[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, 10 insertions, 11 deletions

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 23e540365a14..1bdf0fb8bf8a 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -585,17 +585,16 @@ static int icmpv6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
         daddr = &skb->nh.ipv6h->daddr;
 
         /* Perform checksum. */
-        if (skb->ip_summed == CHECKSUM_HW) {
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
-                if (csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_ICMPV6,
-                                    skb->csum)) {
-                        LIMIT_NETDEBUG(KERN_DEBUG "ICMPv6 hw checksum failed\n");
-                        skb->ip_summed = CHECKSUM_NONE;
-                }
-        }
-        if (skb->ip_summed == CHECKSUM_NONE) {
-                if (csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_ICMPV6,
-                                    skb_checksum(skb, 0, skb->len, 0))) {
+        switch (skb->ip_summed) {
+        case CHECKSUM_HW:
+                if (!csum_ipv6_magic(saddr, daddr, skb->len, IPPROTO_ICMPV6,
+                                     skb->csum))
+                        break;
+                /* fall through */
+        case CHECKSUM_NONE:
+                skb->csum = ~csum_ipv6_magic(saddr, daddr, skb->len,
+                                             IPPROTO_ICMPV6, 0);
+                if (__skb_checksum_complete(skb)) {
                         LIMIT_NETDEBUG(KERN_DEBUG "ICMPv6 checksum failed [%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x > %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x]\n",
                                        NIP6(*saddr), NIP6(*daddr));
                         goto discard_it;