[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 fc620a7c1db4..86368832d481 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 b28fe1edf98b..f34fd686a8f1 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)