[PATCH 5/8] mac80211: A-MPDU Rx handling aggregation reordering

Ron Rindjunsky
2007-12-17T16:13:34Z

This patch handles the reordering of the Rx A-MPDU.
This issue occurs when the sequence of the internal MPDUs is not in the
right order. such a case can be encountered for example when some MPDUs from
previous aggregations were recieved, while others failed, so current A-MPDU
will contain a mix of re-transmited MPDUs and new ones.

Signed-off-by: Ron Rindjunsky <ron.rindjunsky@intel.com>
---
include/net/mac80211.h | 2 +
net/mac80211/ieee80211_sta.c | 16 ++++
net/mac80211/rx.c | 172 +++++++++++++++++++++++++++++++++++++++++-
3 files changed, 189 insertions(+), 1 deletions(-)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index f50c28a..27a15f0 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -376,6 +376,7 @@ enum mac80211_rx_flags {
* @noise: PHY noise when receiving this frame
* @antenna: antenna used
* @rate: data rate
+ * @ordered: used in A-MPSDU reordering scheme
* @flag: %RX_FLAG_*
*/
struct ieee80211_rx_status {
@@ -388,6 +389,7 @@ struct ieee80211_rx_status {
int noise;
int antenna;
int rate;
+ int ordered;
int flag;
};

diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index ca98d06..4fa0301 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -1212,6 +1212,8 @@ void ieee80211_sta_stop_rx_BA_session(struct net_device *dev, u8 *ra, u16 tid,
struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
struct ieee80211_hw *hw = &local->hw;
struct sta_info *sta;
+ struct ieee80211_rx_status status;
+ int i;

sta = sta_info_get(local, ra);
if (!sta)
@@ -1252,6 +1254,20 @@ void ieee80211_sta_stop_rx_BA_session(struct net_device *dev, u8 *ra, u16 tid,
ieee80211_send_delba(dev, ra, tid, 0, reason);

/* free the reordering buffer */
+ for (i = 0; i < sta->ampdu_mlme.tid_rx[tid].buf_size; i++) {
+ if (sta->ampdu_mlme.tid_rx[tid].reorder_buf[i]) {
+ /* release the reordered frames to stack,
+ * but drop them there */
+ memcpy(&status, sta->ampdu_mlme.tid_rx[tid].
+ reorder_buf[i]->cb, sizeof(status));
+ status.ordered = TXRX_DROP;
+ __ieee80211_rx(hw, sta->ampdu_mlme.
+ tid_rx[tid].reorder_buf[i],
+ &status);
+ sta->ampdu_mlme.tid_rx[tid].stored_mpdu_num--;
+ sta->ampdu_mlme.tid_rx[tid].reorder_buf[i] = NULL;
+ }
+ }
kfree(sta->ampdu_mlme.tid_rx[tid].reorder_buf);

sta->ampdu_mlme.tid_rx[tid].state = HT_AGG_STATE_IDLE;
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 5dbf5d6..7a705eb 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -226,6 +226,114 @@ ieee80211_rx_monitor(struct ieee80211_local *local, struct sk_buff *origskb,
return origskb;
}

+#define SEQ_MODULO 0x1000
+#define SEQ_MASK 0xfff
+
+static inline int seq_less(u16 sq1, u16 sq2)
+{
+ return (((sq1 - sq2) & SEQ_MASK) > (SEQ_MODULO >> 1));
+}
+
+static inline u16 seq_inc(u16 sq)
+{
+ return ((sq + 1) & SEQ_MASK);
+}
+
+static inline u16 seq_sub(u16 sq1, u16 sq2)
+{
+ return ((sq1 - sq2) & SEQ_MASK);
+}
+
+ieee80211_txrx_result
+ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
+ struct ieee80211_txrx_data *rx,
+ struct tid_ampdu_rx *tid_agg_rx,
+ struct sk_buff *skb, u16 mpdu_seq_num,
+ int bar_req)
+{
+ struct ieee80211_rx_status status;
+ u16 head_seq_num, buf_size;
+ int index;
+
+ buf_size = tid_agg_rx->buf_size;
+ head_seq_num = tid_agg_rx->head_seq_num;
+
+ /* frame with out of date sequence number */
+ if (seq_less(mpdu_seq_num, head_seq_num))
+ return TXRX_DROP;
+
+ /* if frame sequence number exceeds our buffering window size or
+ * block Ack Request arrived - release stored frames */
+ if ((!seq_less(mpdu_seq_num, head_seq_num + buf_size)) || (bar_req)) {
+ /* new head to the ordering buffer */
+ if (bar_req)
+ head_seq_num = mpdu_seq_num;
+ else
+ head_seq_num =
+ seq_inc(seq_sub(mpdu_seq_num, buf_size));
+ /* release stored frames up to new head to stack */
+ while (seq_less(tid_agg_rx->head_seq_num, head_seq_num)) {
+ index = seq_sub(tid_agg_rx->head_seq_num,
+ tid_agg_rx->ssn)
+ % tid_agg_rx->buf_size;
+
+ if (tid_agg_rx->reorder_buf[index]) {
+ /* release the reordered frames to stack */
+ memcpy(&status,
+ tid_agg_rx->reorder_buf[index]->cb,
+ sizeof(status));
+
+ status.ordered = TXRX_QUEUED;
+ __ieee80211_rx(hw,
+ tid_agg_rx->reorder_buf[index],
+ &status);
+ tid_agg_rx->stored_mpdu_num--;
+ tid_agg_rx->reorder_buf[index] = NULL;
+ }
+ tid_agg_rx->head_seq_num =
+ seq_inc(tid_agg_rx->head_seq_num);
+ }
+ if (bar_req)
+ return TXRX_DROP;
+ }
+
+ /* now the new frame is always in the range of the reordering */
+ /* buffer window */
+ index = seq_sub(mpdu_seq_num, tid_agg_rx->ssn)
+ % tid_agg_rx->buf_size;
+ /* check if we already stored this frame */
+ if (tid_agg_rx->reorder_buf[index])
+ return TXRX_DROP;
+
+ /* if arrived mpdu is in the right order and nothing else stored */
+ /* release it immediately */
+ if (mpdu_seq_num == tid_agg_rx->head_seq_num &&
+ tid_agg_rx->stored_mpdu_num == 0) {
+ tid_agg_rx->head_seq_num =
+ seq_inc(tid_agg_rx->head_seq_num);
+ return TXRX_CONTINUE;
+ }
+
+ /* put the frame in the reordering buffer */
+ tid_agg_rx->reorder_buf[index] = skb;
+ tid_agg_rx->stored_mpdu_num++;
+ /* release the buffer until next missing frame */
+ index = seq_sub(tid_agg_rx->head_seq_num, tid_agg_rx->ssn)
+ % tid_agg_rx->buf_size;
+ while (tid_agg_rx->reorder_buf[index]) {
+ /* release the reordered frame back to stack */
+ memcpy(&status, tid_agg_rx->reorder_buf[index]->cb,
+ sizeof(status));
+ status.ordered = TXRX_QUEUED;
+ __ieee80211_rx(hw, tid_agg_rx->reorder_buf[index], &status);
+ tid_agg_rx->stored_mpdu_num--;
+ tid_agg_rx->reorder_buf[index] = NULL;
+ tid_agg_rx->head_seq_num = seq_inc(tid_agg_rx->head_seq_num);
+ index = seq_sub(tid_agg_rx->head_seq_num,
+ tid_agg_rx->ssn) % tid_agg_rx->buf_size;
+ }
+ return TXRX_QUEUED;
+}

/* pre-rx handlers
*
@@ -285,7 +393,7 @@ ieee80211_rx_h_load_stats(struct ieee80211_txrx_data *rx)

/* Estimate total channel use caused by this frame */

- if (unlikely(mode->num_rates < 0))
+ if (unlikely(mode->num_rates < 0) || (rx->u.rx.status->ordered))
return TXRX_CONTINUE;

rate = &mode->rates[0];
@@ -320,10 +428,72 @@ ieee80211_rx_h_load_stats(struct ieee80211_txrx_data *rx)
return TXRX_CONTINUE;
}

+static ieee80211_txrx_result
+ieee80211_rx_h_reorder_ampdu(struct ieee80211_txrx_data *rx)
+{
+ struct ieee80211_local *local = rx->local;
+ struct ieee80211_hw *hw = &local->hw;
+ struct sk_buff *skb = rx->skb;
+ struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+ struct tid_ampdu_rx *tid_agg_rx;
+ u16 sc;
+ u16 mpdu_seq_num;
+
+ if (!rx->sta)
+ return TXRX_CONTINUE;
+
+ tid_agg_rx = &(rx->sta->ampdu_mlme.tid_rx[rx->u.rx.queue]);
+
+ /* filter the QoS data rx stream according to
+ * STA/TID and check if this STA/TID is on aggregation */
+ if ((tid_agg_rx->state != HT_AGG_STATE_OPERATIONAL) ||
+ (!WLAN_FC_IS_QOS_DATA(rx->fc)))
+ return TXRX_CONTINUE;
+
+ /* null data frames are excluded */
+ if (rx->fc & IEEE80211_STYPE_QOS_NULLFUNC)
+ return TXRX_CONTINUE;
+
+ /* check if this frame has already been queued and ordered */
+ if (rx->u.rx.status->ordered == TXRX_QUEUED)
+ return TXRX_CONTINUE;
+
+ /* check if this frame has already been queued and ordered but
+ * should be deleted */
+ if (rx->u.rx.status->ordered == TXRX_DROP) {
+ if (skb)
+ dev_kfree_skb(skb);
+ return TXRX_DROP;
+ }
+
+ /* new un-ordered ampdu frame - process it */
+
+ /* reset session timer */
+ if (tid_agg_rx->timeout) {
+ unsigned long expires =
+ jiffies + (tid_agg_rx->timeout / 1000) * HZ;
+ mod_timer(&tid_agg_rx->session_timer, expires);
+ }
+
+ /* if this mpdu is fragmented - terminate rx aggregation session */
+ sc = le16_to_cpu(hdr->seq_ctrl);
+ if (sc & IEEE80211_SCTL_FRAG) {
+ ieee80211_sta_stop_rx_BA_session(rx->dev, rx->sta->addr,
+ rx->u.rx.queue, 0, WLAN_REASON_QSTA_REQUIRE_SETUP);
+ return TXRX_CONTINUE;
+ }
+
+ /* according to mpdu sequence number deal with reordering buffer */
+ mpdu_seq_num = (sc & IEEE80211_SCTL_SEQ) >> 4;
+ return ieee80211_sta_manage_reorder_buf(hw, rx, tid_agg_rx, skb,
+ mpdu_seq_num, 0);
+}
+
ieee80211_rx_handler ieee80211_rx_pre_handlers[] =
{
ieee80211_rx_h_parse_qos,
ieee80211_rx_h_load_stats,
+ ieee80211_rx_h_reorder_ampdu,
NULL
};

--
1.5.3.3

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