[PATCH 4.14 15/94] drivers/net/wan/lapbether: Set network_header before transmitting

From: Greg Kroah-Hartman
Date: Mon Sep 21 2020 - 12:37:32 EST

From: Xie He <xie.he.0141@xxxxxxxxx>

[ Upstream commit 91244d108441013b7367b3b4dcc6869998676473 ]

Set the skb's network_header before it is passed to the underlying
Ethernet device for transmission.

This patch fixes the following issue:

When we use this driver with AF_PACKET sockets, there would be error
messages of:
protocol 0805 is buggy, dev (Ethernet interface name)
printed in the system "dmesg" log.

This is because skbs passed down to the Ethernet device for transmission
don't have their network_header properly set, and the dev_queue_xmit_nit
function in net/core/dev.c complains about this.

Reason of setting the network_header to this place (at the end of the
Ethernet header, and at the beginning of the Ethernet payload):

Because when this driver receives an skb from the Ethernet device, the
network_header is also set at this place.

Cc: Martin Schiller <ms@xxxxxxxxxx>
Signed-off-by: Xie He <xie.he.0141@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/wan/lapbether.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
index 6b2553e893aca..15177a54b17d7 100644
--- a/drivers/net/wan/lapbether.c
+++ b/drivers/net/wan/lapbether.c
@@ -213,6 +213,8 @@ static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)

skb->dev = dev = lapbeth->ethdev;

+ skb_reset_network_header(skb);
dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);