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>

5 files changed, 14 insertions, 4 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 0070ab87109b..d5e6836cf772 100644
--- a/net/ipv4/af_inet.c
+++ b/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 |
diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index fbfd829f4049..4e9619bca732 100644
--- a/net/ipv4/gre_demux.c
+++ b/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));
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index f1d32280cb54..24deb3928b9e 100644
--- a/net/ipv4/gre_offload.c
+++ b/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);
 
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index c02f2d2e7bab..4e86c59ec7f7 100644
--- a/net/ipv4/tcp_offload.c
+++ b/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 |
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 5c23f4765af9..7b1840110173 100644
--- a/net/ipv4/udp_offload.c
+++ b/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;