Merge branch 'csums-next'

Tom Herbert says:

====================
net: Checksum offload changes - Part VI

I am working on overhauling RX checksum offload. Goals of this effort
are:

- Specify what exactly it means when driver returns CHECKSUM_UNNECESSARY
- Preserve CHECKSUM_COMPLETE through encapsulation layers
- Don't do skb_checksum more than once per packet
- Unify GRO and non-GRO csum verification as much as possible
- Unify the checksum functions (checksum_init)
- Simplify code

What is in this sixth patch set:

- Clarify the specific requirements of devices returning
  CHECKSUM_UNNECESSARY (comments in skbuff.h).
- Add csum_level field to skbuff. This is used to express how
  many checksums are covered by CHECKSUM_UNNECESSARY (stores n - 1).
- Change __skb_checksum_validate_needed to "consume" each checksum
  as indicated by csum_level as layers of the the packet are parsed.
- Remove skb_pop_rcv_encapsulation, no longer needed in the new
  csum_level model.
- Allow GRO path to "consume" checksums provided in CHECKSUM_UNNECESSARY
  and to report new verfied checksums for use in normal path fallback.
- Add proper support to SCTP to accept CHECKSUM_UNNECESSARY to validate
  header CRC.
- Modify drivers to set skb->csum_level instead of setting
  skb->encapsulation to indicate validation of an encapsulated
  checksum on receive.

v2:

Allocate a new 16 bits for flags in skbuff.

Please review carefully and test if possible, mucking with basic
checksum functions is always a little precarious :-)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 14 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index dfc1d8b8bd0f..456eb1fe51e8 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1883,8 +1883,8 @@ struct napi_gro_cb {
 	/* GRO checksum is valid */
 	u8	csum_valid:1;
 
-	/* Number encapsulation layers crossed */
-	u8	encapsulation;
+	/* Number of checksums via CHECKSUM_UNNECESSARY */
+	u8	csum_cnt:3;
 
 	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
 	__wsum	csum;
@@ -2179,8 +2179,7 @@ static inline bool __skb_gro_checksum_validate_needed(struct sk_buff *skb,
 						      __sum16 check)
 {
 	return (skb->ip_summed != CHECKSUM_PARTIAL &&
-		(skb->ip_summed != CHECKSUM_UNNECESSARY ||
-		 (NAPI_GRO_CB(skb)->encapsulation > skb->encapsulation)) &&
+		NAPI_GRO_CB(skb)->csum_cnt == 0 &&
 		(!zero_okay || check));
 }
 
@@ -2196,18 +2195,17 @@ static inline __sum16 __skb_gro_checksum_validate_complete(struct sk_buff *skb,
 	return __skb_gro_checksum_complete(skb);
 }
 
-/* Update skb for CHECKSUM_UNNECESSARY when we verified a top level
- * checksum or an encapsulated one during GRO. This saves work
- * if we fallback to normal path with the packet.
- */
 static inline void skb_gro_incr_csum_unnecessary(struct sk_buff *skb)
 {
-	if (skb->ip_summed == CHECKSUM_UNNECESSARY) {
-		if (NAPI_GRO_CB(skb)->encapsulation)
-			skb->encapsulation = 1;
-	} else if (skb->ip_summed != CHECKSUM_PARTIAL) {
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
-		skb->encapsulation = 0;
+	if (NAPI_GRO_CB(skb)->csum_cnt > 0) {
+		/* Consume a checksum from CHECKSUM_UNNECESSARY */
+		NAPI_GRO_CB(skb)->csum_cnt--;
+	} else {
+		/* Update skb for CHECKSUM_UNNECESSARY and csum_level when we
+		 * verified a new top level checksum or an encapsulated one
+		 * during GRO. This saves work if we fallback to normal path.
+		 */
+		__skb_incr_checksum_unnecessary(skb);
 	}
 }