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 TOFFSET_MINIMUM_ADJUSTMENT 10
  26
  27 /* This is not in the standard. It is a margin added to the
  28  * Toffset setpoint to mitigate TSF overcorrection
  29  * introduced by TSF adjustment latency.
  30  */
  31 #define TOFFSET_SET_MARGIN 20
  32
  33 /* This is not in the standard.  It represents the maximum Toffset jump above
  34  * which we'll invalidate the Toffset setpoint and choose a new setpoint.  This
  35  * could be, for instance, in case a neighbor is restarted and its TSF counter
  36  * reset.
  37  */
  38 #define TOFFSET_MAXIMUM_ADJUSTMENT 30000                /* 30 ms */
  39
  40 struct sync_method {
  41         u8 method;
  42         struct ieee80211_mesh_sync_ops ops;
  43 };
  44
  45 /**
  46  * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
  47  *
  48  * @ie: information elements of a management frame from the mesh peer
  49  */
  50 static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
  51 {
  52         return (ie->mesh_config->meshconf_cap &
  53             MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
  54 }
  55
  56 void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
  57 {
  58         struct ieee80211_local *local = sdata->local;
  59         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  60         /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
  61         u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
  62         u64 tsf;
  63         u64 tsfdelta;
  64
  65         spin_lock_bh(&ifmsh->sync_offset_lock);
  66
  67         if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
  68                 msync_dbg("TBTT : max clockdrift=%lld; adjusting",
  69                         (long long) ifmsh->sync_offset_clockdrift_max);
  70                 tsfdelta = -ifmsh->sync_offset_clockdrift_max;
  71                 ifmsh->sync_offset_clockdrift_max = 0;
  72         } else {
  73                 msync_dbg("TBTT : max clockdrift=%lld; adjusting by %llu",
  74                         (long long) ifmsh->sync_offset_clockdrift_max,
  75                         (unsigned long long) beacon_int_fraction);
  76                 tsfdelta = -beacon_int_fraction;
  77                 ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
  78         }
  79
  80         tsf = drv_get_tsf(local, sdata);
  81         if (tsf != -1ULL)
  82                 drv_set_tsf(local, sdata, tsf + tsfdelta);
  83         spin_unlock_bh(&ifmsh->sync_offset_lock);
  84 }
  85
  86 static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
  87                                    u16 stype,
  88                                    struct ieee80211_mgmt *mgmt,
  89                                    struct ieee802_11_elems *elems,
  90                                    struct ieee80211_rx_status *rx_status)
  91 {
  92         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  93         struct ieee80211_local *local = sdata->local;
  94         struct sta_info *sta;
  95         u64 t_t, t_r;
  96
  97         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
  98
  99         /* standard mentions only beacons */
 100         if (stype != IEEE80211_STYPE_BEACON)
 101                 return;
 102
 103         /* The current tsf is a first approximation for the timestamp
 104          * for the received beacon.  Further down we try to get a
 105          * better value from the rx_status->mactime field if
 106          * available. Also we have to call drv_get_tsf() before
 107          * entering the rcu-read section.*/
 108         t_r = drv_get_tsf(local, sdata);
 109
 110         rcu_read_lock();
 111         sta = sta_info_get(sdata, mgmt->sa);
 112         if (!sta)
 113                 goto no_sync;
 114
 115         /* check offset sync conditions (13.13.2.2.1)
 116          *
 117          * TODO also sync to
 118          * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
 119          */
 120
 121         if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
 122                 clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 123                 msync_dbg("STA %pM : is adjusting TBTT", sta->sta.addr);
 124                 goto no_sync;
 125         }
 126
 127         if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) {
 128                 /*
 129                  * The mactime is defined as the time the first data symbol
 130                  * of the frame hits the PHY, and the timestamp of the beacon
 131                  * is defined as "the time that the data symbol containing the
 132                  * first bit of the timestamp is transmitted to the PHY plus
 133                  * the transmitting STA's delays through its local PHY from the
 134                  * MAC-PHY interface to its interface with the WM" (802.11
 135                  * 11.1.2)
 136                  *
 137                  * T_r, in 13.13.2.2.2, is just defined as "the frame reception
 138                  * time" but we unless we interpret that time to be the same
 139                  * time of the beacon timestamp, the offset calculation will be
 140                  * off.  Below we adjust t_r to be "the time at which the first
 141                  * symbol of the timestamp element in the beacon is received".
 142                  * This correction depends on the rate.
 143                  *
 144                  * Based on similar code in ibss.c
 145                  */
 146                 int rate;
 147
 148                 if (rx_status->flag & RX_FLAG_HT) {
 149                         /* TODO:
 150                          * In principle there could be HT-beacons (Dual Beacon
 151                          * HT Operation options), but for now ignore them and
 152                          * just use the primary (i.e. non-HT) beacons for
 153                          * synchronization.
 154                          * */
 155                         goto no_sync;
 156                 } else
 157                         rate = local->hw.wiphy->bands[rx_status->band]->
 158                                 bitrates[rx_status->rate_idx].bitrate;
 159
 160                 /* 24 bytes of header * 8 bits/byte *
 161                  * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/
 162                 t_r = rx_status->mactime + (24 * 8 * 10 / rate);
 163         }
 164
 165         /* Timing offset calculation (see 13.13.2.2.2) */
 166         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 167         sta->t_offset = t_t - t_r;
 168
 169         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 170                 s64 t_clockdrift = sta->t_offset_setpoint
 171                                    - sta->t_offset;
 172                 msync_dbg("STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld",
 173                           sta->sta.addr,
 174                           (long long) sta->t_offset,
 175                           (long long)
 176                           sta->t_offset_setpoint,
 177                           (long long) t_clockdrift);
 178
 179                 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
 180                         t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
 181                         msync_dbg("STA %pM : t_clockdrift=%lld too large, setpoint reset",
 182                                   sta->sta.addr,
 183                                   (long long) t_clockdrift);
 184                         clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 185                         goto no_sync;
 186                 }
 187
 188                 rcu_read_unlock();
 189
 190                 spin_lock_bh(&ifmsh->sync_offset_lock);
 191                 if (t_clockdrift >
 192                     ifmsh->sync_offset_clockdrift_max)
 193                         ifmsh->sync_offset_clockdrift_max
 194                                 = t_clockdrift;
 195                 spin_unlock_bh(&ifmsh->sync_offset_lock);
 196
 197         } else {
 198                 sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
 199                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 200                 msync_dbg("STA %pM : offset was invalid, "
 201                           " sta->t_offset=%lld",
 202                           sta->sta.addr,
 203                           (long long) sta->t_offset);
 204                 rcu_read_unlock();
 205         }
 206         return;
 207
 208 no_sync:
 209         rcu_read_unlock();
 210 }
 211
 212 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 213 {
 214         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 215
 216         WARN_ON(ifmsh->mesh_sp_id
 217                 != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 218         BUG_ON(!rcu_read_lock_held());
 219
 220         spin_lock_bh(&ifmsh->sync_offset_lock);
 221
 222         if (ifmsh->sync_offset_clockdrift_max >
 223                 TOFFSET_MINIMUM_ADJUSTMENT) {
 224                 /* Since ajusting the tsf here would
 225                  * require a possibly blocking call
 226                  * to the driver tsf setter, we punt
 227                  * the tsf adjustment to the mesh tasklet
 228                  */
 229                 msync_dbg("TBTT : kicking off TBTT "
 230                           "adjustment with "
 231                           "clockdrift_max=%lld",
 232                   ifmsh->sync_offset_clockdrift_max);
 233                 set_bit(MESH_WORK_DRIFT_ADJUST,
 234                         &ifmsh->wrkq_flags);
 235         } else {
 236                 msync_dbg("TBTT : max clockdrift=%lld; "
 237                           "too small to adjust",
 238                           (long long)
 239                        ifmsh->sync_offset_clockdrift_max);
 240                 ifmsh->sync_offset_clockdrift_max = 0;
 241         }
 242         spin_unlock_bh(&ifmsh->sync_offset_lock);
 243 }
 244
 245 static const u8 *mesh_get_vendor_oui(struct ieee80211_sub_if_data *sdata)
 246 {
 247         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 248         u8 offset;
 249
 250         if (!ifmsh->ie || !ifmsh->ie_len)
 251                 return NULL;
 252
 253         offset = ieee80211_ie_split_vendor(ifmsh->ie,
 254                                         ifmsh->ie_len, 0);
 255
 256         if (!offset)
 257                 return NULL;
 258
 259         return ifmsh->ie + offset + 2;
 260 }
 261
 262 static void mesh_sync_vendor_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
 263                                    u16 stype,
 264                                    struct ieee80211_mgmt *mgmt,
 265                                    struct ieee802_11_elems *elems,
 266                                    struct ieee80211_rx_status *rx_status)
 267 {
 268         const u8 *oui;
 269
 270         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 271         msync_dbg("called mesh_sync_vendor_rx_bcn_presp");
 272         oui = mesh_get_vendor_oui(sdata);
 273         /*  here you would implement the vendor offset tracking for this oui */
 274 }
 275
 276 static void mesh_sync_vendor_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 277 {
 278         const u8 *oui;
 279
 280         WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
 281         msync_dbg("called mesh_sync_vendor_adjust_tbtt");
 282         oui = mesh_get_vendor_oui(sdata);
 283         /*  here you would implement the vendor tsf adjustment for this oui */
 284 }
 285
 286 /* global variable */
 287 static struct sync_method sync_methods[] = {
 288         {
 289                 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 290                 .ops = {
 291                         .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 292                         .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
 293                 }
 294         },
 295         {
 296                 .method = IEEE80211_SYNC_METHOD_VENDOR,
 297                 .ops = {
 298                         .rx_bcn_presp = &mesh_sync_vendor_rx_bcn_presp,
 299                         .adjust_tbtt = &mesh_sync_vendor_adjust_tbtt,
 300                 }
 301         },
 302 };
 303
 304 struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 305 {
 306         struct ieee80211_mesh_sync_ops *ops = NULL;
 307         u8 i;
 308
 309         for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 310                 if (sync_methods[i].method == method) {
 311                         ops = &sync_methods[i].ops;
 312                         break;
 313                 }
 314         }
 315         return ops;
 316 }