rsi: Fix TX EAPOL packet handling against iwlwifi AP

[ Upstream commit 6527710 ]

In case RSI9116 SDIO WiFi operates in STA mode against Intel 9260 in AP mode,
the association fails. The former is using wpa_supplicant during association,
the later is set up using hostapd:

iwl$ cat hostapd.conf
interface=wlp1s0
ssid=test
country_code=DE
hw_mode=g
channel=1
wpa=2
wpa_passphrase=test
wpa_key_mgmt=WPA-PSK
iwl$ hostapd -d hostapd.conf

rsi$ wpa_supplicant -i wlan0 -c <(wpa_passphrase test test)

The problem is that the TX EAPOL data descriptor RSI_DESC_REQUIRE_CFM_TO_HOST
flag and extended descriptor EAPOL4_CONFIRM frame type are not set in case the
AP is iwlwifi, because in that case the TX EAPOL packet is 2 bytes shorter.

The downstream vendor driver has this change in place already [1], however
there is no explanation for it, neither is there any commit history from which
such explanation could be obtained.

[1] https://github.com/SiliconLabs/RS911X-nLink-OSD/blob/master/rsi/rsi_91x_hal.c#L238

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Angus Ainslie <angus@akkea.ca>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Martin Kepplinger <martink@posteo.de>
Cc: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
Cc: Siva Rebbagondla <siva8118@gmail.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201015111616.429220-1-marex@denx.de
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/wireless/rsi/rsi_91x_hal.c

@@ -248,7 +248,8 @@ int rsi_prepare_data_desc(struct rsi_common *common, struct sk_buff *skb)
 			rsi_set_len_qno(&data_desc->len_qno,
 					(skb->len - FRAME_DESC_SZ),
 					RSI_WIFI_MGMT_Q);
-		if ((skb->len - header_size) == EAPOL4_PACKET_LEN) {
+		if (((skb->len - header_size) == EAPOL4_PACKET_LEN) ||
+		    ((skb->len - header_size) == EAPOL4_PACKET_LEN - 2)) {
 			data_desc->misc_flags |=
 				RSI_DESC_REQUIRE_CFM_TO_HOST;
 			xtend_desc->confirm_frame_type = EAPOL4_CONFIRM;