linux/net/mac80211/offchannel.c
Seth Forshee 9c35d7d236 mac80211: Add flushes before going off-channel
We've got a couple of races when enabling powersave with an AP for
off-channel operation. The first is fairly simple. If we go off-channel
before the nullfunc frame to enable PS is transmitted then it may not be
received by the AP. Add a flush after enabling off-channel PS to prevent
this from happening.

The second race is a bit more subtle. If the driver supports QoS and has
frames queued when the nullfunc frame is queued, those frames may get
transmitted after the nullfunc frame. If PM is not set then the AP is
being told that we've exited PS before we go off-channel and may try to
deliver frames. To prevent this, add a flush after stopping the queues
but before passing the nullfunc frame to the driver.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-02-11 22:52:21 +01:00

474 lines
12 KiB
C

/*
* Off-channel operation helpers
*
* Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
* Copyright 2004, Instant802 Networks, Inc.
* Copyright 2005, Devicescape Software, Inc.
* Copyright 2006-2007 Jiri Benc <jbenc@suse.cz>
* Copyright 2007, Michael Wu <flamingice@sourmilk.net>
* Copyright 2009 Johannes Berg <johannes@sipsolutions.net>
*
* 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 <linux/export.h>
#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "driver-ops.h"
/*
* Tell our hardware to disable PS.
* Optionally inform AP that we will go to sleep so that it will buffer
* the frames while we are doing off-channel work. This is optional
* because we *may* be doing work on-operating channel, and want our
* hardware unconditionally awake, but still let the AP send us normal frames.
*/
static void ieee80211_offchannel_ps_enable(struct ieee80211_sub_if_data *sdata)
{
struct ieee80211_local *local = sdata->local;
struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
local->offchannel_ps_enabled = false;
/* FIXME: what to do when local->pspolling is true? */
del_timer_sync(&local->dynamic_ps_timer);
del_timer_sync(&ifmgd->bcn_mon_timer);
del_timer_sync(&ifmgd->conn_mon_timer);
cancel_work_sync(&local->dynamic_ps_enable_work);
if (local->hw.conf.flags & IEEE80211_CONF_PS) {
local->offchannel_ps_enabled = true;
local->hw.conf.flags &= ~IEEE80211_CONF_PS;
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
}
if (!local->offchannel_ps_enabled ||
!(local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK))
/*
* If power save was enabled, no need to send a nullfunc
* frame because AP knows that we are sleeping. But if the
* hardware is creating the nullfunc frame for power save
* status (ie. IEEE80211_HW_PS_NULLFUNC_STACK is not
* enabled) and power save was enabled, the firmware just
* sent a null frame with power save disabled. So we need
* to send a new nullfunc frame to inform the AP that we
* are again sleeping.
*/
ieee80211_send_nullfunc(local, sdata, 1);
}
/* inform AP that we are awake again, unless power save is enabled */
static void ieee80211_offchannel_ps_disable(struct ieee80211_sub_if_data *sdata)
{
struct ieee80211_local *local = sdata->local;
if (!local->ps_sdata)
ieee80211_send_nullfunc(local, sdata, 0);
else if (local->offchannel_ps_enabled) {
/*
* In !IEEE80211_HW_PS_NULLFUNC_STACK case the hardware
* will send a nullfunc frame with the powersave bit set
* even though the AP already knows that we are sleeping.
* This could be avoided by sending a null frame with power
* save bit disabled before enabling the power save, but
* this doesn't gain anything.
*
* When IEEE80211_HW_PS_NULLFUNC_STACK is enabled, no need
* to send a nullfunc frame because AP already knows that
* we are sleeping, let's just enable power save mode in
* hardware.
*/
/* TODO: Only set hardware if CONF_PS changed?
* TODO: Should we set offchannel_ps_enabled to false?
*/
local->hw.conf.flags |= IEEE80211_CONF_PS;
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
} else if (local->hw.conf.dynamic_ps_timeout > 0) {
/*
* If IEEE80211_CONF_PS was not set and the dynamic_ps_timer
* had been running before leaving the operating channel,
* restart the timer now and send a nullfunc frame to inform
* the AP that we are awake.
*/
ieee80211_send_nullfunc(local, sdata, 0);
mod_timer(&local->dynamic_ps_timer, jiffies +
msecs_to_jiffies(local->hw.conf.dynamic_ps_timeout));
}
ieee80211_sta_reset_beacon_monitor(sdata);
ieee80211_sta_reset_conn_monitor(sdata);
}
void ieee80211_offchannel_stop_vifs(struct ieee80211_local *local)
{
struct ieee80211_sub_if_data *sdata;
if (WARN_ON(local->use_chanctx))
return;
/*
* notify the AP about us leaving the channel and stop all
* STA interfaces.
*/
/*
* Stop queues and transmit all frames queued by the driver
* before sending nullfunc to enable powersave at the AP.
*/
ieee80211_stop_queues_by_reason(&local->hw,
IEEE80211_QUEUE_STOP_REASON_OFFCHANNEL);
drv_flush(local, false);
mutex_lock(&local->iflist_mtx);
list_for_each_entry(sdata, &local->interfaces, list) {
if (!ieee80211_sdata_running(sdata))
continue;
if (sdata->vif.type == NL80211_IFTYPE_P2P_DEVICE)
continue;
if (sdata->vif.type != NL80211_IFTYPE_MONITOR)
set_bit(SDATA_STATE_OFFCHANNEL, &sdata->state);
/* Check to see if we should disable beaconing. */
if (sdata->vif.bss_conf.enable_beacon) {
set_bit(SDATA_STATE_OFFCHANNEL_BEACON_STOPPED,
&sdata->state);
sdata->vif.bss_conf.enable_beacon = false;
ieee80211_bss_info_change_notify(
sdata, BSS_CHANGED_BEACON_ENABLED);
}
if (sdata->vif.type == NL80211_IFTYPE_STATION &&
sdata->u.mgd.associated)
ieee80211_offchannel_ps_enable(sdata);
}
mutex_unlock(&local->iflist_mtx);
}
void ieee80211_offchannel_return(struct ieee80211_local *local)
{
struct ieee80211_sub_if_data *sdata;
if (WARN_ON(local->use_chanctx))
return;
mutex_lock(&local->iflist_mtx);
list_for_each_entry(sdata, &local->interfaces, list) {
if (sdata->vif.type == NL80211_IFTYPE_P2P_DEVICE)
continue;
if (sdata->vif.type != NL80211_IFTYPE_MONITOR)
clear_bit(SDATA_STATE_OFFCHANNEL, &sdata->state);
if (!ieee80211_sdata_running(sdata))
continue;
/* Tell AP we're back */
if (sdata->vif.type == NL80211_IFTYPE_STATION &&
sdata->u.mgd.associated)
ieee80211_offchannel_ps_disable(sdata);
if (test_and_clear_bit(SDATA_STATE_OFFCHANNEL_BEACON_STOPPED,
&sdata->state)) {
sdata->vif.bss_conf.enable_beacon = true;
ieee80211_bss_info_change_notify(
sdata, BSS_CHANGED_BEACON_ENABLED);
}
}
mutex_unlock(&local->iflist_mtx);
ieee80211_wake_queues_by_reason(&local->hw,
IEEE80211_QUEUE_STOP_REASON_OFFCHANNEL);
}
void ieee80211_handle_roc_started(struct ieee80211_roc_work *roc)
{
if (roc->notified)
return;
if (roc->mgmt_tx_cookie) {
if (!WARN_ON(!roc->frame)) {
ieee80211_tx_skb_tid_band(roc->sdata, roc->frame, 7,
roc->chan->band);
roc->frame = NULL;
}
} else {
cfg80211_ready_on_channel(&roc->sdata->wdev, roc->cookie,
roc->chan, roc->req_duration,
GFP_KERNEL);
}
roc->notified = true;
}
static void ieee80211_hw_roc_start(struct work_struct *work)
{
struct ieee80211_local *local =
container_of(work, struct ieee80211_local, hw_roc_start);
struct ieee80211_roc_work *roc, *dep, *tmp;
mutex_lock(&local->mtx);
if (list_empty(&local->roc_list))
goto out_unlock;
roc = list_first_entry(&local->roc_list, struct ieee80211_roc_work,
list);
if (!roc->started)
goto out_unlock;
roc->hw_begun = true;
roc->hw_start_time = local->hw_roc_start_time;
ieee80211_handle_roc_started(roc);
list_for_each_entry_safe(dep, tmp, &roc->dependents, list) {
ieee80211_handle_roc_started(dep);
if (dep->duration > roc->duration) {
u32 dur = dep->duration;
dep->duration = dur - roc->duration;
roc->duration = dur;
list_move(&dep->list, &roc->list);
}
}
out_unlock:
mutex_unlock(&local->mtx);
}
void ieee80211_ready_on_channel(struct ieee80211_hw *hw)
{
struct ieee80211_local *local = hw_to_local(hw);
local->hw_roc_start_time = jiffies;
trace_api_ready_on_channel(local);
ieee80211_queue_work(hw, &local->hw_roc_start);
}
EXPORT_SYMBOL_GPL(ieee80211_ready_on_channel);
void ieee80211_start_next_roc(struct ieee80211_local *local)
{
struct ieee80211_roc_work *roc;
lockdep_assert_held(&local->mtx);
if (list_empty(&local->roc_list)) {
ieee80211_run_deferred_scan(local);
return;
}
roc = list_first_entry(&local->roc_list, struct ieee80211_roc_work,
list);
if (WARN_ON_ONCE(roc->started))
return;
if (local->ops->remain_on_channel) {
int ret, duration = roc->duration;
/* XXX: duplicated, see ieee80211_start_roc_work() */
if (!duration)
duration = 10;
ret = drv_remain_on_channel(local, roc->sdata, roc->chan,
duration);
roc->started = true;
if (ret) {
wiphy_warn(local->hw.wiphy,
"failed to start next HW ROC (%d)\n", ret);
/*
* queue the work struct again to avoid recursion
* when multiple failures occur
*/
ieee80211_remain_on_channel_expired(&local->hw);
}
} else {
/* delay it a bit */
ieee80211_queue_delayed_work(&local->hw, &roc->work,
round_jiffies_relative(HZ/2));
}
}
void ieee80211_roc_notify_destroy(struct ieee80211_roc_work *roc)
{
struct ieee80211_roc_work *dep, *tmp;
/* was never transmitted */
if (roc->frame) {
cfg80211_mgmt_tx_status(&roc->sdata->wdev,
(unsigned long)roc->frame,
roc->frame->data, roc->frame->len,
false, GFP_KERNEL);
kfree_skb(roc->frame);
}
if (!roc->mgmt_tx_cookie)
cfg80211_remain_on_channel_expired(&roc->sdata->wdev,
roc->cookie, roc->chan,
GFP_KERNEL);
list_for_each_entry_safe(dep, tmp, &roc->dependents, list)
ieee80211_roc_notify_destroy(dep);
kfree(roc);
}
void ieee80211_sw_roc_work(struct work_struct *work)
{
struct ieee80211_roc_work *roc =
container_of(work, struct ieee80211_roc_work, work.work);
struct ieee80211_sub_if_data *sdata = roc->sdata;
struct ieee80211_local *local = sdata->local;
bool started;
mutex_lock(&local->mtx);
if (roc->abort)
goto finish;
if (WARN_ON(list_empty(&local->roc_list)))
goto out_unlock;
if (WARN_ON(roc != list_first_entry(&local->roc_list,
struct ieee80211_roc_work,
list)))
goto out_unlock;
if (!roc->started) {
struct ieee80211_roc_work *dep;
/* start this ROC */
/* switch channel etc */
ieee80211_recalc_idle(local);
local->tmp_channel = roc->chan;
ieee80211_hw_config(local, 0);
/* tell userspace or send frame */
ieee80211_handle_roc_started(roc);
list_for_each_entry(dep, &roc->dependents, list)
ieee80211_handle_roc_started(dep);
/* if it was pure TX, just finish right away */
if (!roc->duration)
goto finish;
roc->started = true;
ieee80211_queue_delayed_work(&local->hw, &roc->work,
msecs_to_jiffies(roc->duration));
} else {
/* finish this ROC */
finish:
list_del(&roc->list);
started = roc->started;
ieee80211_roc_notify_destroy(roc);
if (started) {
drv_flush(local, false);
local->tmp_channel = NULL;
ieee80211_hw_config(local, 0);
ieee80211_offchannel_return(local);
}
ieee80211_recalc_idle(local);
if (started)
ieee80211_start_next_roc(local);
}
out_unlock:
mutex_unlock(&local->mtx);
}
static void ieee80211_hw_roc_done(struct work_struct *work)
{
struct ieee80211_local *local =
container_of(work, struct ieee80211_local, hw_roc_done);
struct ieee80211_roc_work *roc;
mutex_lock(&local->mtx);
if (list_empty(&local->roc_list))
goto out_unlock;
roc = list_first_entry(&local->roc_list, struct ieee80211_roc_work,
list);
if (!roc->started)
goto out_unlock;
list_del(&roc->list);
ieee80211_roc_notify_destroy(roc);
/* if there's another roc, start it now */
ieee80211_start_next_roc(local);
out_unlock:
mutex_unlock(&local->mtx);
}
void ieee80211_remain_on_channel_expired(struct ieee80211_hw *hw)
{
struct ieee80211_local *local = hw_to_local(hw);
trace_api_remain_on_channel_expired(local);
ieee80211_queue_work(hw, &local->hw_roc_done);
}
EXPORT_SYMBOL_GPL(ieee80211_remain_on_channel_expired);
void ieee80211_roc_setup(struct ieee80211_local *local)
{
INIT_WORK(&local->hw_roc_start, ieee80211_hw_roc_start);
INIT_WORK(&local->hw_roc_done, ieee80211_hw_roc_done);
INIT_LIST_HEAD(&local->roc_list);
}
void ieee80211_roc_purge(struct ieee80211_sub_if_data *sdata)
{
struct ieee80211_local *local = sdata->local;
struct ieee80211_roc_work *roc, *tmp;
LIST_HEAD(tmp_list);
mutex_lock(&local->mtx);
list_for_each_entry_safe(roc, tmp, &local->roc_list, list) {
if (roc->sdata != sdata)
continue;
if (roc->started && local->ops->remain_on_channel) {
/* can race, so ignore return value */
drv_cancel_remain_on_channel(local);
}
list_move_tail(&roc->list, &tmp_list);
roc->abort = true;
}
mutex_unlock(&local->mtx);
list_for_each_entry_safe(roc, tmp, &tmp_list, list) {
if (local->ops->remain_on_channel) {
list_del(&roc->list);
ieee80211_roc_notify_destroy(roc);
} else {
ieee80211_queue_delayed_work(&local->hw, &roc->work, 0);
/* work will clean up etc */
flush_delayed_work(&roc->work);
}
}
WARN_ON_ONCE(!list_empty(&tmp_list));
}