GNU Linux-libre 4.19.314-gnu1
[releases.git] / net / mac80211 / mesh_sync.c
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 tsf 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 800          /* 0.8 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_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(&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(&ifmsh->sync_offset_lock);
72
73         if (local->ops->offset_tsf) {
74                 drv_offset_tsf(local, sdata, tsfdelta);
75         } else {
76                 tsf = drv_get_tsf(local, sdata);
77                 if (tsf != -1ULL)
78                         drv_set_tsf(local, sdata, tsf + tsfdelta);
79         }
80 }
81
82 static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
83                                    u16 stype,
84                                    struct ieee80211_mgmt *mgmt,
85                                    struct ieee802_11_elems *elems,
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(rx_status))
106                 t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
107                                                        24 + 12 +
108                                                        elems->total_len +
109                                                        FCS_LEN,
110                                                        24);
111         else
112                 t_r = drv_get_tsf(local, sdata);
113
114         rcu_read_lock();
115         sta = sta_info_get(sdata, mgmt->sa);
116         if (!sta)
117                 goto no_sync;
118
119         /* check offset sync conditions (13.13.2.2.1)
120          *
121          * TODO also sync to
122          * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
123          */
124
125         if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
126                 msync_dbg(sdata, "STA %pM : is adjusting TBTT\n",
127                           sta->sta.addr);
128                 goto no_sync;
129         }
130
131         /* Timing offset calculation (see 13.13.2.2.2) */
132         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
133         sta->mesh->t_offset = t_t - t_r;
134
135         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
136                 s64 t_clockdrift = sta->mesh->t_offset_setpoint - sta->mesh->t_offset;
137                 msync_dbg(sdata,
138                           "STA %pM : t_offset=%lld, t_offset_setpoint=%lld, t_clockdrift=%lld\n",
139                           sta->sta.addr, (long long) sta->mesh->t_offset,
140                           (long long) sta->mesh->t_offset_setpoint,
141                           (long long) t_clockdrift);
142
143                 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
144                     t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
145                         msync_dbg(sdata,
146                                   "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
147                                   sta->sta.addr,
148                                   (long long) t_clockdrift);
149                         clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
150                         goto no_sync;
151                 }
152
153                 spin_lock_bh(&ifmsh->sync_offset_lock);
154                 if (t_clockdrift > ifmsh->sync_offset_clockdrift_max)
155                         ifmsh->sync_offset_clockdrift_max = t_clockdrift;
156                 spin_unlock_bh(&ifmsh->sync_offset_lock);
157         } else {
158                 sta->mesh->t_offset_setpoint = sta->mesh->t_offset - TOFFSET_SET_MARGIN;
159                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
160                 msync_dbg(sdata,
161                           "STA %pM : offset was invalid, t_offset=%lld\n",
162                           sta->sta.addr,
163                           (long long) sta->mesh->t_offset);
164         }
165
166 no_sync:
167         rcu_read_unlock();
168 }
169
170 static void mesh_sync_offset_adjust_tsf(struct ieee80211_sub_if_data *sdata,
171                                          struct beacon_data *beacon)
172 {
173         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
174
175         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
176         WARN_ON(!rcu_read_lock_held());
177
178         spin_lock_bh(&ifmsh->sync_offset_lock);
179
180         if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
181                 /* Since ajusting the tsf here would
182                  * require a possibly blocking call
183                  * to the driver tsf setter, we punt
184                  * the tsf adjustment to the mesh tasklet
185                  */
186                 msync_dbg(sdata,
187                           "TSF : kicking off TSF adjustment with clockdrift_max=%lld\n",
188                           ifmsh->sync_offset_clockdrift_max);
189                 set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags);
190         } else {
191                 msync_dbg(sdata,
192                           "TSF : max clockdrift=%lld; too small to adjust\n",
193                           (long long)ifmsh->sync_offset_clockdrift_max);
194                 ifmsh->sync_offset_clockdrift_max = 0;
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_tsf = &mesh_sync_offset_adjust_tsf,
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 }