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 }