[NET]: Detect hardware rx checksum faults correctly

Here is the patch that introduces the generic skb_checksum_complete
which also checks for hardware RX checksum faults.  If that happens,
it'll call netdev_rx_csum_fault which currently prints out a stack
trace with the device name.  In future it can turn off RX checksum.

I've converted every spot under net/ that does RX checksum checks to
use skb_checksum_complete or __skb_checksum_complete with the
exceptions of:

* Those places where checksums are done bit by bit.  These will call
netdev_rx_csum_fault directly.

* The following have not been completely checked/converted:

ipmr
ip_vs
netfilter
dccp

This patch is based on patches and suggestions from Stephen Hemminger
and David S. Miller.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sunrpc/socklib.c b/net/sunrpc/socklib.c
index 8f97e90..eb330d4 100644
--- a/net/sunrpc/socklib.c
+++ b/net/sunrpc/socklib.c
@@ -6,6 +6,9 @@
  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
  */
 
+#include <linux/compiler.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
 #include <linux/types.h>
 #include <linux/pagemap.h>
 #include <linux/udp.h>
@@ -165,6 +168,8 @@
 		return -1;
 	if ((unsigned short)csum_fold(desc.csum))
 		return -1;
+	if (unlikely(skb->ip_summed == CHECKSUM_HW))
+		netdev_rx_csum_fault(skb->dev);
 	return 0;
 no_checksum:
 	if (xdr_partial_copy_from_skb(xdr, 0, &desc, skb_read_bits) < 0)
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index f16e7cd..e50e7cf 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -623,12 +623,9 @@
 		/* we can use it in-place */
 		rqstp->rq_arg.head[0].iov_base = skb->data + sizeof(struct udphdr);
 		rqstp->rq_arg.head[0].iov_len = len;
-		if (skb->ip_summed != CHECKSUM_UNNECESSARY) {
-			if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
-				skb_free_datagram(svsk->sk_sk, skb);
-				return 0;
-			}
-			skb->ip_summed = CHECKSUM_UNNECESSARY;
+		if (skb_checksum_complete(skb)) {
+			skb_free_datagram(svsk->sk_sk, skb);
+			return 0;
 		}
 		rqstp->rq_skbuff = skb;
 	}