1/*
2 * Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
3 * Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
4 * Copyright 2011-2012, cozybit Inc.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include "ieee80211_i.h"
12#include "mesh.h"
13#include "driver-ops.h"
14
15/* This is not in the standard.  It represents a tolerable tbtt drift below
16 * which we do no TSF adjustment.
17 */
18#define TOFFSET_MINIMUM_ADJUSTMENT 10
19
20/* This is not in the standard. It is a margin added to the
21 * Toffset setpoint to mitigate TSF overcorrection
22 * introduced by TSF adjustment latency.
23 */
24#define TOFFSET_SET_MARGIN 20
25
26/* This is not in the standard.  It represents the maximum Toffset jump above
27 * which we'll invalidate the Toffset setpoint and choose a new setpoint.  This
28 * could be, for instance, in case a neighbor is restarted and its TSF counter
29 * reset.
30 */
31#define TOFFSET_MAXIMUM_ADJUSTMENT 30000		/* 30 ms */
32
33struct sync_method {
34	u8 method;
35	struct ieee80211_mesh_sync_ops ops;
36};
37
38/**
39 * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
40 *
41 * @ie: information elements of a management frame from the mesh peer
42 */
43static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
44{
45	return (ie->mesh_config->meshconf_cap &
46			IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
47}
48
49void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
50{
51	struct ieee80211_local *local = sdata->local;
52	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
53	/* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
54	u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
55	u64 tsf;
56	u64 tsfdelta;
57
58	spin_lock_bh(&ifmsh->sync_offset_lock);
59	if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
60		msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting\n",
61			  (long long) ifmsh->sync_offset_clockdrift_max);
62		tsfdelta = -ifmsh->sync_offset_clockdrift_max;
63		ifmsh->sync_offset_clockdrift_max = 0;
64	} else {
65		msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting by %llu\n",
66			  (long long) ifmsh->sync_offset_clockdrift_max,
67			  (unsigned long long) beacon_int_fraction);
68		tsfdelta = -beacon_int_fraction;
69		ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
70	}
71	spin_unlock_bh(&ifmsh->sync_offset_lock);
72
73	tsf = drv_get_tsf(local, sdata);
74	if (tsf != -1ULL)
75		drv_set_tsf(local, sdata, tsf + tsfdelta);
76}
77
78static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
79				   u16 stype,
80				   struct ieee80211_mgmt *mgmt,
81				   struct ieee802_11_elems *elems,
82				   struct ieee80211_rx_status *rx_status)
83{
84	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
85	struct ieee80211_local *local = sdata->local;
86	struct sta_info *sta;
87	u64 t_t, t_r;
88
89	WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
90
91	/* standard mentions only beacons */
92	if (stype != IEEE80211_STYPE_BEACON)
93		return;
94
95	/*
96	 * Get time when timestamp field was received.  If we don't
97	 * have rx timestamps, then use current tsf as an approximation.
98	 * drv_get_tsf() must be called before entering the rcu-read
99	 * section.
100	 */
101	if (ieee80211_have_rx_timestamp(rx_status))
102		t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
103						       24 + 12 +
104						       elems->total_len +
105						       FCS_LEN,
106						       24);
107	else
108		t_r = drv_get_tsf(local, sdata);
109
110	rcu_read_lock();
111	sta = sta_info_get(sdata, mgmt->sa);
112	if (!sta)
113		goto no_sync;
114
115	/* check offset sync conditions (13.13.2.2.1)
116	 *
117	 * TODO also sync to
118	 * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
119	 */
120
121	if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
122		clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
123		msync_dbg(sdata, "STA %pM : is adjusting TBTT\n",
124			  sta->sta.addr);
125		goto no_sync;
126	}
127
128	/* Timing offset calculation (see 13.13.2.2.2) */
129	t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
130	sta->t_offset = t_t - t_r;
131
132	if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
133		s64 t_clockdrift = sta->t_offset_setpoint - sta->t_offset;
134		msync_dbg(sdata,
135			  "STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n",
136			  sta->sta.addr, (long long) sta->t_offset,
137			  (long long) sta->t_offset_setpoint,
138			  (long long) t_clockdrift);
139
140		if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
141		    t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
142			msync_dbg(sdata,
143				  "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
144				  sta->sta.addr,
145				  (long long) t_clockdrift);
146			clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
147			goto no_sync;
148		}
149
150		spin_lock_bh(&ifmsh->sync_offset_lock);
151		if (t_clockdrift > ifmsh->sync_offset_clockdrift_max)
152			ifmsh->sync_offset_clockdrift_max = t_clockdrift;
153		spin_unlock_bh(&ifmsh->sync_offset_lock);
154	} else {
155		sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
156		set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
157		msync_dbg(sdata,
158			  "STA %pM : offset was invalid, sta->t_offset=%lld\n",
159			  sta->sta.addr,
160			  (long long) sta->t_offset);
161	}
162
163no_sync:
164	rcu_read_unlock();
165}
166
167static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata,
168					 struct beacon_data *beacon)
169{
170	struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
171	u8 cap;
172
173	WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
174	WARN_ON(!rcu_read_lock_held());
175	cap = beacon->meshconf->meshconf_cap;
176
177	spin_lock_bh(&ifmsh->sync_offset_lock);
178
179	if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
180		/* Since ajusting the tsf here would
181		 * require a possibly blocking call
182		 * to the driver tsf setter, we punt
183		 * the tsf adjustment to the mesh tasklet
184		 */
185		msync_dbg(sdata,
186			  "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
187			  ifmsh->sync_offset_clockdrift_max);
188		set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags);
189
190		ifmsh->adjusting_tbtt = true;
191	} else {
192		msync_dbg(sdata,
193			  "TBTT : max clockdrift=%lld; too small to adjust\n",
194			  (long long)ifmsh->sync_offset_clockdrift_max);
195		ifmsh->sync_offset_clockdrift_max = 0;
196
197		ifmsh->adjusting_tbtt = false;
198	}
199	spin_unlock_bh(&ifmsh->sync_offset_lock);
200
201	beacon->meshconf->meshconf_cap = ifmsh->adjusting_tbtt ?
202			IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING | cap :
203			~IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING & cap;
204}
205
206static const struct sync_method sync_methods[] = {
207	{
208		.method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
209		.ops = {
210			.rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
211			.adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
212		}
213	},
214};
215
216const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
217{
218	int i;
219
220	for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
221		if (sync_methods[i].method == method)
222			return &sync_methods[i].ops;
223	}
224	return NULL;
225}
226