net/mac80211/mesh_sync.c

   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  * Copyright (C) 2021 Intel Corporation
   7  */
   8
   9 #include "ieee80211_i.h"
  10 #include "mesh.h"
  11 #include "driver-ops.h"
  12
  13 /* This is not in the standard.  It represents a tolerable tsf drift below
  14  * which we do no TSF adjustment.
  15  */
  16 #define TOFFSET_MINIMUM_ADJUSTMENT 10
  17
  18 /* This is not in the standard. It is a margin added to the
  19  * Toffset setpoint to mitigate TSF overcorrection
  20  * introduced by TSF adjustment latency.
  21  */
  22 #define TOFFSET_SET_MARGIN 20
  23
  24 /* This is not in the standard.  It represents the maximum Toffset jump above
  25  * which we'll invalidate the Toffset setpoint and choose a new setpoint.  This
  26  * could be, for instance, in case a neighbor is restarted and its TSF counter
  27  * reset.
  28  */
  29 #define TOFFSET_MAXIMUM_ADJUSTMENT 800          /* 0.8 ms */
  30
  31 struct sync_method {
  32         u8 method;
  33         struct ieee80211_mesh_sync_ops ops;
  34 };
  35
  36 /**
  37  * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
  38  *
  39  * @cfg: mesh config element from the mesh peer (or %NULL)
  40  */
  41 static bool mesh_peer_tbtt_adjusting(const struct ieee80211_meshconf_ie *cfg)
  42 {
  43         return cfg &&
  44                (cfg->meshconf_cap & IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING);
  45 }
  46
  47 void mesh_sync_adjust_tsf(struct ieee80211_sub_if_data *sdata)
  48 {
  49         struct ieee80211_local *local = sdata->local;
  50         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  51         /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
  52         u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
  53         u64 tsf;
  54         u64 tsfdelta;
  55
  56         spin_lock_bh(&ifmsh->sync_offset_lock);
  57         if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
  58                 msync_dbg(sdata, "TSF : max clockdrift=%lld; adjusting\n",
  59                           (long long) ifmsh->sync_offset_clockdrift_max);
  60                 tsfdelta = -ifmsh->sync_offset_clockdrift_max;
  61                 ifmsh->sync_offset_clockdrift_max = 0;
  62         } else {
  63                 msync_dbg(sdata, "TSF : max clockdrift=%lld; adjusting by %llu\n",
  64                           (long long) ifmsh->sync_offset_clockdrift_max,
  65                           (unsigned long long) beacon_int_fraction);
  66                 tsfdelta = -beacon_int_fraction;
  67                 ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
  68         }
  69         spin_unlock_bh(&ifmsh->sync_offset_lock);
  70
  71         if (local->ops->offset_tsf) {
  72                 drv_offset_tsf(local, sdata, tsfdelta);
  73         } else {
  74                 tsf = drv_get_tsf(local, sdata);
  75                 if (tsf != -1ULL)
  76                         drv_set_tsf(local, sdata, tsf + tsfdelta);
  77         }
  78 }
  79
  80 static void
  81 mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata, u16 stype,
  82                               struct ieee80211_mgmt *mgmt, unsigned int len,
  83                               const struct ieee80211_meshconf_ie *mesh_cfg,
  84                               struct ieee80211_rx_status *rx_status)
  85 {
  86         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  87         struct ieee80211_local *local = sdata->local;
  88         struct sta_info *sta;
  89         u64 t_t, t_r;
  90
  91         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
  92
  93         /* standard mentions only beacons */
  94         if (stype != IEEE80211_STYPE_BEACON)
  95                 return;
  96
  97         /*
  98          * Get time when timestamp field was received.  If we don't
  99          * have rx timestamps, then use current tsf as an approximation.
 100          * drv_get_tsf() must be called before entering the rcu-read
 101          * section.
 102          */
 103         if (ieee80211_have_rx_timestamp(rx_status))
 104                 t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
 105                                                        len + FCS_LEN, 24);
 106         else
 107                 t_r = drv_get_tsf(local, sdata);
 108
 109         rcu_read_lock();
 110         sta = sta_info_get(sdata, mgmt->sa);
 111         if (!sta)
 112                 goto no_sync;
 113
 114         /* check offset sync conditions (13.13.2.2.1)
 115          *
 116          * TODO also sync to
 117          * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
 118          */
 119
 120         if (mesh_peer_tbtt_adjusting(mesh_cfg)) {
 121                 msync_dbg(sdata, "STA %pM : is adjusting TBTT\n",
 122                           sta->sta.addr);
 123                 goto no_sync;
 124         }
 125
 126         /* Timing offset calculation (see 13.13.2.2.2) */
 127         t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 128         sta->mesh->t_offset = t_t - t_r;
 129
 130         if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 131                 s64 t_clockdrift = sta->mesh->t_offset_setpoint - sta->mesh->t_offset;
 132                 msync_dbg(sdata,
 133                           "STA %pM : t_offset=%lld, t_offset_setpoint=%lld, t_clockdrift=%lld\n",
 134                           sta->sta.addr, (long long) sta->mesh->t_offset,
 135                           (long long) sta->mesh->t_offset_setpoint,
 136                           (long long) t_clockdrift);
 137
 138                 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
 139                     t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
 140                         msync_dbg(sdata,
 141                                   "STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
 142                                   sta->sta.addr,
 143                                   (long long) t_clockdrift);
 144                         clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 145                         goto no_sync;
 146                 }
 147
 148                 spin_lock_bh(&ifmsh->sync_offset_lock);
 149                 if (t_clockdrift > ifmsh->sync_offset_clockdrift_max)
 150                         ifmsh->sync_offset_clockdrift_max = t_clockdrift;
 151                 spin_unlock_bh(&ifmsh->sync_offset_lock);
 152         } else {
 153                 sta->mesh->t_offset_setpoint = sta->mesh->t_offset - TOFFSET_SET_MARGIN;
 154                 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 155                 msync_dbg(sdata,
 156                           "STA %pM : offset was invalid, t_offset=%lld\n",
 157                           sta->sta.addr,
 158                           (long long) sta->mesh->t_offset);
 159         }
 160
 161 no_sync:
 162         rcu_read_unlock();
 163 }
 164
 165 static void mesh_sync_offset_adjust_tsf(struct ieee80211_sub_if_data *sdata,
 166                                          struct beacon_data *beacon)
 167 {
 168         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 169
 170         WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 171         WARN_ON(!rcu_read_lock_held());
 172
 173         spin_lock_bh(&ifmsh->sync_offset_lock);
 174
 175         if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
 176                 /* Since ajusting the tsf here would
 177                  * require a possibly blocking call
 178                  * to the driver tsf setter, we punt
 179                  * the tsf adjustment to the mesh tasklet
 180                  */
 181                 msync_dbg(sdata,
 182                           "TSF : kicking off TSF adjustment with clockdrift_max=%lld\n",
 183                           ifmsh->sync_offset_clockdrift_max);
 184                 set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags);
 185         } else {
 186                 msync_dbg(sdata,
 187                           "TSF : max clockdrift=%lld; too small to adjust\n",
 188                           (long long)ifmsh->sync_offset_clockdrift_max);
 189                 ifmsh->sync_offset_clockdrift_max = 0;
 190         }
 191         spin_unlock_bh(&ifmsh->sync_offset_lock);
 192 }
 193
 194 static const struct sync_method sync_methods[] = {
 195         {
 196                 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 197                 .ops = {
 198                         .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 199                         .adjust_tsf = &mesh_sync_offset_adjust_tsf,
 200                 }
 201         },
 202 };
 203
 204 const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 205 {
 206         int i;
 207
 208         for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 209                 if (sync_methods[i].method == method)
 210                         return &sync_methods[i].ops;
 211         }
 212         return NULL;
 213 }