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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 | |
33 | struct 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 | */ |
43 | static 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 | |
49 | void 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 | |
78 | static 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 | /* The current tsf is a first approximation for the timestamp |
96 | * for the received beacon. Further down we try to get a |
97 | * better value from the rx_status->mactime field if |
98 | * available. Also we have to call drv_get_tsf() before |
99 | * entering the rcu-read section.*/ |
100 | t_r = drv_get_tsf(local, sdata); |
101 | |
102 | rcu_read_lock(); |
103 | sta = sta_info_get(sdata, mgmt->sa); |
104 | if (!sta) |
105 | goto no_sync; |
106 | |
107 | /* check offset sync conditions (13.13.2.2.1) |
108 | * |
109 | * TODO also sync to |
110 | * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors |
111 | */ |
112 | |
113 | if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) { |
114 | clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); |
115 | msync_dbg(sdata, "STA %pM : is adjusting TBTT\n", |
116 | sta->sta.addr); |
117 | goto no_sync; |
118 | } |
119 | |
120 | if (ieee80211_have_rx_timestamp(rx_status)) |
121 | /* time when timestamp field was received */ |
122 | t_r = ieee80211_calculate_rx_timestamp(local, rx_status, |
123 | 24 + 12 + |
124 | elems->total_len + |
125 | FCS_LEN, |
126 | 24); |
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 | |
163 | no_sync: |
164 | rcu_read_unlock(); |
165 | } |
166 | |
167 | static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata) |
168 | { |
169 | struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; |
170 | |
171 | WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET); |
172 | BUG_ON(!rcu_read_lock_held()); |
173 | |
174 | spin_lock_bh(&ifmsh->sync_offset_lock); |
175 | |
176 | if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) { |
177 | /* Since ajusting the tsf here would |
178 | * require a possibly blocking call |
179 | * to the driver tsf setter, we punt |
180 | * the tsf adjustment to the mesh tasklet |
181 | */ |
182 | msync_dbg(sdata, |
183 | "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n", |
184 | ifmsh->sync_offset_clockdrift_max); |
185 | set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags); |
186 | |
187 | ifmsh->adjusting_tbtt = true; |
188 | } else { |
189 | msync_dbg(sdata, |
190 | "TBTT : max clockdrift=%lld; too small to adjust\n", |
191 | (long long)ifmsh->sync_offset_clockdrift_max); |
192 | ifmsh->sync_offset_clockdrift_max = 0; |
193 | |
194 | ifmsh->adjusting_tbtt = false; |
195 | } |
196 | spin_unlock_bh(&ifmsh->sync_offset_lock); |
197 | } |
198 | |
199 | static const struct sync_method sync_methods[] = { |
200 | { |
201 | .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET, |
202 | .ops = { |
203 | .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp, |
204 | .adjust_tbtt = &mesh_sync_offset_adjust_tbtt, |
205 | } |
206 | }, |
207 | }; |
208 | |
209 | const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method) |
210 | { |
211 | int i; |
212 | |
213 | for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) { |
214 | if (sync_methods[i].method == method) |
215 | return &sync_methods[i].ops; |
216 | } |
217 | return NULL; |
218 | } |
219 |
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