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             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", sta->sta.addr);
 116                 goto no_sync;
 117         }
 118
 119         if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) {
 120                 /*
 121                  * The mactime is defined as the time the first data symbol
 122                  * of the frame hits the PHY, and the timestamp of the beacon
 123                  * is defined as "the time that the data symbol containing the
 124                  * first bit of the timestamp is transmitted to the PHY plus
 125                  * the transmitting STA's delays through its local PHY from the
 126                  * MAC-PHY interface to its interface with the WM" (802.11
 127                  * 11.1.2)
 128                  *
 129                  * T_r, in 13.13.2.2.2, is just defined as "the frame reception
 130                  * time" but we unless we interpret that time to be the same
 131                  * time of the beacon timestamp, the offset calculation will be
 132                  * off.  Below we adjust t_r to be "the time at which the first
 133                  * symbol of the timestamp element in the beacon is received".
 134                  * This correction depends on the rate.
 135                  *
 136                  * Based on similar code in ibss.c
 137                  */
 138                 int rate;
 139
 140                 if (rx_status->flag & RX_FLAG_HT) {
 141                         /* TODO:
 142                          * In principle there could be HT-beacons (Dual Beacon
 143                          * HT Operation options), but for now ignore them and
 144                          * just use the primary (i.e. non-HT) beacons for
 145                          * synchronization.
 146                          * */
 147                         goto no_sync;
 148                 } else
 149                         rate = local->hw.wiphy->bands[rx_status->band]->
 150                                 bitrates[rx_status->rate_idx].bitrate;
 151
 152                 /* 24 bytes of header * 8 bits/byte *
 153                  * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/
 154                 t_r = rx_status->mactime + (24 * 8 * 10 / rate);
 155         }
 156
 157         /* Timing offset calculation (see 13.13.2.2.2) */
 158         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 159         sta->t_offset = t_t - t_r;
 160
 161         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 162                 s64 t_clockdrift = sta->t_offset_setpoint
 163                                    - sta->t_offset;
 164                 msync_dbg(sdata,
 165                           "STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n",
 166                           sta->sta.addr,
 167                           (long long) sta->t_offset,
 168                           (long long)
 169                           sta->t_offset_setpoint,
 170                           (long long) t_clockdrift);
 171
 172                 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
 173                         t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
 174                         msync_dbg(sdata,
 175                                   "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
 176                                   sta->sta.addr,
 177                                   (long long) t_clockdrift);
 178                         clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 179                         goto no_sync;
 180                 }
 181
 182                 rcu_read_unlock();
 183
 184                 spin_lock_bh(&ifmsh->sync_offset_lock);
 185                 if (t_clockdrift >
 186                     ifmsh->sync_offset_clockdrift_max)
 187                         ifmsh->sync_offset_clockdrift_max
 188                                 = t_clockdrift;
 189                 spin_unlock_bh(&ifmsh->sync_offset_lock);
 190
 191         } else {
 192                 sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
 193                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 194                 msync_dbg(sdata,
 195                           "STA %pM : offset was invalid, sta->t_offset=%lld\n",
 196                           sta->sta.addr,
 197                           (long long) sta->t_offset);
 198                 rcu_read_unlock();
 199         }
 200         return;
 201
 202 no_sync:
 203         rcu_read_unlock();
 204 }
 205
 206 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 207 {
 208         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 209
 210         WARN_ON(ifmsh->mesh_sp_id
 211                 != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 212         BUG_ON(!rcu_read_lock_held());
 213
 214         spin_lock_bh(&ifmsh->sync_offset_lock);
 215
 216         if (ifmsh->sync_offset_clockdrift_max >
 217                 TOFFSET_MINIMUM_ADJUSTMENT) {
 218                 /* Since ajusting the tsf here would
 219                  * require a possibly blocking call
 220                  * to the driver tsf setter, we punt
 221                  * the tsf adjustment to the mesh tasklet
 222                  */
 223                 msync_dbg(sdata,
 224                           "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
 225                           ifmsh->sync_offset_clockdrift_max);
 226                 set_bit(MESH_WORK_DRIFT_ADJUST,
 227                         &ifmsh->wrkq_flags);
 228         } else {
 229                 msync_dbg(sdata,
 230                           "TBTT : max clockdrift=%lld; too small to adjust\n",
 231                           (long long)ifmsh->sync_offset_clockdrift_max);
 232                 ifmsh->sync_offset_clockdrift_max = 0;
 233         }
 234         spin_unlock_bh(&ifmsh->sync_offset_lock);
 235 }
 236
 237 static const u8 *mesh_get_vendor_oui(struct ieee80211_sub_if_data *sdata)
 238 {
 239         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 240         u8 offset;
 241
 242         if (!ifmsh->ie || !ifmsh->ie_len)
 243                 return NULL;
 244
 245         offset = ieee80211_ie_split_vendor(ifmsh->ie,
 246                                         ifmsh->ie_len, 0);
 247
 248         if (!offset)
 249                 return NULL;
 250
 251         return ifmsh->ie + offset + 2;
 252 }
 253
 254 static void mesh_sync_vendor_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 255                                    u16 stype,
 256                                    struct ieee80211_mgmt *mgmt,
 257                                    struct ieee802_11_elems *elems,
 258                                    struct ieee80211_rx_status *rx_status)
 259 {
 260         const u8 *oui;
 261
 262         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 263         msync_dbg(sdata, "called mesh_sync_vendor_rx_bcn_presp\n");
 264         oui = mesh_get_vendor_oui(sdata);
 265         /*  here you would implement the vendor offset tracking for this oui */
 266 }
 267
 268 static void mesh_sync_vendor_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 269 {
 270         const u8 *oui;
 271
 272         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 273         msync_dbg(sdata, "called mesh_sync_vendor_adjust_tbtt\n");
 274         oui = mesh_get_vendor_oui(sdata);
 275         /*  here you would implement the vendor tsf adjustment for this oui */
 276 }
 277
 278 /* global variable */
 279 static struct sync_method sync_methods[] = {
 280         {
 281                 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 282                 .ops = {
 283                         .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 284                         .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
 285                 }
 286         },
 287         {
 288                 .method = IEEE80211_SYNC_METHOD_VENDOR,
 289                 .ops = {
 290                         .rx_bcn_presp = &mesh_sync_vendor_rx_bcn_presp,
 291                         .adjust_tbtt = &mesh_sync_vendor_adjust_tbtt,
 292                 }
 293         },
 294 };
 295
 296 struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 297 {
 298         struct ieee80211_mesh_sync_ops *ops = NULL;
 299         u8 i;
 300
 301         for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 302                 if (sync_methods[i].method == method) {
 303                         ops = &sync_methods[i].ops;
 304                         break;
 305                 }
 306         }
 307         return ops;
 308 }