[PATCH 4/4] tcp: set skb checksum unnecessary and encapsulation in TCP GRO

Once checksum has been validated in TCP RO we can assume all
preceeding checksums have been properly validated so ip_summed can
changed to unnecessary. Also, if UDP encapsulation was encountered
we set skb->encapsulation to indicated encapsulated checksums are
verified.

Signed-off-by: Tom Herbert <redacted>
---
 include/linux/netdevice.h | 5 ++++-
 net/ipv4/tcp_offload.c    | 4 ++++
 net/ipv4/udp_offload.c    | 2 ++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 774e539..d39221f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h

@@ -1760,7 +1760,10 @@ struct napi_gro_cb {
 	u16	proto;
 
 	/* Used in udp_gro_receive */
-	u16	udp_mark;
+	u8	udp_mark;
+
+	/* Crossed encpsulation boundary */
+	u8	encapsulation;
 
 	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
 	__wsum	csum;

diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 4e86c59..f40eb4c 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c

@@ -290,7 +290,11 @@ static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *
 	case CHECKSUM_COMPLETE:
 		if (!tcp_v4_check(skb_gro_len(skb), iph->saddr, iph->daddr,
 				  wsum)) {
+			/* Assume all previous checksums have succeeded
+			 * so we can convert to CHECKSUM_UNNECESSARY now.
+			 */
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
+			skb->encapsulation = NAPI_GRO_CB(skb)->encapsulation;
 			break;
 		}
 

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 546d2d4..56749a2 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c

@@ -167,6 +167,8 @@ static struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *s
 	/* mark that this skb passed once through the udp gro layer */
 	NAPI_GRO_CB(skb)->udp_mark = 1;
 
+	NAPI_GRO_CB(skb)->encapsulation = 1;
+
 	off  = skb_gro_offset(skb);
 	hlen = off + sizeof(*uh);
 	uh   = skb_gro_header_fast(skb, off);