[UDP]: Clean up UDP-Lite receive checksum

This patch eliminates some duplicate code for the verification of
receive checksums between UDP-Lite and UDP.  It does this by
introducing __skb_checksum_complete_head which is identical to
__skb_checksum_complete_head apart from the fact that it takes
a length parameter rather than computing the first skb->len bytes.

As a result UDP-Lite will be able to use hardware checksum offload
for packets which do not use partial coverage checksums.  It also
means that UDP-Lite loopback no longer does unnecessary checksum
verification.

If any NICs start support UDP-Lite this would also start working
automatically.

This patch removes the assumption that msg_flags has MSG_TRUNC clear
upon entry in recvmsg.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 4 deletions

diff --git a/include/net/udp.h b/include/net/udp.h
index 1b921fa81474..4a9699f79281 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -72,10 +72,7 @@ struct sk_buff;
  */
 static inline __sum16 __udp_lib_checksum_complete(struct sk_buff *skb)
 {
-        if (! UDP_SKB_CB(skb)->partial_cov)
-                return __skb_checksum_complete(skb);
-        return csum_fold(skb_checksum(skb, 0, UDP_SKB_CB(skb)->cscov,
-                                      skb->csum));
+        return __skb_checksum_complete_head(skb, UDP_SKB_CB(skb)->cscov);
 }
 
 static inline int udp_lib_checksum_complete(struct sk_buff *skb)