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 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 }