[PATCH 5.4 071/344] wan/hdlc_x25: fix skb handling

Greg Kroah-Hartman
2020-02-21T08:36:57Z

From: Martin Schiller <ms@dev.tdt.de>

[ Upstream commit 953c4a08dfc9ffe763a8340ac10f459d6c6cc4eb ]

o call skb_reset_network_header() before hdlc->xmit()
o change skb proto to HDLC (0x0019) before hdlc->xmit()
o call dev_queue_xmit_nit() before hdlc->xmit()

This changes make it possible to trace (tcpdump) outgoing layer2
(ETH_P_HDLC) packets

Additionally call skb_reset_network_header() after each skb_push() /
skb_pull().

Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wan/hdlc_x25.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wan/hdlc_x25.c b/drivers/net/wan/hdlc_x25.c
index 5643675ff7241..bf78073ee7fd9 100644
--- a/drivers/net/wan/hdlc_x25.c
+++ b/drivers/net/wan/hdlc_x25.c
@@ -62,11 +62,12 @@ static int x25_data_indication(struct net_device *dev, struct sk_buff *skb)
{
unsigned char *ptr;

- skb_push(skb, 1);
-
if (skb_cow(skb, 1))
return NET_RX_DROP;

+ skb_push(skb, 1);
+ skb_reset_network_header(skb);
+
ptr = skb->data;
*ptr = X25_IFACE_DATA;

@@ -79,6 +80,13 @@ static int x25_data_indication(struct net_device *dev, struct sk_buff *skb)
static void x25_data_transmit(struct net_device *dev, struct sk_buff *skb)
{
hdlc_device *hdlc = dev_to_hdlc(dev);
+
+ skb_reset_network_header(skb);
+ skb->protocol = hdlc_type_trans(skb, dev);
+
+ if (dev_nit_active(dev))
+ dev_queue_xmit_nit(skb, dev);
+
hdlc->xmit(skb, dev); /* Ignore return value :-( */
}

@@ -93,6 +101,7 @@ static netdev_tx_t x25_xmit(struct sk_buff *skb, struct net_device *dev)
switch (skb->data[0]) {
case X25_IFACE_DATA: /* Data to be transmitted */
skb_pull(skb, 1);
+ skb_reset_network_header(skb);
if ((result = lapb_data_request(dev, skb)) != LAPB_OK)
dev_kfree_skb(skb);
return NETDEV_TX_OK;
--
2.20.1