openvswitch: make skb->csum consistent with rest of networking stack.

Following patch keeps skb->csum correct across ovs.
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

net/openvswitch/actions.c

@@ -130,9 +130,13 @@ static int set_eth_addr(struct sk_buff *skb,
 	if (unlikely(err))
 		return err;
 
+	skb_postpull_rcsum(skb, eth_hdr(skb), ETH_ALEN * 2);
+
 	memcpy(eth_hdr(skb)->h_source, eth_key->eth_src, ETH_ALEN);
 	memcpy(eth_hdr(skb)->h_dest, eth_key->eth_dst, ETH_ALEN);
 
+	ovs_skb_postpush_rcsum(skb, eth_hdr(skb), ETH_ALEN * 2);
+
 	return 0;
 }
 

net/openvswitch/flow.c

@@ -618,6 +618,9 @@ int ovs_flow_extract(struct sk_buff *skb, u16 in_port, struct sw_flow_key *key,
 	memcpy(key->eth.dst, eth->h_dest, ETH_ALEN);
 
 	__skb_pull(skb, 2 * ETH_ALEN);
+	/* We are going to push all headers that we pull, so no need to
+	 * update skb->csum here.
+	 */
 
 	if (vlan_tx_tag_present(skb))
 		key->eth.tci = htons(skb->vlan_tci);

net/openvswitch/vport-internal_dev.c

@@ -221,6 +221,7 @@ static int internal_dev_recv(struct vport *vport, struct sk_buff *skb)
 	skb->dev = netdev;
 	skb->pkt_type = PACKET_HOST;
 	skb->protocol = eth_type_trans(skb, netdev);
+	skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
 
 	netif_rx(skb);
 

net/openvswitch/vport-netdev.c

@@ -49,6 +49,8 @@ static void netdev_port_receive(struct vport *vport, struct sk_buff *skb)
 		return;
 
 	skb_push(skb, ETH_HLEN);
+	ovs_skb_postpush_rcsum(skb, skb->data, ETH_HLEN);
+
 	ovs_vport_receive(vport, skb);
 	return;
 

net/openvswitch/vport.h

@@ -192,4 +192,11 @@ void ovs_vport_record_error(struct vport *, enum vport_err_type err_type);
 extern const struct vport_ops ovs_netdev_vport_ops;
 extern const struct vport_ops ovs_internal_vport_ops;
 
+static inline void ovs_skb_postpush_rcsum(struct sk_buff *skb,
+				      const void *start, unsigned int len)
+{
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
+}
+
 #endif /* vport.h */