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mac80211: fix spurious disconnect issues with disassoc_low_ack=1 (default)

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mac80211 reports a packet loss event to user space when 50 consecutive packets
were not acked. On a high throughput link with long aggregates and sudden
link changes, this can trigger way too easily.
Mitigate false positives by only triggering the event on a packet loss if
no ACK was received for at least a second

Signed-off-by: Felix Fietkau <nbd@nbd.name>
This commit is contained in:
Felix Fietkau 2020-08-08 19:28:07 +02:00
parent e81e625ca3
commit eff8c76aa0
1 changed files with 116 additions and 0 deletions
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116
package/kernel/mac80211/patches/subsys/310-mac80211-reduce-packet-loss-event-false-positives.patch Normal file
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@ -0,0 +1,116 @@
From: Felix Fietkau <nbd@nbd.name>
Date: Sat, 8 Aug 2020 19:20:02 +0200
Subject: [PATCH] mac80211: reduce packet loss event false positives
When running a large number of packets per second with a high data rate
and long A-MPDUs, the packet loss threshold can be reached very quickly
when the link conditions change. This frequently shows up as spurious
disconnects.
Mitigate false positives by using a similar logic for regular stations
as the one being used for TDLS, though with a more aggressive timeout.
Packet loss events are only reported if no ACK was received for a second.
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -522,7 +522,7 @@ struct ieee80211_sta_rx_stats {
* @status_stats.retry_failed: # of frames that failed after retry
* @status_stats.retry_count: # of retries attempted
* @status_stats.lost_packets: # of lost packets
- * @status_stats.last_tdls_pkt_time: timestamp of last TDLS packet
+ * @status_stats.last_pkt_time: timestamp of last ACKed packet
* @status_stats.msdu_retries: # of MSDU retries
* @status_stats.msdu_failed: # of failed MSDUs
* @status_stats.last_ack: last ack timestamp (jiffies)
@@ -595,7 +595,7 @@ struct sta_info {
unsigned long filtered;
unsigned long retry_failed, retry_count;
unsigned int lost_packets;
- unsigned long last_tdls_pkt_time;
+ unsigned long last_pkt_time;
u64 msdu_retries[IEEE80211_NUM_TIDS + 1];
u64 msdu_failed[IEEE80211_NUM_TIDS + 1];
unsigned long last_ack;
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -749,12 +749,16 @@ static void ieee80211_report_used_skb(st
* - current throughput (higher value for higher tpt)?
*/
#define STA_LOST_PKT_THRESHOLD 50
+#define STA_LOST_PKT_TIME HZ /* 1 sec since last ACK */
#define STA_LOST_TDLS_PKT_THRESHOLD 10
#define STA_LOST_TDLS_PKT_TIME (10*HZ) /* 10secs since last ACK */
static void ieee80211_lost_packet(struct sta_info *sta,
struct ieee80211_tx_info *info)
{
+ unsigned long pkt_time = STA_LOST_PKT_TIME;
+ unsigned int pkt_thr = STA_LOST_PKT_THRESHOLD;
+
/* If driver relies on its own algorithm for station kickout, skip
* mac80211 packet loss mechanism.
*/
@@ -767,21 +771,20 @@ static void ieee80211_lost_packet(struct
return;
sta->status_stats.lost_packets++;
- if (!sta->sta.tdls &&
- sta->status_stats.lost_packets < STA_LOST_PKT_THRESHOLD)
- return;
+ if (sta->sta.tdls) {
+ pkt_time = STA_LOST_TDLS_PKT_TIME;
+ pkt_thr = STA_LOST_PKT_THRESHOLD;
+ }
/*
* If we're in TDLS mode, make sure that all STA_LOST_TDLS_PKT_THRESHOLD
* of the last packets were lost, and that no ACK was received in the
* last STA_LOST_TDLS_PKT_TIME ms, before triggering the CQM packet-loss
* mechanism.
+ * For non-TDLS, use STA_LOST_PKT_THRESHOLD and STA_LOST_PKT_TIME
*/
- if (sta->sta.tdls &&
- (sta->status_stats.lost_packets < STA_LOST_TDLS_PKT_THRESHOLD ||
- time_before(jiffies,
- sta->status_stats.last_tdls_pkt_time +
- STA_LOST_TDLS_PKT_TIME)))
+ if (sta->status_stats.lost_packets < pkt_thr ||
+ !time_after(jiffies, sta->status_stats.last_pkt_time + pkt_time))
return;
cfg80211_cqm_pktloss_notify(sta->sdata->dev, sta->sta.addr,
@@ -1034,9 +1037,7 @@ static void __ieee80211_tx_status(struct
sta->status_stats.lost_packets = 0;
/* Track when last TDLS packet was ACKed */
- if (test_sta_flag(sta, WLAN_STA_TDLS_PEER_AUTH))
- sta->status_stats.last_tdls_pkt_time =
- jiffies;
+ sta->status_stats.last_pkt_time = jiffies;
} else if (noack_success) {
/* nothing to do here, do not account as lost */
} else {
@@ -1169,9 +1170,8 @@ void ieee80211_tx_status_ext(struct ieee
if (sta->status_stats.lost_packets)
sta->status_stats.lost_packets = 0;
- /* Track when last TDLS packet was ACKed */
- if (test_sta_flag(sta, WLAN_STA_TDLS_PEER_AUTH))
- sta->status_stats.last_tdls_pkt_time = jiffies;
+ /* Track when last packet was ACKed */
+ sta->status_stats.last_pkt_time = jiffies;
} else if (test_sta_flag(sta, WLAN_STA_PS_STA)) {
return;
} else if (noack_success) {
@@ -1260,8 +1260,7 @@ void ieee80211_tx_status_8023(struct iee
if (sta->status_stats.lost_packets)
sta->status_stats.lost_packets = 0;
- if (test_sta_flag(sta, WLAN_STA_TDLS_PEER_AUTH))
- sta->status_stats.last_tdls_pkt_time = jiffies;
+ sta->status_stats.last_pkt_time = jiffies;
} else {
ieee80211_lost_packet(sta, info);
}