mac80211: AMPDU handling for rekeys with Extended Key ID

Extended Key ID allows A-MPDU sessions while rekeying as long as each
A-MPDU aggregates only MPDUs with one keyid together.

Drivers able to segregate MPDUs accordingly can tell mac80211 to not
stop A-MPDU sessions when rekeying by setting the new flag
IEEE80211_HW_AMPDU_KEYBORDER_SUPPORT.
Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
Link: https://lore.kernel.org/r/20190629195015.19680-3-alexander@wetzel-home.deSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -2268,6 +2268,10 @@ struct ieee80211_txq {
  * @IEEE80211_HW_SUPPORTS_ONLY_HE_MULTI_BSSID: Hardware supports multi BSSID
  *	only for HE APs. Applies if @IEEE80211_HW_SUPPORTS_MULTI_BSSID is set.
  *
+ * @IEEE80211_HW_AMPDU_KEYBORDER_SUPPORT: The card and driver is only
+ *	aggregating MPDUs with the same keyid, allowing mac80211 to keep Tx
+ *	A-MPDU sessions active while rekeying with Extended Key ID.
+ *
  * @NUM_IEEE80211_HW_FLAGS: number of hardware flags, used for sizing arrays
  */
 enum ieee80211_hw_flags {
@@ -2319,6 +2323,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_TX_STATUS_NO_AMPDU_LEN,
 	IEEE80211_HW_SUPPORTS_MULTI_BSSID,
 	IEEE80211_HW_SUPPORTS_ONLY_HE_MULTI_BSSID,
+	IEEE80211_HW_AMPDU_KEYBORDER_SUPPORT,
 
 	/* keep last, obviously */
 	NUM_IEEE80211_HW_FLAGS

net/mac80211/debugfs.c

@@ -271,6 +271,7 @@ static const char *hw_flag_names[] = {
 	FLAG(TX_STATUS_NO_AMPDU_LEN),
 	FLAG(SUPPORTS_MULTI_BSSID),
 	FLAG(SUPPORTS_ONLY_HE_MULTI_BSSID),
+	FLAG(AMPDU_KEYBORDER_SUPPORT),
 #undef FLAG
 };
 

net/mac80211/key.c

@@ -270,7 +270,8 @@ int ieee80211_set_tx_key(struct ieee80211_key *key)
 
 	sta->ptk_idx = key->conf.keyidx;
 
-	clear_sta_flag(sta, WLAN_STA_BLOCK_BA);
+	if (!ieee80211_hw_check(&local->hw, AMPDU_KEYBORDER_SUPPORT))
+		clear_sta_flag(sta, WLAN_STA_BLOCK_BA);
 	ieee80211_check_fast_xmit(sta);
 
 	return 0;
@@ -288,15 +289,16 @@ static void ieee80211_pairwise_rekey(struct ieee80211_key *old,
 	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) {
+		if (sta->ptk_idx != INVALID_PTK_KEYIDX &&
+		    !ieee80211_hw_check(&local->hw, AMPDU_KEYBORDER_SUPPORT)) {
 			/* Aggregation Sessions with Extended Key ID must not
 			 * mix MPDUs with different keyIDs within one A-MPDU.
 			 * Tear down running Tx aggregation sessions and block
 			 * new Rx/Tx aggregation requests during rekey to
-			 * ensure there are no A-MPDUs for the driver to
-			 * aggregate. (Blocking Tx only would be sufficient but
-			 * WLAN_STA_BLOCK_BA gets the job done for the few ms
-			 * we need it.)
+			 * ensure there are no A-MPDUs when the driver is not
+			 * supporting A-MPDU key borders. (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);