[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, 16 deletions

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index bf9519341fd..e671153b47b 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -248,7 +248,7 @@ try_again:
 		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
 					      copied);
 	} else if (msg->msg_flags&MSG_TRUNC) {
-		if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum)))
+		if (__skb_checksum_complete(skb))
 			goto csum_copy_err;
 		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
 					      copied);
@@ -363,13 +363,10 @@ static inline int udpv6_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
 		return -1;
 	}
 
-	if (skb->ip_summed != CHECKSUM_UNNECESSARY) {
-		if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
-			UDP6_INC_STATS_BH(UDP_MIB_INERRORS);
-			kfree_skb(skb);
-			return 0;
-		}
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
+	if (skb_checksum_complete(skb)) {
+		UDP6_INC_STATS_BH(UDP_MIB_INERRORS);
+		kfree_skb(skb);
+		return 0;
 	}
 
 	if (sock_queue_rcv_skb(sk,skb)<0) {
@@ -491,13 +488,10 @@ static int udpv6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
 		uh = skb->h.uh;
 	}
 
-	if (skb->ip_summed==CHECKSUM_HW) {
+	if (skb->ip_summed == CHECKSUM_HW &&
+	    !csum_ipv6_magic(saddr, daddr, ulen, IPPROTO_UDP, skb->csum))
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
-		if (csum_ipv6_magic(saddr, daddr, ulen, IPPROTO_UDP, skb->csum)) {
-			LIMIT_NETDEBUG(KERN_DEBUG "udp v6 hw csum failure.\n");
-			skb->ip_summed = CHECKSUM_NONE;
-		}
-	}
+
 	if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 		skb->csum = ~csum_ipv6_magic(saddr, daddr, ulen, IPPROTO_UDP, 0);
 
@@ -521,8 +515,7 @@ static int udpv6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
 		if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
 			goto discard;
 
-		if (skb->ip_summed != CHECKSUM_UNNECESSARY &&
-		    (unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum)))
+		if (skb_checksum_complete(skb))
 			goto discard;
 		UDP6_INC_STATS_BH(UDP_MIB_NOPORTS);