[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, 16 insertions, 26 deletions

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 651c79b..8e9628f 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -298,13 +298,10 @@ void rawv6_err(struct sock *sk, struct sk_buff *skb,
 static inline int rawv6_rcv_skb(struct sock * sk, struct sk_buff * skb)
 {
 	if ((raw6_sk(sk)->checksum || sk->sk_filter) && 
-	    skb->ip_summed != CHECKSUM_UNNECESSARY) {
-		if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
-			/* FIXME: increment a raw6 drops counter here */
-			kfree_skb(skb);
-			return 0;
-		}
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
+	    skb_checksum_complete(skb)) {
+		/* FIXME: increment a raw6 drops counter here */
+		kfree_skb(skb);
+		return 0;
 	}
 
 	/* Charge it to the socket. */
@@ -337,32 +334,25 @@ int rawv6_rcv(struct sock *sk, struct sk_buff *skb)
 	if (!rp->checksum)
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
-	if (skb->ip_summed != CHECKSUM_UNNECESSARY) {
-		if (skb->ip_summed == CHECKSUM_HW) {
-			skb_postpull_rcsum(skb, skb->nh.raw,
-			                   skb->h.raw - skb->nh.raw);
+	if (skb->ip_summed == CHECKSUM_HW) {
+		skb_postpull_rcsum(skb, skb->nh.raw,
+		                   skb->h.raw - skb->nh.raw);
+		if (!csum_ipv6_magic(&skb->nh.ipv6h->saddr,
+				     &skb->nh.ipv6h->daddr,
+				     skb->len, inet->num, skb->csum))
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
-			if (csum_ipv6_magic(&skb->nh.ipv6h->saddr,
-					    &skb->nh.ipv6h->daddr,
-					    skb->len, inet->num, skb->csum)) {
-				LIMIT_NETDEBUG(KERN_DEBUG "raw v6 hw csum failure.\n");
-				skb->ip_summed = CHECKSUM_NONE;
-			}
-		}
-		if (skb->ip_summed == CHECKSUM_NONE)
-			skb->csum = ~csum_ipv6_magic(&skb->nh.ipv6h->saddr,
-						     &skb->nh.ipv6h->daddr,
-						     skb->len, inet->num, 0);
 	}
+	if (skb->ip_summed != CHECKSUM_UNNECESSARY)
+		skb->csum = ~csum_ipv6_magic(&skb->nh.ipv6h->saddr,
+					     &skb->nh.ipv6h->daddr,
+					     skb->len, inet->num, 0);
 
 	if (inet->hdrincl) {
-		if (skb->ip_summed != CHECKSUM_UNNECESSARY &&
-		    (unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
+		if (skb_checksum_complete(skb)) {
 			/* FIXME: increment a raw6 drops counter here */
 			kfree_skb(skb);
 			return 0;
 		}
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
 
 	rawv6_rcv_skb(sk, skb);
@@ -407,7 +397,7 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 	if (skb->ip_summed==CHECKSUM_UNNECESSARY) {
 		err = skb_copy_datagram_iovec(skb, 0, 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, 0, msg->msg_iov, copied);
 	} else {