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mac80211: rework TX filtered frame code
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This reworks the code for TX filtered frames, splitting it out to
a new function to handle those cases, making the clear instruction
a flag and renaming a few things to be easier to understand and
less Atheros hardware specific. Finally, it also makes the comments
explain more.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Johannes Berg authored and John W. Linville committed Feb 29, 2008
1 parent d97cf01 commit d46e144
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Showing 4 changed files with 91 additions and 51 deletions.
3 changes: 2 additions & 1 deletion include/net/mac80211.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -228,7 +228,8 @@ struct ieee80211_tx_control {
#define IEEE80211_TXCTL_NO_ACK (1<<4) /* tell the low level not to
* wait for an ack */
#define IEEE80211_TXCTL_RATE_CTRL_PROBE (1<<5)
#define IEEE80211_TXCTL_CLEAR_DST_MASK (1<<6)
#define IEEE80211_TXCTL_CLEAR_PS_FILT (1<<6) /* clear powersave filter
* for destination station */
#define IEEE80211_TXCTL_REQUEUE (1<<7)
#define IEEE80211_TXCTL_FIRST_FRAGMENT (1<<8) /* this is a first fragment of
* the frame */
Expand Down
121 changes: 79 additions & 42 deletions net/mac80211/ieee80211.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1178,6 +1178,77 @@ static void ieee80211_remove_tx_extra(struct ieee80211_local *local,
}
}

static void ieee80211_handle_filtered_frame(struct ieee80211_local *local,
struct sta_info *sta,
struct sk_buff *skb,
struct ieee80211_tx_status *status)
{
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
* happen when it wakes up for the next time.
*/
sta->flags |= 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.
*/
if (sta->flags & WLAN_STA_PS &&
skb_queue_len(&sta->tx_filtered) < STA_MAX_TX_BUFFER) {
ieee80211_remove_tx_extra(local, sta->key, skb,
&status->control);
skb_queue_tail(&sta->tx_filtered, skb);
return;
}

if (!(sta->flags & WLAN_STA_PS) &&
!(status->control.flags & IEEE80211_TXCTL_REQUEUE)) {
/* Software retry the packet once */
status->control.flags |= IEEE80211_TXCTL_REQUEUE;
ieee80211_remove_tx_extra(local, sta->key, skb,
&status->control);
dev_queue_xmit(skb);
return;
}

if (net_ratelimit())
printk(KERN_DEBUG "%s: dropped TX filtered frame, "
"queue_len=%d PS=%d @%lu\n",
wiphy_name(local->hw.wiphy),
skb_queue_len(&sta->tx_filtered),
!!(sta->flags & WLAN_STA_PS), jiffies);
dev_kfree_skb(skb);
}

void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
struct ieee80211_tx_status *status)
{
Expand All @@ -1202,11 +1273,16 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
sta = sta_info_get(local, hdr->addr1);
if (sta) {
if (sta->flags & WLAN_STA_PS) {
/* The STA is in power save mode, so assume
/*
* The STA is in power save mode, so assume
* that this TX packet failed because of that.
*/
status->excessive_retries = 0;
status->flags |= IEEE80211_TX_STATUS_TX_FILTERED;
ieee80211_handle_filtered_frame(local, sta,
skb, status);
sta_info_put(sta);
return;
}
sta_info_put(sta);
}
Expand All @@ -1216,47 +1292,8 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
struct sta_info *sta;
sta = sta_info_get(local, hdr->addr1);
if (sta) {
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 is waking up for the next
* time. */
sta->clear_dst_mask = 1;

/* TODO: Is the WLAN_STA_PS flag always set here or is
* the race between RX and TX status causing some
* packets to be filtered out before 80211.o gets an
* update for PS status? This seems to be the case, so
* no changes are likely to be needed. */
if (sta->flags & WLAN_STA_PS &&
skb_queue_len(&sta->tx_filtered) <
STA_MAX_TX_BUFFER) {
ieee80211_remove_tx_extra(local, sta->key,
skb,
&status->control);
skb_queue_tail(&sta->tx_filtered, skb);
} else if (!(sta->flags & WLAN_STA_PS) &&
!(status->control.flags & IEEE80211_TXCTL_REQUEUE)) {
/* Software retry the packet once */
status->control.flags |= IEEE80211_TXCTL_REQUEUE;
ieee80211_remove_tx_extra(local, sta->key,
skb,
&status->control);
dev_queue_xmit(skb);
} else {
if (net_ratelimit()) {
printk(KERN_DEBUG "%s: dropped TX "
"filtered frame queue_len=%d "
"PS=%d @%lu\n",
wiphy_name(local->hw.wiphy),
skb_queue_len(
&sta->tx_filtered),
!!(sta->flags & WLAN_STA_PS),
jiffies);
}
dev_kfree_skb(skb);
}
ieee80211_handle_filtered_frame(local, sta, skb,
status);
sta_info_put(sta);
return;
}
Expand Down
6 changes: 4 additions & 2 deletions net/mac80211/sta_info.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,9 @@
* @WLAN_STA_WME: Station is a QoS-STA.
* @WLAN_STA_WDS: Station is one of our WDS peers.
* @WLAN_STA_PSPOLL: Station has just PS-polled us.
* @WLAN_STA_CLEAR_PS_FILT: Clear PS filter in hardware (using the
* IEEE80211_TXCTL_CLEAR_PS_FILT control flag) when the next
* frame to this station is transmitted.
*/
enum ieee80211_sta_info_flags {
WLAN_STA_AUTH = 1<<0,
Expand All @@ -43,6 +46,7 @@ enum ieee80211_sta_info_flags {
WLAN_STA_WME = 1<<6,
WLAN_STA_WDS = 1<<7,
WLAN_STA_PSPOLL = 1<<8,
WLAN_STA_CLEAR_PS_FILT = 1<<9,
};

#define STA_TID_NUM 16
Expand Down Expand Up @@ -136,8 +140,6 @@ struct sta_info {
struct sk_buff_head tx_filtered; /* buffer of TX frames that were
* already given to low-level driver,
* but were filtered */
int clear_dst_mask;

unsigned long rx_packets, tx_packets; /* number of RX/TX MSDUs */
unsigned long rx_bytes, tx_bytes;
unsigned long tx_retry_failed, tx_retry_count;
Expand Down
12 changes: 6 additions & 6 deletions net/mac80211/tx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1020,10 +1020,10 @@ __ieee80211_tx_prepare(struct ieee80211_txrx_data *tx,
}

if (!tx->sta)
control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
else if (tx->sta->clear_dst_mask) {
control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
tx->sta->clear_dst_mask = 0;
control->flags |= IEEE80211_TXCTL_CLEAR_PS_FILT;
else if (tx->sta->flags & WLAN_STA_CLEAR_PS_FILT) {
control->flags |= IEEE80211_TXCTL_CLEAR_PS_FILT;
tx->sta->flags &= ~WLAN_STA_CLEAR_PS_FILT;
}

hdrlen = ieee80211_get_hdrlen(tx->fc);
Expand Down Expand Up @@ -1084,7 +1084,7 @@ static int __ieee80211_tx(struct ieee80211_local *local, struct sk_buff *skb,
if (tx->u.tx.extra_frag) {
control->flags &= ~(IEEE80211_TXCTL_USE_RTS_CTS |
IEEE80211_TXCTL_USE_CTS_PROTECT |
IEEE80211_TXCTL_CLEAR_DST_MASK |
IEEE80211_TXCTL_CLEAR_PS_FILT |
IEEE80211_TXCTL_FIRST_FRAGMENT);
for (i = 0; i < tx->u.tx.num_extra_frag; i++) {
if (!tx->u.tx.extra_frag[i])
Expand Down Expand Up @@ -1806,7 +1806,7 @@ struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
control->antenna_sel_tx = local->hw.conf.antenna_sel_tx;
control->flags |= IEEE80211_TXCTL_NO_ACK;
control->retry_limit = 1;
control->flags |= IEEE80211_TXCTL_CLEAR_DST_MASK;
control->flags |= IEEE80211_TXCTL_CLEAR_PS_FILT;
}

ap->num_beacons++;
Expand Down

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