gre: Call gso_make_checksum

Call gso_make_checksum. This should have the benefit of using a
checksum that may have been previously computed for the packet.

This also adds NETIF_F_GSO_GRE_CSUM to differentiate devices that
offload GRE GSO with and without the GRE checksum offloaed.
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdev_features.h

@@ -42,6 +42,7 @@ enum {
 	NETIF_F_TSO6_BIT,		/* ... TCPv6 segmentation */
 	NETIF_F_FSO_BIT,		/* ... FCoE segmentation */
 	NETIF_F_GSO_GRE_BIT,		/* ... GRE with TSO */
+	NETIF_F_GSO_GRE_CSUM_BIT,	/* ... GRE with csum with TSO */
 	NETIF_F_GSO_IPIP_BIT,		/* ... IPIP tunnel with TSO */
 	NETIF_F_GSO_SIT_BIT,		/* ... SIT tunnel with TSO */
 	NETIF_F_GSO_UDP_TUNNEL_BIT,	/* ... UDP TUNNEL with TSO */
@@ -112,6 +113,7 @@ enum {
 #define NETIF_F_RXFCS		__NETIF_F(RXFCS)
 #define NETIF_F_RXALL		__NETIF_F(RXALL)
 #define NETIF_F_GSO_GRE		__NETIF_F(GSO_GRE)
+#define NETIF_F_GSO_GRE_CSUM	__NETIF_F(GSO_GRE_CSUM)
 #define NETIF_F_GSO_IPIP	__NETIF_F(GSO_IPIP)
 #define NETIF_F_GSO_SIT		__NETIF_F(GSO_SIT)
 #define NETIF_F_GSO_UDP_TUNNEL	__NETIF_F(GSO_UDP_TUNNEL)

include/linux/skbuff.h

@@ -347,6 +347,8 @@ enum {
 	SKB_GSO_MPLS = 1 << 10,
 
 	SKB_GSO_UDP_TUNNEL_CSUM = 1 << 11,
+
+	SKB_GSO_GRE_CSUM = 1 << 12,
 };
 
 #if BITS_PER_LONG > 32

include/net/gre.h

@@ -37,9 +37,10 @@ void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
 		      int hdr_len);
 
 static inline struct sk_buff *gre_handle_offloads(struct sk_buff *skb,
-						  bool gre_csum)
+						  bool csum)
 {
-	return iptunnel_handle_offloads(skb, gre_csum, SKB_GSO_GRE);
+	return iptunnel_handle_offloads(skb, csum,
+					csum ? SKB_GSO_GRE_CSUM : SKB_GSO_GRE);
 }
 
 

net/ipv4/af_inet.c

@@ -1254,6 +1254,7 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 		       SKB_GSO_DODGY |
 		       SKB_GSO_TCP_ECN |
 		       SKB_GSO_GRE |
+		       SKB_GSO_GRE_CSUM |
 		       SKB_GSO_IPIP |
 		       SKB_GSO_SIT |
 		       SKB_GSO_TCPV6 |

net/ipv4/gre_demux.c

@@ -84,7 +84,8 @@ void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
 			ptr--;
 		}
 		if (tpi->flags&TUNNEL_CSUM &&
-		    !(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) {
+		    !(skb_shinfo(skb)->gso_type &
+		      (SKB_GSO_GRE|SKB_GSO_GRE_CSUM))) {
 			*ptr = 0;
 			*(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
 								 skb->len, 0));

net/ipv4/gre_offload.c

@@ -42,6 +42,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 				  SKB_GSO_DODGY |
 				  SKB_GSO_TCP_ECN |
 				  SKB_GSO_GRE |
+				  SKB_GSO_GRE_CSUM |
 				  SKB_GSO_IPIP)))
 		goto out;
 
@@ -55,6 +56,8 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 		goto out;
 
 	csum = !!(greh->flags & GRE_CSUM);
+	if (csum)
+		skb->encap_hdr_csum = 1;
 
 	if (unlikely(!pskb_may_pull(skb, ghl)))
 		goto out;
@@ -94,10 +97,13 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 				}
 			}
 
-			greh = (struct gre_base_hdr *)(skb->data);
+			skb_reset_transport_header(skb);
+
+			greh = (struct gre_base_hdr *)
+			    skb_transport_header(skb);
 			pcsum = (__be32 *)(greh + 1);
 			*pcsum = 0;
-			*(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
+			*(__sum16 *)pcsum = gso_make_checksum(skb, 0);
 		}
 		__skb_push(skb, tnl_hlen - ghl);
 

net/ipv4/tcp_offload.c

@@ -57,6 +57,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 			       SKB_GSO_TCP_ECN |
 			       SKB_GSO_TCPV6 |
 			       SKB_GSO_GRE |
+			       SKB_GSO_GRE_CSUM |
 			       SKB_GSO_IPIP |
 			       SKB_GSO_SIT |
 			       SKB_GSO_MPLS |

net/ipv4/udp_offload.c

@@ -74,7 +74,8 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 				      SKB_GSO_UDP_TUNNEL |
 				      SKB_GSO_UDP_TUNNEL_CSUM |
 				      SKB_GSO_IPIP |
-				      SKB_GSO_GRE | SKB_GSO_MPLS) ||
+				      SKB_GSO_GRE | SKB_GSO_GRE_CSUM |
+				      SKB_GSO_MPLS) ||
 			     !(type & (SKB_GSO_UDP))))
 			goto out;
 

net/ipv6/ip6_offload.c

@@ -97,6 +97,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 		       SKB_GSO_DODGY |
 		       SKB_GSO_TCP_ECN |
 		       SKB_GSO_GRE |
+		       SKB_GSO_GRE_CSUM |
 		       SKB_GSO_IPIP |
 		       SKB_GSO_SIT |
 		       SKB_GSO_UDP_TUNNEL |

net/ipv6/udp_offload.c

@@ -65,6 +65,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 				      SKB_GSO_UDP_TUNNEL |
 				      SKB_GSO_UDP_TUNNEL_CSUM |
 				      SKB_GSO_GRE |
+				      SKB_GSO_GRE_CSUM |
 				      SKB_GSO_IPIP |
 				      SKB_GSO_SIT |
 				      SKB_GSO_MPLS) ||

net/mpls/mpls_gso.c

@@ -33,6 +33,7 @@ static struct sk_buff *mpls_gso_segment(struct sk_buff *skb,
 				  SKB_GSO_DODGY |
 				  SKB_GSO_TCP_ECN |
 				  SKB_GSO_GRE |
+				  SKB_GSO_GRE_CSUM |
 				  SKB_GSO_IPIP |
 				  SKB_GSO_MPLS)))
 		goto out;