mac80211: AMPDU handling for Extended Key ID

IEEE 802.11 - 2016 forbids mixing MPDUs with different keyIDs in one
A-MPDU. Drivers supporting A-MPDUs and Extended Key ID must actively
enforce that requirement due to the available two unicast keyIDs.

Allow driver to signal mac80211 that they will not check the keyID in
MPDUs when aggregating them and that they expect mac80211 to stop Tx
aggregation when rekeying a connection using Extended Key ID.
Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -2269,6 +2269,9 @@ struct ieee80211_txq {
  * @IEEE80211_HW_EXT_KEY_ID_NATIVE: Driver and hardware are supporting Extended
  *	Key ID and can handle two unicast keys per station for Rx and Tx.
  *
+ * @IEEE80211_HW_NO_AMPDU_KEYBORDER_SUPPORT: The card/driver can't handle
+ *	active Tx A-MPDU sessions with Extended Key IDs during rekey.
+ *
  * @NUM_IEEE80211_HW_FLAGS: number of hardware flags, used for sizing arrays
  */
 enum ieee80211_hw_flags {
@@ -2321,6 +2324,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_SUPPORTS_MULTI_BSSID,
 	IEEE80211_HW_SUPPORTS_ONLY_HE_MULTI_BSSID,
 	IEEE80211_HW_EXT_KEY_ID_NATIVE,
+	IEEE80211_HW_NO_AMPDU_KEYBORDER_SUPPORT,
 
 	/* keep last, obviously */
 	NUM_IEEE80211_HW_FLAGS

net/mac80211/debugfs.c

@@ -274,6 +274,7 @@ static const char *hw_flag_names[] = {
 	FLAG(SUPPORTS_MULTI_BSSID),
 	FLAG(SUPPORTS_ONLY_HE_MULTI_BSSID),
 	FLAG(EXT_KEY_ID_NATIVE),
+	FLAG(NO_AMPDU_KEYBORDER_SUPPORT),
 #undef FLAG
 };
 

net/mac80211/key.c

@@ -274,50 +274,61 @@ int ieee80211_set_tx_key(struct ieee80211_key *key)
 
 	old = key_mtx_dereference(local, sta->ptk[sta->ptk_idx]);
 	sta->ptk_idx = key->conf.keyidx;
+
+	if (ieee80211_hw_check(&local->hw, NO_AMPDU_KEYBORDER_SUPPORT))
+		clear_sta_flag(sta, WLAN_STA_BLOCK_BA);
 	ieee80211_check_fast_xmit(sta);
 
 	return 0;
 }
 
-static int ieee80211_hw_key_replace(struct ieee80211_key *old_key,
-				    struct ieee80211_key *new_key,
-				    bool pairwise)
+static void ieee80211_pairwise_rekey(struct ieee80211_key *old,
+				     struct ieee80211_key *new)
 {
-	struct ieee80211_sub_if_data *sdata;
-	struct ieee80211_local *local;
-	struct sta_info *sta;
-	int ret;
-
-	/* Aggregation sessions are OK when running on SW crypto.
-	 * A broken remote STA may cause issues not observed with HW
-	 * crypto, though.
-	 */
-	if (!(old_key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
-		return 0;
+	struct ieee80211_local *local = new->local;
+	struct sta_info *sta = new->sta;
+	int i;
 
-	assert_key_lock(old_key->local);
-	sta = old_key->sta;
+	assert_key_lock(local);
 
-	/* Unicast rekey without Extended Key ID needs special handling */
-	if (new_key && sta && pairwise &&
-	    rcu_access_pointer(sta->ptk[sta->ptk_idx]) == old_key) {
-		local = old_key->local;
-		sdata = old_key->sdata;
+	if (new->conf.flags & IEEE80211_KEY_FLAG_NO_AUTO_TX) {
+		/* Extended Key ID key install, initial one or rekey */
+
+		if (sta->ptk_idx != INVALID_PTK_KEYIDX &&
+		    ieee80211_hw_check(&local->hw,
+				       NO_AMPDU_KEYBORDER_SUPPORT)) {
+			/* Aggregation Sessions with Extended Key ID must not
+			 * mix MPDUs with different keyIDs within one A-MPDU.
+			 * Tear down any running Tx aggregation and all new
+			 * Rx/Tx aggregation request during rekey if the driver
+			 * asks us to do so. (Blocking Tx only would be
+			 * sufficient but WLAN_STA_BLOCK_BA gets the job done
+			 * for the few ms we need it.)
+			 */
+			set_sta_flag(sta, WLAN_STA_BLOCK_BA);
+			mutex_lock(&sta->ampdu_mlme.mtx);
+			for (i = 0; i <  IEEE80211_NUM_TIDS; i++)
+				___ieee80211_stop_tx_ba_session(sta, i,
+								AGG_STOP_LOCAL_REQUEST);
+			mutex_unlock(&sta->ampdu_mlme.mtx);
+		}
+	} else if (old) {
+		/* Rekey without Extended Key ID.
+		 * Aggregation sessions are OK when running on SW crypto.
+		 * A broken remote STA may cause issues not observed with HW
+		 * crypto, though.
+		 */
+		if (!(old->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
+			return;
 
-		/* Stop TX till we are on the new key */
-		old_key->flags |= KEY_FLAG_TAINTED;
+		/* Stop Tx till we are on the new key */
+		old->flags |= KEY_FLAG_TAINTED;
 		ieee80211_clear_fast_xmit(sta);
-
-		/* Aggregation sessions during rekey are complicated due to the
-		 * reorder buffer and retransmits. Side step that by blocking
-		 * aggregation during rekey and tear down running sessions.
-		 */
 		if (ieee80211_hw_check(&local->hw, AMPDU_AGGREGATION)) {
 			set_sta_flag(sta, WLAN_STA_BLOCK_BA);
 			ieee80211_sta_tear_down_BA_sessions(sta,
 							    AGG_STOP_LOCAL_REQUEST);
 		}
-
 		if (!wiphy_ext_feature_isset(local->hw.wiphy,
 					     NL80211_EXT_FEATURE_CAN_REPLACE_PTK0)) {
 			pr_warn_ratelimited("Rekeying PTK for STA %pM but driver can't safely do that.",
@@ -325,18 +336,9 @@ static int ieee80211_hw_key_replace(struct ieee80211_key *old_key,
 			/* Flushing the driver queues *may* help prevent
 			 * the clear text leaks and freezes.
 			 */
-			ieee80211_flush_queues(local, sdata, false);
+			ieee80211_flush_queues(local, old->sdata, false);
 		}
 	}
-
-	ieee80211_key_disable_hw_accel(old_key);
-
-	if (new_key)
-		ret = ieee80211_key_enable_hw_accel(new_key);
-	else
-		ret = 0;
-
-	return ret;
 }
 
 static void __ieee80211_set_default_key(struct ieee80211_sub_if_data *sdata,
@@ -394,7 +396,6 @@ void ieee80211_set_default_mgmt_key(struct ieee80211_sub_if_data *sdata,
 	mutex_unlock(&sdata->local->key_mtx);
 }
 
-
 static int ieee80211_key_replace(struct ieee80211_sub_if_data *sdata,
 				  struct sta_info *sta,
 				  bool pairwise,
@@ -402,7 +403,7 @@ static int ieee80211_key_replace(struct ieee80211_sub_if_data *sdata,
 				  struct ieee80211_key *new)
 {
 	int idx;
-	int ret;
+	int ret = 0;
 	bool defunikey, defmultikey, defmgmtkey;
 
 	/* caller must provide at least one old/new */
@@ -414,16 +415,27 @@ static int ieee80211_key_replace(struct ieee80211_sub_if_data *sdata,
 
 	WARN_ON(new && old && new->conf.keyidx != old->conf.keyidx);
 
+	if (new && sta && pairwise) {
+		/* Unicast rekey needs special handling. With Extended Key ID
+		 * old is still NULL for the first rekey.
+		 */
+		ieee80211_pairwise_rekey(old, new);
+	}
+
 	if (old) {
 		idx = old->conf.keyidx;
-		ret = ieee80211_hw_key_replace(old, new, pairwise);
+
+		if (old->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
+			ieee80211_key_disable_hw_accel(old);
+
+			if (new)
+				ret = ieee80211_key_enable_hw_accel(new);
+		}
 	} else {
 		/* new must be provided in case old is not */
 		idx = new->conf.keyidx;
 		if (!new->local->wowlan)
 			ret = ieee80211_key_enable_hw_accel(new);
-		else
-			ret = 0;
 	}
 
 	if (ret)