[PATCH 4.4 28/48] net: mvpp2: Extract the correct ethtype from the skb for tx csum offload

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maxime Chevallier <maxime.chevallier@bootlin.com>

[ Upstream commit 35f3625c21852ad839f20c91c7d81c4c1101e207 ]

When offloading the L3 and L4 csum computation on TX, we need to extract
the l3_proto from the ethtype, independently of the presence of a vlan
tag.

The actual driver uses skb->protocol as-is, resulting in packets with
the wrong L4 checksum being sent when there's a vlan tag in the packet
header and checksum offloading is enabled.

This commit makes use of vlan_protocol_get() to get the correct ethtype
regardless the presence of a vlan tag.

Fixes: 3f518509dedc ("ethernet: Add new driver for Marvell Armada 375 network unit")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/marvell/mvpp2.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/net/ethernet/marvell/mvpp2.c
+++ b/drivers/net/ethernet/marvell/mvpp2.c
@@ -29,6 +29,7 @@
 #include <linux/clk.h>
 #include <linux/hrtimer.h>
 #include <linux/ktime.h>
+#include <linux/if_vlan.h>
 #include <uapi/linux/ppp_defs.h>
 #include <net/ip.h>
 #include <net/ipv6.h>
@@ -4268,7 +4269,7 @@ static void mvpp2_txq_desc_put(struct mv
 }
 
 /* Set Tx descriptors fields relevant for CSUM calculation */
-static u32 mvpp2_txq_desc_csum(int l3_offs, int l3_proto,
+static u32 mvpp2_txq_desc_csum(int l3_offs, __be16 l3_proto,
 			       int ip_hdr_len, int l4_proto)
 {
 	u32 command;
@@ -5032,14 +5033,15 @@ static u32 mvpp2_skb_tx_csum(struct mvpp
 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
 		int ip_hdr_len = 0;
 		u8 l4_proto;
+		__be16 l3_proto = vlan_get_protocol(skb);
 
-		if (skb->protocol == htons(ETH_P_IP)) {
+		if (l3_proto == htons(ETH_P_IP)) {
 			struct iphdr *ip4h = ip_hdr(skb);
 
 			/* Calculate IPv4 checksum and L4 checksum */
 			ip_hdr_len = ip4h->ihl;
 			l4_proto = ip4h->protocol;
-		} else if (skb->protocol == htons(ETH_P_IPV6)) {
+		} else if (l3_proto == htons(ETH_P_IPV6)) {
 			struct ipv6hdr *ip6h = ipv6_hdr(skb);
 
 			/* Read l4_protocol from one of IPv6 extra headers */
@@ -5051,7 +5053,7 @@ static u32 mvpp2_skb_tx_csum(struct mvpp
 		}
 
 		return mvpp2_txq_desc_csum(skb_network_offset(skb),
-				skb->protocol, ip_hdr_len, l4_proto);
+					   l3_proto, ip_hdr_len, l4_proto);
 	}
 
 	return MVPP2_TXD_L4_CSUM_NOT | MVPP2_TXD_IP_CSUM_DISABLE;