linux-kernel - [PATCH AUTOSEL 4.4 03/10] drivers/net/wan/lapbether: Set network

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Date:   Mon,  7 Sep 2020 12:35:36 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Xie He <xie.he.0141@...il.com>, Martin Schiller <ms@....tdt.de>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 03/10] drivers/net/wan/lapbether: Set network_header before transmitting

From: Xie He <xie.he.0141@...il.com>

[ 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@....tdt.de>
Signed-off-by: Xie He <xie.he.0141@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 5befc7f3f0e7a..c6db9a4e7c457 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);

 	dev_queue_xmit(skb);
-- 
2.25.1