mlx5: fix get_ip_proto()

mainline inclusion
from mainline-4.20
commit ef6fcd455278
category: bugfix
bugzilla: 6077
CVE: NA

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

IP header is not necessarily located right after struct ethhdr,
there could be multiple 802.1Q headers in between, this is why
we call __vlan_get_protocol().

Fixes: fe1dc069990c ("net/mlx5e: don't set CHECKSUM_COMPLETE on SCTP packets")
Cc: Alaa Hleihel <alaa@mellanox.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: NTariq Toukan <tariqt@mellanox.com>
Acked-by: NSaeed Mahameed <saeedm@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NKeefe LIU <liuqifa@huawei.com>
Reviewed-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/ethernet/mellanox/mlx5/core/en_rx.c

@@ -727,9 +727,9 @@ static u32 mlx5e_get_fcs(const struct sk_buff *skb)
 
 #define short_frame(size) ((size) <= ETH_ZLEN + ETH_FCS_LEN)
 
-static u8 get_ip_proto(struct sk_buff *skb, __be16 proto)
+static u8 get_ip_proto(struct sk_buff *skb, int network_depth, __be16 proto)
 {
-	void *ip_p = skb->data + sizeof(struct ethhdr);
+	void *ip_p = skb->data + network_depth;
 
 	return (proto == htons(ETH_P_IP)) ? ((struct iphdr *)ip_p)->protocol :
 					    ((struct ipv6hdr *)ip_p)->nexthdr;
@@ -766,7 +766,7 @@ static inline void mlx5e_handle_csum(struct net_device *netdev,
 		goto csum_unnecessary;
 
 	if (likely(is_last_ethertype_ip(skb, &network_depth, &proto))) {
-		if (unlikely(get_ip_proto(skb, proto) == IPPROTO_SCTP))
+		if (unlikely(get_ip_proto(skb, network_depth, proto) == IPPROTO_SCTP))
 			goto csum_unnecessary;
 
 		skb->ip_summed = CHECKSUM_COMPLETE;