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/*
* Copyright 2011-2012, Pavel Zubarev <pavel.zubarev@gmail.com>
* Copyright 2011-2012, Marco Porsch <marco.porsch@s2005.tu-chemnitz.de>
* 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;
}
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