1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
4 * Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
5 * Copyright 2011-2012, cozybit Inc.
6 * Copyright (C) 2021,2023 Intel Corporation
7 */
8
9#include "ieee80211_i.h"
10#include "mesh.h"
11#include "driver-ops.h"
12
13/* This is not in the standard. It represents a tolerable tsf drift below
14 * which we do no TSF adjustment.
15 */
16#define TOFFSET_MINIMUM_ADJUSTMENT 10
17
18/* This is not in the standard. It is a margin added to the
19 * Toffset setpoint to mitigate TSF overcorrection
20 * introduced by TSF adjustment latency.
21 */
22#define TOFFSET_SET_MARGIN 20
23
24/* This is not in the standard. It represents the maximum Toffset jump above
25 * which we'll invalidate the Toffset setpoint and choose a new setpoint. This
26 * could be, for instance, in case a neighbor is restarted and its TSF counter
27 * reset.
28 */
29#define TOFFSET_MAXIMUM_ADJUSTMENT 800 /* 0.8 ms */
30
31struct sync_method {
32 u8 method;
33 struct ieee80211_mesh_sync_ops ops;
34};
35
36/**
37 * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
38 *
39 * @cfg: mesh config element from the mesh peer (or %NULL)
40 *
41 * Returns: If the mesh peer is currently adjusting its TBTT
42 */
43static bool mesh_peer_tbtt_adjusting(const struct ieee80211_meshconf_ie *cfg)
44{
45 return cfg &&
46 (cfg->meshconf_cap & IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING);
47}
48
49void mesh_sync_adjust_tsf(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(lock: &ifmsh->sync_offset_lock);
59 if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
60 msync_dbg(sdata, "TSF : 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, "TSF : 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(lock: &ifmsh->sync_offset_lock);
72
73 if (local->ops->offset_tsf) {
74 drv_offset_tsf(local, sdata, offset: tsfdelta);
75 } else {
76 tsf = drv_get_tsf(local, sdata);
77 if (tsf != -1ULL)
78 drv_set_tsf(local, sdata, tsf: tsf + tsfdelta);
79 }
80}
81
82static void
83mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata, u16 stype,
84 struct ieee80211_mgmt *mgmt, unsigned int len,
85 const struct ieee80211_meshconf_ie *mesh_cfg,
86 struct ieee80211_rx_status *rx_status)
87{
88 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
89 struct ieee80211_local *local = sdata->local;
90 struct sta_info *sta;
91 u64 t_t, t_r;
92
93 WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
94
95 /* standard mentions only beacons */
96 if (stype != IEEE80211_STYPE_BEACON)
97 return;
98
99 /*
100 * Get time when timestamp field was received. If we don't
101 * have rx timestamps, then use current tsf as an approximation.
102 * drv_get_tsf() must be called before entering the rcu-read
103 * section.
104 */
105 if (ieee80211_have_rx_timestamp(status: rx_status))
106 t_r = ieee80211_calculate_rx_timestamp(local, status: rx_status,
107 mpdu_len: len + FCS_LEN, mpdu_offset: 24);
108 else
109 t_r = drv_get_tsf(local, sdata);
110
111 rcu_read_lock();
112 sta = sta_info_get(sdata, addr: mgmt->sa);
113 if (!sta)
114 goto no_sync;
115
116 /* check offset sync conditions (13.13.2.2.1)
117 *
118 * TODO also sync to
119 * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
120 */
121
122 if (mesh_peer_tbtt_adjusting(cfg: mesh_cfg)) {
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->mesh->t_offset = t_t - t_r;
131
132 if (test_sta_flag(sta, flag: WLAN_STA_TOFFSET_KNOWN)) {
133 s64 t_clockdrift = sta->mesh->t_offset_setpoint - sta->mesh->t_offset;
134 msync_dbg(sdata,
135 "STA %pM : t_offset=%lld, t_offset_setpoint=%lld, t_clockdrift=%lld\n",
136 sta->sta.addr, (long long) sta->mesh->t_offset,
137 (long long) sta->mesh->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, flag: WLAN_STA_TOFFSET_KNOWN);
147 goto no_sync;
148 }
149
150 spin_lock_bh(lock: &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(lock: &ifmsh->sync_offset_lock);
154 } else {
155 sta->mesh->t_offset_setpoint = sta->mesh->t_offset - TOFFSET_SET_MARGIN;
156 set_sta_flag(sta, flag: WLAN_STA_TOFFSET_KNOWN);
157 msync_dbg(sdata,
158 "STA %pM : offset was invalid, t_offset=%lld\n",
159 sta->sta.addr,
160 (long long) sta->mesh->t_offset);
161 }
162
163no_sync:
164 rcu_read_unlock();
165}
166
167static void mesh_sync_offset_adjust_tsf(struct ieee80211_sub_if_data *sdata,
168 struct beacon_data *beacon)
169{
170 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
171
172 WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
173 WARN_ON(!rcu_read_lock_held());
174
175 spin_lock_bh(lock: &ifmsh->sync_offset_lock);
176
177 if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
178 /* Since adjusting the tsf here would
179 * require a possibly blocking call
180 * to the driver tsf setter, we punt
181 * the tsf adjustment to the mesh tasklet
182 */
183 msync_dbg(sdata,
184 "TSF : kicking off TSF adjustment with clockdrift_max=%lld\n",
185 ifmsh->sync_offset_clockdrift_max);
186 set_bit(nr: MESH_WORK_DRIFT_ADJUST, addr: &ifmsh->wrkq_flags);
187 } else {
188 msync_dbg(sdata,
189 "TSF : max clockdrift=%lld; too small to adjust\n",
190 (long long)ifmsh->sync_offset_clockdrift_max);
191 ifmsh->sync_offset_clockdrift_max = 0;
192 }
193 spin_unlock_bh(lock: &ifmsh->sync_offset_lock);
194}
195
196static const struct sync_method sync_methods[] = {
197 {
198 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
199 .ops = {
200 .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
201 .adjust_tsf = &mesh_sync_offset_adjust_tsf,
202 }
203 },
204};
205
206const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
207{
208 int i;
209
210 for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
211 if (sync_methods[i].method == method)
212 return &sync_methods[i].ops;
213 }
214 return NULL;
215}
216

source code of linux/net/mac80211/mesh_sync.c