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 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 /* 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", sta->sta.addr); 116 goto no_sync; 117 } 118 119 if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) { 120 /* 121 * The mactime is defined as the time the first data symbol 122 * of the frame hits the PHY, and the timestamp of the beacon 123 * is defined as "the time that the data symbol containing the 124 * first bit of the timestamp is transmitted to the PHY plus 125 * the transmitting STA's delays through its local PHY from the 126 * MAC-PHY interface to its interface with the WM" (802.11 127 * 11.1.2) 128 * 129 * T_r, in 13.13.2.2.2, is just defined as "the frame reception 130 * time" but we unless we interpret that time to be the same 131 * time of the beacon timestamp, the offset calculation will be 132 * off. Below we adjust t_r to be "the time at which the first 133 * symbol of the timestamp element in the beacon is received". 134 * This correction depends on the rate. 135 * 136 * Based on similar code in ibss.c 137 */ 138 int rate; 139 140 if (rx_status->flag & RX_FLAG_HT) { 141 /* TODO: 142 * In principle there could be HT-beacons (Dual Beacon 143 * HT Operation options), but for now ignore them and 144 * just use the primary (i.e. non-HT) beacons for 145 * synchronization. 146 * */ 147 goto no_sync; 148 } else 149 rate = local->hw.wiphy->bands[rx_status->band]-> 150 bitrates[rx_status->rate_idx].bitrate; 151 152 /* 24 bytes of header * 8 bits/byte * 153 * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/ 154 t_r = rx_status->mactime + (24 * 8 * 10 / rate); 155 } 156 157 /* Timing offset calculation (see 13.13.2.2.2) */ 158 t_t = le64_to_cpu(mgmt->u.beacon.timestamp); 159 sta->t_offset = t_t - t_r; 160 161 if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) { 162 s64 t_clockdrift = sta->t_offset_setpoint 163 - sta->t_offset; 164 msync_dbg(sdata, 165 "STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n", 166 sta->sta.addr, 167 (long long) sta->t_offset, 168 (long long) 169 sta->t_offset_setpoint, 170 (long long) t_clockdrift); 171 172 if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT || 173 t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) { 174 msync_dbg(sdata, 175 "STA %pM : t_clockdrift=%lld too large, setpoint reset\n", 176 sta->sta.addr, 177 (long long) t_clockdrift); 178 clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); 179 goto no_sync; 180 } 181 182 rcu_read_unlock(); 183 184 spin_lock_bh(&ifmsh->sync_offset_lock); 185 if (t_clockdrift > 186 ifmsh->sync_offset_clockdrift_max) 187 ifmsh->sync_offset_clockdrift_max 188 = t_clockdrift; 189 spin_unlock_bh(&ifmsh->sync_offset_lock); 190 191 } else { 192 sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN; 193 set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); 194 msync_dbg(sdata, 195 "STA %pM : offset was invalid, sta->t_offset=%lld\n", 196 sta->sta.addr, 197 (long long) sta->t_offset); 198 rcu_read_unlock(); 199 } 200 return; 201 202 no_sync: 203 rcu_read_unlock(); 204 } 205 206 static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata) 207 { 208 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; 209 210 WARN_ON(ifmsh->mesh_sp_id 211 != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET); 212 BUG_ON(!rcu_read_lock_held()); 213 214 spin_lock_bh(&ifmsh->sync_offset_lock); 215 216 if (ifmsh->sync_offset_clockdrift_max > 217 TOFFSET_MINIMUM_ADJUSTMENT) { 218 /* Since ajusting the tsf here would 219 * require a possibly blocking call 220 * to the driver tsf setter, we punt 221 * the tsf adjustment to the mesh tasklet 222 */ 223 msync_dbg(sdata, 224 "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n", 225 ifmsh->sync_offset_clockdrift_max); 226 set_bit(MESH_WORK_DRIFT_ADJUST, 227 &ifmsh->wrkq_flags); 228 } else { 229 msync_dbg(sdata, 230 "TBTT : max clockdrift=%lld; too small to adjust\n", 231 (long long)ifmsh->sync_offset_clockdrift_max); 232 ifmsh->sync_offset_clockdrift_max = 0; 233 } 234 spin_unlock_bh(&ifmsh->sync_offset_lock); 235 } 236 237 static const u8 *mesh_get_vendor_oui(struct ieee80211_sub_if_data *sdata) 238 { 239 struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; 240 u8 offset; 241 242 if (!ifmsh->ie || !ifmsh->ie_len) 243 return NULL; 244 245 offset = ieee80211_ie_split_vendor(ifmsh->ie, 246 ifmsh->ie_len, 0); 247 248 if (!offset) 249 return NULL; 250 251 return ifmsh->ie + offset + 2; 252 } 253 254 static void mesh_sync_vendor_rx_bcn_presp(struct ieee80211_sub_if_data *sdata, 255 u16 stype, 256 struct ieee80211_mgmt *mgmt, 257 struct ieee802_11_elems *elems, 258 struct ieee80211_rx_status *rx_status) 259 { 260 const u8 *oui; 261 262 WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR); 263 msync_dbg(sdata, "called mesh_sync_vendor_rx_bcn_presp\n"); 264 oui = mesh_get_vendor_oui(sdata); 265 /* here you would implement the vendor offset tracking for this oui */ 266 } 267 268 static void mesh_sync_vendor_adjust_tbtt(struct ieee80211_sub_if_data *sdata) 269 { 270 const u8 *oui; 271 272 WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR); 273 msync_dbg(sdata, "called mesh_sync_vendor_adjust_tbtt\n"); 274 oui = mesh_get_vendor_oui(sdata); 275 /* here you would implement the vendor tsf adjustment for this oui */ 276 } 277 278 /* global variable */ 279 static struct sync_method sync_methods[] = { 280 { 281 .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET, 282 .ops = { 283 .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp, 284 .adjust_tbtt = &mesh_sync_offset_adjust_tbtt, 285 } 286 }, 287 { 288 .method = IEEE80211_SYNC_METHOD_VENDOR, 289 .ops = { 290 .rx_bcn_presp = &mesh_sync_vendor_rx_bcn_presp, 291 .adjust_tbtt = &mesh_sync_vendor_adjust_tbtt, 292 } 293 }, 294 }; 295 296 struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method) 297 { 298 struct ieee80211_mesh_sync_ops *ops = NULL; 299 u8 i; 300 301 for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) { 302 if (sync_methods[i].method == method) { 303 ops = &sync_methods[i].ops; 304 break; 305 } 306 } 307 return ops; 308 } 309