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 #ifdef CONFIG_MAC80211_VERBOSE_MESH_SYNC_DEBUG
  16 #define msync_dbg(fmt, args...) \
  17         printk(KERN_DEBUG "Mesh sync (%s): " fmt "\n", sdata->name, ##args)
  18 #else
  19 #define msync_dbg(fmt, args...)   do { (void)(0); } while (0)
  20 #endif
  21
  22 /* This is not in the standard.  It represents a tolerable tbtt drift below
  23  * which we do no TSF adjustment.
  24  */
  25 #define TBTT_MINIMUM_ADJUSTMENT 10
  26
  27 struct sync_method {
  28         u8 method;
  29         struct ieee80211_mesh_sync_ops ops;
  30 };
  31
  32 /**
  33  * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
  34  *
  35  * @ie: information elements of a management frame from the mesh peer
  36  */
  37 static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
  38 {
  39         return (ie->mesh_config->meshconf_cap &
  40             MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
  41 }
  42
  43 void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
  44 {
  45         struct ieee80211_local *local = sdata->local;
  46         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  47         /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
  48         u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
  49         u64 tsf;
  50         u64 tsfdelta;
  51
  52         spin_lock_bh(&ifmsh->sync_offset_lock);
  53
  54         if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
  55                 msync_dbg("TBTT : max clockdrift=%lld; adjusting",
  56                         (long long) ifmsh->sync_offset_clockdrift_max);
  57                 tsfdelta = -ifmsh->sync_offset_clockdrift_max;
  58                 ifmsh->sync_offset_clockdrift_max = 0;
  59         } else {
  60                 msync_dbg("TBTT : max clockdrift=%lld; adjusting by %llu",
  61                         (long long) ifmsh->sync_offset_clockdrift_max,
  62                         (unsigned long long) beacon_int_fraction);
  63                 tsfdelta = -beacon_int_fraction;
  64                 ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
  65         }
  66
  67         tsf = drv_get_tsf(local, sdata);
  68         if (tsf != -1ULL)
  69                 drv_set_tsf(local, sdata, tsf + tsfdelta);
  70         spin_unlock_bh(&ifmsh->sync_offset_lock);
  71 }
  72
  73 static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
  74                                    u16 stype,
  75                                    struct ieee80211_mgmt *mgmt,
  76                                    struct ieee802_11_elems *elems,
  77                                    struct ieee80211_rx_status *rx_status)
  78 {
  79         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  80         struct ieee80211_local *local = sdata->local;
  81         struct sta_info *sta;
  82         u64 t_t, t_r;
  83
  84         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
  85
  86         /* standard mentions only beacons */
  87         if (stype != IEEE80211_STYPE_BEACON)
  88                 return;
  89
  90         /* The current tsf is a first approximation for the timestamp
  91          * for the received beacon.  Further down we try to get a
  92          * better value from the rx_status->mactime field if
  93          * available. Also we have to call drv_get_tsf() before
  94          * entering the rcu-read section.*/
  95         t_r = drv_get_tsf(local, sdata);
  96
  97         rcu_read_lock();
  98         sta = sta_info_get(sdata, mgmt->sa);
  99         if (!sta)
 100                 goto no_sync;
 101
 102         /* check offset sync conditions (13.13.2.2.1)
 103          *
 104          * TODO also sync to
 105          * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
 106          */
 107
 108         if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
 109                 clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 110                 msync_dbg("STA %pM : is adjusting TBTT", sta->sta.addr);
 111                 goto no_sync;
 112         }
 113
 114         if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) {
 115                 /*
 116                  * The mactime is defined as the time the first data symbol
 117                  * of the frame hits the PHY, and the timestamp of the beacon
 118                  * is defined as "the time that the data symbol containing the
 119                  * first bit of the timestamp is transmitted to the PHY plus
 120                  * the transmitting STA's delays through its local PHY from the
 121                  * MAC-PHY interface to its interface with the WM" (802.11
 122                  * 11.1.2)
 123                  *
 124                  * T_r, in 13.13.2.2.2, is just defined as "the frame reception
 125                  * time" but we unless we interpret that time to be the same
 126                  * time of the beacon timestamp, the offset calculation will be
 127                  * off.  Below we adjust t_r to be "the time at which the first
 128                  * symbol of the timestamp element in the beacon is received".
 129                  * This correction depends on the rate.
 130                  *
 131                  * Based on similar code in ibss.c
 132                  */
 133                 int rate;
 134
 135                 if (rx_status->flag & RX_FLAG_HT) {
 136                         /* TODO:
 137                          * In principle there could be HT-beacons (Dual Beacon
 138                          * HT Operation options), but for now ignore them and
 139                          * just use the primary (i.e. non-HT) beacons for
 140                          * synchronization.
 141                          * */
 142                         goto no_sync;
 143                 } else
 144                         rate = local->hw.wiphy->bands[rx_status->band]->
 145                                 bitrates[rx_status->rate_idx].bitrate;
 146
 147                 /* 24 bytes of header * 8 bits/byte *
 148                  * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/
 149                 t_r = rx_status->mactime + (24 * 8 * 10 / rate);
 150         }
 151
 152         /* Timing offset calculation (see 13.13.2.2.2) */
 153         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 154         sta->t_offset = t_t - t_r;
 155
 156         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 157                 s64 t_clockdrift = sta->t_offset_setpoint
 158                                    - sta->t_offset;
 159
 160                 msync_dbg("STA %pM : sta->t_offset=%lld,"
 161                           " sta->t_offset_setpoint=%lld,"
 162                           " t_clockdrift=%lld",
 163                           sta->sta.addr,
 164                           (long long) sta->t_offset,
 165                           (long long)
 166                           sta->t_offset_setpoint,
 167                           (long long) t_clockdrift);
 168                 rcu_read_unlock();
 169
 170                 spin_lock_bh(&ifmsh->sync_offset_lock);
 171                 if (t_clockdrift >
 172                     ifmsh->sync_offset_clockdrift_max)
 173                         ifmsh->sync_offset_clockdrift_max
 174                                 = t_clockdrift;
 175                 spin_unlock_bh(&ifmsh->sync_offset_lock);
 176
 177         } else {
 178                 sta->t_offset_setpoint = sta->t_offset;
 179                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 180                 msync_dbg("STA %pM : offset was invalid, "
 181                           " sta->t_offset=%lld",
 182                           sta->sta.addr,
 183                           (long long) sta->t_offset);
 184                 rcu_read_unlock();
 185         }
 186         return;
 187
 188 no_sync:
 189         rcu_read_unlock();
 190 }
 191
 192 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 193 {
 194         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 195
 196         WARN_ON(ifmsh->mesh_sp_id
 197                 != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 198         BUG_ON(!rcu_read_lock_held());
 199
 200         spin_lock_bh(&ifmsh->sync_offset_lock);
 201
 202         if (ifmsh->sync_offset_clockdrift_max >
 203                 TBTT_MINIMUM_ADJUSTMENT) {
 204                 /* Since ajusting the tsf here would
 205                  * require a possibly blocking call
 206                  * to the driver tsf setter, we punt
 207                  * the tsf adjustment to the mesh tasklet
 208                  */
 209                 msync_dbg("TBTT : kicking off TBTT "
 210                           "adjustment with "
 211                           "clockdrift_max=%lld",
 212                   ifmsh->sync_offset_clockdrift_max);
 213                 set_bit(MESH_WORK_DRIFT_ADJUST,
 214                         &ifmsh->wrkq_flags);
 215         } else {
 216                 msync_dbg("TBTT : max clockdrift=%lld; "
 217                           "too small to adjust",
 218                           (long long)
 219                        ifmsh->sync_offset_clockdrift_max);
 220                 ifmsh->sync_offset_clockdrift_max = 0;
 221         }
 222         spin_unlock_bh(&ifmsh->sync_offset_lock);
 223 }
 224
 225 static const u8 *mesh_get_vendor_oui(struct ieee80211_sub_if_data *sdata)
 226 {
 227         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 228         u8 offset;
 229
 230         if (!ifmsh->ie || !ifmsh->ie_len)
 231                 return NULL;
 232
 233         offset = ieee80211_ie_split_vendor(ifmsh->ie,
 234                                         ifmsh->ie_len, 0);
 235
 236         if (!offset)
 237                 return NULL;
 238
 239         return ifmsh->ie + offset + 2;
 240 }
 241
 242 static void mesh_sync_vendor_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 243                                    u16 stype,
 244                                    struct ieee80211_mgmt *mgmt,
 245                                    struct ieee802_11_elems *elems,
 246                                    struct ieee80211_rx_status *rx_status)
 247 {
 248         const u8 *oui;
 249
 250         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 251         msync_dbg("called mesh_sync_vendor_rx_bcn_presp");
 252         oui = mesh_get_vendor_oui(sdata);
 253         /*  here you would implement the vendor offset tracking for this oui */
 254 }
 255
 256 static void mesh_sync_vendor_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 257 {
 258         const u8 *oui;
 259
 260         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 261         msync_dbg("called mesh_sync_vendor_adjust_tbtt");
 262         oui = mesh_get_vendor_oui(sdata);
 263         /*  here you would implement the vendor tsf adjustment for this oui */
 264 }
 265
 266 /* global variable */
 267 static struct sync_method sync_methods[] = {
 268         {
 269                 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 270                 .ops = {
 271                         .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 272                         .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
 273                 }
 274         },
 275         {
 276                 .method = IEEE80211_SYNC_METHOD_VENDOR,
 277                 .ops = {
 278                         .rx_bcn_presp = &mesh_sync_vendor_rx_bcn_presp,
 279                         .adjust_tbtt = &mesh_sync_vendor_adjust_tbtt,
 280                 }
 281         },
 282 };
 283
 284 struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 285 {
 286         struct ieee80211_mesh_sync_ops *ops = NULL;
 287         u8 i;
 288
 289         for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 290                 if (sync_methods[i].method == method) {
 291                         ops = &sync_methods[i].ops;
 292                         break;
 293                 }
 294         }
 295         return ops;
 296 }