root/net/mac80211/mesh_sync.c

DEFINITIONS

1. mesh_peer_tbtt_adjusting
2. mesh_sync_adjust_tsf
3. mesh_sync_offset_rx_bcn_presp
4. mesh_sync_offset_adjust_tsf
5. ieee80211_mesh_sync_ops_get

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
   4  * Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
   5  * Copyright 2011-2012, cozybit Inc.
   6  */
   7 
   8 #include "ieee80211_i.h"
   9 #include "mesh.h"
  10 #include "driver-ops.h"
  11 
  12 /* This is not in the standard.  It represents a tolerable tsf drift below
  13  * which we do no TSF adjustment.
  14  */
  15 #define TOFFSET_MINIMUM_ADJUSTMENT 10
  16 
  17 /* This is not in the standard. It is a margin added to the
  18  * Toffset setpoint to mitigate TSF overcorrection
  19  * introduced by TSF adjustment latency.
  20  */
  21 #define TOFFSET_SET_MARGIN 20
  22 
  23 /* This is not in the standard.  It represents the maximum Toffset jump above
  24  * which we'll invalidate the Toffset setpoint and choose a new setpoint.  This
  25  * could be, for instance, in case a neighbor is restarted and its TSF counter
  26  * reset.
  27  */
  28 #define TOFFSET_MAXIMUM_ADJUSTMENT 800          /* 0.8 ms */
  29 
  30 struct sync_method {
  31         u8 method;
  32         struct ieee80211_mesh_sync_ops ops;
  33 };
  34 
  35 /**
  36  * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
  37  *
  38  * @ie: information elements of a management frame from the mesh peer
  39  */
  40 static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
  41 {
  42         return (ie->mesh_config->meshconf_cap &
  43                         IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
  44 }
  45 
  46 void mesh_sync_adjust_tsf(struct ieee80211_sub_if_data *sdata)
  47 {
  48         struct ieee80211_local *local = sdata->local;
  49         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  50         /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
  51         u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
  52         u64 tsf;
  53         u64 tsfdelta;
  54 
  55         spin_lock_bh(&ifmsh->sync_offset_lock);
  56         if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
  57                 msync_dbg(sdata, "TSF : max clockdrift=%lld; adjusting\n",
  58                           (long long) ifmsh->sync_offset_clockdrift_max);
  59                 tsfdelta = -ifmsh->sync_offset_clockdrift_max;
  60                 ifmsh->sync_offset_clockdrift_max = 0;
  61         } else {
  62                 msync_dbg(sdata, "TSF : max clockdrift=%lld; adjusting by %llu\n",
  63                           (long long) ifmsh->sync_offset_clockdrift_max,
  64                           (unsigned long long) beacon_int_fraction);
  65                 tsfdelta = -beacon_int_fraction;
  66                 ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
  67         }
  68         spin_unlock_bh(&ifmsh->sync_offset_lock);
  69 
  70         if (local->ops->offset_tsf) {
  71                 drv_offset_tsf(local, sdata, tsfdelta);
  72         } else {
  73                 tsf = drv_get_tsf(local, sdata);
  74                 if (tsf != -1ULL)
  75                         drv_set_tsf(local, sdata, tsf + tsfdelta);
  76         }
  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         /*
  97          * Get time when timestamp field was received.  If we don't
  98          * have rx timestamps, then use current tsf as an approximation.
  99          * drv_get_tsf() must be called before entering the rcu-read
 100          * section.
 101          */
 102         if (ieee80211_have_rx_timestamp(rx_status))
 103                 t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
 104                                                        24 + 12 +
 105                                                        elems->total_len +
 106                                                        FCS_LEN,
 107                                                        24);
 108         else
 109                 t_r = drv_get_tsf(local, sdata);
 110 
 111         rcu_read_lock();
 112         sta = sta_info_get(sdata, mgmt->sa);
 113         if (!sta)
 114                 goto no_sync;
 115 
 116         /* check offset sync conditions (13.13.2.2.1)
 117          *
 118          * TODO also sync to
 119          * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
 120          */
 121 
 122         if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
 123                 msync_dbg(sdata, "STA %pM : is adjusting TBTT\n",
 124                           sta->sta.addr);
 125                 goto no_sync;
 126         }
 127 
 128         /* Timing offset calculation (see 13.13.2.2.2) */
 129         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 130         sta->mesh->t_offset = t_t - t_r;
 131 
 132         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 133                 s64 t_clockdrift = sta->mesh->t_offset_setpoint - sta->mesh->t_offset;
 134                 msync_dbg(sdata,
 135                           "STA %pM : t_offset=%lld, t_offset_setpoint=%lld, t_clockdrift=%lld\n",
 136                           sta->sta.addr, (long long) sta->mesh->t_offset,
 137                           (long long) sta->mesh->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->mesh->t_offset_setpoint = sta->mesh->t_offset - TOFFSET_SET_MARGIN;
 156                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 157                 msync_dbg(sdata,
 158                           "STA %pM : offset was invalid, t_offset=%lld\n",
 159                           sta->sta.addr,
 160                           (long long) sta->mesh->t_offset);
 161         }
 162 
 163 no_sync:
 164         rcu_read_unlock();
 165 }
 166 
 167 static void mesh_sync_offset_adjust_tsf(struct ieee80211_sub_if_data *sdata,
 168                                          struct beacon_data *beacon)
 169 {
 170         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 171 
 172         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 173         WARN_ON(!rcu_read_lock_held());
 174 
 175         spin_lock_bh(&ifmsh->sync_offset_lock);
 176 
 177         if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
 178                 /* Since ajusting the tsf here would
 179                  * require a possibly blocking call
 180                  * to the driver tsf setter, we punt
 181                  * the tsf adjustment to the mesh tasklet
 182                  */
 183                 msync_dbg(sdata,
 184                           "TSF : kicking off TSF adjustment with clockdrift_max=%lld\n",
 185                           ifmsh->sync_offset_clockdrift_max);
 186                 set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags);
 187         } else {
 188                 msync_dbg(sdata,
 189                           "TSF : max clockdrift=%lld; too small to adjust\n",
 190                           (long long)ifmsh->sync_offset_clockdrift_max);
 191                 ifmsh->sync_offset_clockdrift_max = 0;
 192         }
 193         spin_unlock_bh(&ifmsh->sync_offset_lock);
 194 }
 195 
 196 static const struct sync_method sync_methods[] = {
 197         {
 198                 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 199                 .ops = {
 200                         .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 201                         .adjust_tsf = &mesh_sync_offset_adjust_tsf,
 202                 }
 203         },
 204 };
 205 
 206 const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 207 {
 208         int i;
 209 
 210         for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 211                 if (sync_methods[i].method == method)
 212                         return &sync_methods[i].ops;
 213         }
 214         return NULL;
 215 }