net: Infrastructure for CHECKSUM_PARTIAL with remote checsum offload

This patch adds infrastructure so that remote checksum offload can
set CHECKSUM_PARTIAL instead of calling csum_partial and writing
the modfied checksum field.

Add skb_remcsum_adjust_partial function to set an skb for using
CHECKSUM_PARTIAL with remote checksum offload.  Changed
skb_remcsum_process and skb_gro_remcsum_process to take a boolean
argument to indicate if checksum partial can be set or the
checksum needs to be modified using the normal algorithm.

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

2 files changed, 3 insertions, 2 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index d030575532a2..48c6ecb18f3c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4024,6 +4024,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
                 NAPI_GRO_CB(skb)->flush = 0;
                 NAPI_GRO_CB(skb)->free = 0;
                 NAPI_GRO_CB(skb)->udp_mark = 0;
+                NAPI_GRO_CB(skb)->gro_remcsum_start = 0;
 
                 /* Setup for GRO checksum validation */
                 switch (skb->ip_summed) {
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 7fa8d36e56d4..d320f575cc62 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -75,7 +75,7 @@ static struct guehdr *gue_remcsum(struct sk_buff *skb, struct guehdr *guehdr,
                 return NULL;
         guehdr = (struct guehdr *)&udp_hdr(skb)[1];
 
-        skb_remcsum_process(skb, (void *)guehdr + hdrlen, start, offset);
+        skb_remcsum_process(skb, (void *)guehdr + hdrlen, start, offset, true);
 
         return guehdr;
 }
@@ -230,7 +230,7 @@ static struct guehdr *gue_gro_remcsum(struct sk_buff *skb, unsigned int off,
         }
 
         skb_gro_remcsum_process(skb, (void *)guehdr + hdrlen,
-                                start, offset, grc);
+                                start, offset, grc, true);
 
         skb->remcsum_offload = 1;