iwlwifi: mvm: track the number of Rx BA sessions

The firmware / HW can't support more than 16 Rx BA sessions.
Deny any attemps to open more sessions than that.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

drivers/net/wireless/iwlwifi/mvm/mac80211.c

@@ -389,6 +389,7 @@ static void iwl_mvm_restart_cleanup(struct iwl_mvm *mvm)
 	ieee80211_wake_queues(mvm->hw);
 
 	mvm->vif_count = 0;
+	mvm->rx_ba_sessions = 0;
 }
 
 static int iwl_mvm_mac_start(struct ieee80211_hw *hw)

drivers/net/wireless/iwlwifi/mvm/mvm.h

@@ -419,6 +419,7 @@ struct iwl_mvm {
 	struct work_struct sta_drained_wk;
 	unsigned long sta_drained[BITS_TO_LONGS(IWL_MVM_STATION_COUNT)];
 	atomic_t pending_frames[IWL_MVM_STATION_COUNT];
+	u8 rx_ba_sessions;
 
 	/* configured by mac80211 */
 	u32 rts_threshold;

drivers/net/wireless/iwlwifi/mvm/sta.c

@@ -608,6 +608,8 @@ int iwl_mvm_rm_bcast_sta(struct iwl_mvm *mvm, struct iwl_mvm_int_sta *bsta)
 	return ret;
 }
 
+#define IWL_MAX_RX_BA_SESSIONS 16
+
 int iwl_mvm_sta_rx_agg(struct iwl_mvm *mvm, struct ieee80211_sta *sta,
 		       int tid, u16 ssn, bool start)
 {
@@ -618,6 +620,11 @@ int iwl_mvm_sta_rx_agg(struct iwl_mvm *mvm, struct ieee80211_sta *sta,
 
 	lockdep_assert_held(&mvm->mutex);
 
+	if (start && mvm->rx_ba_sessions >= IWL_MAX_RX_BA_SESSIONS) {
+		IWL_WARN(mvm, "Not enough RX BA SESSIONS\n");
+		return -ENOSPC;
+	}
+
 	cmd.mac_id_n_color = cpu_to_le32(mvm_sta->mac_id_n_color);
 	cmd.sta_id = mvm_sta->sta_id;
 	cmd.add_modify = STA_MODE_MODIFY;
@@ -652,6 +659,14 @@ int iwl_mvm_sta_rx_agg(struct iwl_mvm *mvm, struct ieee80211_sta *sta,
 		break;
 	}
 
+	if (!ret) {
+		if (start)
+			mvm->rx_ba_sessions++;
+		else if (mvm->rx_ba_sessions > 0)
+			/* check that restart flow didn't zero the counter */
+			mvm->rx_ba_sessions--;
+	}
+
 	return ret;
 }