[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>

2 files changed, 50 insertions, 48 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index fc620a7..8636883 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -810,7 +810,9 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 	struct inet_sock *inet = inet_sk(sk);
 	struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
 	struct sk_buff *skb;
-	int copied, err, copy_only, is_udplite = IS_UDPLITE(sk);
+	unsigned int ulen, copied;
+	int err;
+	int is_udplite = IS_UDPLITE(sk);
 
 	/*
 	 *	Check any passed addresses
@@ -826,28 +828,25 @@ try_again:
 	if (!skb)
 		goto out;
 
-	copied = skb->len - sizeof(struct udphdr);
-	if (copied > len) {
-		copied = len;
+	ulen = skb->len - sizeof(struct udphdr);
+	copied = len;
+	if (copied > ulen)
+		copied = ulen;
+	else if (copied < ulen)
 		msg->msg_flags |= MSG_TRUNC;
-	}
 
 	/*
-	 * 	Decide whether to checksum and/or copy data.
-	 *
-	 * 	UDP:      checksum may have been computed in HW,
-	 * 	          (re-)compute it if message is truncated.
-	 * 	UDP-Lite: always needs to checksum, no HW support.
+	 * If checksum is needed at all, try to do it while copying the
+	 * data.  If the data is truncated, or if we only want a partial
+	 * coverage checksum (UDP-Lite), do it before the copy.
 	 */
-	copy_only = (skb->ip_summed==CHECKSUM_UNNECESSARY);
 
-	if (is_udplite  ||  (!copy_only  &&  msg->msg_flags&MSG_TRUNC)) {
-		if (__udp_lib_checksum_complete(skb))
+	if (copied < ulen || UDP_SKB_CB(skb)->partial_cov) {
+		if (udp_lib_checksum_complete(skb))
 			goto csum_copy_err;
-		copy_only = 1;
 	}
 
-	if (copy_only)
+	if (skb->ip_summed == CHECKSUM_UNNECESSARY)
 		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
 					      msg->msg_iov, copied       );
 	else {
@@ -875,7 +874,7 @@ try_again:
 
 	err = copied;
 	if (flags & MSG_TRUNC)
-		err = skb->len - sizeof(struct udphdr);
+		err = ulen;
 
 out_free:
 	skb_free_datagram(sk, skb);
@@ -1095,10 +1094,9 @@ int udp_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
 		}
 	}
 
-	if (sk->sk_filter && skb->ip_summed != CHECKSUM_UNNECESSARY) {
-		if (__udp_lib_checksum_complete(skb))
+	if (sk->sk_filter) {
+		if (udp_lib_checksum_complete(skb))
 			goto drop;
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
 
 	if ((rc = sock_queue_rcv_skb(sk,skb)) < 0) {
@@ -1166,25 +1164,36 @@ static int __udp4_lib_mcast_deliver(struct sk_buff *skb,
  * Otherwise, csum completion requires chacksumming packet body,
  * including udp header and folding it to skb->csum.
  */
-static inline void udp4_csum_init(struct sk_buff *skb, struct udphdr *uh)
+static inline int udp4_csum_init(struct sk_buff *skb, struct udphdr *uh,
+				 int proto)
 {
+	int err;
+
+	UDP_SKB_CB(skb)->partial_cov = 0;
+	UDP_SKB_CB(skb)->cscov = skb->len;
+
+	if (proto == IPPROTO_UDPLITE) {
+		err = udplite_checksum_init(skb, uh);
+		if (err)
+			return err;
+	}
+
 	if (uh->check == 0) {
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 	} else if (skb->ip_summed == CHECKSUM_COMPLETE) {
 	       if (!csum_tcpudp_magic(skb->nh.iph->saddr, skb->nh.iph->daddr,
-				      skb->len, IPPROTO_UDP, skb->csum       ))
+				      skb->len, proto, skb->csum))
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
 	if (skb->ip_summed != CHECKSUM_UNNECESSARY)
 		skb->csum = csum_tcpudp_nofold(skb->nh.iph->saddr,
 					       skb->nh.iph->daddr,
-					       skb->len, IPPROTO_UDP, 0);
+					       skb->len, proto, 0);
 	/* Probably, we should checksum udp header (it should be in cache
 	 * in any case) and data in tiny packets (< rx copybreak).
 	 */
 
-	/* UDP = UDP-Lite with a non-partial checksum coverage */
-	UDP_SKB_CB(skb)->partial_cov = 0;
+	return 0;
 }
 
 /*
@@ -1192,7 +1201,7 @@ static inline void udp4_csum_init(struct sk_buff *skb, struct udphdr *uh)
  */
 
 int __udp4_lib_rcv(struct sk_buff *skb, struct hlist_head udptable[],
-		   int is_udplite)
+		   int proto)
 {
 	struct sock *sk;
 	struct udphdr *uh = skb->h.uh;
@@ -1211,19 +1220,16 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct hlist_head udptable[],
 	if (ulen > skb->len)
 		goto short_packet;
 
-	if(! is_udplite ) {		/* UDP validates ulen. */
-
+	if (proto == IPPROTO_UDP) {
+		/* UDP validates ulen. */
 		if (ulen < sizeof(*uh) || pskb_trim_rcsum(skb, ulen))
 			goto short_packet;
 		uh = skb->h.uh;
-
-		udp4_csum_init(skb, uh);
-
-	} else 	{			/* UDP-Lite validates cscov. */
-		if (udplite4_csum_init(skb, uh))
-			goto csum_error;
 	}
 
+	if (udp4_csum_init(skb, uh, proto))
+		goto csum_error;
+
 	if(rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
 		return __udp4_lib_mcast_deliver(skb, uh, saddr, daddr, udptable);
 
@@ -1250,7 +1256,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct hlist_head udptable[],
 	if (udp_lib_checksum_complete(skb))
 		goto csum_error;
 
-	UDP_INC_STATS_BH(UDP_MIB_NOPORTS, is_udplite);
+	UDP_INC_STATS_BH(UDP_MIB_NOPORTS, proto == IPPROTO_UDPLITE);
 	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 
 	/*
@@ -1262,7 +1268,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct hlist_head udptable[],
 
 short_packet:
 	LIMIT_NETDEBUG(KERN_DEBUG "UDP%s: short packet: From %u.%u.%u.%u:%u %d/%d to %u.%u.%u.%u:%u\n",
-		       is_udplite? "-Lite" : "",
+		       proto == IPPROTO_UDPLITE ? "-Lite" : "",
 		       NIPQUAD(saddr),
 		       ntohs(uh->source),
 		       ulen,
@@ -1277,21 +1283,21 @@ csum_error:
 	 * the network is concerned, anyway) as per 4.1.3.4 (MUST).
 	 */
 	LIMIT_NETDEBUG(KERN_DEBUG "UDP%s: bad checksum. From %d.%d.%d.%d:%d to %d.%d.%d.%d:%d ulen %d\n",
-		       is_udplite? "-Lite" : "",
+		       proto == IPPROTO_UDPLITE ? "-Lite" : "",
 		       NIPQUAD(saddr),
 		       ntohs(uh->source),
 		       NIPQUAD(daddr),
 		       ntohs(uh->dest),
 		       ulen);
 drop:
-	UDP_INC_STATS_BH(UDP_MIB_INERRORS, is_udplite);
+	UDP_INC_STATS_BH(UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
 	kfree_skb(skb);
 	return(0);
 }
 
 __inline__ int udp_rcv(struct sk_buff *skb)
 {
-	return __udp4_lib_rcv(skb, udp_hash, 0);
+	return __udp4_lib_rcv(skb, udp_hash, IPPROTO_UDP);
 }
 
 int udp_destroy_sock(struct sock *sk)
@@ -1486,15 +1492,11 @@ unsigned int udp_poll(struct file *file, struct socket *sock, poll_table *wait)
 		struct sk_buff *skb;
 
 		spin_lock_bh(&rcvq->lock);
-		while ((skb = skb_peek(rcvq)) != NULL) {
-			if (udp_lib_checksum_complete(skb)) {
-				UDP_INC_STATS_BH(UDP_MIB_INERRORS, is_lite);
-				__skb_unlink(skb, rcvq);
-				kfree_skb(skb);
-			} else {
-				skb->ip_summed = CHECKSUM_UNNECESSARY;
-				break;
-			}
+		while ((skb = skb_peek(rcvq)) != NULL &&
+		       udp_lib_checksum_complete(skb)) {
+			UDP_INC_STATS_BH(UDP_MIB_INERRORS, is_lite);
+			__skb_unlink(skb, rcvq);
+			kfree_skb(skb);
 		}
 		spin_unlock_bh(&rcvq->lock);
 
diff --git a/net/ipv4/udplite.c b/net/ipv4/udplite.c
index b28fe1e..f34fd68 100644
--- a/net/ipv4/udplite.c
+++ b/net/ipv4/udplite.c
@@ -31,7 +31,7 @@ static int udplite_v4_get_port(struct sock *sk, unsigned short snum)
 
 static int udplite_rcv(struct sk_buff *skb)
 {
-	return __udp4_lib_rcv(skb, udplite_hash, 1);
+	return __udp4_lib_rcv(skb, udplite_hash, IPPROTO_UDPLITE);
 }
 
 static void udplite_err(struct sk_buff *skb, u32 info)