[RFC PATCH v1 0/2] mac80211: ps-poll implementation

[RFC PATCH v1 0/2] mac80211: ps-poll implementation

[Kalle Valo]

Here's my suggestion for how to implement ps-poll in mac80211. Also
this fixes power save again for p54/stlc45xx, but most probably breaks
ath9k. I would like to hear opinions from others, especially from
Atheros. How does ath9k cope with the ps-poll method? Also I highly
recommend to get hardware waking up for multicast frames, it would be
a lot easier and reliable that way.

Open question is that should power save be disabled whenever mac80211
is ps-polling the frames. For example, p54/stlc45xx does not require to
disable power save in that case, it just stays awake long enough to
receive the data frame from the AP. So I did not disable power save
mode in this case, but I would like to hear comments what other
hardware need.

---

Kalle Valo (2):
      mac80211: use ps-poll to request frames in power save mode
      mac80211: remove multicast check from check_tim()


 net/mac80211/ieee80211_i.h |    3 +++
 net/mac80211/mlme.c        |   51 +++++++++++++++++++++++++++++++++++---------
 net/mac80211/rx.c          |   35 ++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 10 deletions(-)

[RFC PATCH v1 1/2] mac80211: remove multicast check from check_tim()

[Kalle Valo]

Currently mac80211 checks for the multicast tim bit from beacons and
disables power save if the bit is set. This was added to support
ath9k. But this is a bit controversial because the AP will send
multicast frames immediately after the beacon and the time constraints
are really high. Relying mac80211 to be fast enough here might not be
reliable in all situations.

Also with current implementation mac80211 disables power save whenever
multicast bit is set but it's never enabled again. So if dynamic power
save is disabled (iwconfig wlan0 power timeout 0), the power save mode
is enabled only until first multicast/broadcast frame is received, which
isn't a long time in a normal network.

The current implementation is not usable on p54/stlc45xx and the
easiest way to fix this is to remove the multicast tim bit check
altogether. Handling multicast tim bit in host is rare, most of the
designs do this in firmware/hardware, so it's better not to have it in
mac80211. It's a lot better to do this in firmware/hardware, or if
that's not possible it could be done in the driver.

Also renamed the function to ieee80211_check_tim() to follow the style
of the file.

Signed-off-by: Kalle Valo <kalle.valo@iki.fi>
---

 net/mac80211/mlme.c |   11 ++++-------
 1 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 51f021f..c7e61e2 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -575,7 +575,7 @@ static void ieee80211_sta_wmm_params(struct ieee80211_local *local,
 	}
 }
 
-static bool check_tim(struct ieee802_11_elems *elems, u16 aid, bool *is_mc)
+static bool ieee80211_check_tim(struct ieee802_11_elems *elems, u16 aid)
 {
 	u8 mask;
 	u8 index, indexn1, indexn2;
@@ -585,9 +585,6 @@ static bool check_tim(struct ieee802_11_elems *elems, u16 aid, bool *is_mc)
 	index = aid / 8;
 	mask  = 1 << (aid & 7);
 
-	if (tim->bitmap_ctrl & 0x01)
-		*is_mc = true;
-
 	indexn1 = tim->bitmap_ctrl & 0xfe;
 	indexn2 = elems->tim_len + indexn1 - 4;
 
@@ -1788,7 +1785,7 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 	struct ieee802_11_elems elems;
 	struct ieee80211_local *local = sdata->local;
 	u32 changed = 0;
-	bool erp_valid, directed_tim, is_mc = false;
+	bool erp_valid, directed_tim;
 	u8 erp_value = 0;
 
 	/* Process beacon from the current BSS */
@@ -1816,9 +1813,9 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 
 	if (local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK &&
 	    local->hw.conf.flags & IEEE80211_CONF_PS) {
-		directed_tim = check_tim(&elems, ifsta->aid, &is_mc);
+		directed_tim = ieee80211_check_tim(&elems, ifsta->aid);
 
-		if (directed_tim || is_mc) {
+		if (directed_tim) {
 			local->hw.conf.flags &= ~IEEE80211_CONF_PS;
 			ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
 			ieee80211_send_nullfunc(local, sdata, 0);

[RFC PATCH v1 2/2] mac80211: use ps-poll to request frames in power save mode

[Kalle Valo]

When a directed tim bit is set, mac80211 currently disables power save
ands sends a null frame to the AP. But if dynamic power save is
disabled, mac80211 will not enable power save again. Fix this by
adding ps-poll functionality to mac80211. When a directed tim bit is
set, mac80211 sends a ps-poll frame to the AP and checks for the more
data bit in the returned data frames. Power save mode is not disabled
during ps-polling, the assumption is that firmware still receives
responses to the ps-poll frame.

Using ps-poll is slower than waking up with null frame, but I
recommend using dynamic power save in cases where throughput is
important. User space can enable it with 'iwconfig wlan0 power timeout
<value>'.

Signed-off-by: Kalle Valo <kalle.valo@iki.fi>
---

 net/mac80211/ieee80211_i.h |    3 +++
 net/mac80211/mlme.c        |   40 +++++++++++++++++++++++++++++++++++++---
 net/mac80211/rx.c          |   35 +++++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index c9ffadb..76814e9 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -710,6 +710,7 @@ struct ieee80211_local {
 	unsigned int wmm_acm; /* bit field of ACM bits (BIT(802.1D tag)) */
 
 	bool powersave;
+	bool pspolling;
 	struct work_struct dynamic_ps_enable_work;
 	struct work_struct dynamic_ps_disable_work;
 	struct timer_list dynamic_ps_timer;
@@ -902,6 +903,8 @@ u64 ieee80211_sta_get_rates(struct ieee80211_local *local,
 			    enum ieee80211_band band);
 void ieee80211_send_probe_req(struct ieee80211_sub_if_data *sdata, u8 *dst,
 			      u8 *ssid, size_t ssid_len);
+void ieee80211_send_pspoll(struct ieee80211_local *local,
+			   struct ieee80211_sub_if_data *sdata);
 
 /* scan/BSS handling */
 int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index c7e61e2..c8778f3 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -475,6 +475,41 @@ static void ieee80211_send_deauth_disassoc(struct ieee80211_sub_if_data *sdata,
 	ieee80211_tx_skb(sdata, skb, ifsta->flags & IEEE80211_STA_MFP_ENABLED);
 }
 
+void ieee80211_send_pspoll(struct ieee80211_local *local,
+			   struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_if_sta *ifsta = &sdata->u.sta;
+	struct ieee80211_pspoll *pspoll;
+	struct sk_buff *skb;
+	u16 fc;
+
+	skb = dev_alloc_skb(local->hw.extra_tx_headroom + sizeof(*pspoll));
+	if (!skb) {
+		printk(KERN_DEBUG "%s: failed to allocate buffer for "
+		       "pspoll frame\n", sdata->dev->name);
+		return;
+	}
+	skb_reserve(skb, local->hw.extra_tx_headroom);
+
+	pspoll = (struct ieee80211_pspoll *) skb_put(skb, sizeof(*pspoll));
+	memset(pspoll, 0, sizeof(*pspoll));
+	fc = IEEE80211_FTYPE_CTL | IEEE80211_STYPE_PSPOLL;
+	pspoll->frame_control = cpu_to_le16(fc);
+	pspoll->aid = cpu_to_le16(ifsta->aid);
+
+	/* aid in PS-Poll has its two MSBs each set to 1 */
+	pspoll->aid |= cpu_to_le16(1 << 15 | 1 << 14);
+
+	memcpy(pspoll->bssid, ifsta->bssid, ETH_ALEN);
+	memcpy(pspoll->ta, sdata->dev->dev_addr, ETH_ALEN);
+
+	printk(KERN_DEBUG "sending ps-poll");
+
+	ieee80211_tx_skb(sdata, skb, 0);
+
+	return;
+}
+
 /* MLME */
 static void ieee80211_sta_def_wmm_params(struct ieee80211_sub_if_data *sdata,
 					 struct ieee80211_bss *bss)
@@ -1816,9 +1851,8 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 		directed_tim = ieee80211_check_tim(&elems, ifsta->aid);
 
 		if (directed_tim) {
-			local->hw.conf.flags &= ~IEEE80211_CONF_PS;
-			ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_PS);
-			ieee80211_send_nullfunc(local, sdata, 0);
+			local->pspolling = true;
+			ieee80211_send_pspoll(local, sdata);
 		}
 	}
 
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 9fd9d21..7d24dde 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -740,6 +740,40 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 	return result;
 }
 
+static ieee80211_rx_result debug_noinline
+ieee80211_rx_h_check_more_data(struct ieee80211_rx_data *rx)
+{
+	struct ieee80211_local *local;
+	struct ieee80211_hdr *hdr;
+	struct sk_buff *skb;
+
+	local = rx->local;
+	skb = rx->skb;
+	hdr = (struct ieee80211_hdr *) skb->data;
+
+	if (!local->pspolling)
+		return RX_CONTINUE;
+
+	if (!ieee80211_has_fromds(hdr->frame_control))
+		/* this is not from AP */
+		return RX_CONTINUE;
+
+	if (!ieee80211_is_data(hdr->frame_control))
+		return RX_CONTINUE;
+
+	if (!ieee80211_has_moredata(hdr->frame_control)) {
+		/* AP has no more frames buffered for us */
+		printk(KERN_DEBUG "no more data");
+		local->pspolling = false;
+		return RX_CONTINUE;
+	}
+
+	/* more data bit is set, let's request a new frame from the AP */
+	ieee80211_send_pspoll(local, rx->sdata);
+
+	return 0;
+}
+
 static void ap_sta_ps_start(struct sta_info *sta)
 {
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
@@ -2006,6 +2040,7 @@ static void ieee80211_invoke_rx_handlers(struct ieee80211_sub_if_data *sdata,
 	CALL_RXH(ieee80211_rx_h_passive_scan)
 	CALL_RXH(ieee80211_rx_h_check)
 	CALL_RXH(ieee80211_rx_h_decrypt)
+	CALL_RXH(ieee80211_rx_h_check_more_data)
 	CALL_RXH(ieee80211_rx_h_sta_process)
 	CALL_RXH(ieee80211_rx_h_defragment)
 	CALL_RXH(ieee80211_rx_h_ps_poll)

Re: [RFC PATCH v1 2/2] mac80211: use ps-poll to request frames in power save mode

[Kalle Valo]

Kalle Valo <kalle.valo@iki.fi> writes:

> +static ieee80211_rx_result debug_noinline
> +ieee80211_rx_h_check_more_data(struct ieee80211_rx_data *rx)
> +{

[...]

> +	if (!ieee80211_has_moredata(hdr->frame_control)) {
> +		/* AP has no more frames buffered for us */
> +		printk(KERN_DEBUG "no more data");
> +		local->pspolling = false;
> +		return RX_CONTINUE;
> +	}
> +
> +	/* more data bit is set, let's request a new frame from the AP */
> +	ieee80211_send_pspoll(local, rx->sdata);
> +
> +	return 0;

This should obviously return RX_CONTINUE, I'll fix it in the next
round.

-- 
Kalle Valo

Re: [RFC PATCH v1 2/2] mac80211: use ps-poll to request frames in power save mode

[Vivek Natarajan]

On Sun, Jan 11, 2009 at 12:33 PM, Kalle Valo <kalle.valo@iki.fi> wrote:
> When a directed tim bit is set, mac80211 currently disables power save
> and sends a null frame to the AP. But if dynamic power save is
> disabled, mac80211 will not enable power save again.

The patch I had sent earlier, 'mac80211: Reset the power save timer
from master_start_xmit' (44378a8e64b9399...) addresses this issue.
This enables mac80211 to start the dynamic ps timer after sending a
null data frame. Hence when the specified time lapses, power save is
enabled again.

Vivek.

Re: [RFC PATCH v1 2/2] mac80211: use ps-poll to request frames in power save mode

[Johannes Berg]

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On Mon, 2009-01-12 at 14:27 +0530, Vivek Natarajan wrote:
> On Sun, Jan 11, 2009 at 12:33 PM, Kalle Valo <kalle.valo@iki.fi> wrote:
> > When a directed tim bit is set, mac80211 currently disables power save
> > and sends a null frame to the AP. But if dynamic power save is
> > disabled, mac80211 will not enable power save again.
> 
> The patch I had sent earlier, 'mac80211: Reset the power save timer
> from master_start_xmit' (44378a8e64b9399...) addresses this issue.
> This enables mac80211 to start the dynamic ps timer after sending a
> null data frame. Hence when the specified time lapses, power save is
> enabled again.

Except when dynamic PS is disabled.

johannes

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Re: [RFC PATCH v1 2/2] mac80211: use ps-poll to request frames in power save mode

[Kalle Valo]

On Mon, Jan 12, 2009 at 10:57 AM, Vivek Natarajan
<vivek.natraj@gmail.com> wrote:
> On Sun, Jan 11, 2009 at 12:33 PM, Kalle Valo <kalle.valo@iki.fi> wrote:
>> When a directed tim bit is set, mac80211 currently disables power save
>> and sends a null frame to the AP. But if dynamic power save is
>> disabled, mac80211 will not enable power save again.
>
> The patch I had sent earlier, 'mac80211: Reset the power save timer
> from master_start_xmit' (44378a8e64b9399...) addresses this issue.
> This enables mac80211 to start the dynamic ps timer after sending a
> null data frame. Hence when the specified time lapses, power save is
> enabled again.

Not based on my tests. Then I tested this few days back power save
mode was suddenly disabled after few seconds and never enabled again.
Please note that his was without dynamic power save, ie. 'iwconfig
wlan0 timeout 0'.

Kalle