[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>

3 files changed, 8 insertions, 37 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 30089ad..df229bd 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1372,6 +1372,7 @@ static inline void __net_timestamp(struct sk_buff *skb)
 }
 
 
+extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
 extern __sum16 __skb_checksum_complete(struct sk_buff *skb);
 
 /**
diff --git a/include/net/udp.h b/include/net/udp.h
index 1b921fa..4a9699f 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)
diff --git a/include/net/udplite.h b/include/net/udplite.h
index 67ac514..d99df75 100644
--- a/include/net/udplite.h
+++ b/include/net/udplite.h
@@ -47,11 +47,10 @@ static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
 		return 1;
 	}
 
-        UDP_SKB_CB(skb)->partial_cov = 0;
 	cscov = ntohs(uh->len);
 
 	if (cscov == 0)		 /* Indicates that full coverage is required. */
-		cscov = skb->len;
+		;
 	else if (cscov < 8  || cscov > skb->len) {
 		/*
 		 * Coverage length violates RFC 3828: log and discard silently.
@@ -60,42 +59,16 @@ static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh)
 			       cscov, skb->len);
 		return 1;
 
-	} else if (cscov < skb->len)
+	} else if (cscov < skb->len) {
         	UDP_SKB_CB(skb)->partial_cov = 1;
-
-        UDP_SKB_CB(skb)->cscov = cscov;
-
-	/*
-	 * There is no known NIC manufacturer supporting UDP-Lite yet,
-	 * hence ip_summed is always (re-)set to CHECKSUM_NONE.
-	 */
-	skb->ip_summed = CHECKSUM_NONE;
+		UDP_SKB_CB(skb)->cscov = cscov;
+		if (skb->ip_summed == CHECKSUM_COMPLETE)
+			skb->ip_summed = CHECKSUM_NONE;
+        }
 
 	return 0;
 }
 
-static __inline__ int udplite4_csum_init(struct sk_buff *skb, struct udphdr *uh)
-{
-	int rc = udplite_checksum_init(skb, uh);
-
-	if (!rc)
-		skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr,
-					       skb->nh.iph->daddr,
-					       skb->len, IPPROTO_UDPLITE, 0);
-	return rc;
-}
-
-static __inline__ int udplite6_csum_init(struct sk_buff *skb, struct udphdr *uh)
-{
-	int rc = udplite_checksum_init(skb, uh);
-
-	if (!rc)
-		skb->csum = ~csum_unfold(csum_ipv6_magic(&skb->nh.ipv6h->saddr,
-					     &skb->nh.ipv6h->daddr,
-					     skb->len, IPPROTO_UDPLITE, 0));
-	return rc;
-}
-
 static inline int udplite_sender_cscov(struct udp_sock *up, struct udphdr *uh)
 {
 	int cscov = up->len;