commit 7e3cead5172927732f51fde77fef6f521e22f209
author Tom Herbert <therbert@google.com> Tue Jun 10 18:54:19 2014 -0700
committer David S. Miller <davem@davemloft.net> Wed Jun 11 15:46:13 2014 -0700
tree 7b7cad61aa68ba302c395b9a1ea3dafb69881d0d
parent 5d0c2b95bc57cf8fdc0e7b3e9d7e751eb65ad052

net: Save software checksum complete

In skb_checksum complete, if we need to compute the checksum for the
packet (via skb_checksum) save the result as CHECKSUM_COMPLETE.
Subsequent checksum verification can use this.

Also, added csum_complete_sw flag to distinguish between software and
hardware generated checksum complete, we should always be able to trust
the software computation.

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

include/linux/skbuff.h

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 72a5380..5b5cd31 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -573,7 +573,8 @@
 	__u8			encapsulation:1;
 	__u8			encap_hdr_csum:1;
 	__u8			csum_valid:1;
-	/* 4/6 bit hole (depending on ndisc_nodetype presence) */
+	__u8			csum_complete_sw:1;
+	/* 3/5 bit hole (depending on ndisc_nodetype presence) */
 	kmemcheck_bitfield_end(flags2);
 
 #if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL

net/core/datagram.c

diff --git a/net/core/datagram.c b/net/core/datagram.c
index a16ed7b..6b1c04c 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -739,11 +739,15 @@
 	__sum16 sum;
 
 	sum = csum_fold(skb_checksum(skb, 0, len, skb->csum));
-	if (likely(!sum)) {
-		if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
-			netdev_rx_csum_fault(skb->dev);
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
-	}
+	if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) && !sum &&
+	    !skb->csum_complete_sw)
+		netdev_rx_csum_fault(skb->dev);
+
+	/* Save checksum complete for later use */
+	skb->csum = sum;
+	skb->ip_summed = CHECKSUM_COMPLETE;
+	skb->csum_complete_sw = 1;
+
 	return sum;
 }
 EXPORT_SYMBOL(__skb_checksum_complete_head);

net/ipv4/gre_offload.c

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 24deb39..eb92deb 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -131,10 +131,12 @@
 		csum_partial(skb->data, skb_gro_offset(skb), 0));
 	sum = csum_fold(NAPI_GRO_CB(skb)->csum);
 	if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE)) {
-		if (unlikely(!sum))
+		if (unlikely(!sum) && !skb->csum_complete_sw)
 			netdev_rx_csum_fault(skb->dev);
-	} else
+	} else {
 		skb->ip_summed = CHECKSUM_COMPLETE;
+		skb->csum_complete_sw = 1;
+	}
 
 	return sum;
 }

net/sunrpc/socklib.c

diff --git a/net/sunrpc/socklib.c b/net/sunrpc/socklib.c
index 0a648c5..2df87f7 100644
--- a/net/sunrpc/socklib.c
+++ b/net/sunrpc/socklib.c
@@ -173,7 +173,8 @@
 		return -1;
 	if (csum_fold(desc.csum))
 		return -1;
-	if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))
+	if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE) &&
+	    !skb->csum_complete_sw)
 		netdev_rx_csum_fault(skb->dev);
 	return 0;
 no_checksum: