wifi: ath11k: fix group data packet drops during rekey

wifi: ath11k: fix group data packet drops during rekey

During GTK rekey, mac80211 issues a clear key (if the old key exists)
followed by an install key operation in the same context. This causes
ath11k to send two WMI commands in quick succession: one to clear the
old key and another to install the new key in the same slot.

Under certain conditions—especially under high load or time sensitive
scenarios, firmware may process these commands asynchronously in a way
that firmware assumes the key is cleared whereas hardware has a valid key.
This inconsistency between hardware and firmware leads to group addressed
packet drops. Only setting the same key again can restore a valid key in
firmware and allow packets to be transmitted.

This issue remained latent because the host's clear key commands were
not effective in firmware until commit 436a4e886598 ("ath11k: clear the
keys properly via DISABLE_KEY"). That commit enabled the host to
explicitly clear group keys, which inadvertently exposed the race.

To mitigate this, restrict group key clearing across all modes (AP, STA,
MESH). During rekey, the new key can simply be set on top of the previous
one, avoiding the need for a clear followed by a set.

However, in AP mode specifically, permit group key clearing when no
stations are associated. This exception supports transitions from secure
modes (e.g., WPA2/WPA3) to open mode, during which all associated peers
are removed and the group key is cleared as part of the transition.

Add a per-BSS station counter to track the presence of stations during
set key operations. Also add a reset_group_keys flag to track the key
re-installation state and avoid repeated installation of the same key
when the number of connected stations transitions to non-zero within a
rekey period.

Additionally, for AP and Mesh modes, when the first station associates,
reinstall the same group key that was last set. This ensures that the
firmware recovers from any race that may have occurred during a previous
key clear when no stations were associated.

This change ensures that key clearing is permitted only when no clients
are connected, avoiding packet loss while enabling dynamic security mode
transitions.

Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.9.0.1-02146-QCAHKSWPL_SILICONZ-1
Tested-on: WCN6855 hw2.1 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.41

Reported-by: Steffen Moser <lists@steffen-moser.de>
Closes: https://lore.kernel.org/linux-wireless/c6366409-9928-4dd7-bf7b-ba7fcf20eabf@steffen-moser.de
Fixes: 436a4e886598 ("ath11k: clear the keys properly via DISABLE_KEY")
Signed-off-by: Rameshkumar Sundaram <rameshkumar.sundaram@oss.qualcomm.com>
Tested-by: Nicolas Escande <nico.escande@gmail.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20250810170018.1124014-1-rameshkumar.sundaram@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>