Re: ath10k firmware sends probes on DFS channels without radar detection

From: Jouni Malinen <j@w1.fi>
To: Jean-Pierre Tosoni <jp.tosoni@acksys.fr>
Cc: ath10k@lists.infradead.org, linux-wireless@vger.kernel.org,
	Cedric VONCKEN <cedric.voncken@acksys.fr>
Subject: Re: ath10k firmware sends probes on DFS channels without radar detection
Date: Wed, 14 Dec 2016 21:58:05 +0200	[thread overview]
Message-ID: <20161214195805.GA15022@w1.fi> (raw)
In-Reply-To: <004a01d24fe2$94da8dc0$be8fa940$@acksys.fr>

On Tue, Dec 06, 2016 at 06:02:52PM +0100, Jean-Pierre Tosoni wrote:
> This follows on the previous discussion
> 	"Client station sends probes on DFS channels"
> 
> Problem:
> The combination of QCA988X firmware v10.2.4.70-2 + ath10k +
> wpa_supplicant do not comply with the norm ETSI/EN 301-893
> section 4.7; because they can send probes for 600s when no
> AP is around.
> 
> Analysis:
> The problem seems to lie in the firmware, which regards the presence
> of *any* beacon as a proof that the channel is radar-clean for 600s.

I don't think this is really firmware, but cfg80211 regulatory code and
how it interacts with ath10k..

> - there is no obvious fix working in ath10k.
> - the issue does not show up with other mac80211 devices like ath9k.
> - wpa_supplicant considers this is a kernel issue [2]

There seems to be a difference between ath9k (mac80211-based Probe
Request frame sending) and ath10k (firmware) in this area for active
scanning. mac80211 uses IEEE80211_CHAN_NO_IR | IEEE80211_CHAN_RADAR
while ath10k uses IEEE80211_CHAN_NO_IR. I'd assume this difference
results in ath10k using cfg80211 beacon hints (etc.) to update the NO_IR
flag and that might be behind the difference you see.

Could you check whether the following change gets you the behavior you
want to see here? I have not had a chance to test this yet, but based on
code review, it looks like something that brings the same behavior to
ath10k that ath9k has for this through mac80211.

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index aa545a1..758dbbd 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -2973,7 +2973,8 @@ static int ath10k_update_channel_list(struct ath10k *ar)
 			ch->chan_radar =
 				!!(channel->flags & IEEE80211_CHAN_RADAR);
 
-			passive = channel->flags & IEEE80211_CHAN_NO_IR;
+			passive = channel->flags & (IEEE80211_CHAN_NO_IR |
+						    IEEE80211_CHAN_RADAR);
 			ch->passive = passive;
 
 			ch->freq = channel->center_freq;

-- 
Jouni Malinen                                            PGP id EFC895FA
