ath10k firmware sends probes on DFS channels without radar detection

[Jean-Pierre Tosoni]

Jouni,

Thanks for the suggestion, I already tried something like this in wmi.c,
with the same result:

- Before patching the firmware scans DFS channels actively (with probes).

- After patching, the firmware scans DFS channels passively *until* any
beacon is received on the DFS channel. When *any* beacon is seen, the
firmware decides to scan actively on its own, without any new IR/RADAR
info from the driver.

So, your patch is required but not sufficient.

Somehow I was able to overcome this by reloading the regulation domain
in the radio card before each scan request:

////// awful patch ahead ////////

--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -2842,7 +2842,9 @@ static int ath10k_update_channel_list(st
 			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;
@@ -3548,6 +3550,9 @@ static int ath10k_start_scan(struct ath1
 
 	lockdep_assert_held(&ar->conf_mutex);
 
+	if (ar->state == ATH10K_STATE_ON)
+		ath10k_regd_update(ar);
+
 	ret = ath10k_wmi_start_scan(ar, arg);
 	if (ret)
 		return ret;

////////////////////////////////////////

...But this sets a terrible penalty on performance when applied to
background scan.


On 12/14/16 20:58 Jouni Malinen wrote:
> 
> 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
> 
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