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>
diff --git a/drivers/net/wireless/iwlwifi/mvm/sta.c b/drivers/net/wireless/iwlwifi/mvm/sta.c
index b6ab076..85d4bbe 100644
--- a/drivers/net/wireless/iwlwifi/mvm/sta.c
+++ b/drivers/net/wireless/iwlwifi/mvm/sta.c
@@ -608,6 +608,8 @@
 	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 @@
 
 	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 @@
 		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;
 }