The 802.11 subsystems – for kernel developers

Explaining wireless 802.11 networking in the Linux kernel

This documentation is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation.

This documentation 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.

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Abstract

These books attempt to give a description of the various subsystems that play a role in 802.11 wireless networking in Linux. Since these books are for kernel developers they attempts to document the structures and functions used in the kernel as well as giving a higher-level overview.

The reader is expected to be familiar with the 802.11 standard as published by the IEEE in 802.11-2007 (or possibly later versions). References to this standard will be given as "802.11-2007 8.1.5".


Table of Contents

The cfg80211 subsystem
1. Device registration
enum ieee80211_channel_flags — channel flags
struct ieee80211_channel — channel definition
enum ieee80211_rate_flags — rate flags
struct ieee80211_rate — bitrate definition
struct ieee80211_sta_ht_cap — STA's HT capabilities
struct ieee80211_supported_band — frequency band definition
enum cfg80211_signal_type — signal type
enum wiphy_params_flags — set_wiphy_params bitfield values
enum wiphy_flags — wiphy capability flags
struct wiphy — wireless hardware description
struct wireless_dev — wireless device state
wiphy_new — create a new wiphy for use with cfg80211
wiphy_register — register a wiphy with cfg80211
wiphy_unregister — deregister a wiphy from cfg80211
wiphy_free — free wiphy
wiphy_name — get wiphy name
wiphy_dev — get wiphy dev pointer
wiphy_priv — return priv from wiphy
priv_to_wiphy — return the wiphy containing the priv
set_wiphy_dev — set device pointer for wiphy
wdev_priv — return wiphy priv from wireless_dev
struct ieee80211_iface_limit — limit on certain interface types
struct ieee80211_iface_combination — possible interface combination
cfg80211_check_combinations — check interface combinations
2. Actions and configuration
struct cfg80211_ops — backend description for wireless configuration
struct vif_params — describes virtual interface parameters
struct key_params — key information
enum survey_info_flags — survey information flags
struct survey_info — channel survey response
struct cfg80211_beacon_data — beacon data
struct cfg80211_ap_settings — AP configuration
struct station_parameters — station parameters
enum rate_info_flags — bitrate info flags
struct rate_info — bitrate information
struct station_info — station information
enum monitor_flags — monitor flags
enum mpath_info_flags — mesh path information flags
struct mpath_info — mesh path information
struct bss_parameters — BSS parameters
struct ieee80211_txq_params — TX queue parameters
struct cfg80211_crypto_settings — Crypto settings
struct cfg80211_auth_request — Authentication request data
struct cfg80211_assoc_request — (Re)Association request data
struct cfg80211_deauth_request — Deauthentication request data
struct cfg80211_disassoc_request — Disassociation request data
struct cfg80211_ibss_params — IBSS parameters
struct cfg80211_connect_params — Connection parameters
struct cfg80211_pmksa — PMK Security Association
cfg80211_rx_mlme_mgmt — notification of processed MLME management frame
cfg80211_auth_timeout — notification of timed out authentication
cfg80211_rx_assoc_resp — notification of processed association response
cfg80211_assoc_timeout — notification of timed out association
cfg80211_tx_mlme_mgmt — notification of transmitted deauth/disassoc frame
cfg80211_ibss_joined — notify cfg80211 that device joined an IBSS
cfg80211_connect_result — notify cfg80211 of connection result
cfg80211_connect_bss — notify cfg80211 of connection result
cfg80211_roamed — notify cfg80211 of roaming
cfg80211_disconnected — notify cfg80211 that connection was dropped
cfg80211_ready_on_channel — notification of remain_on_channel start
cfg80211_remain_on_channel_expired — remain_on_channel duration expired
cfg80211_new_sta — notify userspace about station
cfg80211_rx_mgmt — notification of received, unprocessed management frame
cfg80211_mgmt_tx_status — notification of TX status for management frame
cfg80211_cqm_rssi_notify — connection quality monitoring rssi event
cfg80211_cqm_pktloss_notify — notify userspace about packetloss to peer
cfg80211_michael_mic_failure — notification of Michael MIC failure (TKIP)
3. Scanning and BSS list handling
struct cfg80211_ssid — SSID description
struct cfg80211_scan_request — scan request description
cfg80211_scan_done — notify that scan finished
struct cfg80211_bss — BSS description
struct cfg80211_inform_bss — BSS inform data
cfg80211_inform_bss_frame_data — inform cfg80211 of a received BSS frame
cfg80211_inform_bss_data — inform cfg80211 of a new BSS
cfg80211_unlink_bss — unlink BSS from internal data structures
cfg80211_find_ie — find information element in data
ieee80211_bss_get_ie — find IE with given ID
4. Utility functions
ieee80211_channel_to_frequency — convert channel number to frequency
ieee80211_frequency_to_channel — convert frequency to channel number
ieee80211_get_channel — get channel struct from wiphy for specified frequency
ieee80211_get_response_rate — get basic rate for a given rate
ieee80211_hdrlen — get header length in bytes from frame control
ieee80211_get_hdrlen_from_skb — get header length from data
struct ieee80211_radiotap_iterator — tracks walk thru present radiotap args
5. Data path helpers
ieee80211_data_to_8023 — convert an 802.11 data frame to 802.3
ieee80211_data_from_8023 — convert an 802.3 frame to 802.11
ieee80211_amsdu_to_8023s — decode an IEEE 802.11n A-MSDU frame
cfg80211_classify8021d — determine the 802.1p/1d tag for a data frame
6. Regulatory enforcement infrastructure
regulatory_hint — driver hint to the wireless core a regulatory domain
wiphy_apply_custom_regulatory — apply a custom driver regulatory domain
freq_reg_info — get regulatory information for the given frequency
7. RFkill integration
wiphy_rfkill_set_hw_state — notify cfg80211 about hw block state
wiphy_rfkill_start_polling — start polling rfkill
wiphy_rfkill_stop_polling — stop polling rfkill
8. Test mode
cfg80211_testmode_alloc_reply_skb — allocate testmode reply
cfg80211_testmode_reply — send the reply skb
cfg80211_testmode_alloc_event_skb — allocate testmode event
cfg80211_testmode_event — send the event
The mac80211 subsystem
I. The basic mac80211 driver interface
1. Basic hardware handling
struct ieee80211_hw — hardware information and state
enum ieee80211_hw_flags — hardware flags
SET_IEEE80211_DEV — set device for 802.11 hardware
SET_IEEE80211_PERM_ADDR — set the permanent MAC address for 802.11 hardware
struct ieee80211_ops — callbacks from mac80211 to the driver
ieee80211_alloc_hw — Allocate a new hardware device
ieee80211_register_hw — Register hardware device
ieee80211_unregister_hw — Unregister a hardware device
ieee80211_free_hw — free hardware descriptor
2. PHY configuration
struct ieee80211_conf — configuration of the device
enum ieee80211_conf_flags — configuration flags
3. Virtual interfaces
struct ieee80211_vif — per-interface data
4. Receive and transmit processing
what should be here
Frame format
Packet alignment
Calling into mac80211 from interrupts
functions/definitions
5. Frame filtering
enum ieee80211_filter_flags — hardware filter flags
6. The mac80211 workqueue
ieee80211_queue_work — add work onto the mac80211 workqueue
ieee80211_queue_delayed_work — add work onto the mac80211 workqueue
II. Advanced driver interface
7. LED support
ieee80211_get_tx_led_name — get name of TX LED
ieee80211_get_rx_led_name — get name of RX LED
ieee80211_get_assoc_led_name — get name of association LED
ieee80211_get_radio_led_name — get name of radio LED
struct ieee80211_tpt_blink — throughput blink description
enum ieee80211_tpt_led_trigger_flags — throughput trigger flags
ieee80211_create_tpt_led_trigger — create throughput LED trigger
8. Hardware crypto acceleration
enum set_key_cmd — key command
struct ieee80211_key_conf — key information
enum ieee80211_key_flags — key flags
ieee80211_get_tkip_p1k — get a TKIP phase 1 key
ieee80211_get_tkip_p1k_iv — get a TKIP phase 1 key for IV32
ieee80211_get_tkip_p2k — get a TKIP phase 2 key
9. Powersave support
10. Beacon filter support
ieee80211_beacon_loss — inform hardware does not receive beacons
11. Multiple queues and QoS support
struct ieee80211_tx_queue_params — transmit queue configuration
12. Access point mode support
support for powersaving clients
ieee80211_get_buffered_bc — accessing buffered broadcast and multicast frames
ieee80211_beacon_get — beacon generation function
ieee80211_sta_eosp — notify mac80211 about end of SP
enum ieee80211_frame_release_type — frame release reason
ieee80211_sta_ps_transition — PS transition for connected sta
ieee80211_sta_ps_transition_ni — PS transition for connected sta (in process context)
ieee80211_sta_set_buffered — inform mac80211 about driver-buffered frames
ieee80211_sta_block_awake — block station from waking up
13. Supporting multiple virtual interfaces
ieee80211_iterate_active_interfaces — iterate active interfaces
ieee80211_iterate_active_interfaces_atomic — iterate active interfaces
14. Station handling
struct ieee80211_sta — station table entry
enum sta_notify_cmd — sta notify command
ieee80211_find_sta — find a station
ieee80211_find_sta_by_ifaddr — find a station on hardware
15. Hardware scan offload
ieee80211_scan_completed — completed hardware scan
16. Aggregation
TX A-MPDU aggregation
RX A-MPDU aggregation
17. Spatial Multiplexing Powersave (SMPS)
ieee80211_request_smps — request SM PS transition
enum ieee80211_smps_mode — spatial multiplexing power save mode
III. Rate control interface
18. Rate Control API
ieee80211_start_tx_ba_session — Start a tx Block Ack session.
ieee80211_start_tx_ba_cb_irqsafe — low level driver ready to aggregate.
ieee80211_stop_tx_ba_session — Stop a Block Ack session.
ieee80211_stop_tx_ba_cb_irqsafe — low level driver ready to stop aggregate.
enum ieee80211_rate_control_changed — flags to indicate what changed
struct ieee80211_tx_rate_control — rate control information for/from RC algo
rate_control_send_low — helper for drivers for management/no-ack frames
IV. Internals
19. Key handling
Key handling basics
MORE TBD
20. Receive processing
21. Transmit processing
22. Station info handling
Programming information
STA information lifetime rules
23. Aggregation
struct sta_ampdu_mlme — STA aggregation information.
struct tid_ampdu_tx — TID aggregation information (Tx).
struct tid_ampdu_rx — TID aggregation information (Rx).
24. Synchronisation