[PATCH v2] cfg80211: Use the HE operation IE to determine a 6GHz BSS channel

From: Luca Coelho <luca@coelho.fi>
To: johannes@sipsolutions.net
Cc: luca@coelho.fi, linux-wireless@vger.kernel.org
Subject: [PATCH v2] cfg80211: Use the HE operation IE to determine a 6GHz BSS channel
Date: Thu,  2 Dec 2021 14:36:10 +0200	[thread overview]
Message-ID: <iwlwifi.20211202143322.71eb2176e54e.I130f678e4aa390973ab39d838bbfe7b2d54bff8e@changeid> (raw)
In-Reply-To: <iwlwifi.20211129152938.8efcf1856975.I130f678e4aa390973ab39d838bbfe7b2d54bff8e@changeid>

From: Ayala Beker <ayala.beker@intel.com>

A non-collocated AP whose primary channel is not a PSC channel
may transmit a duplicated beacon on the corresponding PSC channel
in which it would indicate its true primary channel.
Use this inforamtion contained in the HE operation IE to determine
the primary channel of the AP.
In case of invalid infomration ignore it and use the channel
the frame was received on.

Signed-off-by: Ayala Beker <ayala.beker@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
---

In v2, I  changed the patch so it will fit the code after the refactor.  This includes:

    * add the ftype to cfg80211_get_ies_channel_number();
    * return the channel number if !beacon or it's a dup beacon;
    * move the other checks to the caller function.

include/net/cfg80211.h | 24 ++++++++++---------
 net/wireless/scan.c    | 54 ++++++++++++++++++++++++++++++++++++------
 2 files changed, 60 insertions(+), 18 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index b9b269504591..28f135873286 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -6385,17 +6385,6 @@ static inline void cfg80211_gen_new_bssid(const u8 *bssid, u8 max_bssid,
 	u64_to_ether_addr(new_bssid_u64, new_bssid);
 }
 
-/**
- * cfg80211_get_ies_channel_number - returns the channel number from ies
- * @ie: IEs
- * @ielen: length of IEs
- * @band: enum nl80211_band of the channel
- *
- * Returns the channel number, or -1 if none could be determined.
- */
-int cfg80211_get_ies_channel_number(const u8 *ie, size_t ielen,
-				    enum nl80211_band band);
-
 /**
  * cfg80211_is_element_inherited - returns if element ID should be inherited
  * @element: element to check
@@ -6431,6 +6420,19 @@ enum cfg80211_bss_frame_type {
 	CFG80211_BSS_FTYPE_PRESP,
 };
 
+/**
+ * cfg80211_get_ies_channel_number - returns the channel number from ies
+ * @ie: IEs
+ * @ielen: length of IEs
+ * @band: enum nl80211_band of the channel
+ * @ftype: frame type
+ *
+ * Returns the channel number, or -1 if none could be determined.
+ */
+int cfg80211_get_ies_channel_number(const u8 *ie, size_t ielen,
+				    enum nl80211_band band,
+				    enum cfg80211_bss_frame_type ftype);
+
 /**
  * cfg80211_inform_bss_data - inform cfg80211 of a new BSS
  *
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 22e92be61938..350d90d7b01c 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -1795,12 +1795,31 @@ cfg80211_bss_update(struct cfg80211_registered_device *rdev,
 }
 
 int cfg80211_get_ies_channel_number(const u8 *ie, size_t ielen,
-				    enum nl80211_band band)
+				    enum nl80211_band band,
+				    enum cfg80211_bss_frame_type ftype)
 {
 	const u8 *tmp;
 	int channel_number = -1;
 
-	if (band == NL80211_BAND_S1GHZ) {
+	if (band == NL80211_BAND_6GHZ) {
+		const struct element *elem;
+
+		elem = cfg80211_find_ext_elem(WLAN_EID_EXT_HE_OPERATION, ie,
+					      ielen);
+		if (elem && elem->datalen >= ieee80211_he_oper_size(&elem->data[1])) {
+			struct ieee80211_he_operation *he_oper =
+				(void *)(&elem->data[1]);
+			const struct ieee80211_he_6ghz_oper *he_6ghz_oper;
+
+			he_6ghz_oper = ieee80211_he_6ghz_oper(he_oper);
+			if (!he_6ghz_oper)
+				return channel_number;
+
+			if (ftype != CFG80211_BSS_FTYPE_BEACON ||
+			    he_6ghz_oper->control & IEEE80211_HE_6GHZ_OPER_CTRL_DUP_BEACON)
+				channel_number = he_6ghz_oper->primary;
+		}
+	} else if (band == NL80211_BAND_S1GHZ) {
 		tmp = cfg80211_find_ie(WLAN_EID_S1G_OPERATION, ie, ielen);
 		if (tmp && tmp[1] >= sizeof(struct ieee80211_s1g_oper_ie)) {
 			struct ieee80211_s1g_oper_ie *s1gop = (void *)(tmp + 2);
@@ -1831,18 +1850,20 @@ EXPORT_SYMBOL(cfg80211_get_ies_channel_number);
  * from neighboring channels and the Beacon frames use the DSSS Parameter Set
  * element to indicate the current (transmitting) channel, but this might also
  * be needed on other bands if RX frequency does not match with the actual
- * operating channel of a BSS.
+ * operating channel of a BSS, or if the AP reports a different primary channel.
  */
 static struct ieee80211_channel *
 cfg80211_get_bss_channel(struct wiphy *wiphy, const u8 *ie, size_t ielen,
 			 struct ieee80211_channel *channel,
-			 enum nl80211_bss_scan_width scan_width)
+			 enum nl80211_bss_scan_width scan_width,
+			 enum cfg80211_bss_frame_type ftype)
 {
 	u32 freq;
 	int channel_number;
 	struct ieee80211_channel *alt_channel;
 
-	channel_number = cfg80211_get_ies_channel_number(ie, ielen, channel->band);
+	channel_number = cfg80211_get_ies_channel_number(ie, ielen,
+							 channel->band, ftype);
 
 	if (channel_number < 0) {
 		/* No channel information in frame payload */
@@ -1850,6 +1871,16 @@ cfg80211_get_bss_channel(struct wiphy *wiphy, const u8 *ie, size_t ielen,
 	}
 
 	freq = ieee80211_channel_to_freq_khz(channel_number, channel->band);
+
+	/*
+	 * In 6GHz, duplicated beacon indication is relevant for
+	 * beacons only.
+	 */
+	if (channel->band == NL80211_BAND_6GHZ &&
+	    (freq == channel->center_freq ||
+	     abs(freq - channel->center_freq) > 80))
+		return channel;
+
 	alt_channel = ieee80211_get_channel_khz(wiphy, freq);
 	if (!alt_channel) {
 		if (channel->band == NL80211_BAND_2GHZ) {
@@ -1911,7 +1942,7 @@ cfg80211_inform_single_bss_data(struct wiphy *wiphy,
 		return NULL;
 
 	channel = cfg80211_get_bss_channel(wiphy, ie, ielen, data->chan,
-					   data->scan_width);
+					   data->scan_width, ftype);
 	if (!channel)
 		return NULL;
 
@@ -2333,6 +2364,7 @@ cfg80211_inform_single_bss_frame_data(struct wiphy *wiphy,
 	size_t ielen, min_hdr_len = offsetof(struct ieee80211_mgmt,
 					     u.probe_resp.variable);
 	int bss_type;
+	enum cfg80211_bss_frame_type ftype;
 
 	BUILD_BUG_ON(offsetof(struct ieee80211_mgmt, u.probe_resp.variable) !=
 			offsetof(struct ieee80211_mgmt, u.beacon.variable));
@@ -2369,8 +2401,16 @@ cfg80211_inform_single_bss_frame_data(struct wiphy *wiphy,
 			variable = ext->u.s1g_beacon.variable;
 	}
 
+	if (ieee80211_is_beacon(mgmt->frame_control))
+		ftype = CFG80211_BSS_FTYPE_BEACON;
+	else if (ieee80211_is_probe_resp(mgmt->frame_control))
+		ftype = CFG80211_BSS_FTYPE_PRESP;
+	else
+		ftype = CFG80211_BSS_FTYPE_UNKNOWN;
+
 	channel = cfg80211_get_bss_channel(wiphy, variable,
-					   ielen, data->chan, data->scan_width);
+					   ielen, data->chan, data->scan_width,
+					   ftype);
 	if (!channel)
 		return NULL;
 
-- 
2.33.1

