net80211.h

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#ifndef _IPXE_NET80211_H
#define _IPXE_NET80211_H
 
#include <ipxe/process.h>
#include <ipxe/ieee80211.h>
#include <ipxe/iobuf.h>
#include <ipxe/netdevice.h>
#include <ipxe/rc80211.h>
 
/** @file
 *
 * The iPXE 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      0
/** The band from 4.9 GHz to 5.7 GHz, which tends to be more restricted */
#define NET80211_BAND_5GHZ      1
/** Number of RF bands */
#define NET80211_NR_BANDS       2
 
/** Bitmask for the 2GHz band */
#define NET80211_BAND_BIT_2GHZ  (1 << 0)
/** Bitmask for the 5GHz band */
#define NET80211_BAND_BIT_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,
 
        /** Dummy value used when the handshaking type can't be detected */
        NET80211_SECPROT_UNKNOWN = 3,
};
 
 
/** 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 iPXE 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,
 
        /** Dummy value used when the cryptosystem can't be detected */
        NET80211_CRYPT_UNKNOWN = 4,
};
 
 
/** @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   40
 
/** 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;
 
        /** Hardware channel value */
        u16 hw_value;
 
        /** 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 RF channels supported by the card */
        struct net80211_channel channels[NET80211_MAX_CHANNELS];
 
        /** Number of supported channels */
        int nr_channels;
 
        /** List of transmission rates supported by the card, indexed by band
         *
         * Rates should be in 100kbps increments (e.g. 11 Mbps would
         * be represented as the number 110).
         */
        u16 rates[NET80211_NR_BANDS][NET80211_MAX_RATES];
 
        /** Number of supported rates, indexed by band */
        int nr_rates[NET80211_NR_BANDS];
 
        /** 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 security handshaking protocol
 *
 * Security handshaking protocols handle parsing a user-specified key
 * into a suitable input to the encryption algorithm, and for WPA and
 * better systems, manage performing whatever authentication with the
 * network is necessary.
 *
 * At all times when any method in this structure is called with a
 * net80211_device argument @a dev, a dynamically allocated copy of
 * the handshaker structure itself with space for the requested amount
 * of private data may be accessed as @c dev->handshaker. The
 * structure will not be modified, and will only be freed during
 * reassociation and device closing after the @a stop method has been
 * called.
 */
struct net80211_handshaker
{
        /** The security handshaking protocol implemented */
        enum net80211_security_proto protocol;
 
        /** Initialize security handshaking protocol
         *
         * @v dev       802.11 device
         * @ret rc      Return status code
         *
         * This method is expected to access @c netX/key or other
         * applicable settings to determine the parameters for
         * handshaking. If no handshaking is required, it should call
         * sec80211_install() with the cryptosystem and key that are
         * to be used, and @c start and @c step should be set to @c
         * NULL.
         *
         * This is always called just before association is performed,
         * but after its parameters have been set; in particular, you
         * may rely on the contents of the @a essid field in @a dev.
         */
        int ( * init ) ( struct net80211_device *dev );
 
        /** Start handshaking
         *
         * @v dev       802.11 device
         * @ret rc      Return status code
         *
         * This method is expected to set up internal state so that
         * packets sent immediately after association, before @a step
         * can be called, will be handled appropriately.
         *
         * This is always called just before association is attempted.
         */
        int ( * start ) ( struct net80211_device *dev );
 
        /** Process handshaking state
         *
         * @v dev       802.11 device
         * @ret rc      Return status code, or positive if done
         *
         * This method is expected to perform as much progress on the
         * protocol it implements as is possible without blocking. It
         * should return 0 if it wishes to be called again, a negative
         * return status code on error, or a positive value if
         * handshaking is complete. In the case of a positive return,
         * net80211_crypto_install() must have been called.
         *
         * If handshaking may require further action (e.g. an AP that
         * might decide to rekey), handlers must be installed by this
         * function that will act without further calls to @a step.
         */
        int ( * step ) ( struct net80211_device *dev );
 
        /** Change cryptographic key based on setting
         *
         * @v dev       802.11 device
         * @ret rc      Return status code
         *
         * This method is called whenever the @c netX/key setting
         * @e may have been changed. It is expected to determine
         * whether it did in fact change, and if so, to install the
         * new key using net80211_crypto_install(). If it is not
         * possible to do this immediately, this method should return
         * an error; in that case the 802.11 stack will reassociate,
         * following the usual init/start/step sequence.
         *
         * This method is only relevant when it is possible to
         * associate successfully with an incorrect key. When it is
         * not, a failed association will be retried until the user
         * changes the key setting, and a successful association will
         * not be dropped due to such a change. When association with
         * an incorrect key is impossible, this function should return
         * 0 after performing no action.
         */
        int ( * change_key ) ( struct net80211_device *dev );
 
        /** Stop security handshaking handlers
         *
         * @v dev       802.11 device
         *
         * This method is called just before freeing a security
         * handshaker; it could, for example, delete a process that @a
         * start had created to manage the security of the connection.
         * If not needed it may be set to NULL.
         */
        void ( * stop ) ( struct net80211_device *dev );
 
        /** Amount of private data requested
         *
         * Before @c init is called for the first time, this structure's
         * @c priv pointer will point to this many bytes of allocated
         * data, where the allocation will be performed separately for
         * each net80211_device.
         */
        int priv_len;
 
        /** Whether @a start has been called
         *
         * Reset to 0 after @a stop is called.
         */
        int started;
 
        /** Pointer to private data
         *
         * In initializing this structure statically for a linker
         * table, set this to NULL.
         */
        void *priv;
};
 
#define NET80211_HANDSHAKERS __table ( struct net80211_handshaker, \
                                       "net80211_handshakers" )
#define __net80211_handshaker __table_entry ( NET80211_HANDSHAKERS, 01 )
 
 
/** Interface to an 802.11 cryptosystem
 *
 * Cryptosystems define a net80211_crypto structure statically, using
 * a iPXE linker table to make it available to the 802.11 layer. When
 * the cryptosystem 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 or
 * net80211_device::gcrypto at it.
 */
struct net80211_crypto
{
        /** The cryptographic algorithm implemented */
        enum net80211_crypto_alg algorithm;
 
        /** Initialize cryptosystem using a given key
         *
         * @v crypto    802.11 cryptosystem
         * @v key       Pointer to key bytes
         * @v keylen    Number of key bytes
         * @v rsc       Initial receive sequence counter, if applicable
         * @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. It may not store a pointer to the
         * key after returning; it must copy it to its private storage.
         */
        int ( * init ) ( struct net80211_crypto *crypto, const void *key,
                         int keylen, const void *rsc );
 
        /** Encrypt a frame using the cryptosystem
         *
         * @v crypto    802.11 cryptosystem
         * @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 cryptosystem
         *
         * @v crypto    802.11 cryptosystem
         * @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;
};
 
#define NET80211_CRYPTOS __table ( struct net80211_crypto, "net80211_cryptos" )
#define __net80211_crypto __table_entry ( NET80211_CRYPTOS, 01 )
 
 
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;
 
        /** Security handshaker being used */
        struct net80211_handshaker *handshaker;
 
        /** 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 iPXE-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;
 
        /** RSN or WPA information element to include with association
         *
         * If set to @c NULL, none will be included. It is expected
         * that this will be set by the @a init function of a security
         * handshaker if it is needed.
         */
        union ieee80211_ie *rsn_ie;
 
        /* ---------- Parameters of currently associated network ---------- */
 
        /** 802.11 cryptosystem for our current network
         *
         * For an open network, this will be set to NULL.
         */
        struct net80211_crypto *crypto;
 
        /** 802.11 cryptosystem for multicast and broadcast frames
         *
         * If this is NULL, the cryptosystem used for receiving
         * unicast frames will also be used for receiving multicast
         * and broadcast frames. Transmitted multicast and broadcast
         * frames are always sent unicast to the AP, who multicasts
         * them on our behalf; thus they always use the unicast
         * cryptosystem.
         */
        struct net80211_crypto *gcrypto;
 
        /** 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 iPXE 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;
};
 
 
/** 802.11 encryption key setting */
extern const struct setting
net80211_key_setting __setting ( SETTING_NETDEV_EXTRA, key );
 
 
/**
 * @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 );
void net80211_deauthenticate ( struct net80211_device *dev, int rc );
/** @} */
 
 
/**
 * @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 );
u16 net80211_duration ( struct net80211_device *dev, int bytes, u16 rate );
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 );
/** @} */
 
/**
 * Calculate duration field for a CTS control frame
 *
 * @v dev       802.11 device
 * @v size      Size of the packet being cleared to send
 *
 * A CTS control frame's duration field captures the frame being
 * protected and its 10-byte ACK.
 */
static inline u16 net80211_cts_duration ( struct net80211_device *dev,
                                          int size )
{
        return ( net80211_duration ( dev, 10,
                                     dev->rates[dev->rtscts_rate] ) +
                 net80211_duration ( dev, size, dev->rates[dev->rate] ) );
}
 
#endif