net/mac80211/mesh_sync.c - maze/linux - Git at Google

 /*
  * Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
  * Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
  * Copyright 2011-2012, cozybit Inc.
  *
  * This program 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.
  */

 #include "ieee80211_i.h"
 #include "mesh.h"
 #include "driver-ops.h"

 /* This is not in the standard.  It represents a tolerable tbtt drift below
  * which we do no TSF adjustment.
  */
 #define TOFFSET_MINIMUM_ADJUSTMENT 10

 /* This is not in the standard. It is a margin added to the
  * Toffset setpoint to mitigate TSF overcorrection
  * introduced by TSF adjustment latency.
  */
 #define TOFFSET_SET_MARGIN 20

 /* This is not in the standard.  It represents the maximum Toffset jump above
  * which we'll invalidate the Toffset setpoint and choose a new setpoint.  This
  * could be, for instance, in case a neighbor is restarted and its TSF counter
  * reset.
  */
 #define TOFFSET_MAXIMUM_ADJUSTMENT 30000		/* 30 ms */

 struct sync_method {
 	u8 method;
 	struct ieee80211_mesh_sync_ops ops;
 };

 /**
  * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
  *
  * @ie: information elements of a management frame from the mesh peer
  */
 static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
 {
 	return (ie->mesh_config->meshconf_cap &
 	    MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
 }

 void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_local *local = sdata->local;
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 	/* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
 	u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
 	u64 tsf;
 	u64 tsfdelta;

 	spin_lock_bh(&ifmsh->sync_offset_lock);
 	if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
 		msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting\n",
 			  (long long) ifmsh->sync_offset_clockdrift_max);
 		tsfdelta = -ifmsh->sync_offset_clockdrift_max;
 		ifmsh->sync_offset_clockdrift_max = 0;
 	} else {
 		msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting by %llu\n",
 			  (long long) ifmsh->sync_offset_clockdrift_max,
 			  (unsigned long long) beacon_int_fraction);
 		tsfdelta = -beacon_int_fraction;
 		ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
 	}
 	spin_unlock_bh(&ifmsh->sync_offset_lock);

 	tsf = drv_get_tsf(local, sdata);
 	if (tsf != -1ULL)
 		drv_set_tsf(local, sdata, tsf + tsfdelta);
 }

 static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 				   u16 stype,
 				   struct ieee80211_mgmt *mgmt,
 				   struct ieee802_11_elems *elems,
 				   struct ieee80211_rx_status *rx_status)
 {
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 	struct ieee80211_local *local = sdata->local;
 	struct sta_info *sta;
 	u64 t_t, t_r;

 	WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);

 	/* standard mentions only beacons */
 	if (stype != IEEE80211_STYPE_BEACON)
 		return;

 	/* The current tsf is a first approximation for the timestamp
 	 * for the received beacon.  Further down we try to get a
 	 * better value from the rx_status->mactime field if
 	 * available. Also we have to call drv_get_tsf() before
 	 * entering the rcu-read section.*/
 	t_r = drv_get_tsf(local, sdata);

 	rcu_read_lock();
 	sta = sta_info_get(sdata, mgmt->sa);
 	if (!sta)
 		goto no_sync;

 	/* check offset sync conditions (13.13.2.2.1)
 	 *
 	 * TODO also sync to
 	 * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
 	 */

 	if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
 		clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 		msync_dbg(sdata, "STA %pM : is adjusting TBTT\n", sta->sta.addr);
 		goto no_sync;
 	}

 	if (ieee80211_have_rx_timestamp(rx_status))
 		/* time when timestamp field was received */
 		t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
 						       24 + 12 +
 						       elems->total_len +
 						       FCS_LEN,
 						       24);

 	/* Timing offset calculation (see 13.13.2.2.2) */
 	t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 	sta->t_offset = t_t - t_r;

 	if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 		s64 t_clockdrift = sta->t_offset_setpoint
 				   - sta->t_offset;
 		msync_dbg(sdata,
 			  "STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n",
 			  sta->sta.addr,
 			  (long long) sta->t_offset,
 			  (long long)
 			  sta->t_offset_setpoint,
 			  (long long) t_clockdrift);

 		if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
 			t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
 			msync_dbg(sdata,
 				  "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
 				  sta->sta.addr,
 				  (long long) t_clockdrift);
 			clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 			goto no_sync;
 		}

 		rcu_read_unlock();

 		spin_lock_bh(&ifmsh->sync_offset_lock);
 		if (t_clockdrift >
 		    ifmsh->sync_offset_clockdrift_max)
 			ifmsh->sync_offset_clockdrift_max
 				= t_clockdrift;
 		spin_unlock_bh(&ifmsh->sync_offset_lock);

 	} else {
 		sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
 		set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 		msync_dbg(sdata,
 			  "STA %pM : offset was invalid, sta->t_offset=%lld\n",
 			  sta->sta.addr,
 			  (long long) sta->t_offset);
 		rcu_read_unlock();
 	}
 	return;

 no_sync:
 	rcu_read_unlock();
 }

 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;

 	WARN_ON(ifmsh->mesh_sp_id
 		!= IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 	BUG_ON(!rcu_read_lock_held());

 	spin_lock_bh(&ifmsh->sync_offset_lock);

 	if (ifmsh->sync_offset_clockdrift_max >
 		TOFFSET_MINIMUM_ADJUSTMENT) {
 		/* Since ajusting the tsf here would
 		 * require a possibly blocking call
 		 * to the driver tsf setter, we punt
 		 * the tsf adjustment to the mesh tasklet
 		 */
 		msync_dbg(sdata,
 			  "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
 			  ifmsh->sync_offset_clockdrift_max);
 		set_bit(MESH_WORK_DRIFT_ADJUST,
 			&ifmsh->wrkq_flags);
 	} else {
 		msync_dbg(sdata,
 			  "TBTT : max clockdrift=%lld; too small to adjust\n",
 			  (long long)ifmsh->sync_offset_clockdrift_max);
 		ifmsh->sync_offset_clockdrift_max = 0;
 	}
 	spin_unlock_bh(&ifmsh->sync_offset_lock);
 }

 static const struct sync_method sync_methods[] = {
 	{
 		.method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 		.ops = {
 			.rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 			.adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
 		}
 	},
 };

 const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 {
 	const struct ieee80211_mesh_sync_ops *ops = NULL;
 	u8 i;

 	for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 		if (sync_methods[i].method == method) {
 			ops = &sync_methods[i].ops;
 			break;
 		}
 	}
 	return ops;
 }
	/*
	* Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
	* Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
	* Copyright 2011-2012, cozybit Inc.
	*
	* This program 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.
	*/

	#include "ieee80211_i.h"
	#include "mesh.h"
	#include "driver-ops.h"

	/* This is not in the standard. It represents a tolerable tbtt drift below
	* which we do no TSF adjustment.
	*/
	#define TOFFSET_MINIMUM_ADJUSTMENT 10

	/* This is not in the standard. It is a margin added to the
	* Toffset setpoint to mitigate TSF overcorrection
	* introduced by TSF adjustment latency.
	*/
	#define TOFFSET_SET_MARGIN 20

	/* This is not in the standard. It represents the maximum Toffset jump above
	* which we'll invalidate the Toffset setpoint and choose a new setpoint. This
	* could be, for instance, in case a neighbor is restarted and its TSF counter
	* reset.
	*/
	#define TOFFSET_MAXIMUM_ADJUSTMENT 30000 /* 30 ms */

	struct sync_method {
	u8 method;
	struct ieee80211_mesh_sync_ops ops;
	};

	/**
	* mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
	*
	* @ie: information elements of a management frame from the mesh peer
	*/
	static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
	{
	return (ie->mesh_config->meshconf_cap &
	MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
	}

	void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
	{
	struct ieee80211_local *local = sdata->local;
	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
	/* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
	u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
	u64 tsf;
	u64 tsfdelta;

	spin_lock_bh(&ifmsh->sync_offset_lock);
	if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
	msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting\n",
	(long long) ifmsh->sync_offset_clockdrift_max);
	tsfdelta = -ifmsh->sync_offset_clockdrift_max;
	ifmsh->sync_offset_clockdrift_max = 0;
	} else {
	msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting by %llu\n",
	(long long) ifmsh->sync_offset_clockdrift_max,
	(unsigned long long) beacon_int_fraction);
	tsfdelta = -beacon_int_fraction;
	ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
	}
	spin_unlock_bh(&ifmsh->sync_offset_lock);

	tsf = drv_get_tsf(local, sdata);
	if (tsf != -1ULL)
	drv_set_tsf(local, sdata, tsf + tsfdelta);
	}

	static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
	u16 stype,
	struct ieee80211_mgmt *mgmt,
	struct ieee802_11_elems *elems,
	struct ieee80211_rx_status *rx_status)
	{
	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
	struct ieee80211_local *local = sdata->local;
	struct sta_info *sta;
	u64 t_t, t_r;

	WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);

	/* standard mentions only beacons */
	if (stype != IEEE80211_STYPE_BEACON)
	return;

	/* The current tsf is a first approximation for the timestamp
	* for the received beacon. Further down we try to get a
	* better value from the rx_status->mactime field if
	* available. Also we have to call drv_get_tsf() before
	* entering the rcu-read section.*/
	t_r = drv_get_tsf(local, sdata);

	rcu_read_lock();
	sta = sta_info_get(sdata, mgmt->sa);
	if (!sta)
	goto no_sync;

	/* check offset sync conditions (13.13.2.2.1)
	*
	* TODO also sync to
	* dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
	*/

	if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
	clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
	msync_dbg(sdata, "STA %pM : is adjusting TBTT\n", sta->sta.addr);
	goto no_sync;
	}

	if (ieee80211_have_rx_timestamp(rx_status))
	/* time when timestamp field was received */
	t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
	24 + 12 +
	elems->total_len +
	FCS_LEN,
	24);

	/* Timing offset calculation (see 13.13.2.2.2) */
	t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
	sta->t_offset = t_t - t_r;

	if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
	s64 t_clockdrift = sta->t_offset_setpoint
	- sta->t_offset;
	msync_dbg(sdata,
	"STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n",
	sta->sta.addr,
	(long long) sta->t_offset,
	(long long)
	sta->t_offset_setpoint,
	(long long) t_clockdrift);

	if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT \|\|
	t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
	msync_dbg(sdata,
	"STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
	sta->sta.addr,
	(long long) t_clockdrift);
	clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
	goto no_sync;
	}

	rcu_read_unlock();

	spin_lock_bh(&ifmsh->sync_offset_lock);
	if (t_clockdrift >
	ifmsh->sync_offset_clockdrift_max)
	ifmsh->sync_offset_clockdrift_max
	= t_clockdrift;
	spin_unlock_bh(&ifmsh->sync_offset_lock);

	} else {
	sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
	set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
	msync_dbg(sdata,
	"STA %pM : offset was invalid, sta->t_offset=%lld\n",
	sta->sta.addr,
	(long long) sta->t_offset);
	rcu_read_unlock();
	}
	return;

	no_sync:
	rcu_read_unlock();
	}

	static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
	{
	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;

	WARN_ON(ifmsh->mesh_sp_id
	!= IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
	BUG_ON(!rcu_read_lock_held());

	spin_lock_bh(&ifmsh->sync_offset_lock);

	if (ifmsh->sync_offset_clockdrift_max >
	TOFFSET_MINIMUM_ADJUSTMENT) {
	/* Since ajusting the tsf here would
	* require a possibly blocking call
	* to the driver tsf setter, we punt
	* the tsf adjustment to the mesh tasklet
	*/
	msync_dbg(sdata,
	"TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
	ifmsh->sync_offset_clockdrift_max);
	set_bit(MESH_WORK_DRIFT_ADJUST,
	&ifmsh->wrkq_flags);
	} else {
	msync_dbg(sdata,
	"TBTT : max clockdrift=%lld; too small to adjust\n",
	(long long)ifmsh->sync_offset_clockdrift_max);
	ifmsh->sync_offset_clockdrift_max = 0;
	}
	spin_unlock_bh(&ifmsh->sync_offset_lock);
	}

	static const struct sync_method sync_methods[] = {
	{
	.method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
	.ops = {
	.rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
	.adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
	}
	},
	};

	const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
	{
	const struct ieee80211_mesh_sync_ops *ops = NULL;
	u8 i;

	for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
	if (sync_methods[i].method == method) {
	ops = &sync_methods[i].ops;
	break;
	}
	}
	return ops;
	}