[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, 11 insertions, 7 deletions

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 802fe11efad0..49424a42a2c0 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -101,16 +101,20 @@ void netpoll_queue(struct sk_buff *skb)
 static int checksum_udp(struct sk_buff *skb, struct udphdr *uh,
                              unsigned short ulen, u32 saddr, u32 daddr)
 {
-        if (uh->check == 0)
+        unsigned int psum;
+
+        if (uh->check == 0 || skb->ip_summed == CHECKSUM_UNNECESSARY)
                 return 0;
 
-        if (skb->ip_summed == CHECKSUM_HW)
-                return csum_tcpudp_magic(
-                        saddr, daddr, ulen, IPPROTO_UDP, skb->csum);
+        psum = csum_tcpudp_nofold(saddr, daddr, ulen, IPPROTO_UDP, 0);
+
+        if (skb->ip_summed == CHECKSUM_HW &&
+            !(u16)csum_fold(csum_add(psum, skb->csum)))
+                return 0;
 
-        skb->csum = csum_tcpudp_nofold(saddr, daddr, ulen, IPPROTO_UDP, 0);
+        skb->csum = psum;
 
-        return csum_fold(skb_checksum(skb, 0, skb->len, skb->csum));
+        return __skb_checksum_complete(skb);
 }
 
 /*
@@ -489,7 +493,7 @@ int __netpoll_rx(struct sk_buff *skb)
 
         if (ulen != len)
                 goto out;
-        if (checksum_udp(skb, uh, ulen, iph->saddr, iph->daddr) < 0)
+        if (checksum_udp(skb, uh, ulen, iph->saddr, iph->daddr))
                 goto out;
         if (np->local_ip && np->local_ip != ntohl(iph->daddr))
                 goto out;