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Date:   Mon, 28 Sep 2020 21:31:25 -0400
From:   Sasha Levin <>
Cc:     Xie He <>, Martin Schiller <>,
        "David S . Miller" <>,
        Sasha Levin <>,
Subject: [PATCH AUTOSEL 4.19 07/11] drivers/net/wan/lapbether: Make skb->protocol consistent with the header

From: Xie He <>

[ Upstream commit 83f9a9c8c1edc222846dc1bde6e3479703e8e5a3 ]

This driver is a virtual driver stacked on top of Ethernet interfaces.

When this driver transmits data on the Ethernet device, the skb->protocol
setting is inconsistent with the Ethernet header prepended to the skb.

This causes a user listening on the Ethernet interface with an AF_PACKET
socket, to see different sll_protocol values for incoming and outgoing
frames, because incoming frames would have this value set by parsing the
Ethernet header.

This patch changes the skb->protocol value for outgoing Ethernet frames,
making it consistent with the Ethernet header prepended. This makes a
user listening on the Ethernet device with an AF_PACKET socket, to see
the same sll_protocol value for incoming and outgoing frames.

Cc: Martin Schiller <>
Signed-off-by: Xie He <>
Signed-off-by: David S. Miller <>
Signed-off-by: Sasha Levin <>
 drivers/net/wan/lapbether.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
index 15177a54b17d7..e5fc1b95cea6a 100644
--- a/drivers/net/wan/lapbether.c
+++ b/drivers/net/wan/lapbether.c
@@ -201,8 +201,6 @@ static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
 	struct net_device *dev;
 	int size = skb->len;
-	skb->protocol = htons(ETH_P_X25);
 	ptr = skb_push(skb, 2);
 	*ptr++ = size % 256;
@@ -213,6 +211,8 @@ static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
 	skb->dev = dev = lapbeth->ethdev;
+	skb->protocol = htons(ETH_P_DEC);
 	dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);

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