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alistair23-linux/net/mac80211/status.c
Helmut Schaa e69deded2b mac80211: Tear down BA session on BAR tx failure 
As described at [1] some STAs (i.e. Intel 5100 Windows) can end up
correctly BlockAcking incoming frames without delivering them to user
space if a AMPDU subframe got lost and we don't flush the receipients
reorder buffer with a BlockAckReq. This in turn results in stuck
connections.

According to 802.11n-2009 it is not necessary to send a BAR to flush
the recepients RX reorder buffer but we still do that to be polite.

However, assume the following frame exchange:

AP -> STA, AMPDU (failed)
AP -> STA, BAR (failed)

The client in question then ends up in the same situation and won't
deliver frames to userspace anymore since we weren't able to flush
its reorder buffer.

This is not a hypothetical situation but I was able to observe this
exact behavior during a stress test between a rt2800pci AP and a Intel
5100 Windows client.

In order to work around this issue just tear down the BA session as
soon as a BAR failed to be TX'ed.

[1] http://comments.gmane.org/gmane.linux.kernel.wireless.general/66867

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2011-08-22 14:45:58 -04:00

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/*
* Copyright 2002-2005, Instant802 Networks, Inc.
* Copyright 2005-2006, Devicescape Software, Inc.
* Copyright 2006-2007 Jiri Benc <jbenc@suse.cz>
* Copyright 2008-2010 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 <net/mac80211.h>
#include "ieee80211_i.h"
#include "rate.h"
#include "mesh.h"
#include "led.h"
void ieee80211_tx_status_irqsafe(struct ieee80211_hw *hw,
struct sk_buff *skb)
{
struct ieee80211_local *local = hw_to_local(hw);
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
int tmp;
skb->pkt_type = IEEE80211_TX_STATUS_MSG;
skb_queue_tail(info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS ?
&local->skb_queue : &local->skb_queue_unreliable, skb);
tmp = skb_queue_len(&local->skb_queue) +
skb_queue_len(&local->skb_queue_unreliable);
while (tmp > IEEE80211_IRQSAFE_QUEUE_LIMIT &&
(skb = skb_dequeue(&local->skb_queue_unreliable))) {
dev_kfree_skb_irq(skb);
tmp--;
I802_DEBUG_INC(local->tx_status_drop);
}
tasklet_schedule(&local->tasklet);
}
EXPORT_SYMBOL(ieee80211_tx_status_irqsafe);
static void ieee80211_handle_filtered_frame(struct ieee80211_local *local,
struct sta_info *sta,
struct sk_buff *skb)
{
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
/*
* This skb 'survived' a round-trip through the driver, and
* hopefully the driver didn't mangle it too badly. However,
* we can definitely not rely on the control information
* being correct. Clear it so we don't get junk there, and
* indicate that it needs new processing, but must not be
* modified/encrypted again.
*/
memset(&info->control, 0, sizeof(info->control));
info->control.jiffies = jiffies;
info->control.vif = &sta->sdata->vif;
info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING |
IEEE80211_TX_INTFL_RETRANSMISSION;
info->flags &= ~IEEE80211_TX_TEMPORARY_FLAGS;
sta->tx_filtered_count++;
/*
* Clear the TX filter mask for this STA when sending the next
* packet. If the STA went to power save mode, this will happen
* when it wakes up for the next time.
*/
set_sta_flags(sta, WLAN_STA_CLEAR_PS_FILT);
/*
* This code races in the following way:
*
* (1) STA sends frame indicating it will go to sleep and does so
* (2) hardware/firmware adds STA to filter list, passes frame up
* (3) hardware/firmware processes TX fifo and suppresses a frame
* (4) we get TX status before having processed the frame and
* knowing that the STA has gone to sleep.
*
* This is actually quite unlikely even when both those events are
* processed from interrupts coming in quickly after one another or
* even at the same time because we queue both TX status events and
* RX frames to be processed by a tasklet and process them in the
* same order that they were received or TX status last. Hence, there
* is no race as long as the frame RX is processed before the next TX
* status, which drivers can ensure, see below.
*
* Note that this can only happen if the hardware or firmware can
* actually add STAs to the filter list, if this is done by the
* driver in response to set_tim() (which will only reduce the race
* this whole filtering tries to solve, not completely solve it)
* this situation cannot happen.
*
* To completely solve this race drivers need to make sure that they
* (a) don't mix the irq-safe/not irq-safe TX status/RX processing
* functions and
* (b) always process RX events before TX status events if ordering
* can be unknown, for example with different interrupt status
* bits.
* (c) if PS mode transitions are manual (i.e. the flag
* %IEEE80211_HW_AP_LINK_PS is set), always process PS state
* changes before calling TX status events if ordering can be
* unknown.
*/
if (test_sta_flags(sta, WLAN_STA_PS_STA) &&
skb_queue_len(&sta->tx_filtered) < STA_MAX_TX_BUFFER) {
skb_queue_tail(&sta->tx_filtered, skb);
return;
}
if (!test_sta_flags(sta, WLAN_STA_PS_STA) &&
!(info->flags & IEEE80211_TX_INTFL_RETRIED)) {
/* Software retry the packet once */
info->flags |= IEEE80211_TX_INTFL_RETRIED;
ieee80211_add_pending_skb(local, skb);
return;
}
#ifdef CONFIG_MAC80211_VERBOSE_DEBUG
if (net_ratelimit())
wiphy_debug(local->hw.wiphy,
"dropped TX filtered frame, queue_len=%d PS=%d @%lu\n",
skb_queue_len(&sta->tx_filtered),
!!test_sta_flags(sta, WLAN_STA_PS_STA), jiffies);
#endif
dev_kfree_skb(skb);
}
static void ieee80211_frame_acked(struct sta_info *sta, struct sk_buff *skb)
{
struct ieee80211_mgmt *mgmt = (void *) skb->data;
struct ieee80211_local *local = sta->local;
struct ieee80211_sub_if_data *sdata = sta->sdata;
if (ieee80211_is_action(mgmt->frame_control) &&
sdata->vif.type == NL80211_IFTYPE_STATION &&
mgmt->u.action.category == WLAN_CATEGORY_HT &&
mgmt->u.action.u.ht_smps.action == WLAN_HT_ACTION_SMPS) {
/*
* This update looks racy, but isn't -- if we come
* here we've definitely got a station that we're
* talking to, and on a managed interface that can
* only be the AP. And the only other place updating
* this variable is before we're associated.
*/
switch (mgmt->u.action.u.ht_smps.smps_control) {
case WLAN_HT_SMPS_CONTROL_DYNAMIC:
sta->sdata->u.mgd.ap_smps = IEEE80211_SMPS_DYNAMIC;
break;
case WLAN_HT_SMPS_CONTROL_STATIC:
sta->sdata->u.mgd.ap_smps = IEEE80211_SMPS_STATIC;
break;
case WLAN_HT_SMPS_CONTROL_DISABLED:
default: /* shouldn't happen since we don't send that */
sta->sdata->u.mgd.ap_smps = IEEE80211_SMPS_OFF;
break;
}
ieee80211_queue_work(&local->hw, &local->recalc_smps);
}
}
/*
* Use a static threshold for now, best value to be determined
* by testing ...
* Should it depend on:
* - on # of retransmissions
* - current throughput (higher value for higher tpt)?
*/
#define STA_LOST_PKT_THRESHOLD 50
void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
{
struct sk_buff *skb2;
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
struct ieee80211_local *local = hw_to_local(hw);
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
u16 frag, type;
__le16 fc;
struct ieee80211_supported_band *sband;
struct ieee80211_tx_status_rtap_hdr *rthdr;
struct ieee80211_sub_if_data *sdata;
struct net_device *prev_dev = NULL;
struct sta_info *sta, *tmp;
int retry_count = -1, i;
int rates_idx = -1;
bool send_to_cooked;
bool acked;
struct ieee80211_bar *bar;
u16 tid;
for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
if (info->status.rates[i].idx < 0) {
break;
} else if (i >= hw->max_report_rates) {
/* the HW cannot have attempted that rate */
info->status.rates[i].idx = -1;
info->status.rates[i].count = 0;
break;
}
retry_count += info->status.rates[i].count;
}
rates_idx = i - 1;
if (retry_count < 0)
retry_count = 0;
rcu_read_lock();
sband = local->hw.wiphy->bands[info->band];
fc = hdr->frame_control;
for_each_sta_info(local, hdr->addr1, sta, tmp) {
/* skip wrong virtual interface */
if (memcmp(hdr->addr2, sta->sdata->vif.addr, ETH_ALEN))
continue;
acked = !!(info->flags & IEEE80211_TX_STAT_ACK);
if (!acked && test_sta_flags(sta, WLAN_STA_PS_STA)) {
/*
* The STA is in power save mode, so assume
* that this TX packet failed because of that.
*/
ieee80211_handle_filtered_frame(local, sta, skb);
rcu_read_unlock();
return;
}
if ((local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL) &&
(rates_idx != -1))
sta->last_tx_rate = info->status.rates[rates_idx];
if ((info->flags & IEEE80211_TX_STAT_AMPDU_NO_BACK) &&
(ieee80211_is_data_qos(fc))) {
u16 tid, ssn;
u8 *qc;
qc = ieee80211_get_qos_ctl(hdr);
tid = qc[0] & 0xf;
ssn = ((le16_to_cpu(hdr->seq_ctrl) + 0x10)
& IEEE80211_SCTL_SEQ);
ieee80211_send_bar(sta->sdata, hdr->addr1,
tid, ssn);
}
if (!acked && ieee80211_is_back_req(fc)) {
/*
* BAR failed, let's tear down the BA session as a
* last resort as some STAs (Intel 5100 on Windows)
* can get stuck when the BA window isn't flushed
* correctly.
*/
bar = (struct ieee80211_bar *) skb->data;
if (!(bar->control & IEEE80211_BAR_CTRL_MULTI_TID)) {
tid = (bar->control &
IEEE80211_BAR_CTRL_TID_INFO_MASK) >>
IEEE80211_BAR_CTRL_TID_INFO_SHIFT;
ieee80211_stop_tx_ba_session(&sta->sta, tid);
}
}
if (info->flags & IEEE80211_TX_STAT_TX_FILTERED) {
ieee80211_handle_filtered_frame(local, sta, skb);
rcu_read_unlock();
return;
} else {
if (!acked)
sta->tx_retry_failed++;
sta->tx_retry_count += retry_count;
}
rate_control_tx_status(local, sband, sta, skb);
if (ieee80211_vif_is_mesh(&sta->sdata->vif))
ieee80211s_update_metric(local, sta, skb);
if (!(info->flags & IEEE80211_TX_CTL_INJECTED) && acked)
ieee80211_frame_acked(sta, skb);
if ((sta->sdata->vif.type == NL80211_IFTYPE_STATION) &&
(local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS))
ieee80211_sta_tx_notify(sta->sdata, (void *) skb->data, acked);
if (local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) {
if (info->flags & IEEE80211_TX_STAT_ACK) {
if (sta->lost_packets)
sta->lost_packets = 0;
} else if (++sta->lost_packets >= STA_LOST_PKT_THRESHOLD) {
cfg80211_cqm_pktloss_notify(sta->sdata->dev,
sta->sta.addr,
sta->lost_packets,
GFP_ATOMIC);
sta->lost_packets = 0;
}
}
}
rcu_read_unlock();
ieee80211_led_tx(local, 0);
/* SNMP counters
* Fragments are passed to low-level drivers as separate skbs, so these
* are actually fragments, not frames. Update frame counters only for
* the first fragment of the frame. */
frag = le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG;
type = le16_to_cpu(hdr->frame_control) & IEEE80211_FCTL_FTYPE;
if (info->flags & IEEE80211_TX_STAT_ACK) {
if (frag == 0) {
local->dot11TransmittedFrameCount++;
if (is_multicast_ether_addr(hdr->addr1))
local->dot11MulticastTransmittedFrameCount++;
if (retry_count > 0)
local->dot11RetryCount++;
if (retry_count > 1)
local->dot11MultipleRetryCount++;
}
/* This counter shall be incremented for an acknowledged MPDU
* with an individual address in the address 1 field or an MPDU
* with a multicast address in the address 1 field of type Data
* or Management. */
if (!is_multicast_ether_addr(hdr->addr1) ||
type == IEEE80211_FTYPE_DATA ||
type == IEEE80211_FTYPE_MGMT)
local->dot11TransmittedFragmentCount++;
} else {
if (frag == 0)
local->dot11FailedCount++;
}
if (ieee80211_is_nullfunc(fc) && ieee80211_has_pm(fc) &&
(local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) &&
!(info->flags & IEEE80211_TX_CTL_INJECTED) &&
local->ps_sdata && !(local->scanning)) {
if (info->flags & IEEE80211_TX_STAT_ACK) {
local->ps_sdata->u.mgd.flags |=
IEEE80211_STA_NULLFUNC_ACKED;
} else
mod_timer(&local->dynamic_ps_timer, jiffies +
msecs_to_jiffies(10));
}
if (info->flags & IEEE80211_TX_INTFL_NL80211_FRAME_TX) {
struct ieee80211_work *wk;
u64 cookie = (unsigned long)skb;
rcu_read_lock();
list_for_each_entry_rcu(wk, &local->work_list, list) {
if (wk->type != IEEE80211_WORK_OFFCHANNEL_TX)
continue;
if (wk->offchan_tx.frame != skb)
continue;
wk->offchan_tx.frame = NULL;
break;
}
rcu_read_unlock();
if (local->hw_roc_skb_for_status == skb) {
cookie = local->hw_roc_cookie ^ 2;
local->hw_roc_skb_for_status = NULL;
}
cfg80211_mgmt_tx_status(
skb->dev, cookie, skb->data, skb->len,
!!(info->flags & IEEE80211_TX_STAT_ACK), GFP_ATOMIC);
}
/* this was a transmitted frame, but now we want to reuse it */
skb_orphan(skb);
/* Need to make a copy before skb->cb gets cleared */
send_to_cooked = !!(info->flags & IEEE80211_TX_CTL_INJECTED) ||
(type != IEEE80211_FTYPE_DATA);
/*
* This is a bit racy but we can avoid a lot of work
* with this test...
*/
if (!local->monitors && (!send_to_cooked || !local->cooked_mntrs)) {
dev_kfree_skb(skb);
return;
}
/* send frame to monitor interfaces now */
if (skb_headroom(skb) < sizeof(*rthdr)) {
printk(KERN_ERR "ieee80211_tx_status: headroom too small\n");
dev_kfree_skb(skb);
return;
}
rthdr = (struct ieee80211_tx_status_rtap_hdr *)
skb_push(skb, sizeof(*rthdr));
memset(rthdr, 0, sizeof(*rthdr));
rthdr->hdr.it_len = cpu_to_le16(sizeof(*rthdr));
rthdr->hdr.it_present =
cpu_to_le32((1 << IEEE80211_RADIOTAP_TX_FLAGS) |
(1 << IEEE80211_RADIOTAP_DATA_RETRIES) |
(1 << IEEE80211_RADIOTAP_RATE));
if (!(info->flags & IEEE80211_TX_STAT_ACK) &&
!is_multicast_ether_addr(hdr->addr1))
rthdr->tx_flags |= cpu_to_le16(IEEE80211_RADIOTAP_F_TX_FAIL);
/*
* XXX: Once radiotap gets the bitmap reset thing the vendor
* extensions proposal contains, we can actually report
* the whole set of tries we did.
*/
if ((info->status.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS) ||
(info->status.rates[0].flags & IEEE80211_TX_RC_USE_CTS_PROTECT))
rthdr->tx_flags |= cpu_to_le16(IEEE80211_RADIOTAP_F_TX_CTS);
else if (info->status.rates[0].flags & IEEE80211_TX_RC_USE_RTS_CTS)
rthdr->tx_flags |= cpu_to_le16(IEEE80211_RADIOTAP_F_TX_RTS);
if (info->status.rates[0].idx >= 0 &&
!(info->status.rates[0].flags & IEEE80211_TX_RC_MCS))
rthdr->rate = sband->bitrates[
info->status.rates[0].idx].bitrate / 5;
/* for now report the total retry_count */
rthdr->data_retries = retry_count;
/* XXX: is this sufficient for BPF? */
skb_set_mac_header(skb, 0);
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->pkt_type = PACKET_OTHERHOST;
skb->protocol = htons(ETH_P_802_2);
memset(skb->cb, 0, sizeof(skb->cb));
rcu_read_lock();
list_for_each_entry_rcu(sdata, &local->interfaces, list) {
if (sdata->vif.type == NL80211_IFTYPE_MONITOR) {
if (!ieee80211_sdata_running(sdata))
continue;
if ((sdata->u.mntr_flags & MONITOR_FLAG_COOK_FRAMES) &&
!send_to_cooked)
continue;
if (prev_dev) {
skb2 = skb_clone(skb, GFP_ATOMIC);
if (skb2) {
skb2->dev = prev_dev;
netif_rx(skb2);
}
}
prev_dev = sdata->dev;
}
}
if (prev_dev) {
skb->dev = prev_dev;
netif_rx(skb);
skb = NULL;
}
rcu_read_unlock();
dev_kfree_skb(skb);
}
EXPORT_SYMBOL(ieee80211_tx_status);
void ieee80211_report_low_ack(struct ieee80211_sta *pubsta, u32 num_packets)
{
struct sta_info *sta = container_of(pubsta, struct sta_info, sta);
cfg80211_cqm_pktloss_notify(sta->sdata->dev, sta->sta.addr,
num_packets, GFP_ATOMIC);
}
EXPORT_SYMBOL(ieee80211_report_low_ack);
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