[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 d746d3b27efb..62c0e5bd931c 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;