[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>

1 files changed, 9 insertions, 11 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d746d3b27ef..62c0e5bd931 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1401,20 +1401,18 @@ out:
 static int tcp_v6_checksum_init(struct sk_buff *skb)
 {
 	if (skb->ip_summed == CHECKSUM_HW) {
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
 		if (!tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
-				  &skb->nh.ipv6h->daddr,skb->csum))
+				  &skb->nh.ipv6h->daddr,skb->csum)) {
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
 			return 0;
-		LIMIT_NETDEBUG(KERN_DEBUG "hw tcp v6 csum failed\n");
+		}
 	}
+
+	skb->csum = ~tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
+				  &skb->nh.ipv6h->daddr, 0);
+
 	if (skb->len <= 76) {
-		if (tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
-				 &skb->nh.ipv6h->daddr,skb_checksum(skb, 0, skb->len, 0)))
-			return -1;
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
-	} else {
-		skb->csum = ~tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
-					  &skb->nh.ipv6h->daddr,0);
+		return __skb_checksum_complete(skb);
 	}
 	return 0;
 }
@@ -1575,7 +1573,7 @@ static int tcp_v6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
 		goto discard_it;
 
 	if ((skb->ip_summed != CHECKSUM_UNNECESSARY &&
-	     tcp_v6_checksum_init(skb) < 0))
+	     tcp_v6_checksum_init(skb)))
 		goto bad_packet;
 
 	th = skb->h.th;