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From:   Cedric VONCKEN <cedric.voncken@acksys.fr>
To:     "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: mac80211: background scan issue
Thread-Topic: mac80211: background scan issue
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Date:   Mon, 3 Feb 2020 15:47:13 +0000
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	I'm working on background scan algorithm.

	In backport 5.4-rc8-1 from openwrt I found an issue on background scan in =
mac80211.

	In background scan we must send a power save indication to the AP to avoid=
 packets lost during the scan. The previous version of  mac80211 (a very ol=
d version) used a null function to send the power save status to the AP.
	In this backport (5.4-rc8-1) this null function was replaced by QOS null f=
unction, and this frame is never sent when the power save bit is set to 1.

	I found the origin of this issue and she still present in the latest versi=
on of mac80211.

	In the function ieee80211_tx_h_check_assoc from net/mac80211/tx.c a test i=
s wrong. Please find below the part of the patch necessary to fix this issu=
e (the other hunk in my patch concern my work).
=09
@@ -297,7 +297,8 @@ ieee80211_tx_h_check_assoc(struct ieee80
       if (unlikely(test_bit(SCAN_SW_SCANNING, &tx->local->scanning)) &&
           test_bit(SDATA_STATE_OFFCHANNEL, &tx->sdata->state) &&
           !ieee80211_is_probe_req(hdr->frame_control) &&
-          !ieee80211_is_nullfunc(hdr->frame_control))
+          !ieee80211_is_nullfunc(hdr->frame_control) &&
+              !ieee80211_is_qos_nullfunc(hdr->frame_control))
               /*
                * When software scanning only nullfunc frames (to notify
                * the sleep state to the AP) and probe requests (for the

Sorry I know it is not correctly formated, but at this time I cannot genera=
ted a correct patch. This patch is very easy to apply in the main branch.

Regards.

C=E9dric Voncken