openvswitch: update checksum in {push,pop}_mpls

In the case of CHECKSUM_COMPLETE the skb checksum should be updated in
{push,pop}_mpls() as they the type in the ethernet header.

As suggested by Pravin Shelar.

Cc: Pravin Shelar <pshelar@nicira.com>
Fixes: 25cd9ba0 ("openvswitch: Add basic MPLS support to kernel")
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/actions.c

@@ -137,11 +137,23 @@ static bool is_flow_key_valid(const struct sw_flow_key *key)
 	return !!key->eth.type;
 }
 
+static void update_ethertype(struct sk_buff *skb, struct ethhdr *hdr,
+			     __be16 ethertype)
+{
+	if (skb->ip_summed == CHECKSUM_COMPLETE) {
+		__be16 diff[] = { ~(hdr->h_proto), ethertype };
+
+		skb->csum = ~csum_partial((char *)diff, sizeof(diff),
+					~skb->csum);
+	}
+
+	hdr->h_proto = ethertype;
+}
+
 static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 		     const struct ovs_action_push_mpls *mpls)
 {
 	__be32 *new_mpls_lse;
-	struct ethhdr *hdr;
 
 	/* Networking stack do not allow simultaneous Tunnel and MPLS GSO. */
 	if (skb->encapsulation)
@@ -160,9 +172,7 @@ static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 
 	skb_postpush_rcsum(skb, new_mpls_lse, MPLS_HLEN);
 
-	hdr = eth_hdr(skb);
-	hdr->h_proto = mpls->mpls_ethertype;
-
+	update_ethertype(skb, eth_hdr(skb), mpls->mpls_ethertype);
 	if (!skb->inner_protocol)
 		skb_set_inner_protocol(skb, skb->protocol);
 	skb->protocol = mpls->mpls_ethertype;
@@ -193,7 +203,7 @@ static int pop_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 	 * field correctly in the presence of VLAN tags.
 	 */
 	hdr = (struct ethhdr *)(skb_mpls_header(skb) - ETH_HLEN);
-	hdr->h_proto = ethertype;
+	update_ethertype(skb, hdr, ethertype);
 	if (eth_p_mpls(skb->protocol))
 		skb->protocol = ethertype;