mac80211: ignore CSA to same channel

If the AP is confused and starts doing a CSA to the same channel,
just ignore that request instead of trying to act it out since it
was likely sent in error anyway.

In the case of the bug I was investigating the GO was misbehaving
and sending out a beacon with CSA IEs still included after having
actually done the channel switch.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -464,6 +464,7 @@ struct ieee80211_if_managed {
 	unsigned int flags;
 
 	bool csa_waiting_bcn;
+	bool csa_ignored_same_chan;
 
 	bool beacon_crc_valid;
 	u32 beacon_crc;

net/mac80211/mlme.c

@@ -1150,6 +1150,17 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 		return;
 	}
 
+	if (cfg80211_chandef_identical(&csa_ie.chandef,
+				       &sdata->vif.bss_conf.chandef)) {
+		if (ifmgd->csa_ignored_same_chan)
+			return;
+		sdata_info(sdata,
+			   "AP %pM tries to chanswitch to same channel, ignore\n",
+			   ifmgd->associated->bssid);
+		ifmgd->csa_ignored_same_chan = true;
+		return;
+	}
+
 	mutex_lock(&local->mtx);
 	mutex_lock(&local->chanctx_mtx);
 	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
@@ -1210,6 +1221,7 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 	sdata->vif.csa_active = true;
 	sdata->csa_chandef = csa_ie.chandef;
 	sdata->csa_block_tx = csa_ie.mode;
+	ifmgd->csa_ignored_same_chan = false;
 
 	if (sdata->csa_block_tx)
 		ieee80211_stop_vif_queues(local, sdata,
@@ -2090,6 +2102,7 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata,
 
 	sdata->vif.csa_active = false;
 	ifmgd->csa_waiting_bcn = false;
+	ifmgd->csa_ignored_same_chan = false;
 	if (sdata->csa_block_tx) {
 		ieee80211_wake_vif_queues(local, sdata,
 					  IEEE80211_QUEUE_STOP_REASON_CSA);