From: Felix Fietkau <nbd@nbd.name>
To: linux-wireless@vger.kernel.org
Cc: =?utf-8?q?Thibaut_VAR=C3=88NE?= <hacks+kernel@slashdirt.org>
Subject: [PATCH] mt76: fix encap offload ethernet type check
Date: Wed, 20 Apr 2022 14:33:08 +0200
Message-Id: <20220420123308.70104-1-nbd@nbd.name>

The driver needs to check if the format is 802.2 vs 802.3 in order to set
a tx descriptor flag. skb->protocol can't be used, since it may not be properly
initialized for packets coming in from a packet socket.
Fix misdetection by checking the ethertype from the skb data instead

Reported-by: Thibaut VARÈNE <hacks+kernel@slashdirt.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 drivers/net/wireless/mediatek/mt76/mt7915/mac.c | 4 +++-
 drivers/net/wireless/mediatek/mt76/mt7921/mac.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

--- a/mt7915/mac.c
+++ b/mt7915/mac.c
@@ -977,6 +977,7 @@ mt7915_mac_write_txwi_8023(struct mt7915
 
 	u8 tid = skb->priority & IEEE80211_QOS_CTL_TID_MASK;
 	u8 fc_type, fc_stype;
+	u16 ethertype;
 	bool wmm = false;
 	u32 val;
 
@@ -990,7 +991,8 @@ mt7915_mac_write_txwi_8023(struct mt7915
 	val = FIELD_PREP(MT_TXD1_HDR_FORMAT, MT_HDR_FORMAT_802_3) |
 	      FIELD_PREP(MT_TXD1_TID, tid);
 
-	if (be16_to_cpu(skb->protocol) >= ETH_P_802_3_MIN)
+	ethertype = get_unaligned_be16(&skb->data[12]);
+	if (ethertype >= ETH_P_802_3_MIN)
 		val |= MT_TXD1_ETH_802_3;
 
 	txwi[1] |= cpu_to_le32(val);
--- a/mt7921/mac.c
+++ b/mt7921/mac.c
@@ -811,6 +811,7 @@ mt7921_mac_write_txwi_8023(struct mt7921
 {
 	u8 tid = skb->priority & IEEE80211_QOS_CTL_TID_MASK;
 	u8 fc_type, fc_stype;
+	u16 ethertype;
 	bool wmm = false;
 	u32 val;
 
@@ -824,7 +825,8 @@ mt7921_mac_write_txwi_8023(struct mt7921
 	val = FIELD_PREP(MT_TXD1_HDR_FORMAT, MT_HDR_FORMAT_802_3) |
 	      FIELD_PREP(MT_TXD1_TID, tid);
 
-	if (be16_to_cpu(skb->protocol) >= ETH_P_802_3_MIN)
+	ethertype = get_unaligned_be16(&skb->data[12]);
+	if (ethertype >= ETH_P_802_3_MIN)
 		val |= MT_TXD1_ETH_802_3;
 
 	txwi[1] |= cpu_to_le32(val);
