[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, 42 insertions, 32 deletions

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 3413fc22ce4a..733371689795 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -120,8 +120,9 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
         struct ipv6_pinfo *np = inet6_sk(sk);
         struct inet_sock *inet = inet_sk(sk);
         struct sk_buff *skb;
-        size_t copied;
-        int err, copy_only, is_udplite = IS_UDPLITE(sk);
+        unsigned int ulen, copied;
+        int err;
+        int is_udplite = IS_UDPLITE(sk);
 
         if (addr_len)
                 *addr_len=sizeof(struct sockaddr_in6);
@@ -134,24 +135,25 @@ 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.
+         * 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 {
@@ -194,7 +196,7 @@ try_again:
 
         err = copied;
         if (flags & MSG_TRUNC)
-                err = skb->len - sizeof(struct udphdr);
+                err = ulen;
 
 out_free:
         skb_free_datagram(sk, skb);
@@ -368,9 +370,20 @@ out:
         return 0;
 }
 
-static inline int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh)
-
+static inline int udp6_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) {
                 /* RFC 2460 section 8.1 says that we SHOULD log
                    this error. Well, it is reasonable.
@@ -380,20 +393,19 @@ static inline int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh)
         }
         if (skb->ip_summed == CHECKSUM_COMPLETE &&
             !csum_ipv6_magic(&skb->nh.ipv6h->saddr, &skb->nh.ipv6h->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_unfold(csum_ipv6_magic(&skb->nh.ipv6h->saddr,
                                                          &skb->nh.ipv6h->daddr,
-                                                         skb->len, IPPROTO_UDP,
-                                                         0));
+                                                         skb->len, proto, 0));
 
-        return (UDP_SKB_CB(skb)->partial_cov = 0);
+        return 0;
 }
 
 int __udp6_lib_rcv(struct sk_buff **pskb, struct hlist_head udptable[],
-                   int is_udplite)
+                   int proto)
 {
         struct sk_buff *skb = *pskb;
         struct sock *sk;
@@ -413,7 +425,8 @@ int __udp6_lib_rcv(struct sk_buff **pskb, struct hlist_head udptable[],
         if (ulen > skb->len)
                 goto short_packet;
 
-        if(! is_udplite ) {             /* UDP validates ulen. */
+        if (proto == IPPROTO_UDP) {
+                /* UDP validates ulen. */
 
                 /* Check for jumbo payload */
                 if (ulen == 0)
@@ -429,15 +442,11 @@ int __udp6_lib_rcv(struct sk_buff **pskb, struct hlist_head udptable[],
                         daddr = &skb->nh.ipv6h->daddr;
                         uh = skb->h.uh;
                 }
-
-                if (udp6_csum_init(skb, uh))
-                        goto discard;
-
-        } else  {                       /* UDP-Lite validates cscov. */
-                if (udplite6_csum_init(skb, uh))
-                        goto discard;
         }
 
+        if (udp6_csum_init(skb, uh, proto))
+                goto discard;
+
         /*
          *      Multicast receive code
          */
@@ -459,7 +468,7 @@ int __udp6_lib_rcv(struct sk_buff **pskb, struct hlist_head udptable[],
 
                 if (udp_lib_checksum_complete(skb))
                         goto discard;
-                UDP6_INC_STATS_BH(UDP_MIB_NOPORTS, is_udplite);
+                UDP6_INC_STATS_BH(UDP_MIB_NOPORTS, proto == IPPROTO_UDPLITE);
 
                 icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0, dev);
 
@@ -475,17 +484,18 @@ int __udp6_lib_rcv(struct sk_buff **pskb, struct hlist_head udptable[],
 
 short_packet:
         LIMIT_NETDEBUG(KERN_DEBUG "UDP%sv6: short packet: %d/%u\n",
-                       is_udplite? "-Lite" : "",  ulen, skb->len);
+                       proto == IPPROTO_UDPLITE ? "-Lite" : "",
+                       ulen, skb->len);
 
 discard:
-        UDP6_INC_STATS_BH(UDP_MIB_INERRORS, is_udplite);
+        UDP6_INC_STATS_BH(UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
         kfree_skb(skb);
         return(0);
 }
 
 static __inline__ int udpv6_rcv(struct sk_buff **pskb)
 {
-        return __udp6_lib_rcv(pskb, udp_hash, 0);
+        return __udp6_lib_rcv(pskb, udp_hash, IPPROTO_UDP);
 }
 
 /*