mac80211: fix regression in SSN handling of addba tx

Some drivers that do their own sequence number allocation (e.g. ath9k) rely
on being able to modify params->ssn on starting tx ampdu sessions.
This was broken by a change that modified it to use sta->tid_seq[tid] instead.

Cc: stable@vger.kernel.org
Fixes: 31d8bb4e ("mac80211: agg-tx: refactor sending addba")
Reported-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20211124094024.43222-1-nbd@nbd.nameSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/agg-tx.c

@@ -480,8 +480,7 @@ static void ieee80211_send_addba_with_timeout(struct sta_info *sta,
 
 	/* send AddBA request */
 	ieee80211_send_addba_request(sdata, sta->sta.addr, tid,
-				     tid_tx->dialog_token,
-				     sta->tid_seq[tid] >> 4,
+				     tid_tx->dialog_token, tid_tx->ssn,
 				     buf_size, tid_tx->timeout);
 
 	WARN_ON(test_and_set_bit(HT_AGG_STATE_SENT_ADDBA, &tid_tx->state));
@@ -523,6 +522,7 @@ void ieee80211_tx_ba_session_handle_start(struct sta_info *sta, int tid)
 
 	params.ssn = sta->tid_seq[tid] >> 4;
 	ret = drv_ampdu_action(local, sdata, &params);
+	tid_tx->ssn = params.ssn;
 	if (ret == IEEE80211_AMPDU_TX_START_DELAY_ADDBA) {
 		return;
 	} else if (ret == IEEE80211_AMPDU_TX_START_IMMEDIATE) {

net/mac80211/sta_info.h

@@ -199,6 +199,7 @@ struct tid_ampdu_tx {
 	u8 stop_initiator;
 	bool tx_stop;
 	u16 buf_size;
+	u16 ssn;
 
 	u16 failed_bar_ssn;
 	bool bar_pending;