From: Johannes Berg <johannes.berg@xxxxxxxxx>
For PS-poll, there's a possible race between
us expiring a frame and the station polling
for it -- send it a null frame in that case.
For uAPSD, the standard says that we have to
send a frame in each SP, so send null if we
don't have any other frames.
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
net/mac80211/ieee80211_i.h | 1
net/mac80211/sta_info.c | 100 ++++++++++++++++++++++++++++++++++++++++-----
net/mac80211/tx.c | 3 -
3 files changed, 92 insertions(+), 12 deletions(-)
--- a/net/mac80211/tx.c 2011-09-29 16:03:17.000000000 +0200
+++ b/net/mac80211/tx.c 2011-09-29 16:03:20.000000000 +0200
@@ -1520,8 +1520,7 @@ static int ieee80211_skb_resize(struct i
return 0;
}
-static void ieee80211_xmit(struct ieee80211_sub_if_data *sdata,
- struct sk_buff *skb)
+void ieee80211_xmit(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
{
struct ieee80211_local *local = sdata->local;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
--- a/net/mac80211/ieee80211_i.h 2011-09-29 16:03:12.000000000 +0200
+++ b/net/mac80211/ieee80211_i.h 2011-09-29 16:03:20.000000000 +0200
@@ -1272,6 +1272,7 @@ void mac80211_ev_michael_mic_failure(str
struct ieee80211_hdr *hdr, const u8 *tsc,
gfp_t gfp);
void ieee80211_set_wmm_default(struct ieee80211_sub_if_data *sdata);
+void ieee80211_xmit(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb);
void ieee80211_tx_skb(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb);
void ieee802_11_parse_elems(u8 *start, size_t len,
struct ieee802_11_elems *elems);
--- a/net/mac80211/sta_info.c 2011-09-29 16:03:17.000000000 +0200
+++ b/net/mac80211/sta_info.c 2011-09-29 16:03:20.000000000 +0200
@@ -24,6 +24,7 @@
#include "sta_info.h"
#include "debugfs_sta.h"
#include "mesh.h"
+#include "wme.h"
/**
* DOC: STA information lifetime rules
@@ -247,10 +248,16 @@ static void sta_unblock(struct work_stru
ieee80211_sta_ps_deliver_wakeup(sta);
else if (test_and_clear_sta_flags(sta, WLAN_STA_PSPOLL)) {
clear_sta_flags(sta, WLAN_STA_PS_DRIVER);
+
+ local_bh_disable();
ieee80211_sta_ps_deliver_poll_response(sta);
+ local_bh_enable();
} else if (test_and_clear_sta_flags(sta, WLAN_STA_UAPSD)) {
clear_sta_flags(sta, WLAN_STA_PS_DRIVER);
+
+ local_bh_disable();
ieee80211_sta_ps_deliver_uapsd(sta);
+ local_bh_enable();
} else
clear_sta_flags(sta, WLAN_STA_PS_DRIVER);
}
@@ -1157,6 +1164,70 @@ void ieee80211_sta_ps_deliver_wakeup(str
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
}
+static void ieee80211_send_null_response(struct ieee80211_sub_if_data *sdata,
+ struct sta_info *sta, int tid,
+ bool uapsd)
+{
+ struct ieee80211_local *local = sdata->local;
+ struct ieee80211_qos_hdr *nullfunc;
+ struct sk_buff *skb;
+ int size = sizeof(*nullfunc);
+ __le16 fc;
+ bool qos = test_sta_flags(sta, WLAN_STA_WME);
+ struct ieee80211_tx_info *info;
+
+ if (qos) {
+ fc = cpu_to_le16(IEEE80211_FTYPE_DATA |
+ IEEE80211_STYPE_QOS_NULLFUNC |
+ IEEE80211_FCTL_FROMDS);
+ } else {
+ size -= 2;
+ fc = cpu_to_le16(IEEE80211_FTYPE_DATA |
+ IEEE80211_STYPE_NULLFUNC |
+ IEEE80211_FCTL_FROMDS);
+ }
+
+ skb = dev_alloc_skb(local->hw.extra_tx_headroom + size);
+ if (!skb)
+ return;
+
+ skb_reserve(skb, local->hw.extra_tx_headroom);
+
+ nullfunc = (void *) skb_put(skb, size);
+ nullfunc->frame_control = fc;
+ nullfunc->duration_id = 0;
+ memcpy(nullfunc->addr1, sta->sta.addr, ETH_ALEN);
+ memcpy(nullfunc->addr2, sdata->vif.addr, ETH_ALEN);
+ memcpy(nullfunc->addr3, sdata->vif.addr, ETH_ALEN);
+
+ if (qos) {
+ skb->priority = tid;
+
+ skb_set_queue_mapping(skb, ieee802_1d_to_ac[tid]);
+
+ nullfunc->qos_ctrl = cpu_to_le16(tid);
+
+ if (uapsd)
+ nullfunc->qos_ctrl |=
+ cpu_to_le16(IEEE80211_QOS_CTL_EOSP);
+ }
+
+ info = IEEE80211_SKB_CB(skb);
+
+ /*
+ * Tell TX path to send this frame even though the
+ * STA may still remain is PS mode after this frame
+ * exchange.
+ */
+ info->flags |= IEEE80211_TX_CTL_POLL_RESPONSE;
+
+ if (uapsd)
+ info->flags |= IEEE80211_TX_STATUS_EOSP |
+ IEEE80211_TX_CTL_REQ_TX_STATUS;
+
+ ieee80211_xmit(sdata, skb);
+}
+
static void
ieee80211_sta_ps_deliver_response(struct sta_info *sta,
int n_frames, u8 ignored_acs,
@@ -1228,19 +1299,28 @@ ieee80211_sta_ps_deliver_response(struct
}
if (!found) {
-#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
+ int tid;
+
/*
- * FIXME: This can be the result of a race condition between
- * us expiring a frame and the station polling for it.
- * Should we send it a null-func frame indicating we
- * have nothing buffered for it?
+ * For PS-Poll, this can only happen due to a race condition
+ * when we set the TIM bit and the station notices it, but
+ * before it can poll for the frame we expire it.
+ *
+ * For uAPSD, this is said in the standard (11.2.1.5 h):
+ * At each unscheduled SP for a non-AP STA, the AP shall
+ * attempt to transmit at least one MSDU or MMPDU, but no
+ * more than the value specified in the Max SP Length field
+ * in the QoS Capability element from delivery-enabled ACs,
+ * that are destined for the non-AP STA.
+ *
+ * Since we have no other MSDU/MMPDU, transmit a QoS null frame.
*/
- if (reason == IEEE80211_FRAME_RELEASE_PSPOLL)
- printk(KERN_DEBUG "%s: STA %pM sent PS Poll even "
- "though there are no buffered frames for it\n",
- sdata->name, sta->sta.addr);
-#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
+ /* This will evaluate to 1, 3, 5 or 7. */
+ tid = 7 - ((ffs(~ignored_acs) - 1) << 1);
+
+ ieee80211_send_null_response(sdata, sta, tid,
+ reason == IEEE80211_FRAME_RELEASE_UAPSD);
return;
}
--
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