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
  60         if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
  61                 msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting\n",
  62                           (long long) ifmsh->sync_offset_clockdrift_max);
  63                 tsfdelta = -ifmsh->sync_offset_clockdrift_max;
  64                 ifmsh->sync_offset_clockdrift_max = 0;
  65         } else {
  66                 msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting by %llu\n",
  67                           (long long) ifmsh->sync_offset_clockdrift_max,
  68                           (unsigned long long) beacon_int_fraction);
  69                 tsfdelta = -beacon_int_fraction;
  70                 ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
  71         }
  72
  73         tsf = drv_get_tsf(local, sdata);
  74         if (tsf != -1ULL)
  75                 drv_set_tsf(local, sdata, tsf + tsfdelta);
  76         spin_unlock_bh(&ifmsh->sync_offset_lock);
  77 }
  78
  79 static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
  80                                    u16 stype,
  81                                    struct ieee80211_mgmt *mgmt,
  82                                    struct ieee802_11_elems *elems,
  83                                    struct ieee80211_rx_status *rx_status)
  84 {
  85         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  86         struct ieee80211_local *local = sdata->local;
  87         struct sta_info *sta;
  88         u64 t_t, t_r;
  89
  90         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
  91
  92         /* standard mentions only beacons */
  93         if (stype != IEEE80211_STYPE_BEACON)
  94                 return;
  95
  96         /* The current tsf is a first approximation for the timestamp
  97          * for the received beacon.  Further down we try to get a
  98          * better value from the rx_status->mactime field if
  99          * available. Also we have to call drv_get_tsf() before
 100          * entering the rcu-read section.*/
 101         t_r = drv_get_tsf(local, sdata);
 102
 103         rcu_read_lock();
 104         sta = sta_info_get(sdata, mgmt->sa);
 105         if (!sta)
 106                 goto no_sync;
 107
 108         /* check offset sync conditions (13.13.2.2.1)
 109          *
 110          * TODO also sync to
 111          * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
 112          */
 113
 114         if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
 115                 clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 116                 msync_dbg(sdata, "STA %pM : is adjusting TBTT\n", sta->sta.addr);
 117                 goto no_sync;
 118         }
 119
 120         if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) {
 121                 /*
 122                  * The mactime is defined as the time the first data symbol
 123                  * of the frame hits the PHY, and the timestamp of the beacon
 124                  * is defined as "the time that the data symbol containing the
 125                  * first bit of the timestamp is transmitted to the PHY plus
 126                  * the transmitting STA's delays through its local PHY from the
 127                  * MAC-PHY interface to its interface with the WM" (802.11
 128                  * 11.1.2)
 129                  *
 130                  * T_r, in 13.13.2.2.2, is just defined as "the frame reception
 131                  * time" but we unless we interpret that time to be the same
 132                  * time of the beacon timestamp, the offset calculation will be
 133                  * off.  Below we adjust t_r to be "the time at which the first
 134                  * symbol of the timestamp element in the beacon is received".
 135                  * This correction depends on the rate.
 136                  *
 137                  * Based on similar code in ibss.c
 138                  */
 139                 int rate;
 140
 141                 if (rx_status->flag & RX_FLAG_HT) {
 142                         /* TODO:
 143                          * In principle there could be HT-beacons (Dual Beacon
 144                          * HT Operation options), but for now ignore them and
 145                          * just use the primary (i.e. non-HT) beacons for
 146                          * synchronization.
 147                          * */
 148                         goto no_sync;
 149                 } else
 150                         rate = local->hw.wiphy->bands[rx_status->band]->
 151                                 bitrates[rx_status->rate_idx].bitrate;
 152
 153                 /* 24 bytes of header * 8 bits/byte *
 154                  * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/
 155                 t_r = rx_status->mactime + (24 * 8 * 10 / rate);
 156         }
 157
 158         /* Timing offset calculation (see 13.13.2.2.2) */
 159         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 160         sta->t_offset = t_t - t_r;
 161
 162         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 163                 s64 t_clockdrift = sta->t_offset_setpoint
 164                                    - sta->t_offset;
 165                 msync_dbg(sdata,
 166                           "STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n",
 167                           sta->sta.addr,
 168                           (long long) sta->t_offset,
 169                           (long long)
 170                           sta->t_offset_setpoint,
 171                           (long long) t_clockdrift);
 172
 173                 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
 174                         t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
 175                         msync_dbg(sdata,
 176                                   "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
 177                                   sta->sta.addr,
 178                                   (long long) t_clockdrift);
 179                         clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 180                         goto no_sync;
 181                 }
 182
 183                 rcu_read_unlock();
 184
 185                 spin_lock_bh(&ifmsh->sync_offset_lock);
 186                 if (t_clockdrift >
 187                     ifmsh->sync_offset_clockdrift_max)
 188                         ifmsh->sync_offset_clockdrift_max
 189                                 = t_clockdrift;
 190                 spin_unlock_bh(&ifmsh->sync_offset_lock);
 191
 192         } else {
 193                 sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
 194                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 195                 msync_dbg(sdata,
 196                           "STA %pM : offset was invalid, sta->t_offset=%lld\n",
 197                           sta->sta.addr,
 198                           (long long) sta->t_offset);
 199                 rcu_read_unlock();
 200         }
 201         return;
 202
 203 no_sync:
 204         rcu_read_unlock();
 205 }
 206
 207 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 208 {
 209         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 210
 211         WARN_ON(ifmsh->mesh_sp_id
 212                 != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 213         BUG_ON(!rcu_read_lock_held());
 214
 215         spin_lock_bh(&ifmsh->sync_offset_lock);
 216
 217         if (ifmsh->sync_offset_clockdrift_max >
 218                 TOFFSET_MINIMUM_ADJUSTMENT) {
 219                 /* Since ajusting the tsf here would
 220                  * require a possibly blocking call
 221                  * to the driver tsf setter, we punt
 222                  * the tsf adjustment to the mesh tasklet
 223                  */
 224                 msync_dbg(sdata,
 225                           "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
 226                           ifmsh->sync_offset_clockdrift_max);
 227                 set_bit(MESH_WORK_DRIFT_ADJUST,
 228                         &ifmsh->wrkq_flags);
 229         } else {
 230                 msync_dbg(sdata,
 231                           "TBTT : max clockdrift=%lld; too small to adjust\n",
 232                           (long long)ifmsh->sync_offset_clockdrift_max);
 233                 ifmsh->sync_offset_clockdrift_max = 0;
 234         }
 235         spin_unlock_bh(&ifmsh->sync_offset_lock);
 236 }
 237
 238 static const u8 *mesh_get_vendor_oui(struct ieee80211_sub_if_data *sdata)
 239 {
 240         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 241         u8 offset;
 242
 243         if (!ifmsh->ie || !ifmsh->ie_len)
 244                 return NULL;
 245
 246         offset = ieee80211_ie_split_vendor(ifmsh->ie,
 247                                         ifmsh->ie_len, 0);
 248
 249         if (!offset)
 250                 return NULL;
 251
 252         return ifmsh->ie + offset + 2;
 253 }
 254
 255 static void mesh_sync_vendor_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 256                                    u16 stype,
 257                                    struct ieee80211_mgmt *mgmt,
 258                                    struct ieee802_11_elems *elems,
 259                                    struct ieee80211_rx_status *rx_status)
 260 {
 261         const u8 *oui;
 262
 263         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 264         msync_dbg(sdata, "called mesh_sync_vendor_rx_bcn_presp\n");
 265         oui = mesh_get_vendor_oui(sdata);
 266         /*  here you would implement the vendor offset tracking for this oui */
 267 }
 268
 269 static void mesh_sync_vendor_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 270 {
 271         const u8 *oui;
 272
 273         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 274         msync_dbg(sdata, "called mesh_sync_vendor_adjust_tbtt\n");
 275         oui = mesh_get_vendor_oui(sdata);
 276         /*  here you would implement the vendor tsf adjustment for this oui */
 277 }
 278
 279 /* global variable */
 280 static struct sync_method sync_methods[] = {
 281         {
 282                 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 283                 .ops = {
 284                         .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 285                         .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
 286                 }
 287         },
 288         {
 289                 .method = IEEE80211_SYNC_METHOD_VENDOR,
 290                 .ops = {
 291                         .rx_bcn_presp = &mesh_sync_vendor_rx_bcn_presp,
 292                         .adjust_tbtt = &mesh_sync_vendor_adjust_tbtt,
 293                 }
 294         },
 295 };
 296
 297 struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 298 {
 299         struct ieee80211_mesh_sync_ops *ops = NULL;
 300         u8 i;
 301
 302         for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 303                 if (sync_methods[i].method == method) {
 304                         ops = &sync_methods[i].ops;
 305                         break;
 306                 }
 307         }
 308         return ops;
 309 }