234 lines
6.7 KiB
C
234 lines
6.7 KiB
C
/*
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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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#include "ieee80211_i.h"
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#include "mesh.h"
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#include "driver-ops.h"
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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 TOFFSET_MINIMUM_ADJUSTMENT 10
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/* This is not in the standard. It is a margin added to the
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* Toffset setpoint to mitigate TSF overcorrection
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* introduced by TSF adjustment latency.
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*/
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#define TOFFSET_SET_MARGIN 20
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/* This is not in the standard. It represents the maximum Toffset jump above
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* which we'll invalidate the Toffset setpoint and choose a new setpoint. This
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* could be, for instance, in case a neighbor is restarted and its TSF counter
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* reset.
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*/
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#define TOFFSET_MAXIMUM_ADJUSTMENT 30000 /* 30 ms */
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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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* 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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IEEE80211_MESHCONF_CAPAB_TBTT_ADJUSTING) != 0;
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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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spin_lock_bh(&ifmsh->sync_offset_lock);
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if (ifmsh->sync_offset_clockdrift_max < beacon_int_fraction) {
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msync_dbg(sdata, "TBTT : max clockdrift=%lld; adjusting\n",
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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(sdata, "TBTT : max clockdrift=%lld; adjusting by %llu\n",
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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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spin_unlock_bh(&ifmsh->sync_offset_lock);
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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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}
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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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WARN_ON(ifmsh->mesh_sp_id != IEEE80211_SYNC_METHOD_NEIGHBOR_OFFSET);
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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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/* 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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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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/* 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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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(sdata, "STA %pM : is adjusting TBTT\n", sta->sta.addr);
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goto no_sync;
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}
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if (ieee80211_have_rx_timestamp(rx_status))
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/* time when timestamp field was received */
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t_r = ieee80211_calculate_rx_timestamp(local, rx_status,
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24 + 12 +
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elems->total_len +
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FCS_LEN,
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24);
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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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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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msync_dbg(sdata,
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"STA %pM : sta->t_offset=%lld, sta->t_offset_setpoint=%lld, t_clockdrift=%lld\n",
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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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if (t_clockdrift > TOFFSET_MAXIMUM_ADJUSTMENT ||
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t_clockdrift < -TOFFSET_MAXIMUM_ADJUSTMENT) {
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msync_dbg(sdata,
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"STA %pM : t_clockdrift=%lld too large, setpoint reset\n",
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sta->sta.addr,
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(long long) t_clockdrift);
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clear_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
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goto no_sync;
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}
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rcu_read_unlock();
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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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} else {
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sta->t_offset_setpoint = sta->t_offset - TOFFSET_SET_MARGIN;
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set_sta_flag(sta, WLAN_STA_TOFFSET_KNOWN);
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msync_dbg(sdata,
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"STA %pM : offset was invalid, sta->t_offset=%lld\n",
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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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no_sync:
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rcu_read_unlock();
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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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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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spin_lock_bh(&ifmsh->sync_offset_lock);
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if (ifmsh->sync_offset_clockdrift_max >
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TOFFSET_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(sdata,
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"TBTT : kicking off TBTT adjustment with clockdrift_max=%lld\n",
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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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ifmsh->adjusting_tbtt = true;
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} else {
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msync_dbg(sdata,
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"TBTT : max clockdrift=%lld; too small to adjust\n",
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(long long)ifmsh->sync_offset_clockdrift_max);
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ifmsh->sync_offset_clockdrift_max = 0;
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ifmsh->adjusting_tbtt = false;
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}
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spin_unlock_bh(&ifmsh->sync_offset_lock);
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}
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static const 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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const struct ieee80211_mesh_sync_ops *ieee80211_mesh_sync_ops_get(u8 method)
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{
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const struct ieee80211_mesh_sync_ops *ops = NULL;
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u8 i;
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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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