/* * Copyright 2011-2012, Pavel Zubarev * Copyright 2011-2012, Marco Porsch * Copyright 2011-2012, cozybit Inc. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include "ieee80211_i.h" #include "mesh.h" #include "driver-ops.h" /* This is not in the standard. It represents a tolerable tbtt drift below * which we do no TSF adjustment. */ #define TOFFSET_MINIMUM_ADJUSTMENT 10 /* This is not in the standard. It is a margin added to the * Toffset setpoint to mitigate TSF overcorrection * introduced by TSF adjustment latency. */ #define TOFFSET_SET_MARGIN 20 /* This is not in the standard. It represents the maximum Toffset jump above * which we'll invalidate the Toffset setpoint and choose a new setpoint. This * could be, for instance, in case a neighbor is restarted and its TSF counter * reset. */ #define TOFFSET_MAXIMUM_ADJUSTMENT 30000 /* 30 ms */ struct sync_method { u8 method; struct ieee80211_mesh_sync_ops ops; }; /** * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT * * @ie: information elements of a management frame from the mesh peer */ static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie) { return (ie->mesh_config->meshconf_cap & MESHCONF_CAPAB_TBTT_ADJUSTING) != 0; } void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata) { struct ieee80211_local *local = sdata->local; struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */ u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500; u64 tsf; u64 tsfdelta; spin_lock_bh(&ifmsh->sync_offset_lock); if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) { msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting\n", (long long) ifmsh->sync_offset_clockdrift_max); tsfdelta = -ifmsh->sync_offset_clockdrift_max; ifmsh->sync_offset_clockdrift_max = 0; } else { msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting by %llu\n", (long long) ifmsh->sync_offset_clockdrift_max, (unsigned long long) beacon_int_fraction); tsfdelta = -beacon_int_fraction; ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction; } spin_unlock_bh(&ifmsh->sync_offset_lock); tsf = drv_get_tsf(local, sdata); if (tsf != -1ULL) drv_set_tsf(local, sdata, tsf + tsfdelta); } static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata, u16 stype, struct ieee80211_mgmt *mgmt, struct ieee802_11_elems *elems, struct ieee80211_rx_status *rx_status) { struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; struct ieee80211_local *local = sdata->local; struct sta_info *sta; u64 t_t, t_r; WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET); /* standard mentions only beacons */ if (stype != IEEE80211_STYPE_BEACON) return; /* The current tsf is a first approximation for the timestamp * for the received beacon. Further down we try to get a * better value from the rx_status->mactime field if * available. Also we have to call drv_get_tsf() before * entering the rcu-read section.*/ t_r = drv_get_tsf(local, sdata); rcu_read_lock(); sta = sta_info_get(sdata, mgmt->sa); if (!sta) goto no_sync; /* check offset sync conditions (13.13.2.2.1) * * TODO also sync to * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors */ if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) { clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); msync_dbg(sdata, "STA %pM : is adjusting TBTT\n", sta->sta.addr); goto no_sync; } if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) { /* * The mactime is defined as the time the first data symbol * of the frame hits the PHY, and the timestamp of the beacon * is defined as "the time that the data symbol containing the * first bit of the timestamp is transmitted to the PHY plus * the transmitting STA's delays through its local PHY from the * MAC-PHY interface to its interface with the WM" (802.11 * 11.1.2) * * T_r, in 13.13.2.2.2, is just defined as "the frame reception * time" but we unless we interpret that time to be the same * time of the beacon timestamp, the offset calculation will be * off. Below we adjust t_r to be "the time at which the first * symbol of the timestamp element in the beacon is received". * This correction depends on the rate. * * Based on similar code in ibss.c */ int rate; if (rx_status->flag & RX_FLAG_HT) { /* TODO: * In principle there could be HT-beacons (Dual Beacon * HT Operation options), but for now ignore them and * just use the primary (i.e. non-HT) beacons for * synchronization. * */ goto no_sync; } else rate = local->hw.wiphy->bands[rx_status->band]-> bitrates[rx_status->rate_idx].bitrate; /* 24 bytes of header * 8 bits/byte * * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/ t_r = rx_status->mactime + (24 * 8 * 10 / rate); } /* Timing offset calculation (see 13.13.2.2.2) */ t_t = le64_to_cpu(mgmt->u.beacon.timestamp); sta->t_offset = t_t - t_r; if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) { s64 t_clockdrift = sta->t_offset_setpoint - sta->t_offset; msync_dbg(sdata, "STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n", sta->sta.addr, (long long) sta->t_offset, (long long) sta->t_offset_setpoint, (long long) t_clockdrift); if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT || t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) { msync_dbg(sdata, "STA %pM : t_clockdrift=%lld too large, setpoint reset\n", sta->sta.addr, (long long) t_clockdrift); clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); goto no_sync; } rcu_read_unlock(); spin_lock_bh(&ifmsh->sync_offset_lock); if (t_clockdrift > ifmsh->sync_offset_clockdrift_max) ifmsh->sync_offset_clockdrift_max = t_clockdrift; spin_unlock_bh(&ifmsh->sync_offset_lock); } else { sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN; set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN); msync_dbg(sdata, "STA %pM : offset was invalid, sta->t_offset=%lld\n", sta->sta.addr, (long long) sta->t_offset); rcu_read_unlock(); } return; no_sync: rcu_read_unlock(); } static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata) { struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh; WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET); BUG_ON(!rcu_read_lock_held()); spin_lock_bh(&ifmsh->sync_offset_lock); if (ifmsh->sync_offset_clockdrift_max > TOFFSET_MINIMUM_ADJUSTMENT) { /* Since ajusting the tsf here would * require a possibly blocking call * to the driver tsf setter, we punt * the tsf adjustment to the mesh tasklet */ msync_dbg(sdata, "TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n", ifmsh->sync_offset_clockdrift_max); set_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags); } else { msync_dbg(sdata, "TBTT : max clockdrift=%lld; too small to adjust\n", (long long)ifmsh->sync_offset_clockdrift_max); ifmsh->sync_offset_clockdrift_max = 0; } spin_unlock_bh(&ifmsh->sync_offset_lock); } static const struct sync_method sync_methods[] = { { .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET, .ops = { .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp, .adjust_tbtt = &mesh_sync_offset_adjust_tbtt, } }, }; const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method) { const struct ieee80211_mesh_sync_ops *ops = NULL; u8 i; for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) { if (sync_methods[i].method == method) { ops = &sync_methods[i].ops; break; } } return ops; }