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 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_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 78 static 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 /* 96 * Get time when timestamp field was received. If we don't 97 * have rx timestamps, then use current tsf as an approximation. 98 * drv_get_tsf() must be called before entering the rcu-read 99 * section. 100 */ 101 if (ieee80211_have_rx_timestamp(rx_status)) 102 t_r = ieee80211_calculate_rx_timestamp(local, rx_status, 103 24 + 12 + 104 elems->total_len + 105 FCS_LEN, 106 24); 107 else 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(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->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 } 162 163 no_sync: 164 rcu_read_unlock(); 165 } 166 167 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata, 168 struct beacon_data *beacon) 169 { 170 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; 171 u8 cap; 172 173 WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET); 174 WARN_ON(!rcu_read_lock_held()); 175 cap = beacon->meshconf->meshconf_cap; 176 177 spin_lock_bh(&ifmsh->sync_offset_lock); 178 179 if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) { 180 /* Since ajusting the tsf here would 181 * require a possibly blocking call 182 * to the driver tsf setter, we punt 183 * the tsf adjustment to the mesh tasklet 184 */ 185 msync_dbg(sdata, 186 "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n", 187 ifmsh->sync_offset_clockdrift_max); 188 set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags); 189 190 ifmsh->adjusting_tbtt = true; 191 } else { 192 msync_dbg(sdata, 193 "TBTT : max clockdrift=%lld; too small to adjust\n", 194 (long long)ifmsh->sync_offset_clockdrift_max); 195 ifmsh->sync_offset_clockdrift_max = 0; 196 197 ifmsh->adjusting_tbtt = false; 198 } 199 spin_unlock_bh(&ifmsh->sync_offset_lock); 200 201 beacon->meshconf->meshconf_cap = ifmsh->adjusting_tbtt ? 202 IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING | cap : 203 ~IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING & cap; 204 } 205 206 static const struct sync_method sync_methods[] = { 207 { 208 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET, 209 .ops = { 210 .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp, 211 .adjust_tbtt = &mesh_sync_offset_adjust_tbtt, 212 } 213 }, 214 }; 215 216 const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method) 217 { 218 int i; 219 220 for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) { 221 if (sync_methods[i].method == method) 222 return &sync_methods[i].ops; 223 } 224 return NULL; 225 } 226