of an 802.11 hardware device
+ *
+ * In its probe callback, an 802.11 driver must read hardware
+ * registers to determine the appropriate contents of this structure,
+ * fill it, and pass it to net80211_register() so that the 802.11
+ * layer knows how to treat the hardware and what to advertise as
+ * supported to access points.
+ */
+struct net80211_hw_info
+{
+	/** Default hardware MAC address.
+	 *
+	 * The user may change this by setting the @c netX/mac setting
+	 * before the driver's open function is called; in that case
+	 * the driver must set the hardware MAC address to the address
+	 * contained in the wrapping net_device's ll_addr field, or if
+	 * that is impossible, set that ll_addr field back to the
+	 * unchangeable hardware MAC address.
+	 */
+	u8 hwaddr[ETH_ALEN];
+
+	/** A bitwise OR of the 802.11x modes supported by this device */
+	int modes;
+
+	/** A bitwise OR of the bands on which this device can communicate */
+	int bands;
+
+	/** A set of flags indicating peculiarities of this device. */
+	enum {
+		/** Received frames include a frame check sequence. */
+		NET80211_HW_RX_HAS_FCS = (1 << 1),
+
+		/** Hardware doesn't support 2.4GHz short preambles
+		 *
+		 * This is only relevant for 802.11b operation above
+		 * 2Mbps. All 802.11g devices support short preambles.
+		 */
+		NET80211_HW_NO_SHORT_PREAMBLE = (1 << 2),
+
+		/** Hardware doesn't support 802.11g short slot operation */
+		NET80211_HW_NO_SHORT_SLOT = (1 << 3),
+	} flags;
+
+	/** Signal strength information that can be provided by the device
+	 *
+	 * Signal strength is passed to net80211_rx(), primarily to
+	 * allow determination of the closest access point for a
+	 * multi-AP network. The units are provided for completeness
+	 * of status displays.
+	 */
+	enum {
+		/** No signal strength information supported */
+		NET80211_SIGNAL_NONE = 0,
+		/** Signal strength in arbitrary units */
+		NET80211_SIGNAL_ARBITRARY,
+		/** Signal strength in decibels relative to arbitrary base */
+		NET80211_SIGNAL_DB,
+		/** Signal strength in decibels relative to 1mW */
+		NET80211_SIGNAL_DBM,
+	} signal_type;
+
+	/** Maximum signal in arbitrary cases
+	 *
+	 * If signal_type is NET80211_SIGNAL_ARBITRARY or
+	 * NET80211_SIGNAL_DB, the driver should report it on a scale
+	 * from 0 to signal_max.
+	 */
+	unsigned signal_max;
+
+	/** List of transmission rates supported by the card
+	 *
+	 * Rates should be in 100kbps increments (e.g. 11 Mbps would
+	 * be represented as the number 110).
+	 */
+	u16 supported_rates[NET80211_MAX_RATES];
+
+	/** Number of supported rates */
+	int nr_supported_rates;
+
+	/** Estimate of the time required to change channels, in microseconds
+	 *
+	 * If this is not known, a guess on the order of a few
+	 * milliseconds (value of 1000-5000) is reasonable.
+	 */
+	unsigned channel_change_time;
+};
+
+/** Structure tracking received fragments for a packet
+ *
+ * We set up a fragment cache entry when we receive a packet marked as
+ * fragment 0 with the "more fragments" bit set in its frame control
+ * header. We are required by the 802.11 standard to track 3
+ * fragmented packets arriving simultaneously; if we receive more we
+ * may drop some. Upon receipt of a new fragment-0 packet, if no entry
+ * is available or expired, we take over the most @e recent entry for
+ * the new packet, since we don't want to starve old entries from ever
+ * finishing at all. If we get a fragment after the zeroth with no
+ * cache entry for its packet, we drop it.
+ */
+struct net80211_frag_cache
+{
+	/** Whether this cache entry is in use */
+	u8 in_use;
+
+	/** Sequence number of this MSDU (packet) */
+	u16 seqnr;
+
+	/** Timestamp from point at which first fragment was collected */
+	u32 start_ticks;
+
+	/** Buffers for each fragment */
+	struct io_buffer *iob[16];
+};
+
+/** Interface to an 802.11 cryptographic algorithm
+ *
+ * Cryptographic algorithms define a net80211_crypto structure
+ * statically, using a gPXE linker table to make it available to the
+ * 802.11 layer. When the algorithm needs to be used, the 802.11 code
+ * will allocate a copy of the static definition plus whatever space
+ * the algorithm has requested for private state, and point
+ * net80211_device::crypto at it.
+ */
+struct net80211_crypto
+{
+	/** The cryptographic algorithm implemented */
+	enum net80211_crypto_alg algorithm;
+
+	/** Initialize cryptographic algorithm using a given key
+	 *
+	 * @v crypto	802.11 cryptographic algorithm
+	 * @v key	Pointer to key bytes
+	 * @v keylen	Number of key bytes
+	 * @ret rc	Return status code
+	 *
+	 * This method is passed the communication key provided by the
+	 * security handshake handler, which will already be in the
+	 * low-level form required.
+	 */
+	int ( * initialize ) ( struct net80211_crypto *crypto, u8 *key,
+			       int keylen );
+
+	/** Encrypt a frame using the cryptographic algorithm
+	 *
+	 * @v crypto	802.11 cryptographic algorithm
+	 * @v iob	I/O buffer
+	 * @ret eiob	Newly allocated I/O buffer with encrypted packet
+	 *
+	 * This method is called to encrypt a single frame. It is
+	 * guaranteed that initialize() will have completed
+	 * successfully before this method is called.
+	 *
+	 * The frame passed already has an 802.11 header prepended,
+	 * but the PROTECTED bit in the frame control field will not
+	 * be set; this method is responsible for setting it. The
+	 * returned I/O buffer should contain a complete copy of @a
+	 * iob, including the 802.11 header, but with the PROTECTED
+	 * bit set, the data encrypted, and whatever encryption
+	 * headers/trailers are necessary added.
+	 *
+	 * This method should never free the passed I/O buffer.
+	 *
+	 * Return NULL if the packet could not be encrypted, due to
+	 * memory limitations or otherwise.
+	 */
+	struct io_buffer * ( * encrypt ) ( struct net80211_crypto *crypto,
+					   struct io_buffer *iob );
+
+	/** Decrypt a frame using the cryptographic algorithm
+	 *
+	 * @v crypto	802.11 cryptographic algorithm
+	 * @v eiob	Encrypted I/O buffer
+	 * @ret iob	Newly allocated I/O buffer with decrypted packet
+	 *
+	 * This method is called to decrypt a single frame. It is
+	 * guaranteed that initialize() will have completed
+	 * successfully before this method is called.
+	 *
+	 * Decryption follows the reverse of the pattern used for
+	 * encryption: this method must copy the 802.11 header into
+	 * the returned packet, decrypt the data stream, remove any
+	 * encryption header or trailer, and clear the PROTECTED bit
+	 * in the frame control header.
+	 *
+	 * This method should never free the passed I/O buffer.
+	 *
+	 * Return NULL if memory was not available for decryption, if
+	 * a consistency or integrity check on the decrypted frame
+	 * failed, or if the decrypted frame should not be processed
+	 * by the network stack for any other reason.
+	 */
+	struct io_buffer * ( * decrypt ) ( struct net80211_crypto *crypto,
+					   struct io_buffer *iob );
+
+	/** Length of private data requested to be allocated */
+	int priv_len;
+
+	/** Private data for the algorithm to store key and state info */
+	void *priv;
+};
+
+
+struct net80211_probe_ctx;
+struct net80211_assoc_ctx;
+
+
+/** Structure encapsulating the complete state of an 802.11 device
+ *
+ * An 802.11 device is always wrapped by a network device, and this
+ * network device is always pointed to by the @a netdev field. In
+ * general, operations should never be performed by 802.11 code using
+ * netdev functions directly. It is usually the case that the 802.11
+ * layer might need to do some processing or bookkeeping on top of
+ * what the netdevice code will do.
+ */
+struct net80211_device
+{
+	/** The net_device that wraps us. */
+	struct net_device *netdev;
+
+	/** List of 802.11 devices. */
+	struct list_head list;
+
+	/** 802.11 device operations */
+	struct net80211_device_operations *op;
+
+	/** Driver private data */
+	void *priv;
+
+	/** Information about the hardware, provided to net80211_register() */
+	struct net80211_hw_info *hw;
+
+	/* ---------- Channel and rate fields ---------- */
+
+	/** A list of all possible channels we might use */
+	struct net80211_channel channels[NET80211_MAX_CHANNELS];
+
+	/** The number of channels in the channels array */
+	u8 nr_channels;
+
+	/** The channel currently in use, as an index into the channels array */
+	u8 channel;
+
+	/** A list of all possible TX rates we might use
+	 *
+	 * Rates are in units of 100 kbps.
+	 */
+	u16 rates[NET80211_MAX_RATES];
+
+	/** The number of transmission rates in the rates array */
+	u8 nr_rates;
+
+	/** The rate currently in use, as an index into the rates array */
+	u8 rate;
+
+	/** The rate to use for RTS/CTS transmissions
+	 *
+	 * This is always the fastest basic rate that is not faster
+	 * than the data rate in use. Also an index into the rates array.
+	 */
+	u8 rtscts_rate;
+
+	/** Bitmask of basic rates
+	 *
+	 * If bit N is set in this value, with the LSB considered to
+	 * be bit 0, then rate N in the rates array is a "basic" rate.
+	 *
+	 * We don't decide which rates are "basic"; our AP does, and
+	 * we respect its wishes. We need to be able to identify basic
+	 * rates in order to calculate the duration of a CTS packet
+	 * used for 802.11 g/b interoperability.
+	 */
+	u32 basic_rates;
+
+	/* ---------- Association fields ---------- */
+
+	/** The asynchronous association process.
+	 *
+	 * When an 802.11 netdev is opened, or when the user changes
+	 * the SSID setting on an open 802.11 device, an
+	 * autoassociation task is started by net80211_autoassocate()
+	 * to associate with the new best network. The association is
+	 * asynchronous, but no packets can be transmitted until it is
+	 * complete. If it is successful, the wrapping net_device is
+	 * set as "link up". If it fails, @c assoc_rc will be set with
+	 * an error indication.
+	 */
+	struct process proc_assoc;
+
+	/** Network with which we are associating
+	 *
+	 * This will be NULL when we are not actively in the process
+	 * of associating with a network we have already successfully
+	 * probed for.
+	 */
+	struct net80211_wlan *associating;
+
+	/** Context for the association process
+	 *
+	 * This is a probe_ctx if the @c PROBED flag is not set in @c
+	 * state, and an assoc_ctx otherwise.
+	 */
+	union {
+		struct net80211_probe_ctx *probe;
+		struct net80211_assoc_ctx *assoc;
+	} ctx;
+
+	/** State of our association to the network
+	 *
+	 * Since the association process happens asynchronously, it's
+	 * necessary to have some channel of communication so the
+	 * driver can say "I got an association reply and we're OK" or
+	 * similar. This variable provides that link. It is a bitmask
+	 * of any of NET80211_PROBED, NET80211_AUTHENTICATED,
+	 * NET80211_ASSOCIATED, NET80211_CRYPTO_SYNCED to indicate how
+	 * far along in associating we are; NET80211_WORKING if the
+	 * association task is running; and NET80211_WAITING if a
+	 * packet has been sent that we're waiting for a reply to. We
+	 * can only be crypto-synced if we're associated, we can
+	 * only be associated if we're authenticated, we can only be
+	 * authenticated if we've probed.
+	 *
+	 * If an association process fails (that is, we receive a
+	 * packet with an error indication), the error code is copied
+	 * into bits 6-0 of this variable and bit 7 is set to specify
+	 * what type of error code it is. An AP can provide either a
+	 * "status code" (0-51 are defined) explaining why it refused
+	 * an association immediately, or a "reason code" (0-45 are
+	 * defined) explaining why it canceled an association after it
+	 * had originally OK'ed it. Status and reason codes serve
+	 * similar functions, but they use separate error message
+	 * tables. A gPXE-formatted return status code (negative) is
+	 * placed in @c assoc_rc.
+	 *
+	 * If the failure to associate is indicated by a status code,
+	 * the NET80211_IS_REASON bit will be clear; if it is
+	 * indicated by a reason code, the bit will be set. If we were
+	 * successful, both zero status and zero reason mean success,
+	 * so there is no ambiguity.
+	 *
+	 * To prevent association when opening the device, user code
+	 * can set the NET80211_NO_ASSOC bit. The final bit in this
+	 * variable, NET80211_AUTO_SSID, is used to remember whether
+	 * we picked our SSID through automated probing as opposed to
+	 * user specification; the distinction becomes relevant in the
+	 * settings applicator.
+	 */
+	u16 state;
+
+	/** Return status code associated with @c state */
+	int assoc_rc;
+
+	/* ---------- Parameters of currently associated network ---------- */
+
+	/** 802.11 cryptographic algorithm for our current network
+	 *
+	 * For an open network, this will be set to NULL.
+	 */
+	struct net80211_crypto *crypto;
+
+	/** MAC address of the access point most recently associated */
+	u8 bssid[ETH_ALEN];
+
+	/** SSID of the access point we are or will be associated with
+	 *
+	 * Although the SSID field in 802.11 packets is generally not
+	 * NUL-terminated, here and in net80211_wlan we add a NUL for
+	 * convenience.
+	 */
+	char essid[IEEE80211_MAX_SSID_LEN+1];
+
+	/** Association ID given to us by the AP */
+	u16 aid;
+
+	/** TSFT value for last beacon received, microseconds */
+	u64 last_beacon_timestamp;
+
+	/** Time between AP sending beacons, microseconds */
+	u32 tx_beacon_interval;
+
+	/** Smoothed average time between beacons, microseconds */
+	u32 rx_beacon_interval;
+
+	/* ---------- Physical layer information ---------- */
+
+	/** Physical layer options
+	 *
+	 * These control the use of CTS protection, short preambles,
+	 * and short-slot operation.
+	 */
+	int phy_flags;
+
+	/** Signal strength of last received packet */
+	int last_signal;
+
+	/** Rate control state */
+	struct rc80211_ctx *rctl;
+
+	/* ---------- Packet handling state ---------- */
+
+	/** Fragment reassembly state */
+	struct net80211_frag_cache frags[NET80211_NR_CONCURRENT_FRAGS];
+
+	/** The sequence number of the last packet we sent */
+	u16 last_tx_seqnr;
+
+	/** Packet duplication elimination state
+	 *
+	 * We are only required to handle immediate duplicates for
+	 * each direct sender, and since we can only have one direct
+	 * sender (the AP), we need only keep the sequence control
+	 * field from the most recent packet we've received. Thus,
+	 * this field stores the last sequence control field we've
+	 * received for a packet from the AP.
+	 */
+	u16 last_rx_seq;
+
+	/** RX management packet queue
+	 *
+	 * Sometimes we want to keep probe, beacon, and action packets
+	 * that we receive, such as when we're scanning for networks.
+	 * Ordinarily we drop them because they are sent at a large
+	 * volume (ten beacons per second per AP, broadcast) and we
+	 * have no need of them except when we're scanning.
+	 *
+	 * When keep_mgmt is TRUE, received probe, beacon, and action
+	 * management packets will be stored in this queue.
+	 */
+	struct list_head mgmt_queue;
+
+	/** RX management packet info queue
+	 *
+	 * We need to keep track of the signal strength for management
+	 * packets we're keeping, because that provides the only way
+	 * to distinguish between multiple APs for the same network.
+	 * Since we can't extend io_buffer to store signal, this field
+	 * heads a linked list of "RX packet info" structures that
+	 * contain that signal strength field. Its entries always
+	 * parallel the entries in mgmt_queue, because the two queues
+	 * are always added to or removed from in parallel.
+	 */
+	struct list_head mgmt_info_queue;
+
+	/** Whether to store management packets
+	 *
+	 * Received beacon, probe, and action packets will be added to
+	 * mgmt_queue (and their signal strengths added to
+	 * mgmt_info_queue) only when this variable is TRUE. It should
+	 * be set by net80211_keep_mgmt() (which returns the old
+	 * value) only when calling code is prepared to poll the
+	 * management queue frequently, because packets will otherwise
+	 * pile up and exhaust memory.
+	 */
+	int keep_mgmt;
+};
+
+/** Structure representing a probed network.
+ *
+ * This is returned from the net80211_probe_finish functions and
+ * passed to the low-level association functions. At least essid,
+ * bssid, channel, beacon, and security must be filled in if you want
+ * to build this structure manually.
+ */
+struct net80211_wlan
+{
+	/** The human-readable ESSID (network name)
+	 *
+	 * Although the 802.11 SSID field is generally not
+	 * NUL-terminated, the gPXE code adds an extra NUL (and
+	 * expects one in this structure) for convenience.
+	 */
+	char essid[IEEE80211_MAX_SSID_LEN+1];
+
+	/** MAC address of the strongest-signal access point for this ESSID */
+	u8 bssid[ETH_ALEN];
+
+	/** Signal strength of beacon frame from that access point */
+	int signal;
+
+	/** The channel on which that access point communicates
+	 *
+	 * This is a raw channel number (net80211_channel::channel_nr),
+	 * so that it will not be affected by reconfiguration of the
+	 * device channels array.
+	 */
+	int channel;
+
+	/** The complete beacon or probe-response frame received */
+	struct io_buffer *beacon;
+
+	/** Security handshaking method used on the network */
+	enum net80211_security_proto handshaking;
+
+	/** Cryptographic algorithm used on the network */
+	enum net80211_crypto_alg crypto;
+
+	/** Link to allow chaining multiple structures into a list to
+	    be returned from net80211_probe_finish_all(). */
+	struct list_head list;
+};
+
+
+/**
+ * @defgroup net80211_probe 802.11 network location API
+ * @{
+ */
+int net80211_prepare_probe ( struct net80211_device *dev, int band,
+			     int active );
+struct net80211_probe_ctx * net80211_probe_start ( struct net80211_device *dev,
+						   const char *essid,
+						   int active );
+int net80211_probe_step ( struct net80211_probe_ctx *ctx );
+struct net80211_wlan *
+net80211_probe_finish_best ( struct net80211_probe_ctx *ctx );
+struct list_head *net80211_probe_finish_all ( struct net80211_probe_ctx *ctx );
+
+void net80211_free_wlan ( struct net80211_wlan *wlan );
+void net80211_free_wlanlist ( struct list_head *list );
+/** @} */
+
+
+/**
+ * @defgroup net80211_mgmt 802.11 network management API
+ * @{
+ */
+struct net80211_device * net80211_get ( struct net_device *netdev );
+void net80211_autoassociate ( struct net80211_device *dev );
+
+int net80211_change_channel ( struct net80211_device *dev, int channel );
+void net80211_set_rate_idx ( struct net80211_device *dev, int rate );
+
+int net80211_keep_mgmt ( struct net80211_device *dev, int enable );
+struct io_buffer * net80211_mgmt_dequeue ( struct net80211_device *dev,
+					   int *signal );
+int net80211_tx_mgmt ( struct net80211_device *dev, u16 fc,
+		       u8 bssid[ETH_ALEN], struct io_buffer *iob );
+/** @} */
+
+
+/**
+ * @defgroup net80211_assoc 802.11 network association API
+ * @{
+ */
+int net80211_prepare_assoc ( struct net80211_device *dev,
+			     struct net80211_wlan *wlan );
+int net80211_send_auth ( struct net80211_device *dev,
+			 struct net80211_wlan *wlan, int method );
+int net80211_send_assoc ( struct net80211_device *dev,
+			  struct net80211_wlan *wlan );
+/** @} */
+
+
+/**
+ * @defgroup net80211_driver 802.11 driver interface API
+ * @{
+ */
+struct net80211_device *net80211_alloc ( size_t priv_size );
+int net80211_register ( struct net80211_device *dev,
+			struct net80211_device_operations *ops,
+			struct net80211_hw_info *hw );
+void net80211_rx ( struct net80211_device *dev, struct io_buffer *iob,
+		   int signal, u16 rate );
+void net80211_rx_err ( struct net80211_device *dev,
+		       struct io_buffer *iob, int rc );
+void net80211_tx_complete ( struct net80211_device *dev,
+			    struct io_buffer *iob, int retries, int rc );
+void net80211_unregister ( struct net80211_device *dev );
+void net80211_free ( struct net80211_device *dev );
+/** @} */
+
+
+#endif

src/include/gpxe/rc80211.h

@@ -0,0 +1,19 @@
+#ifndef _GPXE_RC80211_H
+#define _GPXE_RC80211_H
+
+/** @file
+ *
+ * Rate-control algorithm prototype for 802.11.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+struct net80211_device;
+struct rc80211_ctx;
+
+struct rc80211_ctx * rc80211_init ( struct net80211_device *dev );
+void rc80211_update_tx ( struct net80211_device *dev, int retries, int rc );
+void rc80211_update_rx ( struct net80211_device *dev, int retry, u16 rate );
+void rc80211_free ( struct rc80211_ctx *ctx );
+
+#endif /* _GPXE_RC80211_H */

src/net/80211/rc80211.c

@@ -0,0 +1,371 @@
+/*
+ * Simple 802.11 rate-control algorithm for gPXE.
+ *
+ * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdlib.h>
+#include <gpxe/net80211.h>
+
+/**
+ * @file
+ *
+ * Simple 802.11 rate-control algorithm
+ */
+
+/** @page rc80211 Rate control philosophy
+ *
+ * We want to maximize our transmission speed, to the extent that we
+ * can do that without dropping undue numbers of packets. We also
+ * don't want to take up very much code space, so our algorithm has to
+ * be pretty simple
+ *
+ * When we receive a packet, we know what rate it was transmitted at,
+ * and whether it had to be retransmitted to get to us.
+ *
+ * When we send a packet, we hear back how many times it had to be
+ * retried to get through, and whether it got through at all.
+ *
+ * Indications of TX success are more reliable than RX success, but RX
+ * information helps us know where to start.
+ *
+ * To handle all of this, we keep for each rate and each direction (TX
+ * and RX separately) some state information for the most recent
+ * packets on that rate and the number of packets for which we have
+ * information. The state is a 32-bit unsigned integer in which two
+ * bits represent a packet: 11 if it went through well, 10 if it went
+ * through with one retry, 01 if it went through with more than one
+ * retry, or 00 if it didn't go through at all. We define the
+ * "goodness" for a particular (rate, direction) combination as the
+ * sum of all the 2-bit fields, times 33, divided by the number of
+ * 2-bit fields containing valid information (16 except when we're
+ * starting out). The number produced is between 0 and 99; we use -1
+ * for rates with less than 4 RX packets or 1 TX, as an indicator that
+ * we do not have enough information to rely on them.
+ *
+ * In deciding which rates are best, we find the weighted average of
+ * TX and RX goodness, where the weighting is by number of packets
+ * with data and TX packets are worth 4 times as much as RX packets.
+ * The weighted average is called "net goodness" and is also a number
+ * between 0 and 99.  If 3 consecutive packets fail transmission
+ * outright, we automatically ratchet down the rate; otherwise, we
+ * switch to the best rate whenever the current rate's goodness falls
+ * below some threshold, and try increasing our rate when the goodness
+ * is very high.
+ *
+ * This system is optimized for gPXE's style of usage. Because normal
+ * operation always involves receiving something, we'll make our way
+ * to the best rate pretty quickly. We tend to follow the lead of the
+ * sending AP in choosing rates, but we won't use rates for long that
+ * don't work well for us in transmission. We assume gPXE won't be
+ * running for long enough that rate patterns will change much, so we
+ * don't have to keep time counters or the like.  And if this doesn't
+ * work well in practice there are many ways it could be tweaked.
+ *
+ * To avoid staying at 1Mbps for a long time, we don't track any
+ * transmitted packets until we've set our rate based on received
+ * packets.
+ */
+
+/** Two-bit packet status indicator for a packet with no retries */
+#define RC_PKT_OK		0x3
+
+/** Two-bit packet status indicator for a packet with one retry */
+#define RC_PKT_RETRIED_ONCE	0x2
+
+/** Two-bit packet status indicator for a TX packet with multiple retries
+ *
+ * It is not possible to tell whether an RX packet had one or multiple
+ * retries; we rely instead on the fact that failed RX packets won't
+ * get to us at all, so if we receive a lot of RX packets on a certain
+ * rate it must be pretty good.
+ */
+#define RC_PKT_RETRIED_MULTI	0x1
+
+/** Two-bit packet status indicator for a TX packet that was never ACKed
+ *
+ * It is not possible to tell whether an RX packet was setn if it
+ * didn't get through to us, but if we don't see one we won't increase
+ * the goodness for its rate. This asymmetry is part of why TX packets
+ * are weighted much more heavily than RX.
+ */
+#define RC_PKT_FAILED		0x0
+
+/** Number of times to weight TX packets more heavily than RX packets */
+#define RC_TX_FACTOR		4
+
+/** Number of consecutive failed TX packets that cause an automatic rate drop */
+#define RC_TX_EMERG_FAIL	3
+
+/** Minimum net goodness below which we will search for a better rate */
+#define RC_GOODNESS_MIN		85
+
+/** Maximum net goodness above which we will try to increase our rate */
+#define RC_GOODNESS_MAX		95
+
+/** Minimum (num RX + @c RC_TX_FACTOR * num TX) to use a certain rate */
+#define RC_UNCERTAINTY_THRESH	4
+
+/** TX direction */
+#define TX	0
+
+/** RX direction */
+#define RX	1
+
+/** A rate control context */
+struct rc80211_ctx
+{
+	/** Goodness state for each rate, TX and RX */
+	u32 goodness[2][NET80211_MAX_RATES];
+
+	/** Number of packets recorded for each rate */
+	u8 count[2][NET80211_MAX_RATES];
+
+	/** Indication of whether we've set the device rate yet */
+	int started;
+
+	/** Counter of all packets sent and received */
+	int packets;
+};
+
+/**
+ * Initialize rate-control algorithm
+ *
+ * @v dev	802.11 device
+ * @ret ctx	Rate-control context, to be stored in @c dev->rctl
+ */
+struct rc80211_ctx * rc80211_init ( struct net80211_device *dev __unused )
+{
+	struct rc80211_ctx *ret = zalloc ( sizeof ( *ret ) );
+	return ret;
+}
+
+/**
+ * Calculate net goodness for a certain rate
+ *
+ * @v ctx	Rate-control context
+ * @v rate_idx	Index of rate to calculate net goodness for
+ */
+static int rc80211_calc_net_goodness ( struct rc80211_ctx *ctx,
+				       int rate_idx )
+{
+	int sum[2], num[2], dir, pkt;
+
+	for ( dir = 0; dir < 2; dir++ ) {
+		u32 good = ctx->goodness[dir][rate_idx];
+
+		num[dir] = ctx->count[dir][rate_idx];
+		sum[dir] = 0;
+
+		for ( pkt = 0; pkt < num[dir]; pkt++ )
+			sum[dir] += ( good >> ( 2 * pkt ) ) & 0x3;
+	}
+
+	if ( ( num[TX] * RC_TX_FACTOR + num[RX] ) < RC_UNCERTAINTY_THRESH )
+		return -1;
+
+	return ( 33 * ( sum[TX] * RC_TX_FACTOR + sum[RX] ) /
+		      ( num[TX] * RC_TX_FACTOR + num[RX] ) );
+}
+
+/**
+ * Determine the best rate to switch to and return it
+ *
+ * @v dev		802.11 device
+ * @ret rate_idx	Index of the best rate to switch to
+ */
+static int rc80211_pick_best ( struct net80211_device *dev )
+{
+	struct rc80211_ctx *ctx = dev->rctl;
+	int best_net_good = 0, best_rate = -1, i;
+
+	for ( i = 0; i < dev->nr_rates; i++ ) {
+		int net_good = rc80211_calc_net_goodness ( ctx, i );
+
+		if ( net_good > best_net_good ||
+		     ( best_net_good > RC_GOODNESS_MIN &&
+		       net_good > RC_GOODNESS_MIN ) ) {
+			best_net_good = net_good;
+			best_rate = i;
+		}
+	}
+
+	if ( best_rate >= 0 ) {
+		int old_good = rc80211_calc_net_goodness ( ctx, dev->rate );
+		if ( old_good != best_net_good )
+			DBGC ( ctx, "802.11 RC %p switching from goodness "
+			       "%d to %d\n", ctx, old_good, best_net_good );
+
+		ctx->started = 1;
+		return best_rate;
+	}
+
+	return dev->rate;
+}
+
+/**
+ * Set 802.11 device rate
+ *
+ * @v dev	802.11 device
+ * @v rate_idx	Index of rate to switch to
+ *
+ * This is a thin wrapper around net80211_set_rate_idx to insert a
+ * debugging message where appropriate.
+ */
+static inline void rc80211_set_rate ( struct net80211_device *dev,
+				      int rate_idx )
+{
+	DBGC ( dev->rctl, "802.11 RC %p changing rate %d->%d Mbps\n", dev->rctl,
+	       dev->rates[dev->rate] / 10, dev->rates[rate_idx] / 10 );
+
+	net80211_set_rate_idx ( dev, rate_idx );
+}
+
+/**
+ * Check rate-control state and change rate if necessary
+ *
+ * @v dev	802.11 device
+ */
+static void rc80211_maybe_set_new ( struct net80211_device *dev )
+{
+	struct rc80211_ctx *ctx = dev->rctl;
+	int net_good;
+
+	net_good = rc80211_calc_net_goodness ( ctx, dev->rate );
+
+	if ( ! ctx->started ) {
+		rc80211_set_rate ( dev, rc80211_pick_best ( dev ) );
+		return;
+	}
+
+	if ( net_good < 0 )	/* insufficient data */
+		return;
+
+	if ( net_good > RC_GOODNESS_MAX && dev->rate + 1 < dev->nr_rates ) {
+		int higher = rc80211_calc_net_goodness ( ctx, dev->rate + 1 );
+		if ( higher > net_good || higher < 0 )
+			rc80211_set_rate ( dev, dev->rate + 1 );
+		else
+			rc80211_set_rate ( dev, rc80211_pick_best ( dev ) );
+	}
+
+	if ( net_good < RC_GOODNESS_MIN ) {
+		rc80211_set_rate ( dev, rc80211_pick_best ( dev ) );
+	}
+}
+
+/**
+ * Update rate-control state
+ *
+ * @v dev		802.11 device
+ * @v direction		One of the direction constants TX or RX
+ * @v rate_idx		Index of rate at which packet was sent or received
+ * @v retries		Number of times packet was retried before success
+ * @v failed		If nonzero, the packet failed to get through
+ */
+static void rc80211_update ( struct net80211_device *dev, int direction,
+			     int rate_idx, int retries, int failed )
+{
+	struct rc80211_ctx *ctx = dev->rctl;
+	u32 goodness = ctx->goodness[direction][rate_idx];
+
+	if ( ctx->count[direction][rate_idx] < 16 )
+		ctx->count[direction][rate_idx]++;
+
+	goodness <<= 2;
+	if ( failed )
+		goodness |= RC_PKT_FAILED;
+	else if ( retries > 1 )
+		goodness |= RC_PKT_RETRIED_MULTI;
+	else if ( retries )
+		goodness |= RC_PKT_RETRIED_ONCE;
+	else
+		goodness |= RC_PKT_OK;
+
+	ctx->goodness[direction][rate_idx] = goodness;
+
+	ctx->packets++;
+
+	rc80211_maybe_set_new ( dev );
+}
+
+/**
+ * Update rate-control state for transmitted packet
+ *
+ * @v dev	802.11 device
+ * @v retries	Number of times packet was transmitted before success
+ * @v rc	Return status code for transmission
+ */
+void rc80211_update_tx ( struct net80211_device *dev, int retries, int rc )
+{
+	struct rc80211_ctx *ctx = dev->rctl;
+
+	if ( ! ctx->started )
+		return;
+
+	rc80211_update ( dev, TX, dev->rate, retries, rc );
+
+	/* Check if the last RC_TX_EMERG_FAIL packets have all failed */
+	if ( ! ( ctx->goodness[TX][dev->rate] &
+		 ( ( 1 << ( 2 * RC_TX_EMERG_FAIL ) ) - 1 ) ) ) {
+		if ( dev->rate == 0 )
+			DBGC ( dev->rctl, "802.11 RC %p saw %d consecutive "
+			       "failed TX, but cannot lower rate any further\n",
+			       dev->rctl, RC_TX_EMERG_FAIL );
+		else {
+			DBGC ( dev->rctl, "802.11 RC %p lowering rate (%d->%d "
+			       "Mbps) due to %d consecutive TX failures\n",
+			       dev->rctl, dev->rates[dev->rate] / 10,
+			       dev->rates[dev->rate - 1] / 10,
+			       RC_TX_EMERG_FAIL );
+
+			rc80211_set_rate ( dev, dev->rate - 1 );
+		}
+	}
+}
+
+/**
+ * Update rate-control state for received packet
+ *
+ * @v dev	802.11 device
+ * @v retry	Whether the received packet had been retransmitted
+ * @v rate	Rate at which packet was received, in 100 kbps units
+ */
+void rc80211_update_rx ( struct net80211_device *dev, int retry, u16 rate )
+{
+	int ridx;
+
+	for ( ridx = 0; ridx < dev->nr_rates && dev->rates[ridx] != rate;
+	      ridx++ )
+		;
+	if ( ridx >= dev->nr_rates )
+		return;		/* couldn't find the rate */
+
+	rc80211_update ( dev, RX, ridx, retry, 0 );
+}
+
+/**
+ * Free rate-control context
+ *
+ * @v ctx	Rate-control context
+ */
+void rc80211_free ( struct rc80211_ctx *ctx )
+{
+	free ( ctx );
+}