FRAME FILTERING(9)

🦋 Frame filtering 🦋

okay so bestie, this is Frame filtering(9) from the Kernel API Manual, and we're about to get into how mac80211 handles frame filtering. no cap, it's kind of iconic.

mac80211 requires to see many management frames for proper operation, and users may want to see many more frames when in monitor mode. However, for best CPU usage and power consumption, having as few frames as possible percolate through the stack is desirable. Hence, the hardware should filter as much as possible.

To achieve this, mac80211 uses filter flags (see below) to tell the driver's configure_filter function which frames should be passed to mac80211 and which should be filtered out.

Before configure_filter is invoked, the prepare_multicast callback is invoked with the parameters mc_count and mc_list for the combined multicast address list of all virtual interfaces. Its use is optional, and it returns a u64 that is passed to configure_filter. Additionally, configure_filter has the arguments changed_flags telling which flags were changed and total_flags with the new flag states.

If your device has no multicast address filters your driver will need to check both the FIF_ALLMULTI flag and the mc_count parameter to see whether multicast frames should be accepted or dropped.

heads up, bestie: all unsupported flags in total_flags must be cleared. Hardware does not support a flag if it is incapable of _passing_ the frame to the stack. Otherwise the driver must ignore the flag, but not clear it. You must _only_ clear the flag (announce no support for the flag to mac80211) if you are not able to pass the packet type to the stack (so the hardware always filters it). So for example, you should clear FIF_CONTROL, if your hardware always filters control frames. If your hardware always passes control frames to the kernel and is incapable of filtering them, you do _not_ clear the FIF_CONTROL flag. This rule applies to all other FIF flags as well.

🌈 SEE ALSO 🌈

the whole friend group is here — every single reference, no cap:

• Kernel file ./include/net/mac80211.h Introduction(9)
• Calling mac80211 from interrupts(9)
• Warning(9)
• Frame format(9)
• mac80211 workqueue(9)
• mac80211 software tx queueing(9)
• HW timestamping(9)
• enum ieee80211_max_queues(9)
• enum ieee80211_ac_numbers(9)
• struct ieee80211_tx_queue_params(9)
• enum ieee80211_chanctx_change(9)
• struct ieee80211_chan_req(9)
• struct ieee80211_chanctx_conf(9)
• enum ieee80211_chanctx_switch_mode(9)
• struct ieee80211_vif_chanctx_switch(9)
• enum ieee80211_bss_change(9)
• enum ieee80211_event_type(9)
• enum ieee80211_rssi_event_data(9)
• struct ieee80211_rssi_event(9)
• enum ieee80211_mlme_event_data(9)
• enum ieee80211_mlme_event_status(9)
• struct ieee80211_mlme_event(9)
• struct ieee80211_ba_event(9)
• struct ieee80211_event(9)
• struct ieee80211_mu_group_data(9)
• struct ieee80211_ftm_responder_params(9)
• struct ieee80211_fils_discovery(9)
• struct ieee80211_parsed_tpe(9)
• struct ieee80211_bss_npca_params(9)
• struct ieee80211_bss_conf(9)
• struct ieee80211_nan_channel(9)
• struct ieee80211_nan_peer_map(9)
• struct ieee80211_nan_peer_sched(9)
• enum mac80211_tx_info_flags(9)
• enum mac80211_tx_control_flags(9)
• enum mac80211_tx_status_flags(9)
• enum mac80211_rate_control_flags(9)
• struct ieee80211_tx_rate(9)
• struct ieee80211_tx_info(9)
• struct ieee80211_tx_status(9)
• struct ieee80211_scan_ies(9)
• ieee80211_tx_info_clear_status(9)
• enum mac80211_rx_flags(9)
• enum mac80211_rx_encoding_flags(9)
• struct ieee80211_rx_status(9)
• enum ieee80211_conf_flags(9)
• enum ieee80211_conf_changed(9)
• enum ieee80211_smps_mode(9)
• struct ieee80211_conf(9)
• struct ieee80211_channel_switch(9)
• enum ieee80211_vif_flags(9)
• enum ieee80211_offload_flags(9)
• struct ieee80211_eml_params(9)
• struct ieee80211_nan_sched_cfg(9)
• struct ieee80211_vif_cfg(9)
• struct ieee80211_neg_ttlm(9)
• enum ieee80211_neg_ttlm_res(9)
• struct ieee80211_vif(9)
• ieee80211_vif_usable_links(9)
• ieee80211_vif_is_mld(9)
• ieee80211_vif_link_active(9)
• wdev_to_ieee80211_vif(9)
• ieee80211_vif_to_wdev(9)
• enum ieee80211_key_flags(9)
• struct ieee80211_key_conf(9)
• struct ieee80211_key_seq(9)
• enum set_key_cmd(9)
• enum ieee80211_sta_state(9)
• enum ieee80211_sta_rx_bandwidth(9)
• struct ieee80211_sta_rates(9)
• struct ieee80211_sta_txpwr(9)
• struct ieee80211_sta_aggregates(9)
• struct ieee80211_link_sta(9)
• struct ieee80211_sta(9)
• enum sta_notify_cmd(9)
• struct ieee80211_tx_control(9)
• struct ieee80211_txq(9)
• enum ieee80211_hw_flags(9)
• struct ieee80211_hw(9)
• struct ieee80211_scan_request(9)
• struct ieee80211_tdls_ch_sw_params(9)
• wiphy_to_ieee80211_hw(9)
• SET_IEEE80211_DEV(9)
• SET_IEEE80211_PERM_ADDR(9)
• ieee80211_free_txskb(9)
• ieee80211_purge_tx_queue(9)
• Hardware crypto acceleration(9)
• Powersave support(9)
• Beacon filter support(9)
• Spatial multiplexing power save(9)
• AP support for powersaving clients(9)
• HW queue control(9)
• enum ieee80211_filter_flags(9)
• enum ieee80211_ampdu_mlme_action(9)
• struct ieee80211_ampdu_params(9)
• enum ieee80211_frame_release_type(9)
• enum ieee80211_rate_control_changed(9)
• enum ieee80211_roc_type(9)
• enum ieee80211_reconfig_type(9)
• struct ieee80211_prep_tx_info(9)
• struct ieee80211_ops(9)
• ieee80211_alloc_hw_nm(9)
• ieee80211_alloc_hw(9)
• ieee80211_register_hw(9)
• struct ieee80211_tpt_blink(9)
• enum ieee80211_tpt_led_trigger_flags(9)
• ieee80211_get_tx_led_name(9)
• ieee80211_get_rx_led_name(9)
• ieee80211_get_assoc_led_name(9)
• ieee80211_get_radio_led_name(9)
• ieee80211_create_tpt_led_trigger(9)
• ieee80211_unregister_hw(9)
• ieee80211_free_hw(9)
• ieee80211_restart_hw(9)
• ieee80211_rx_list(9)
• ieee80211_rx_napi(9)
• ieee80211_rx(9)
• ieee80211_rx_irqsafe(9)
• ieee80211_rx_ni(9)
• ieee80211_sta_ps_transition(9)
• ieee80211_sta_ps_transition_ni(9)
• ieee80211_sta_pspoll(9)
• ieee80211_sta_uapsd_trigger(9)
• ieee80211_sta_set_buffered(9)
• ieee80211_get_tx_rates(9)
• ieee80211_tx_rate_update(9)
• ieee80211_tx_status_skb(9)
• ieee80211_tx_status_ext(9)
• ieee80211_tx_status_noskb(9)
• ieee80211_tx_status_ni(9)
• ieee80211_tx_status_irqsafe(9)
• ieee80211_report_low_ack(9)
• struct ieee80211_mutable_offsets(9)
• ieee80211_beacon_get_template(9)
• ieee80211_beacon_get_template_ema_index(9)
• struct ieee80211_ema_beacons(9)
• ieee80211_beacon_get_template_ema_list(9)
• ieee80211_beacon_free_ema_list(9)
• ieee80211_beacon_get_tim(9)
• ieee80211_beacon_get(9)
• ieee80211_beacon_update_cntdwn(9)
• ieee80211_beacon_set_cntdwn(9)
• ieee80211_csa_finish(9)
• ieee80211_beacon_cntdwn_is_complete(9)
• ieee80211_color_change_finish(9)
• ieee80211_proberesp_get(9)
• ieee80211_pspoll_get(9)
• ieee80211_nullfunc_get(9)
• ieee80211_probereq_get(9)
• ieee80211_rts_get(9)
• ieee80211_rts_duration(9)
• ieee80211_ctstoself_get(9)
• ieee80211_ctstoself_duration(9)
• ieee80211_generic_frame_duration(9)
• ieee80211_get_buffered_bc(9)
• ieee80211_get_tkip_p1k_iv(9)
• ieee80211_get_tkip_p1k(9)
• ieee80211_get_tkip_rx_p1k(9)
• ieee80211_get_tkip_p2k(9)
• ieee80211_tkip_add_iv(9)
• ieee80211_get_key_rx_seq(9)
• ieee80211_set_key_rx_seq(9)
• ieee80211_gtk_rekey_add(9)
• ieee80211_gtk_rekey_notify(9)
• ieee80211_key_mic_failure(9)
• ieee80211_key_replay(9)
• ieee80211_wake_queue(9)
• ieee80211_stop_queue(9)
• ieee80211_queue_stopped(9)
• ieee80211_stop_queues(9)
• ieee80211_wake_queues(9)
• ieee80211_scan_completed(9)
• ieee80211_sched_scan_results(9)
• ieee80211_sched_scan_stopped(9)
• enum ieee80211_interface_iteration_flags(9)
• ieee80211_iterate_interfaces(9)
• ieee80211_iterate_active_interfaces(9)
• ieee80211_iterate_active_interfaces_atomic(9)
• for_each_interface(9)
• for_each_active_interface(9)
• ieee80211_iterate_active_interfaces_mtx(9)
• ieee80211_iterate_stations_atomic(9)
• for_each_station(9)
• ieee80211_iterate_stations_mtx(9)
• ieee80211_queue_work(9)
• ieee80211_queue_delayed_work(9)
• ieee80211_refresh_tx_agg_session_timer(9)
• ieee80211_start_tx_ba_session(9)
• ieee80211_start_tx_ba_cb_irqsafe(9)
• ieee80211_stop_tx_ba_session(9)
• ieee80211_stop_tx_ba_cb_irqsafe(9)
• ieee80211_find_sta(9)
• ieee80211_find_sta_by_ifaddr(9)
• ieee80211_find_sta_by_link_addrs(9)
• ieee80211_sta_block_awake(9)
• ieee80211_sta_eosp(9)
• ieee80211_send_eosp_nullfunc(9)
• ieee80211_sta_recalc_aggregates(9)
• ieee80211_sta_register_airtime(9)
• ieee80211_txq_airtime_check(9)
• ieee80211_txq_aql_pending(9)
• ieee80211_iter_keys(9)
• ieee80211_iter_keys_rcu(9)
• ieee80211_iter_chan_contexts_atomic(9)
• ieee80211_iter_chan_contexts_mtx(9)
• ieee80211_ap_probereq_get(9)
• ieee80211_beacon_loss(9)
• ieee80211_connection_loss(9)
• ieee80211_disconnect(9)
• ieee80211_resume_disconnect(9)
• ieee80211_hw_restart_disconnect(9)
• ieee80211_cqm_rssi_notify(9)
• ieee80211_cqm_beacon_loss_notify(9)
• ieee80211_radar_detected(9)
• ieee80211_chswitch_done(9)
• ieee80211_channel_switch_disconnect(9)
• ieee80211_request_smps(9)
• ieee80211_ready_on_channel(9)
• ieee80211_remain_on_channel_expired(9)
• ieee80211_stop_rx_ba_session(9)
• ieee80211_mark_rx_ba_filtered_frames(9)
• ieee80211_send_bar(9)
• ieee80211_manage_rx_ba_offl(9)
• ieee80211_start_rx_ba_session_offl(9)
• ieee80211_stop_rx_ba_session_offl(9)
• ieee80211_rx_ba_timer_expired(9)
• struct ieee80211_tx_rate_control(9)
• enum rate_control_capabilities(9)
• rate_control_set_rates(9)
• ieee80211_get_he_iftype_cap_vif(9)
• ieee80211_get_he_6ghz_capa_vif(9)
• ieee80211_get_eht_iftype_cap_vif(9)
• ieee80211_get_uhr_iftype_cap_vif(9)
• ieee80211_update_mu_groups(9)
• ieee80211_ave_rssi(9)
• ieee80211_calculate_rx_timestamp(9)
• ieee80211_report_wowlan_wakeup(9)
• ieee80211_tx_prepare_skb(9)
• ieee80211_parse_tx_radiotap(9)
• struct ieee80211_noa_data(9)
• ieee80211_parse_p2p_noa(9)
• ieee80211_update_p2p_noa(9)
• ieee80211_tdls_oper_request(9)
• ieee80211_reserve_tid(9)
• ieee80211_unreserve_tid(9)
• ieee80211_tx_dequeue(9)
• ieee80211_tx_dequeue_ni(9)
• ieee80211_handle_wake_tx_queue(9)
• ieee80211_next_txq(9)
• ieee80211_txq_schedule_start(9)
• ieee80211_schedule_txq(9)
• ieee80211_return_txq(9)
• ieee80211_txq_may_transmit(9)
• ieee80211_txq_get_depth(9)
• ieee80211_nan_func_terminated(9)
• ieee80211_nan_func_match(9)
• ieee80211_nan_sched_update_done(9)
• ieee80211_nan_cluster_joined(9)
• ieee80211_nan_try_evacuate(9)
• ieee80211_calc_rx_airtime(9)
• ieee80211_calc_tx_airtime(9)
• ieee80211_get_fils_discovery_tmpl(9)
• ieee80211_get_unsol_bcast_probe_resp_tmpl(9)
• ieee80211_obss_color_collision_notify(9)
• ieee80211_is_tx_data(9)
• ieee80211_set_active_links(9)
• ieee80211_set_active_links_async(9)
• ieee80211_send_teardown_neg_ttlm(9)
• ieee80211_chan_width_to_rx_bw(9)
• ieee80211_prepare_rx_omi_bw(9)
• ieee80211_finalize_rx_omi_bw(9)
• ieee80211_vif_nan_started(9)
• ieee80211_encrypt_tx_skb(9)

made with 💖 by your manpage bestie — source ./include/net, dated October 2026, manual Frame filtering(9). periodt. 🫶