net: Infrastructure for checksum unnecessary conversions

For normal path, added skb_checksum_try_convert which is called
to attempt to convert CHECKSUM_UNNECESSARY to CHECKSUM_COMPLETE. The
primary condition to allow this is that ip_summed is CHECKSUM_NONE
and csum_valid is true, which will be the state after consuming
a CHECKSUM_UNNECESSARY.

For GRO path, added skb_gro_checksum_try_convert which is the GRO
analogue of skb_checksum_try_convert. The primary condition to allow
this is that NAPI_GRO_CB(skb)->csum_cnt == 0 and
NAPI_GRO_CB(skb)->csum_valid is set. This implies that we have consumed
all available CHECKSUM_UNNECESSARY checksums in the GRO path.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a0ab6d9d400a..5be20a7bbb0d 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2233,6 +2233,26 @@ static inline void skb_gro_incr_csum_unnecessary(struct sk_buff *skb)
 #define skb_gro_checksum_simple_validate(skb)                           \
         __skb_gro_checksum_validate(skb, 0, false, 0, null_compute_pseudo)
 
+static inline bool __skb_gro_checksum_convert_check(struct sk_buff *skb)
+{
+        return (NAPI_GRO_CB(skb)->csum_cnt == 0 &&
+                !NAPI_GRO_CB(skb)->csum_valid);
+}
+
+static inline void __skb_gro_checksum_convert(struct sk_buff *skb,
+                                              __sum16 check, __wsum pseudo)
+{
+        NAPI_GRO_CB(skb)->csum = ~pseudo;
+        NAPI_GRO_CB(skb)->csum_valid = 1;
+}
+
+#define skb_gro_checksum_try_convert(skb, proto, check, compute_pseudo) \
+do {                                                                    \
+        if (__skb_gro_checksum_convert_check(skb))                      \
+                __skb_gro_checksum_convert(skb, check,                  \
+                                           compute_pseudo(skb, proto)); \
+} while (0)
+
 static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
                                   unsigned short type,
                                   const void *daddr, const void *saddr,