datapath: Use skb_postpush_rcsum()

Use kernel function to update checksum.

Signed-off-by: Pravin B Shelar <pshelar@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>

Author: pshelar

acinclude.m4

@@ -556,6 +556,7 @@ AC_DEFUN([OVS_CHECK_LINUX_COMPAT], [
   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_vlan_pop])
   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_vlan_push])
   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_clear_hash_if_not_l4])
+  OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_postpush_rcsum])
 
   OVS_GREP_IFELSE([$KSRC/include/linux/types.h], [bool],
                   [OVS_DEFINE([HAVE_BOOL_TYPE])])

datapath/actions.c

@@ -160,9 +160,7 @@ static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 	new_mpls_lse = (__be32 *)skb_mpls_header(skb);
 	*new_mpls_lse = mpls->mpls_lse;
 
-	if (skb->ip_summed == CHECKSUM_COMPLETE)
-		skb->csum = csum_add(skb->csum, csum_partial(new_mpls_lse,
-							     MPLS_HLEN, 0));
+	skb_postpush_rcsum(skb, new_mpls_lse, MPLS_HLEN);
 
 	hdr = eth_hdr(skb);
 	hdr->h_proto = mpls->mpls_ethertype;
@@ -281,7 +279,7 @@ static int set_eth_addr(struct sk_buff *skb, struct sw_flow_key *flow_key,
 	ether_addr_copy_masked(eth_hdr(skb)->h_dest, key->eth_dst,
 			       mask->eth_dst);
 
-	ovs_skb_postpush_rcsum(skb, eth_hdr(skb), ETH_ALEN * 2);
+	skb_postpush_rcsum(skb, eth_hdr(skb), ETH_ALEN * 2);
 
 	ether_addr_copy(flow_key->eth.src, eth_hdr(skb)->h_source);
 	ether_addr_copy(flow_key->eth.dst, eth_hdr(skb)->h_dest);
@@ -641,7 +639,7 @@ static int ovs_vport_output(OVS_VPORT_OUTPUT_PARAMS)
 	/* Reconstruct the MAC header.  */
 	skb_push(skb, data->l2_len);
 	memcpy(skb->data, &data->l2_data, data->l2_len);
-	ovs_skb_postpush_rcsum(skb, skb->data, data->l2_len);
+	skb_postpush_rcsum(skb, skb->data, data->l2_len);
 	skb_reset_mac_header(skb);
 
 	ovs_vport_send(vport, skb);

datapath/linux/compat/include/linux/skbuff.h

@@ -348,4 +348,24 @@ static inline void skb_clear_hash_if_not_l4(struct sk_buff *skb)
 		skb_clear_hash(skb);
 }
 #endif
+
+#ifndef HAVE_SKB_POSTPUSH_RCSUM
+static inline void skb_postpush_rcsum(struct sk_buff *skb,
+				      const void *start, unsigned int len)
+{
+	/* For performing the reverse operation to skb_postpull_rcsum(),
+	 * we can instead of ...
+	 *
+	 *   skb->csum = csum_add(skb->csum, csum_partial(start, len, 0));
+	 *
+	 * ... just use this equivalent version here to save a few
+	 * instructions. Feeding csum of 0 in csum_partial() and later
+	 * on adding skb->csum is equivalent to feed skb->csum in the
+	 * first place.
+	 */
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->csum = csum_partial(start, len, skb->csum);
+}
+#endif
+
 #endif

datapath/vport-netdev.c

@@ -59,7 +59,7 @@ void netdev_port_receive(struct sk_buff *skb, struct ip_tunnel_info *tun_info)
 		return;
 
 	skb_push(skb, ETH_HLEN);
-	ovs_skb_postpush_rcsum(skb, skb->data, ETH_HLEN);
+	skb_postpush_rcsum(skb, skb->data, ETH_HLEN);
 	ovs_vport_receive(vport, skb, tun_info);
 	return;
 error:

datapath/vport.h

@@ -187,13 +187,6 @@ static inline struct vport *vport_from_priv(void *priv)
 int ovs_vport_receive(struct vport *, struct sk_buff *,
 		      const struct ip_tunnel_info *);
 
-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));
-}
-
 static inline const char *ovs_vport_name(struct vport *vport)
 {
 	return vport->dev->name;