From: Gregory Greenman <[email protected]>

Advertising reordering window in ADDBA less than 64 can crash some APs,
an example is LinkSys WRT120N (with FW v1.0.07 build 002 Jun 18 2012).
On the other hand, a driver may need to limit Tx A-MPDU size for its own
reasons, like specific HW limitations.

Signed-off-by: Gregory Greenman <[email protected]>
Signed-off-by: Emmanuel Grumbach <[email protected]>
---
 include/net/mac80211.h | 6 ++++--
 net/mac80211/agg-tx.c  | 3 ++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index bcb7022..a68051c 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -2009,8 +2009,10 @@ enum ieee80211_hw_flags {
  *     it shouldn't be set.
  *
  * @max_tx_aggregation_subframes: maximum number of subframes in an
- *     aggregate an HT driver will transmit, used by the peer as a
- *     hint to size its reorder buffer.
+ *     aggregate an HT driver will transmit. Though ADDBA will advertise
+ *     a constant value of 64 as some older APs can crash if the window
+ *     size is smaller (an example is LinkSys WRT120N with FW v1.0.07
+ *     build 002 Jun 18 2012).
  *
  * @offchannel_tx_hw_queue: HW queue ID to use for offchannel TX
  *     (if %IEEE80211_HW_QUEUE_CONTROL is set)
diff --git a/net/mac80211/agg-tx.c b/net/mac80211/agg-tx.c
index a758eb84..ff75718 100644
--- a/net/mac80211/agg-tx.c
+++ b/net/mac80211/agg-tx.c
@@ -500,7 +500,7 @@ void ieee80211_tx_ba_session_handle_start(struct sta_info 
*sta, int tid)
        /* send AddBA request */
        ieee80211_send_addba_request(sdata, sta->sta.addr, tid,
                                     tid_tx->dialog_token, start_seq_num,
-                                    local->hw.max_tx_aggregation_subframes,
+                                    IEEE80211_MAX_AMPDU_BUF,
                                     tid_tx->timeout);
 }
 
@@ -926,6 +926,7 @@ void ieee80211_process_addba_resp(struct ieee80211_local 
*local,
        amsdu = capab & IEEE80211_ADDBA_PARAM_AMSDU_MASK;
        tid = (capab & IEEE80211_ADDBA_PARAM_TID_MASK) >> 2;
        buf_size = (capab & IEEE80211_ADDBA_PARAM_BUF_SIZE_MASK) >> 6;
+       buf_size = min(buf_size, local->hw.max_tx_aggregation_subframes);
 
        mutex_lock(&sta->ampdu_mlme.mtx);
 
-- 
2.5.0

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