udp: Fix bogus UFO packet generation

It has been reported that the new UFO software fallback path
fails under certain conditions with NFS.  I tracked the problem
down to the generation of UFO packets that are smaller than the
MTU.  The software fallback path simply discards these packets.

This patch fixes the problem by not generating such packets on
the UFO path.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 9a4a6c96cb0d634414691da197bf9e337fe18f81..041d41df1224eec36f214cd649467e423be5de96 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -873,8 +873,10 @@ int ip_append_data(struct sock *sk,
            !exthdrlen)
                csummode = CHECKSUM_PARTIAL;
 
+       skb = skb_peek_tail(&sk->sk_write_queue);
+
        inet->cork.length += length;
-       if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
+       if (((length > mtu) || (skb && skb_is_gso(skb))) &&
            (sk->sk_protocol == IPPROTO_UDP) &&
            (rt->u.dst.dev->features & NETIF_F_UFO)) {
                err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
@@ -892,7 +894,7 @@ int ip_append_data(struct sock *sk,
         * adding appropriate IP header.
         */
 
-       if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
+       if (!skb)
                goto alloc_new_skb;
 
        while (length > 0) {
@@ -1121,7 +1123,8 @@ ssize_t   ip_append_page(struct sock *sk, struct page *page,
                return -EINVAL;
 
        inet->cork.length += size;
-       if ((sk->sk_protocol == IPPROTO_UDP) &&
+       if ((size + skb->len > mtu) &&
+           (sk->sk_protocol == IPPROTO_UDP) &&
            (rt->u.dst.dev->features & NETIF_F_UFO)) {
                skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
                skb_shinfo(skb)->gso_type = SKB_GSO_UDP;