Explaining wireless 802.11 networking in the Linux kernel 2007-2009 Johannes Berg Johannes Berg

johannes@sipsolutions.net

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. You should have received a copy of the GNU General Public License along with this documentation; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA For more details see the file COPYING in the source distribution of Linux. 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". !Pinclude/net/cfg80211.h Introduction !Pinclude/net/cfg80211.h Device registration !Finclude/net/cfg80211.h ieee80211_band !Finclude/net/cfg80211.h ieee80211_channel_flags !Finclude/net/cfg80211.h ieee80211_channel !Finclude/net/cfg80211.h ieee80211_rate_flags !Finclude/net/cfg80211.h ieee80211_rate !Finclude/net/cfg80211.h ieee80211_sta_ht_cap !Finclude/net/cfg80211.h ieee80211_supported_band !Finclude/net/cfg80211.h cfg80211_signal_type !Finclude/net/cfg80211.h wiphy_params_flags !Finclude/net/cfg80211.h wiphy_flags !Finclude/net/cfg80211.h wiphy !Finclude/net/cfg80211.h wireless_dev !Finclude/net/cfg80211.h wiphy_new !Finclude/net/cfg80211.h wiphy_register !Finclude/net/cfg80211.h wiphy_unregister !Finclude/net/cfg80211.h wiphy_free !Finclude/net/cfg80211.h wiphy_name !Finclude/net/cfg80211.h wiphy_dev !Finclude/net/cfg80211.h wiphy_priv !Finclude/net/cfg80211.h priv_to_wiphy !Finclude/net/cfg80211.h set_wiphy_dev !Finclude/net/cfg80211.h wdev_priv !Finclude/net/cfg80211.h ieee80211_iface_limit !Finclude/net/cfg80211.h ieee80211_iface_combination !Finclude/net/cfg80211.h cfg80211_check_combinations !Pinclude/net/cfg80211.h Actions and configuration !Finclude/net/cfg80211.h cfg80211_ops !Finclude/net/cfg80211.h vif_params !Finclude/net/cfg80211.h key_params !Finclude/net/cfg80211.h survey_info_flags !Finclude/net/cfg80211.h survey_info !Finclude/net/cfg80211.h cfg80211_beacon_data !Finclude/net/cfg80211.h cfg80211_ap_settings !Finclude/net/cfg80211.h station_parameters !Finclude/net/cfg80211.h station_info_flags !Finclude/net/cfg80211.h rate_info_flags !Finclude/net/cfg80211.h rate_info !Finclude/net/cfg80211.h station_info !Finclude/net/cfg80211.h monitor_flags !Finclude/net/cfg80211.h mpath_info_flags !Finclude/net/cfg80211.h mpath_info !Finclude/net/cfg80211.h bss_parameters !Finclude/net/cfg80211.h ieee80211_txq_params !Finclude/net/cfg80211.h cfg80211_crypto_settings !Finclude/net/cfg80211.h cfg80211_auth_request !Finclude/net/cfg80211.h cfg80211_assoc_request !Finclude/net/cfg80211.h cfg80211_deauth_request !Finclude/net/cfg80211.h cfg80211_disassoc_request !Finclude/net/cfg80211.h cfg80211_ibss_params !Finclude/net/cfg80211.h cfg80211_connect_params !Finclude/net/cfg80211.h cfg80211_pmksa !Finclude/net/cfg80211.h cfg80211_rx_mlme_mgmt !Finclude/net/cfg80211.h cfg80211_auth_timeout !Finclude/net/cfg80211.h cfg80211_rx_assoc_resp !Finclude/net/cfg80211.h cfg80211_assoc_timeout !Finclude/net/cfg80211.h cfg80211_tx_mlme_mgmt !Finclude/net/cfg80211.h cfg80211_ibss_joined !Finclude/net/cfg80211.h cfg80211_connect_result !Finclude/net/cfg80211.h cfg80211_roamed !Finclude/net/cfg80211.h cfg80211_disconnected !Finclude/net/cfg80211.h cfg80211_ready_on_channel !Finclude/net/cfg80211.h cfg80211_remain_on_channel_expired !Finclude/net/cfg80211.h cfg80211_new_sta !Finclude/net/cfg80211.h cfg80211_rx_mgmt !Finclude/net/cfg80211.h cfg80211_mgmt_tx_status !Finclude/net/cfg80211.h cfg80211_cqm_rssi_notify !Finclude/net/cfg80211.h cfg80211_cqm_pktloss_notify !Finclude/net/cfg80211.h cfg80211_michael_mic_failure !Pinclude/net/cfg80211.h Scanning and BSS list handling !Finclude/net/cfg80211.h cfg80211_ssid !Finclude/net/cfg80211.h cfg80211_scan_request !Finclude/net/cfg80211.h cfg80211_scan_done !Finclude/net/cfg80211.h cfg80211_bss !Finclude/net/cfg80211.h cfg80211_inform_bss_width_frame !Finclude/net/cfg80211.h cfg80211_inform_bss_width !Finclude/net/cfg80211.h cfg80211_unlink_bss !Finclude/net/cfg80211.h cfg80211_find_ie !Finclude/net/cfg80211.h ieee80211_bss_get_ie !Pinclude/net/cfg80211.h Utility functions !Finclude/net/cfg80211.h ieee80211_channel_to_frequency !Finclude/net/cfg80211.h ieee80211_frequency_to_channel !Finclude/net/cfg80211.h ieee80211_get_channel !Finclude/net/cfg80211.h ieee80211_get_response_rate !Finclude/net/cfg80211.h ieee80211_hdrlen !Finclude/net/cfg80211.h ieee80211_get_hdrlen_from_skb !Finclude/net/cfg80211.h ieee80211_radiotap_iterator !Pinclude/net/cfg80211.h Data path helpers !Finclude/net/cfg80211.h ieee80211_data_to_8023 !Finclude/net/cfg80211.h ieee80211_data_from_8023 !Finclude/net/cfg80211.h ieee80211_amsdu_to_8023s !Finclude/net/cfg80211.h cfg80211_classify8021d !Pinclude/net/cfg80211.h Regulatory enforcement infrastructure !Finclude/net/cfg80211.h regulatory_hint !Finclude/net/cfg80211.h wiphy_apply_custom_regulatory !Finclude/net/cfg80211.h freq_reg_info !Pinclude/net/cfg80211.h RFkill integration !Finclude/net/cfg80211.h wiphy_rfkill_set_hw_state !Finclude/net/cfg80211.h wiphy_rfkill_start_polling !Finclude/net/cfg80211.h wiphy_rfkill_stop_polling !Pinclude/net/cfg80211.h Test mode !Finclude/net/cfg80211.h cfg80211_testmode_alloc_reply_skb !Finclude/net/cfg80211.h cfg80211_testmode_reply !Finclude/net/cfg80211.h cfg80211_testmode_alloc_event_skb !Finclude/net/cfg80211.h cfg80211_testmode_event !Pinclude/net/mac80211.h Introduction !Pinclude/net/mac80211.h Warning You should read and understand the information contained within this part of the book while implementing a driver. In some chapters, advanced usage is noted, that may be skipped at first. This part of the book only covers station and monitor mode functionality, additional information required to implement the other modes is covered in the second part of the book. TBD This chapter shall contain information on getting a hw struct allocated and registered with mac80211. Since it is required to allocate rates/modes before registering a hw struct, this chapter shall also contain information on setting up the rate/mode structs. Additionally, some discussion about the callbacks and the general programming model should be in here, including the definition of ieee80211_ops which will be referred to a lot. Finally, a discussion of hardware capabilities should be done with references to other parts of the book. !Finclude/net/mac80211.h ieee80211_hw !Finclude/net/mac80211.h ieee80211_hw_flags !Finclude/net/mac80211.h SET_IEEE80211_DEV !Finclude/net/mac80211.h SET_IEEE80211_PERM_ADDR !Finclude/net/mac80211.h ieee80211_ops !Finclude/net/mac80211.h ieee80211_alloc_hw !Finclude/net/mac80211.h ieee80211_register_hw !Finclude/net/mac80211.h ieee80211_unregister_hw !Finclude/net/mac80211.h ieee80211_free_hw TBD This chapter should describe PHY handling including start/stop callbacks and the various structures used. !Finclude/net/mac80211.h ieee80211_conf !Finclude/net/mac80211.h ieee80211_conf_flags TBD This chapter should describe virtual interface basics that are relevant to the driver (VLANs, MGMT etc are not.) It should explain the use of the add_iface/remove_iface callbacks as well as the interface configuration callbacks. Things related to AP mode should be discussed there. Things related to supporting multiple interfaces should be in the appropriate chapter, a BIG FAT note should be here about this though and the recommendation to allow only a single interface in STA mode at first! !Finclude/net/mac80211.h ieee80211_vif TBD This should describe the receive and transmit paths in mac80211/the drivers as well as transmit status handling. !Pinclude/net/mac80211.h Frame format !Pnet/mac80211/rx.c Packet alignment !Pinclude/net/mac80211.h Calling mac80211 from interrupts !Finclude/net/mac80211.h ieee80211_rx_status !Finclude/net/mac80211.h mac80211_rx_flags !Finclude/net/mac80211.h mac80211_tx_info_flags !Finclude/net/mac80211.h mac80211_tx_control_flags !Finclude/net/mac80211.h mac80211_rate_control_flags !Finclude/net/mac80211.h ieee80211_tx_rate !Finclude/net/mac80211.h ieee80211_tx_info !Finclude/net/mac80211.h ieee80211_tx_info_clear_status !Finclude/net/mac80211.h ieee80211_rx !Finclude/net/mac80211.h ieee80211_rx_ni !Finclude/net/mac80211.h ieee80211_rx_irqsafe !Finclude/net/mac80211.h ieee80211_tx_status !Finclude/net/mac80211.h ieee80211_tx_status_ni !Finclude/net/mac80211.h ieee80211_tx_status_irqsafe !Finclude/net/mac80211.h ieee80211_rts_get !Finclude/net/mac80211.h ieee80211_rts_duration !Finclude/net/mac80211.h ieee80211_ctstoself_get !Finclude/net/mac80211.h ieee80211_ctstoself_duration !Finclude/net/mac80211.h ieee80211_generic_frame_duration !Finclude/net/mac80211.h ieee80211_wake_queue !Finclude/net/mac80211.h ieee80211_stop_queue !Finclude/net/mac80211.h ieee80211_wake_queues !Finclude/net/mac80211.h ieee80211_stop_queues !Finclude/net/mac80211.h ieee80211_queue_stopped !Pinclude/net/mac80211.h Frame filtering !Finclude/net/mac80211.h ieee80211_filter_flags !Pinclude/net/mac80211.h mac80211 workqueue !Finclude/net/mac80211.h ieee80211_queue_work !Finclude/net/mac80211.h ieee80211_queue_delayed_work Information contained within this part of the book is of interest only for advanced interaction of mac80211 with drivers to exploit more hardware capabilities and improve performance. Mac80211 supports various ways of blinking LEDs. Wherever possible, device LEDs should be exposed as LED class devices and hooked up to the appropriate trigger, which will then be triggered appropriately by mac80211. !Finclude/net/mac80211.h ieee80211_get_tx_led_name !Finclude/net/mac80211.h ieee80211_get_rx_led_name !Finclude/net/mac80211.h ieee80211_get_assoc_led_name !Finclude/net/mac80211.h ieee80211_get_radio_led_name !Finclude/net/mac80211.h ieee80211_tpt_blink !Finclude/net/mac80211.h ieee80211_tpt_led_trigger_flags !Finclude/net/mac80211.h ieee80211_create_tpt_led_trigger !Pinclude/net/mac80211.h Hardware crypto acceleration !Finclude/net/mac80211.h set_key_cmd !Finclude/net/mac80211.h ieee80211_key_conf !Finclude/net/mac80211.h ieee80211_key_flags !Finclude/net/mac80211.h ieee80211_get_tkip_p1k !Finclude/net/mac80211.h ieee80211_get_tkip_p1k_iv !Finclude/net/mac80211.h ieee80211_get_tkip_p2k !Pinclude/net/mac80211.h Powersave support !Pinclude/net/mac80211.h Beacon filter support !Finclude/net/mac80211.h ieee80211_beacon_loss TBD !Finclude/net/mac80211.h ieee80211_tx_queue_params TBD Some parts of the if_conf should be discussed here instead Insert notes about VLAN interfaces with hw crypto here or in the hw crypto chapter.

!Pinclude/net/mac80211.h AP support for powersaving clients

!Finclude/net/mac80211.h ieee80211_get_buffered_bc !Finclude/net/mac80211.h ieee80211_beacon_get !Finclude/net/mac80211.h ieee80211_sta_eosp !Finclude/net/mac80211.h ieee80211_frame_release_type !Finclude/net/mac80211.h ieee80211_sta_ps_transition !Finclude/net/mac80211.h ieee80211_sta_ps_transition_ni !Finclude/net/mac80211.h ieee80211_sta_set_buffered !Finclude/net/mac80211.h ieee80211_sta_block_awake TBD Note: WDS with identical MAC address should almost always be OK Insert notes about having multiple virtual interfaces with different MAC addresses here, note which configurations are supported by mac80211, add notes about supporting hw crypto with it. !Finclude/net/mac80211.h ieee80211_iterate_active_interfaces !Finclude/net/mac80211.h ieee80211_iterate_active_interfaces_atomic TODO !Finclude/net/mac80211.h ieee80211_sta !Finclude/net/mac80211.h sta_notify_cmd !Finclude/net/mac80211.h ieee80211_find_sta !Finclude/net/mac80211.h ieee80211_find_sta_by_ifaddr TBD !Finclude/net/mac80211.h ieee80211_scan_completed !Pnet/mac80211/agg-tx.c TX A-MPDU aggregation !Cnet/mac80211/agg-tx.c !Pnet/mac80211/agg-rx.c RX A-MPDU aggregation !Cnet/mac80211/agg-rx.c !Finclude/net/mac80211.h ieee80211_ampdu_mlme_action !Pinclude/net/mac80211.h Spatial multiplexing power save !Finclude/net/mac80211.h ieee80211_request_smps !Finclude/net/mac80211.h ieee80211_smps_mode TBD This part of the book describes the rate control algorithm interface and how it relates to mac80211 and drivers. TBD !Finclude/net/mac80211.h ieee80211_start_tx_ba_session !Finclude/net/mac80211.h ieee80211_start_tx_ba_cb_irqsafe !Finclude/net/mac80211.h ieee80211_stop_tx_ba_session !Finclude/net/mac80211.h ieee80211_stop_tx_ba_cb_irqsafe !Finclude/net/mac80211.h ieee80211_rate_control_changed !Finclude/net/mac80211.h ieee80211_tx_rate_control !Finclude/net/mac80211.h rate_control_send_low TBD This part of the book describes mac80211 internals. !Pnet/mac80211/key.c Key handling basics TBD TBD TBD !Fnet/mac80211/sta_info.h sta_info !Fnet/mac80211/sta_info.h ieee80211_sta_info_flags !Pnet/mac80211/sta_info.c STA information lifetime rules !Fnet/mac80211/sta_info.h sta_ampdu_mlme !Fnet/mac80211/sta_info.h tid_ampdu_tx !Fnet/mac80211/sta_info.h tid_ampdu_rx TBD Locking, lots of RCU