LXR linux/net/mac80211/mesh

   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
  33struct 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 */
  43static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
  44{
  45        return (ie->mesh_config->meshconf_cap &
  46                        IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
  47}
  48
  49void 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        if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
  60                msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting\n",
  61                          (long long) ifmsh->sync_offset_clockdrift_max);
  62                tsfdelta = -ifmsh->sync_offset_clockdrift_max;
  63                ifmsh->sync_offset_clockdrift_max = 0;
  64        } else {
  65                msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting by %llu\n",
  66                          (long long) ifmsh->sync_offset_clockdrift_max,
  67                          (unsigned long long) beacon_int_fraction);
  68                tsfdelta = -beacon_int_fraction;
  69                ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
  70        }
  71        spin_unlock_bh(&ifmsh->sync_offset_lock);
  72
  73        tsf = drv_get_tsf(local, sdata);
  74        if (tsf != -1ULL)
  75                drv_set_tsf(local, sdata, tsf + tsfdelta);
  76}
  77
  78static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
  79                                   u16 stype,
  80                                   struct ieee80211_mgmt *mgmt,
  81                                   struct ieee802_11_elems *elems,
  82                                   struct ieee80211_rx_status *rx_status)
  83{
  84        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
  85        struct ieee80211_local *local = sdata->local;
  86        struct sta_info *sta;
  87        u64 t_t, t_r;
  88
  89        WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
  90
  91        /* standard mentions only beacons */
  92        if (stype != IEEE80211_STYPE_BEACON)
  93                return;
  94
  95        /* The current tsf is a first approximation for the timestamp
  96         * for the received beacon.  Further down we try to get a
  97         * better value from the rx_status->mactime field if
  98         * available. Also we have to call drv_get_tsf() before
  99         * entering the rcu-read section.*/
 100        t_r = drv_get_tsf(local, sdata);
 101
 102        rcu_read_lock();
 103        sta = sta_info_get(sdata, mgmt->sa);
 104        if (!sta)
 105                goto no_sync;
 106
 107        /* check offset sync conditions (13.13.2.2.1)
 108         *
 109         * TODO also sync to
 110         * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
 111         */
 112
 113        if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
 114                clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 115                msync_dbg(sdata, "STA %pM : is adjusting TBTT\n",
 116                          sta->sta.addr);
 117                goto no_sync;
 118        }
 119
 120        if (ieee80211_have_rx_timestamp(rx_status))
 121                /* time when timestamp field was received */
 122                t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
 123                                                       24 + 12 +
 124                                                       elems->total_len +
 125                                                       FCS_LEN,
 126                                                       24);
 127
 128        /* Timing offset calculation (see 13.13.2.2.2) */
 129        t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
 130        sta->t_offset = t_t - t_r;
 131
 132        if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
 133                s64 t_clockdrift = sta->t_offset_setpoint - sta->t_offset;
 134                msync_dbg(sdata,
 135                          "STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n",
 136                          sta->sta.addr, (long long) sta->t_offset,
 137                          (long long) sta->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->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
 156                set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
 157                msync_dbg(sdata,
 158                          "STA %pM : offset was invalid, sta->t_offset=%lld\n",
 159                          sta->sta.addr,
 160                          (long long) sta->t_offset);
 161        }
 162
 163no_sync:
 164        rcu_read_unlock();
 165}
 166
 167static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
 168{
 169        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
 170
 171        WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
 172        BUG_ON(!rcu_read_lock_held());
 173
 174        spin_lock_bh(&ifmsh->sync_offset_lock);
 175
 176        if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) {
 177                /* Since ajusting the tsf here would
 178                 * require a possibly blocking call
 179                 * to the driver tsf setter, we punt
 180                 * the tsf adjustment to the mesh tasklet
 181                 */
 182                msync_dbg(sdata,
 183                          "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
 184                          ifmsh->sync_offset_clockdrift_max);
 185                set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags);
 186
 187                ifmsh->adjusting_tbtt = true;
 188        } else {
 189                msync_dbg(sdata,
 190                          "TBTT : max clockdrift=%lld; too small to adjust\n",
 191                          (long long)ifmsh->sync_offset_clockdrift_max);
 192                ifmsh->sync_offset_clockdrift_max = 0;
 193
 194                ifmsh->adjusting_tbtt = false;
 195        }
 196        spin_unlock_bh(&ifmsh->sync_offset_lock);
 197}
 198
 199static const struct sync_method sync_methods[] = {
 200        {
 201                .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
 202                .ops = {
 203                        .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
 204                        .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
 205                }
 206        },
 207};
 208
 209const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
 210{
 211        int i;
 212
 213        for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
 214                if (sync_methods[i].method == method)
 215                        return &sync_methods[i].ops;
 216        }
 217        return NULL;
 218}
 219