ip_gre: add csum offload support for gre header

This patch is to add csum offload support for gre header:

On the TX path in gre_build_header(), when CHECKSUM_PARTIAL's set
for inner proto, it will calculate the csum for outer proto, and
inner csum will be offloaded later. Otherwise, CHECKSUM_PARTIAL
and csum_start/offset will be set for outer proto, and the outer
csum will be offloaded later.

On the GSO path in gre_gso_segment(), when CHECKSUM_PARTIAL is
not set for inner proto and the hardware supports csum offload,
CHECKSUM_PARTIAL and csum_start/offset will be set for outer
proto, and outer csum will be offloaded later. Otherwise, it
will do csum for outer proto by calling gso_make_checksum().

Note that SCTP has to do the csum by itself for non GSO path in
sctp_packet_pack(), as gre_build_header() can't handle the csum
with CHECKSUM_PARTIAL set for SCTP CRC csum offload.

v1->v2:
  - remove the SCTP part, as GRE dev doesn't support SCTP CRC CSUM
    and it will always do checksum for SCTP in sctp_packet_pack()
    when it's not a GSO packet.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/gre.h b/include/net/gre.h
index b60f212..4e20970 100644 (file)
--- a/include/net/gre.h
+++ b/include/net/gre.h
@@ -106,17 +106,6 @@ static inline __be16 gre_tnl_flags_to_gre_flags(__be16 tflags)
        return flags;
 }
 
-static inline __sum16 gre_checksum(struct sk_buff *skb)
-{
-       __wsum csum;
-
-       if (skb->ip_summed == CHECKSUM_PARTIAL)
-               csum = lco_csum(skb);
-       else
-               csum = skb_checksum(skb, 0, skb->len, 0);
-       return csum_fold(csum);
-}
-
 static inline void gre_build_header(struct sk_buff *skb, int hdr_len,
                                    __be16 flags, __be16 proto,
                                    __be32 key, __be32 seq)
@@ -146,7 +135,13 @@ static inline void gre_build_header(struct sk_buff *skb, int hdr_len,
                    !(skb_shinfo(skb)->gso_type &
                      (SKB_GSO_GRE | SKB_GSO_GRE_CSUM))) {
                        *ptr = 0;
-                       *(__sum16 *)ptr = gre_checksum(skb);
+                       if (skb->ip_summed == CHECKSUM_PARTIAL) {
+                               *(__sum16 *)ptr = csum_fold(lco_csum(skb));
+                       } else {
+                               skb->ip_summed = CHECKSUM_PARTIAL;
+                               skb->csum_start = skb_transport_header(skb) - skb->head;
+                               skb->csum_offset = sizeof(*greh);
+                       }
                }
        }
 }

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 10bc49b..1121a9d 100644 (file)
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -15,10 +15,10 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
                                       netdev_features_t features)
 {
        int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
+       bool need_csum, offload_csum, gso_partial, need_ipsec;
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        u16 mac_offset = skb->mac_header;
        __be16 protocol = skb->protocol;
-       bool need_csum, gso_partial;
        u16 mac_len = skb->mac_len;
        int gre_offset, outer_hlen;
 
@@ -47,6 +47,11 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
        if (need_csum)
                features &= ~NETIF_F_SCTP_CRC;
 
+       need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
+       /* Try to offload checksum if possible */
+       offload_csum = !!(need_csum && !need_ipsec &&
+                         (skb->dev->features & NETIF_F_HW_CSUM));
+
        /* segment inner packet. */
        segs = skb_mac_gso_segment(skb, features);
        if (IS_ERR_OR_NULL(segs)) {
@@ -100,7 +105,13 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
                }
 
                *(pcsum + 1) = 0;
-               *pcsum = gso_make_checksum(skb, 0);
+               if (skb->encapsulation || !offload_csum) {
+                       *pcsum = gso_make_checksum(skb, 0);
+               } else {
+                       skb->ip_summed = CHECKSUM_PARTIAL;
+                       skb->csum_start = skb_transport_header(skb) - skb->head;
+                       skb->csum_offset = sizeof(*greh);
+               }
        } while ((skb = skb->next));
 out:
        return segs;