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From:   Zefir Kurtisi <zefir.kurtisi@neratec.com>
To:     linux-wireless@vger.kernel.org
Cc:     kvalo@codeaurora.org, nbd@nbd.name
Subject: [PATCH] ath9k: corrctly handle short radar pulses (fixes 3c0efb745a)
Date:   Tue, 11 Jun 2019 15:10:06 +0200
Message-Id: <20190611131006.29715-1-zefir.kurtisi@neratec.com>
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

In commit '3c0efb745a17 ("ath9k: discard undersized packets")'
the lower bound of RX packets was set to 10 (min ACK size) to
filter those that would otherwise be treated as invalid at
mac80211.

Alas, short radar pulses are reported as PHY_ERROR frames
with length set to 3. Therefore their detection stopped
working after that commit.

NOTE: ath9k drivers built thereafter will not pass DFS
certification.

This extends the criteria for short packages to explicitly
handle PHY_ERROR frames.

Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
---
 drivers/net/wireless/ath/ath9k/recv.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index 4e97f7f3b2a3..5519c144d1f1 100644
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -815,6 +815,7 @@ static int ath9k_rx_skb_preprocess(struct ath_softc *sc,
 	struct ath_common *common = ath9k_hw_common(ah);
 	struct ieee80211_hdr *hdr;
 	bool discard_current = sc->rx.discard_next;
+	bool is_phyerr;
 
 	/*
 	 * Discard corrupt descriptors which are marked in
@@ -827,8 +828,11 @@ static int ath9k_rx_skb_preprocess(struct ath_softc *sc,
 
 	/*
 	 * Discard zero-length packets and packets smaller than an ACK
+	 * which are not PHY_ERROR (short radar pulses have a length of 3)
 	 */
-	if (rx_stats->rs_datalen < 10) {
+	is_phyerr = rx_stats->rs_status & ATH9K_RXERR_PHY;
+	if (!rx_stats->rs_datalen ||
+	    (rx_stats->rs_datalen < 10 && !is_phyerr)) {
 		RX_STAT_INC(sc, rx_len_err);
 		goto corrupt;
 	}
-- 
2.17.1