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+/*
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+ * Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
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+ * Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
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+ * Copyright 2011-2012, cozybit Inc.
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License version 2 as
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+ * published by the Free Software Foundation.
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+ */
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+
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+#include "ieee80211_i.h"
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+#include "mesh.h"
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+#include "driver-ops.h"
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+
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+#ifdef CONFIG_MAC80211_VERBOSE_MESH_SYNC_DEBUG
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+#define msync_dbg(fmt, args...) \
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+ printk(KERN_DEBUG "Mesh sync (%s): " fmt "\n", sdata->name, ##args)
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+#else
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+#define msync_dbg(fmt, args...) do { (void)(0); } while (0)
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+#endif
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+
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+/* This is not in the standard. It represents a tolerable tbtt drift below
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+ * which we do no TSF adjustment.
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+ */
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+#define TBTT_MINIMUM_ADJUSTMENT 10
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+
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+struct sync_method {
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+ u8 method;
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+ struct ieee80211_mesh_sync_ops ops;
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+};
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+
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+/**
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+ * mesh_peer_tbtt_adjusting - check if an mp is currently adjusting its TBTT
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+ *
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+ * @ie: information elements of a management frame from the mesh peer
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+ */
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+static bool mesh_peer_tbtt_adjusting(struct ieee802_11_elems *ie)
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+{
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+ return (ie->mesh_config->meshconf_cap &
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+ MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
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+}
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+
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+void mesh_sync_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
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+{
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+ struct ieee80211_local *local = sdata->local;
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+ struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
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+ /* sdata->vif.bss_conf.beacon_int in 1024us units, 0.04% */
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+ u64 beacon_int_fraction = sdata->vif.bss_conf.beacon_int * 1024 / 2500;
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+ u64 tsf;
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+ u64 tsfdelta;
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+
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+ spin_lock_bh(&ifmsh->sync_offset_lock);
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+
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+ if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
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+ msync_dbg("TBTT : max clockdrift=%lld; adjusting",
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+ (long long) ifmsh->sync_offset_clockdrift_max);
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+ tsfdelta = -ifmsh->sync_offset_clockdrift_max;
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+ ifmsh->sync_offset_clockdrift_max = 0;
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+ } else {
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+ msync_dbg("TBTT : max clockdrift=%lld; adjusting by %llu",
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+ (long long) ifmsh->sync_offset_clockdrift_max,
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+ (unsigned long long) beacon_int_fraction);
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+ tsfdelta = -beacon_int_fraction;
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+ ifmsh->sync_offset_clockdrift_max -= beacon_int_fraction;
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+ }
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+
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+ tsf = drv_get_tsf(local, sdata);
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+ if (tsf != -1ULL)
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+ drv_set_tsf(local, sdata, tsf + tsfdelta);
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+ spin_unlock_bh(&ifmsh->sync_offset_lock);
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+}
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+
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+static void mesh_sync_offset_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
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+ u16 stype,
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+ struct ieee80211_mgmt *mgmt,
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+ struct ieee802_11_elems *elems,
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+ struct ieee80211_rx_status *rx_status)
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+{
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+ struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
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+ struct ieee80211_local *local = sdata->local;
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+ struct sta_info *sta;
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+ u64 t_t, t_r;
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+
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+ WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
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+
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+ /* standard mentions only beacons */
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+ if (stype != IEEE80211_STYPE_BEACON)
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+ return;
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+
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+ /* The current tsf is a first approximation for the timestamp
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+ * for the received beacon. Further down we try to get a
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+ * better value from the rx_status->mactime field if
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+ * available. Also we have to call drv_get_tsf() before
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+ * entering the rcu-read section.*/
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+ t_r = drv_get_tsf(local, sdata);
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+
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+ rcu_read_lock();
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+ sta = sta_info_get(sdata, mgmt->sa);
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+ if (!sta)
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+ goto no_sync;
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+
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+ /* check offset sync conditions (13.13.2.2.1)
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+ *
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+ * TODO also sync to
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+ * dot11MeshNbrOffsetMaxNeighbor non-peer non-MBSS neighbors
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+ */
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+
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+ if (elems->mesh_config && mesh_peer_tbtt_adjusting(elems)) {
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+ clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
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+ msync_dbg("STA %pM : is adjusting TBTT", sta->sta.addr);
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+ goto no_sync;
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+ }
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+
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+ if (rx_status->flag & RX_FLAG_MACTIME_MPDU && rx_status->mactime) {
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+ /*
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+ * The mactime is defined as the time the first data symbol
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+ * of the frame hits the PHY, and the timestamp of the beacon
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+ * is defined as "the time that the data symbol containing the
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+ * first bit of the timestamp is transmitted to the PHY plus
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+ * the transmitting STA's delays through its local PHY from the
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+ * MAC-PHY interface to its interface with the WM" (802.11
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+ * 11.1.2)
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+ *
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+ * T_r, in 13.13.2.2.2, is just defined as "the frame reception
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+ * time" but we unless we interpret that time to be the same
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+ * time of the beacon timestamp, the offset calculation will be
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+ * off. Below we adjust t_r to be "the time at which the first
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+ * symbol of the timestamp element in the beacon is received".
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+ * This correction depends on the rate.
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+ *
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+ * Based on similar code in ibss.c
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+ */
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+ int rate;
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+
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+ if (rx_status->flag & RX_FLAG_HT) {
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+ /* TODO:
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+ * In principle there could be HT-beacons (Dual Beacon
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+ * HT Operation options), but for now ignore them and
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+ * just use the primary (i.e. non-HT) beacons for
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+ * synchronization.
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+ * */
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+ goto no_sync;
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+ } else
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+ rate = local->hw.wiphy->bands[rx_status->band]->
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+ bitrates[rx_status->rate_idx].bitrate;
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+
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+ /* 24 bytes of header * 8 bits/byte *
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+ * 10*(100 Kbps)/Mbps / rate (100 Kbps)*/
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+ t_r = rx_status->mactime + (24 * 8 * 10 / rate);
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+ }
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+
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+ /* Timing offset calculation (see 13.13.2.2.2) */
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+ t_t = le64_to_cpu(mgmt->u.beacon.timestamp);
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+ sta->t_offset = t_t - t_r;
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+
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+ if (test_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN)) {
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+ s64 t_clockdrift = sta->t_offset_setpoint
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+ - sta->t_offset;
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+
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+ msync_dbg("STA %pM : sta->t_offset=%lld,"
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+ " sta->t_offset_setpoint=%lld,"
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+ " t_clockdrift=%lld",
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+ sta->sta.addr,
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+ (long long) sta->t_offset,
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+ (long long)
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+ sta->t_offset_setpoint,
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+ (long long) t_clockdrift);
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+ rcu_read_unlock();
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+
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+ spin_lock_bh(&ifmsh->sync_offset_lock);
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+ if (t_clockdrift >
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+ ifmsh->sync_offset_clockdrift_max)
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+ ifmsh->sync_offset_clockdrift_max
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+ = t_clockdrift;
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+ spin_unlock_bh(&ifmsh->sync_offset_lock);
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+
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+ } else {
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+ sta->t_offset_setpoint = sta->t_offset;
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+ set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
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+ msync_dbg("STA %pM : offset was invalid, "
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+ " sta->t_offset=%lld",
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+ sta->sta.addr,
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+ (long long) sta->t_offset);
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+ rcu_read_unlock();
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+ }
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+ return;
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+
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+no_sync:
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+ rcu_read_unlock();
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+}
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+
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+static void mesh_sync_offset_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
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+{
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+ struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
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+
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+ WARN_ON(ifmsh->mesh_sp_id
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+ != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
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+ BUG_ON(!rcu_read_lock_held());
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+
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+ spin_lock_bh(&ifmsh->sync_offset_lock);
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+
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+ if (ifmsh->sync_offset_clockdrift_max >
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+ TBTT_MINIMUM_ADJUSTMENT) {
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+ /* Since ajusting the tsf here would
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+ * require a possibly blocking call
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+ * to the driver tsf setter, we punt
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+ * the tsf adjustment to the mesh tasklet
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+ */
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+ msync_dbg("TBTT : kicking off TBTT "
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+ "adjustment with "
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+ "clockdrift_max=%lld",
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+ ifmsh->sync_offset_clockdrift_max);
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+ set_bit(MESH_WORK_DRIFT_ADJUST,
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+ &ifmsh->wrkq_flags);
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+ } else {
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+ msync_dbg("TBTT : max clockdrift=%lld; "
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+ "too small to adjust",
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+ (long long)
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+ ifmsh->sync_offset_clockdrift_max);
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+ ifmsh->sync_offset_clockdrift_max = 0;
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+ }
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+ spin_unlock_bh(&ifmsh->sync_offset_lock);
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+}
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+
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+static const u8 *mesh_get_vendor_oui(struct ieee80211_sub_if_data *sdata)
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+{
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+ struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
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+ u8 offset;
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+
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+ if (!ifmsh->ie || !ifmsh->ie_len)
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+ return NULL;
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+
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+ offset = ieee80211_ie_split_vendor(ifmsh->ie,
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+ ifmsh->ie_len, 0);
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+
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+ if (!offset)
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+ return NULL;
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+
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+ return ifmsh->ie + offset + 2;
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+}
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+
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+static void mesh_sync_vendor_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
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+ u16 stype,
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+ struct ieee80211_mgmt *mgmt,
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+ struct ieee802_11_elems *elems,
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+ struct ieee80211_rx_status *rx_status)
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+{
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+ const u8 *oui;
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+
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+ WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
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+ msync_dbg("called mesh_sync_vendor_rx_bcn_presp");
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+ oui = mesh_get_vendor_oui(sdata);
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+ /* here you would implement the vendor offset tracking for this oui */
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+}
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+
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+static void mesh_sync_vendor_adjust_tbtt(struct ieee80211_sub_if_data *sdata)
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+{
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+ const u8 *oui;
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+
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+ WARN_ON(sdata->u.mesh.mesh_sp_id != IEEE80211_SYNC_METHOD_VENDOR);
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+ msync_dbg("called mesh_sync_vendor_adjust_tbtt");
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+ oui = mesh_get_vendor_oui(sdata);
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+ /* here you would implement the vendor tsf adjustment for this oui */
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+}
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+
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+/* global variable */
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+static struct sync_method sync_methods[] = {
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+ {
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+ .method = IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET,
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+ .ops = {
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+ .rx_bcn_presp = &mesh_sync_offset_rx_bcn_presp,
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+ .adjust_tbtt = &mesh_sync_offset_adjust_tbtt,
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+ }
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+ },
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+ {
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+ .method = IEEE80211_SYNC_METHOD_VENDOR,
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+ .ops = {
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+ .rx_bcn_presp = &mesh_sync_vendor_rx_bcn_presp,
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+ .adjust_tbtt = &mesh_sync_vendor_adjust_tbtt,
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+ }
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+ },
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+};
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+
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+struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
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+{
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+ struct ieee80211_mesh_sync_ops *ops = NULL;
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+ u8 i;
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+
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+ for (i = 0 ; i < ARRAY_SIZE(sync_methods); ++i) {
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+ if (sync_methods[i].method == method) {
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+ ops = &sync_methods[i].ops;
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+ break;
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+ }
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+ }
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+ return ops;
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+}
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Javier Cardona