net: use skb_postpush_rcsum instead of own implementations

[ Upstream commit 6b83d28a,
  skb_postpush_rcsum() added from commit
  f8ffad69 ]

Replace individual implementations with the recently introduced
skb_postpush_rcsum() helper.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Tom Herbert <tom@herbertland.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

include/linux/skbuff.h

@@ -2607,6 +2607,23 @@ static inline void skb_postpull_rcsum(struct sk_buff *skb,
 
 unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
 
+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);
+}
+
 /**
  *	pskb_trim_rcsum - trim received skb and update checksum
  *	@skb: buffer to trim

net/core/skbuff.c

@@ -4362,9 +4362,7 @@ int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
 		skb->mac_len += VLAN_HLEN;
 		__skb_pull(skb, offset);
 
-		if (skb->ip_summed == CHECKSUM_COMPLETE)
-			skb->csum = csum_add(skb->csum, csum_partial(skb->data
-					+ (2 * ETH_ALEN), VLAN_HLEN, 0));
+		skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
 	}
 	__vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
 	return 0;

net/ipv6/reassembly.c

@@ -492,10 +492,8 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
 	IP6CB(head)->flags |= IP6SKB_FRAGMENTED;
 
 	/* Yes, and fold redundant checksum back. 8) */
-	if (head->ip_summed == CHECKSUM_COMPLETE)
-		head->csum = csum_partial(skb_network_header(head),
-					  skb_network_header_len(head),
-					  head->csum);
+	skb_postpush_rcsum(head, skb_network_header(head),
+			   skb_network_header_len(head));
 
 	rcu_read_lock();
 	IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMOKS);

net/openvswitch/actions.c

@@ -140,9 +140,7 @@ 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;
@@ -243,7 +241,7 @@ static int set_eth_addr(struct sk_buff *skb, struct sw_flow_key *key,
 	ether_addr_copy(eth_hdr(skb)->h_source, eth_key->eth_src);
 	ether_addr_copy(eth_hdr(skb)->h_dest, eth_key->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(key->eth.src, eth_key->eth_src);
 	ether_addr_copy(key->eth.dst, eth_key->eth_dst);

net/openvswitch/vport-netdev.c

@@ -52,7 +52,7 @@ 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);
+	skb_postpush_rcsum(skb, skb->data, ETH_HLEN);
 
 	ovs_vport_receive(vport, skb, NULL);
 	return;

net/openvswitch/vport.h

@@ -228,13 +228,6 @@ static inline struct vport *vport_from_priv(void *priv)
 void ovs_vport_receive(struct vport *, struct sk_buff *,
 		       const struct ovs_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));
-}
-
 int ovs_vport_ops_register(struct vport_ops *ops);
 void ovs_vport_ops_unregister(struct vport_ops *ops);