The block-ack policy uses 4 int counters (ba_acc, ba_cnt, ba_acc_rx,
ba_cnt_rx) bumped per data frame in the TX and RX hot paths under
spin_lock_bh(&hw_priv->ba_lock). The lock was the heaviest per-frame
synchronization cost remaining after Patch C v3 (which fixed the
sdio_rx_work relay). Per the Opus structural critique (PR #8), this
pattern matches mac80211 driver convention for per-frame statistics:
atomic_t suffices, no lock needed.
Field-by-field changes in struct bes2600_common:
ba_acc, ba_cnt, ba_acc_rx, ba_cnt_rx: int -> atomic_t
ba_armed: new atomic_t (timer-arm flag)
ba_ena: bool -> atomic_t
ba_lock: removed (spinlock_t deleted)
ba_hist: int (single-writer = ba_timer)
Producer hot path (txrx.c TX submit + RX receive):
- atomic_add for the byte accumulator
- atomic_inc for the frame counter
- atomic_cmpxchg(&ba_armed, 0, 1) to claim the once-per-window
mod_timer arm — at most ONE producer succeeds; race-free
- no spin_lock_bh
Consumer paths (sta.c bes2600_ba_timer, sta.c disconnect-reset, sta.c
bes2600_ba_work, debug.c debugfs reader):
- atomic_read snapshots all 4 counters into locals; the threshold
predicate (acc/cnt >= THLD) tolerates approximate snapshots — the
timer fires periodically, a single misclassification just delays
the policy update by one tick
- atomic_set zeroes the counters at end of timer-callback window;
racing producer increments after the snapshot are lost (acceptable
for stats; same approximation the original lock allowed under
contention)
- atomic_set(&ba_armed, 0) re-enables the next window's arm
Followup-amenable simplification: ba_hist remains int because only
the single ba_timer callback writes it; multiple writers would need
to upgrade it too.
This patch follows the cw1200-mainline-idiom established by Patch C v3
(structural fix, not bandaid). The cw1200 reference doesn't have a
similar lock to compare; bes2600 inherited this from a later
Bestechnic addition rather than the upstream tree.
When the BES2600 firmware reports WSM_STATUS_DECRYPTFAILURE for a burst
of received frames (typically because the host's PTK or GTK has fallen
out of sync with the AP), the AP eventually concludes that the STA is
not authenticated and emits an unprotected deauth-reason-6 ("Class 2
frame received from non-authenticated station"). On the deployed
pinetab2 + bes2600 stack this AP-initiated deauth has been observed to
leave the link blackholed for up to 109 s before userspace finds a
different SSID/channel to recover on. (Receipts at
https://git.reauktion.de/marfrit/besser, notes/phase5-2026-05-06.md.)
Add a sliding-window counter on each bes2600_vif: when 5 decrypt
failures fire within 5 s, schedule a worker that calls
ieee80211_connection_loss(vif). mac80211 then performs immediate
disassociation; userspace (NetworkManager / wpa_supplicant) reconnects
with fresh keys before the AP gets a chance to fire its unprotected
deauth.
Predicted Phase 7 delta vs the unpatched baseline:
- decrypt-burst rate: unchanged (this does not address root cause)
- AP-deauth-6 rate: <= 0.2 of baseline
- conditional probability of >5s blackhole given a burst:
100% -> <= 10%
- worst-case recovery time: 109s -> <5s
Contract pin: ieee80211_connection_loss() per
include/net/mac80211.h: "may also be called if the connection needs to
be terminated for some other reason... will cause immediate change to
disassociated state, without connection recovery attempts." Userspace
recovery is the existing NM/wpa_supplicant path. The worker context
satisfies the implicit process-context expectation.
Files touched:
- bes2600/bes2600.h: 4 new fields on struct bes2600_vif + 2 prototypes
- bes2600/txrx.c: new helpers + the call site at the existing
WSM_STATUS_DECRYPTFAILURE log point (the unconditional "goto drop"
branch in bes2600_rx_cb)
- bes2600/sta.c: bes2600_decrypt_storm_init() in bes2600_vif_setup;
cancel_work_sync() in bes2600_remove_interface, alongside the
existing per-vif cancel_*_work_sync block. Safe under the kernel
cancel_work_sync contract: the work_struct is INIT_WORK'd in setup,
so the call is valid; it blocks until any in-flight handler returns,
ensuring no use-after-free of priv when mac80211 frees the vif; and
it is idempotent (subsequent calls just return false).
- bes2600/debug.c: DecryptStormRecoveries seq_printf in the per-vif
status seq_file output
Threshold (5/5s) is set well above the steady-state per-vif decrypt-
fail rate observed in measurement (~1/min even under sustained 1 MB/s
load), so a true storm is required to trip it. The cw1200/cw1260
ancestor has no equivalent storm-recovery; this is a clean addition.
checkpatch.pl --no-tree --strict: clean (0/0/0).
Signed-off-by: Claude (noether) <claude@reauktion.de>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
test0r
claude-noether
Julian