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 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
31 struct 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 */
mesh_peer_tbtt_adjusting(const struct ieee80211_meshconf_ie * cfg)41 static bool mesh_peer_tbtt_adjusting(const struct ieee80211_meshconf_ie *cfg)
42 {
43 return cfg &&
44 (cfg->meshconf_cap & IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING);
45 }
46
mesh_sync_adjust_tsf(struct ieee80211_sub_if_data * sdata)47 void mesh_sync_adjust_tsf(struct ieee80211_sub_if_data *sdata)
48 {
49 struct ieee80211_local *local = sdata->local;
50 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
51 /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
52 u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
53 u64 tsf;
54 u64 tsfdelta;
55
56 spin_lock_bh(&ifmsh->sync_offset_lock);
57 if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
58 msync_dbg(sdata, "TSF : max clockdrift=%lld; adjusting\n",
59 (long long) ifmsh->sync_offset_clockdrift_max);
60 tsfdelta = -ifmsh->sync_offset_clockdrift_max;
61 ifmsh->sync_offset_clockdrift_max = 0;
62 } else {
63 msync_dbg(sdata, "TSF : max clockdrift=%lld; adjusting by %llu\n",
64 (long long) ifmsh->sync_offset_clockdrift_max,
65 (unsigned long long) beacon_int_fraction);
66 tsfdelta = -beacon_int_fraction;
67 ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
68 }
69 spin_unlock_bh(&ifmsh->sync_offset_lock);
70
71 if (local->ops->offset_tsf) {
72 drv_offset_tsf(local, sdata, tsfdelta);
73 } else {
74 tsf = drv_get_tsf(local, sdata);
75 if (tsf != -1ULL)
76 drv_set_tsf(local, sdata, tsf + tsfdelta);
77 }
78 }
79
80 static void
mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data * sdata,u16 stype,struct ieee80211_mgmt * mgmt,unsigned int len,const struct ieee80211_meshconf_ie * mesh_cfg,struct ieee80211_rx_status * rx_status)81 mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata, u16 stype,
82 struct ieee80211_mgmt *mgmt, unsigned int len,
83 const struct ieee80211_meshconf_ie *mesh_cfg,
84 struct ieee80211_rx_status *rx_status)
85 {
86 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
87 struct ieee80211_local *local = sdata->local;
88 struct sta_info *sta;
89 u64 t_t, t_r;
90
91 WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
92
93 /* standard mentions only beacons */
94 if (stype != IEEE80211_STYPE_BEACON)
95 return;
96
97 /*
98 * Get time when timestamp field was received. If we don't
99 * have rx timestamps, then use current tsf as an approximation.
100 * drv_get_tsf() must be called before entering the rcu-read
101 * section.
102 */
103 if (ieee80211_have_rx_timestamp(rx_status))
104 t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
105 len + FCS_LEN, 24);
106 else
107 t_r = drv_get_tsf(local, sdata);
108
109 rcu_read_lock();
110 sta = sta_info_get(sdata, mgmt->sa);
111 if (!sta)
112 goto no_sync;
113
114 /* check offset sync conditions (13.13.2.2.1)
115 *
116 * TODO also sync to
117 * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
118 */
119
120 if (mesh_peer_tbtt_adjusting(mesh_cfg)) {
121 msync_dbg(sdata, "STA %pM : is adjusting TBTT\n",
122 sta->sta.addr);
123 goto no_sync;
124 }
125
126 /* Timing offset calculation (see 13.13.2.2.2) */
127 t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
128 sta->mesh->t_offset = t_t - t_r;
129
130 if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
131 s64 t_clockdrift = sta->mesh->t_offset_setpoint - sta->mesh->t_offset;
132 msync_dbg(sdata,
133 "STA %pM : t_offset=%lld, t_offset_setpoint=%lld, t_clockdrift=%lld\n",
134 sta->sta.addr, (long long) sta->mesh->t_offset,
135 (long long) sta->mesh->t_offset_setpoint,
136 (long long) t_clockdrift);
137
138 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
139 t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
140 msync_dbg(sdata,
141 "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
142 sta->sta.addr,
143 (long long) t_clockdrift);
144 clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
145 goto no_sync;
146 }
147
148 spin_lock_bh(&ifmsh->sync_offset_lock);
149 if (t_clockdrift > ifmsh->sync_offset_clockdrift_max)
150 ifmsh->sync_offset_clockdrift_max = t_clockdrift;
151 spin_unlock_bh(&ifmsh->sync_offset_lock);
152 } else {
153 sta->mesh->t_offset_setpoint = sta->mesh->t_offset - TOFFSET_SET_MARGIN;
154 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
155 msync_dbg(sdata,
156 "STA %pM : offset was invalid, t_offset=%lld\n",
157 sta->sta.addr,
158 (long long) sta->mesh->t_offset);
159 }
160
161 no_sync:
162 rcu_read_unlock();
163 }
164
mesh_sync_offset_adjust_tsf(struct ieee80211_sub_if_data * sdata,struct beacon_data * beacon)165 static void mesh_sync_offset_adjust_tsf(struct ieee80211_sub_if_data *sdata,
166 struct beacon_data *beacon)
167 {
168 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
169
170 WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
171 WARN_ON(!rcu_read_lock_held());
172
173 spin_lock_bh(&ifmsh->sync_offset_lock);
174
175 if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
176 /* Since ajusting the tsf here would
177 * require a possibly blocking call
178 * to the driver tsf setter, we punt
179 * the tsf adjustment to the mesh tasklet
180 */
181 msync_dbg(sdata,
182 "TSF : kicking off TSF adjustment with clockdrift_max=%lld\n",
183 ifmsh->sync_offset_clockdrift_max);
184 set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags);
185 } else {
186 msync_dbg(sdata,
187 "TSF : max clockdrift=%lld; too small to adjust\n",
188 (long long)ifmsh->sync_offset_clockdrift_max);
189 ifmsh->sync_offset_clockdrift_max = 0;
190 }
191 spin_unlock_bh(&ifmsh->sync_offset_lock);
192 }
193
194 static const struct sync_method sync_methods[] = {
195 {
196 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
197 .ops = {
198 .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
199 .adjust_tsf = &mesh_sync_offset_adjust_tsf,
200 }
201 },
202 };
203
ieee80211_mesh_sync_ops_get(u8 method)204 const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
205 {
206 int i;
207
208 for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
209 if (sync_methods[i].method == method)
210 return &sync_methods[i].ops;
211 }
212 return NULL;
213 }
214