package/kernel/mac80211/patches/subsys/310-mac80211-reduce-packet-loss-event-false-positives.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Date: Sat, 8 Aug 2020 19:20:02 +0200
   3 Subject: [PATCH] mac80211: reduce packet loss event false positives
   4
   5 When running a large number of packets per second with a high data rate
   6 and long A-MPDUs, the packet loss threshold can be reached very quickly
   7 when the link conditions change. This frequently shows up as spurious
   8 disconnects.
   9 Mitigate false positives by using a similar logic for regular stations
  10 as the one being used for TDLS, though with a more aggressive timeout.
  11 Packet loss events are only reported if no ACK was received for a second.
  12
  13 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  14 ---
  15
  16 --- a/net/mac80211/sta_info.h
  17 +++ b/net/mac80211/sta_info.h
  18 @@ -522,7 +522,7 @@ struct ieee80211_sta_rx_stats {
  19   * @status_stats.retry_failed: # of frames that failed after retry
  20   * @status_stats.retry_count: # of retries attempted
  21   * @status_stats.lost_packets: # of lost packets
  22 - * @status_stats.last_tdls_pkt_time: timestamp of last TDLS packet
  23 + * @status_stats.last_pkt_time: timestamp of last ACKed packet
  24   * @status_stats.msdu_retries: # of MSDU retries
  25   * @status_stats.msdu_failed: # of failed MSDUs
  26   * @status_stats.last_ack: last ack timestamp (jiffies)
  27 @@ -595,7 +595,7 @@ struct sta_info {
  28                 unsigned long filtered;
  29                 unsigned long retry_failed, retry_count;
  30                 unsigned int lost_packets;
  31 -               unsigned long last_tdls_pkt_time;
  32 +               unsigned long last_pkt_time;
  33                 u64 msdu_retries[IEEE80211_NUM_TIDS + 1];
  34                 u64 msdu_failed[IEEE80211_NUM_TIDS + 1];
  35                 unsigned long last_ack;
  36 --- a/net/mac80211/status.c
  37 +++ b/net/mac80211/status.c
  38 @@ -749,12 +749,16 @@ static void ieee80211_report_used_skb(st
  39   *  - current throughput (higher value for higher tpt)?
  40   */
  41  #define STA_LOST_PKT_THRESHOLD 50
  42 +#define STA_LOST_PKT_TIME      HZ              /* 1 sec since last ACK */
  43  #define STA_LOST_TDLS_PKT_THRESHOLD    10
  44  #define STA_LOST_TDLS_PKT_TIME         (10*HZ) /* 10secs since last ACK */
  45
  46  static void ieee80211_lost_packet(struct sta_info *sta,
  47                                   struct ieee80211_tx_info *info)
  48  {
  49 +       unsigned long pkt_time = STA_LOST_PKT_TIME;
  50 +       unsigned int pkt_thr = STA_LOST_PKT_THRESHOLD;
  51 +
  52         /* If driver relies on its own algorithm for station kickout, skip
  53          * mac80211 packet loss mechanism.
  54          */
  55 @@ -767,21 +771,20 @@ static void ieee80211_lost_packet(struct
  56                 return;
  57
  58         sta->status_stats.lost_packets++;
  59 -       if (!sta->sta.tdls &&
  60 -           sta->status_stats.lost_packets < STA_LOST_PKT_THRESHOLD)
  61 -               return;
  62 +       if (sta->sta.tdls) {
  63 +               pkt_time = STA_LOST_TDLS_PKT_TIME;
  64 +               pkt_thr = STA_LOST_PKT_THRESHOLD;
  65 +       }
  66
  67         /*
  68          * If we're in TDLS mode, make sure that all STA_LOST_TDLS_PKT_THRESHOLD
  69          * of the last packets were lost, and that no ACK was received in the
  70          * last STA_LOST_TDLS_PKT_TIME ms, before triggering the CQM packet-loss
  71          * mechanism.
  72 +        * For non-TDLS, use STA_LOST_PKT_THRESHOLD and STA_LOST_PKT_TIME
  73          */
  74 -       if (sta->sta.tdls &&
  75 -           (sta->status_stats.lost_packets < STA_LOST_TDLS_PKT_THRESHOLD ||
  76 -            time_before(jiffies,
  77 -                        sta->status_stats.last_tdls_pkt_time +
  78 -                        STA_LOST_TDLS_PKT_TIME)))
  79 +       if (sta->status_stats.lost_packets < pkt_thr ||
  80 +           !time_after(jiffies, sta->status_stats.last_pkt_time + pkt_time))
  81                 return;
  82
  83         cfg80211_cqm_pktloss_notify(sta->sdata->dev, sta->sta.addr,
  84 @@ -1034,9 +1037,7 @@ static void __ieee80211_tx_status(struct
  85                                         sta->status_stats.lost_packets = 0;
  86
  87                                 /* Track when last TDLS packet was ACKed */
  88 -                               if (test_sta_flag(sta, WLAN_STA_TDLS_PEER_AUTH))
  89 -                                       sta->status_stats.last_tdls_pkt_time =
  90 -                                               jiffies;
  91 +                               sta->status_stats.last_pkt_time = jiffies;
  92                         } else if (noack_success) {
  93                                 /* nothing to do here, do not account as lost */
  94                         } else {
  95 @@ -1169,9 +1170,8 @@ void ieee80211_tx_status_ext(struct ieee
  96                         if (sta->status_stats.lost_packets)
  97                                 sta->status_stats.lost_packets = 0;
  98
  99 -                       /* Track when last TDLS packet was ACKed */
 100 -                       if (test_sta_flag(sta, WLAN_STA_TDLS_PEER_AUTH))
 101 -                               sta->status_stats.last_tdls_pkt_time = jiffies;
 102 +                       /* Track when last packet was ACKed */
 103 +                       sta->status_stats.last_pkt_time = jiffies;
 104                 } else if (test_sta_flag(sta, WLAN_STA_PS_STA)) {
 105                         return;
 106                 } else if (noack_success) {
 107 @@ -1260,8 +1260,7 @@ void ieee80211_tx_status_8023(struct iee
 108                         if (sta->status_stats.lost_packets)
 109                                 sta->status_stats.lost_packets = 0;
 110
 111 -                       if (test_sta_flag(sta, WLAN_STA_TDLS_PEER_AUTH))
 112 -                               sta->status_stats.last_tdls_pkt_time = jiffies;
 113 +                       sta->status_stats.last_pkt_time = jiffies;
 114                 } else {
 115                         ieee80211_lost_packet(sta, info);
 116                 }