wifi: rtw88: usb: Fix disconnection after beacon loss

When there is beacon loss, for example due to unrelated Bluetooth
devices transmitting music nearby, the wifi connection dies soon
after the first beacon loss message:

Apr 28 20:47:14 ideapad2 wpa_supplicant[1161]: wlp3s0f3u4:
 CTRL-EVENT-BEACON-LOSS
Apr 28 20:47:15 ideapad2 wpa_supplicant[1161]: wlp3s0f3u4:
 CTRL-EVENT-DISCONNECTED bssid=... reason=4 locally_generated=1

Apr 28 20:47:24 ideapad2 wpa_supplicant[1161]: wlp3s0f3u4:
 CTRL-EVENT-BEACON-LOSS
Apr 28 20:47:25 ideapad2 wpa_supplicant[1161]: wlp3s0f3u4:
 CTRL-EVENT-DISCONNECTED bssid=... reason=4 locally_generated=1

Apr 28 20:47:34 ideapad2 wpa_supplicant[1161]: wlp3s0f3u4:
 CTRL-EVENT-BEACON-LOSS
Apr 28 20:47:35 ideapad2 wpa_supplicant[1161]: wlp3s0f3u4:
 CTRL-EVENT-DISCONNECTED bssid=... reason=4 locally_generated=1

When the beacon loss happens, mac80211 makes rtw88 transmit a QOS
NULL frame and asks to confirm the ACK status. Even though rtw88
confirms to mac80211 that the QOS NULL was transmitted successfully,
the connection still dies. This is because rtw88 is handing the QOS
NULL back to mac80211 with skb->data pointing to the headroom (the
TX descriptor) instead of ieee80211_hdr.

Fix the disconnection by moving skb->data to the correct position
before ieee80211_tx_status_irqsafe().

The problem was observed with RTL8811AU (TP-Link Archer T2U Nano)
and the potential future rtw88_8821au driver. Also tested with
RTL8811CU (Tenda U9).

Cc: [email protected]
Signed-off-by: Bitterblue Smith <[email protected]>
Signed-off-by: Ping-Ke Shih <[email protected]>
Link: https://msgid.link/[email protected]

Author: Bitterblue Smith

drivers/net/wireless/realtek/rtw88/usb.c

@@ -273,6 +273,8 @@ static void rtw_usb_write_port_tx_complete(struct urb *urb)
 		info = IEEE80211_SKB_CB(skb);
 		tx_data = rtw_usb_get_tx_data(skb);
 
+		skb_pull(skb, rtwdev->chip->tx_pkt_desc_sz);
+
 		/* enqueue to wait for tx report */
 		if (info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS) {
 			rtw_tx_report_enqueue(rtwdev, skb, tx_data->sn);