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TOMOYO Linux Cross Reference
Linux/net/mac80211/mesh_sync.c

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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 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_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         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                 clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
127                 msync_dbg(sdata, "STA %pM : is adjusting TBTT\n",
128                           sta->sta.addr);
129                 goto no_sync;
130         }
131 
132         /* Timing offset calculation (see 13.13.2.2.2) */
133         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
134         sta->mesh->t_offset = t_t - t_r;
135 
136         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
137                 s64 t_clockdrift = sta->mesh->t_offset_setpoint - sta->mesh->t_offset;
138                 msync_dbg(sdata,
139                           "STA %pM : t_offset=%lld, t_offset_setpoint=%lld, t_clockdrift=%lld\n",
140                           sta->sta.addr, (long long) sta->mesh->t_offset,
141                           (long long) sta->mesh->t_offset_setpoint,
142                           (long long) t_clockdrift);
143 
144                 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
145                     t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
146                         msync_dbg(sdata,
147                                   "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
148                                   sta->sta.addr,
149                                   (long long) t_clockdrift);
150                         clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
151                         goto no_sync;
152                 }
153 
154                 spin_lock_bh(&ifmsh->sync_offset_lock);
155                 if (t_clockdrift > ifmsh->sync_offset_clockdrift_max)
156                         ifmsh->sync_offset_clockdrift_max = t_clockdrift;
157                 spin_unlock_bh(&ifmsh->sync_offset_lock);
158         } else {
159                 sta->mesh->t_offset_setpoint = sta->mesh->t_offset - TOFFSET_SET_MARGIN;
160                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
161                 msync_dbg(sdata,
162                           "STA %pM : offset was invalid, t_offset=%lld\n",
163                           sta->sta.addr,
164                           (long long) sta->mesh->t_offset);
165         }
166 
167 no_sync:
168         rcu_read_unlock();
169 }
170 
171 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata,
172                                          struct beacon_data *beacon)
173 {
174         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
175         u8 cap;
176 
177         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
178         WARN_ON(!rcu_read_lock_held());
179         cap = beacon->meshconf->meshconf_cap;
180 
181         spin_lock_bh(&ifmsh->sync_offset_lock);
182 
183         if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
184                 /* Since ajusting the tsf here would
185                  * require a possibly blocking call
186                  * to the driver tsf setter, we punt
187                  * the tsf adjustment to the mesh tasklet
188                  */
189                 msync_dbg(sdata,
190                           "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
191                           ifmsh->sync_offset_clockdrift_max);
192                 set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags);
193 
194                 ifmsh->adjusting_tbtt = true;
195         } else {
196                 msync_dbg(sdata,
197                           "TBTT : max clockdrift=%lld; too small to adjust\n",
198                           (long long)ifmsh->sync_offset_clockdrift_max);
199                 ifmsh->sync_offset_clockdrift_max = 0;
200 
201                 ifmsh->adjusting_tbtt = false;
202         }
203         spin_unlock_bh(&ifmsh->sync_offset_lock);
204 
205         beacon->meshconf->meshconf_cap = ifmsh->adjusting_tbtt ?
206                         IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING | cap :
207                         ~IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING & cap;
208 }
209 
210 static const struct sync_method sync_methods[] = {
211         {
212                 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
213                 .ops = {
214                         .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
215                         .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
216                 }
217         },
218 };
219 
220 const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
221 {
222         int i;
223 
224         for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
225                 if (sync_methods[i].method == method)
226                         return &sync_methods[i].ops;
227         }
228         return NULL;
229 }
230 

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