[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, 15 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 634dabb558fd..ac1fcf5b4ebc 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1110,24 +1110,18 @@ static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
 static int tcp_v4_checksum_init(struct sk_buff *skb)
 {
         if (skb->ip_summed == CHECKSUM_HW) {
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
                 if (!tcp_v4_check(skb->h.th, skb->len, skb->nh.iph->saddr,
-                                  skb->nh.iph->daddr, skb->csum))
+                                  skb->nh.iph->daddr, skb->csum)) {
+                        skb->ip_summed = CHECKSUM_UNNECESSARY;
                         return 0;
-
-                LIMIT_NETDEBUG(KERN_DEBUG "hw tcp v4 csum failed\n");
-                skb->ip_summed = CHECKSUM_NONE;
+                }
         }
+
+        skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr, skb->nh.iph->daddr,
+                                       skb->len, IPPROTO_TCP, 0);
+
         if (skb->len <= 76) {
-                if (tcp_v4_check(skb->h.th, skb->len, skb->nh.iph->saddr,
-                                 skb->nh.iph->daddr,
-                                 skb_checksum(skb, 0, skb->len, 0)))
-                        return -1;
-                skb->ip_summed = CHECKSUM_UNNECESSARY;
-        } else {
-                skb->csum = ~tcp_v4_check(skb->h.th, skb->len,
-                                          skb->nh.iph->saddr,
-                                          skb->nh.iph->daddr, 0);
+                return __skb_checksum_complete(skb);
         }
         return 0;
 }
@@ -1219,7 +1213,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
          * provided case of th->doff==0 is elimineted.
          * So, we defer the checks. */
         if ((skb->ip_summed != CHECKSUM_UNNECESSARY &&
-             tcp_v4_checksum_init(skb) < 0))
+             tcp_v4_checksum_init(skb)))
                 goto bad_packet;
 
         th = skb->h.th;