When a Linux Wifi{4,5} device talks to a Wifi6 AP, if the AP proposes a Block
Acknowledgement aggregation size (ADDBA) exceeding its expectations, the code in
mac80211 just bails out, rejecting the aggregation. This yields a big
performance penalty on the ack path, which is observable in comparison with
other OSes (Windows and MacOS) which "play smarter" and accept the proposal with
a "clipped" size.
A typical scenario would be:
AP -> Device : ADDBA_request(size=256)
Current Linux reaction:
Device -> AP : ADDBA_reply(failure)
Other OSes reaction:
Device -> AP : ADDBA_reply(size=64)
Note that the IEEE802.11 standard allows for both reactions, but it sounds
really suboptimal to be bailing out instead of clipping. The patch below does
the latter.
Signed-off-by: Alexandre Ferrieux <alexandre.ferrieux@xxxxxxxxx>
---
diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
index f3fbe5a4395e..264dad847842 100644
--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -317,18 +317,20 @@ void __ieee80211_start_rx_ba_session(struct sta_info *sta,
max_buf_size = IEEE80211_MAX_AMPDU_BUF_HT;
/* sanity check for incoming parameters:
- * check if configuration can support the BA policy
- * and if buffer size does not exceeds max value */
+ * check if configuration can support the BA policy */
/* XXX: check own ht delayed BA capability?? */
if (((ba_policy != 1) &&
- (!(sta->sta.deflink.ht_cap.cap & IEEE80211_HT_CAP_DELAY_BA))) ||
- (buf_size > max_buf_size)) {
- status = WLAN_STATUS_INVALID_QOS_PARAM;
+ (!(sta->sta.deflink.ht_cap.cap & IEEE80211_HT_CAP_DELAY_BA)))) {
+ status = WLAN_STATUS_INVALID_QOS_PARAM;
ht_dbg_ratelimited(sta->sdata,
"AddBA Req with bad params from %pM on tid
%u. policy %d, buffer size %d\n",
sta->sta.addr, tid, ba_policy, buf_size);
goto end;
}
+ if (buf_size > max_buf_size) {
+ buf_size = max_buf_size ; // Clip instead of bailing out
+ }
+
/* determine default buffer size */
if (buf_size == 0)
buf_size = max_buf_size;
