mac80211: remove supported channels element in 6 GHz if ECSA support

We should not include the supported channels element if we have
(advertise) support for extended channel switching. To avoid any
interop issues because we always added it in the past, obey this
restriction only in the (new) 6 GHz band.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/20200131113111.893106-1-luca@coelho.fiSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -671,6 +671,13 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
 	struct ieee80211_chanctx_conf *chanctx_conf;
 	struct ieee80211_channel *chan;
 	u32 rates = 0;
+	struct element *ext_capa = NULL;
+
+	/* we know it's writable, cast away the const */
+	if (assoc_data->ie_len)
+		ext_capa = (void *)cfg80211_find_elem(WLAN_EID_EXT_CAPABILITY,
+						      assoc_data->ie,
+						      assoc_data->ie_len);
 
 	sdata_assert_lock(sdata);
 
@@ -821,7 +828,15 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
 		*pos++ = ieee80211_chandef_max_power(&chanctx_conf->def);
 	}
 
-	if (capab & WLAN_CAPABILITY_SPECTRUM_MGMT) {
+	/*
+	 * Per spec, we shouldn't include the list of channels if we advertise
+	 * support for extended channel switching, but we've always done that;
+	 * (for now?) apply this restriction only on the (new) 6 GHz band.
+	 */
+	if (capab & WLAN_CAPABILITY_SPECTRUM_MGMT &&
+	    (sband->band != NL80211_BAND_6GHZ ||
+	     !ext_capa || ext_capa->datalen < 1 ||
+	     !(ext_capa->data[0] & WLAN_EXT_CAPA1_EXT_CHANNEL_SWITCHING))) {
 		/* TODO: get this in reg domain format */
 		pos = skb_put(skb, 2 * sband->n_channels + 2);
 		*pos++ = WLAN_EID_SUPPORTED_CHANNELS;
@@ -835,18 +850,9 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
 
 	/* Set MBSSID support for HE AP if needed */
 	if (ieee80211_hw_check(&local->hw, SUPPORTS_ONLY_HE_MULTI_BSSID) &&
-	    !(ifmgd->flags & IEEE80211_STA_DISABLE_HE) && assoc_data->ie_len) {
-		struct element *elem;
-
-		/* we know it's writable, cast away the const */
-		elem = (void *)cfg80211_find_elem(WLAN_EID_EXT_CAPABILITY,
-						  assoc_data->ie,
-						  assoc_data->ie_len);
-
-		/* We can probably assume both always true */
-		if (elem && elem->datalen >= 3)
-			elem->data[2] |= WLAN_EXT_CAPA3_MULTI_BSSID_SUPPORT;
-	}
+	    !(ifmgd->flags & IEEE80211_STA_DISABLE_HE) && assoc_data->ie_len &&
+	    ext_capa && ext_capa->datalen >= 3)
+		ext_capa->data[2] |= WLAN_EXT_CAPA3_MULTI_BSSID_SUPPORT;
 
 	/* if present, add any custom IEs that go before HT */
 	if (assoc_data->ie_len) {