Re: [PATCH 1/2] mt76: connac: fix GTK rekey offload failure on WPA mixed mode

[Felix Fietkau <nbd@nbd.name>]

On 2021-07-28 00:59, sean.wang@mediatek.com wrote:
> From: Leon Yen <Leon.Yen@mediatek.com>
> 
> Update the proper firmware programming sequence to fix GTK rekey
> offload failure on WPA mixed mode.
> 
> In the mt76_connac_mcu_key_iter,
> gtk_tlv->proto should be only set up on pairwise key
> and gtk_tlk->group_cipher should be only set up on the group key.
> 
> Otherwise, those parameters required by firmware would be set
> incorrectly to cause GTK rekey offload failure on WPA mixed mode
> and then disconnection follows.
> 
> Fixes: b47e21e75c80 ("mt76: mt7615: add gtk rekey offload support")
> Co-developed-by: Sean Wang <sean.wang@mediatek.com>
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> Signed-off-by: Leon Yen <Leon.Yen@mediatek.com>
> ---
>  .../net/wireless/mediatek/mt76/mt76_connac_mcu.c  | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> index a2555dc0f003..d71393b1c5e6 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> @@ -1957,19 +1957,22 @@ mt76_connac_mcu_key_iter(struct ieee80211_hw *hw,
>  	    key->cipher != WLAN_CIPHER_SUITE_TKIP)
>  		return;
>  
> -	if (key->cipher == WLAN_CIPHER_SUITE_TKIP) {
> -		gtk_tlv->proto = cpu_to_le32(NL80211_WPA_VERSION_1);
> +	if (key->cipher == WLAN_CIPHER_SUITE_TKIP)
>  		cipher = BIT(3);
> -	} else {
> -		gtk_tlv->proto = cpu_to_le32(NL80211_WPA_VERSION_2);
> +	else
>  		cipher = BIT(4);
> -	}
>  
>  	/* we are assuming here to have a single pairwise key */
>  	if (key->flags & IEEE80211_KEY_FLAG_PAIRWISE) {
> +		if (key->cipher == WLAN_CIPHER_SUITE_TKIP)
> +			gtk_tlv->proto = cpu_to_le32(NL80211_WPA_VERSION_1);
> +		else
> +			gtk_tlv->proto = cpu_to_le32(NL80211_WPA_VERSION_2);
Why is gtk_tlv->proto set to WPA version values based on the cipher
suite? That doesn't make much sense to me, since TKIP is supported by
WPA2 as well. I will apply this patch anyway, since this check is there
already, but this does look suspicious to me and should probably be
revisited.

- Felix