[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 bf9519341fd3..e671153b47b2 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);