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 tsf 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 800 /* 0.8 ms */ 32 33 struct 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 */ 43 static 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 49 void mesh_sync_adjust_tsf(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, "TSF : 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, "TSF : 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 if (local->ops->offset_tsf) { 74 drv_offset_tsf(local, sdata, tsfdelta); 75 } else { 76 tsf = drv_get_tsf(local, sdata); 77 if (tsf != -1ULL) 78 drv_set_tsf(local, sdata, tsf + tsfdelta); 79 } 80 } 81 82 static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata, 83 u16 stype, 84 struct ieee80211_mgmt *mgmt, 85 struct ieee802_11_elems *elems, 86 struct ieee80211_rx_status *rx_status) 87 { 88 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; 89 struct ieee80211_local *local = sdata->local; 90 struct sta_info *sta; 91 u64 t_t, t_r; 92 93 WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET); 94 95 /* standard mentions only beacons */ 96 if (stype != IEEE80211_STYPE_BEACON) 97 return; 98 99 /* 100 * Get time when timestamp field was received. If we don't 101 * have rx timestamps, then use current tsf as an approximation. 102 * drv_get_tsf() must be called before entering the rcu-read 103 * section. 104 */ 105 if (ieee80211_have_rx_timestamp(rx_status)) 106 t_r = ieee80211_calculate_rx_timestamp(local, rx_status, 107 24 + 12 + 108 elems->total_len + 109 FCS_LEN, 110 24); 111 else 112 t_r = drv_get_tsf(local, sdata); 113 114 rcu_read_lock(); 115 sta = sta_info_get(sdata, mgmt->sa); 116 if (!sta) 117 goto no_sync; 118 119 /* check offset sync conditions (13.13.2.2.1) 120 * 121 * TODO also sync to 122 * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors 123 */ 124 125 if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) { 126 msync_dbg(sdata, "STA %pM : is adjusting TBTT\n", 127 sta->sta.addr); 128 goto no_sync; 129 } 130 131 /* Timing offset calculation (see 13.13.2.2.2) */ 132 t_t = le64_to_cpu(mgmt->u.beacon.timestamp); 133 sta->mesh->t_offset = t_t - t_r; 134 135 if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) { 136 s64 t_clockdrift = sta->mesh->t_offset_setpoint - sta->mesh->t_offset; 137 msync_dbg(sdata, 138 "STA %pM : t_offset=%lld, t_offset_setpoint=%lld, t_clockdrift=%lld\n", 139 sta->sta.addr, (long long) sta->mesh->t_offset, 140 (long long) sta->mesh->t_offset_setpoint, 141 (long long) t_clockdrift); 142 143 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT || 144 t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) { 145 msync_dbg(sdata, 146 "STA %pM : t_clockdrift=%lld too large, setpoint reset\n", 147 sta->sta.addr, 148 (long long) t_clockdrift); 149 clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); 150 goto no_sync; 151 } 152 153 spin_lock_bh(&ifmsh->sync_offset_lock); 154 if (t_clockdrift > ifmsh->sync_offset_clockdrift_max) 155 ifmsh->sync_offset_clockdrift_max = t_clockdrift; 156 spin_unlock_bh(&ifmsh->sync_offset_lock); 157 } else { 158 sta->mesh->t_offset_setpoint = sta->mesh->t_offset - TOFFSET_SET_MARGIN; 159 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); 160 msync_dbg(sdata, 161 "STA %pM : offset was invalid, t_offset=%lld\n", 162 sta->sta.addr, 163 (long long) sta->mesh->t_offset); 164 } 165 166 no_sync: 167 rcu_read_unlock(); 168 } 169 170 static void mesh_sync_offset_adjust_tsf(struct ieee80211_sub_if_data *sdata, 171 struct beacon_data *beacon) 172 { 173 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; 174 175 WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET); 176 WARN_ON(!rcu_read_lock_held()); 177 178 spin_lock_bh(&ifmsh->sync_offset_lock); 179 180 if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) { 181 /* Since ajusting the tsf here would 182 * require a possibly blocking call 183 * to the driver tsf setter, we punt 184 * the tsf adjustment to the mesh tasklet 185 */ 186 msync_dbg(sdata, 187 "TSF : kicking off TSF adjustment with clockdrift_max=%lld\n", 188 ifmsh->sync_offset_clockdrift_max); 189 set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags); 190 } else { 191 msync_dbg(sdata, 192 "TSF : max clockdrift=%lld; too small to adjust\n", 193 (long long)ifmsh->sync_offset_clockdrift_max); 194 ifmsh->sync_offset_clockdrift_max = 0; 195 } 196 spin_unlock_bh(&ifmsh->sync_offset_lock); 197 } 198 199 static 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_tsf = &mesh_sync_offset_adjust_tsf, 205 } 206 }, 207 }; 208 209 const 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