netdev - udp: Fix bogus UFO packet generation

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Message-ID: <20100615115225.GA7239@gondor.apana.org.au>
Date:	Tue, 15 Jun 2010 21:52:25 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: udp: Fix bogus UFO packet generation

Hi:

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@...dor.apana.org.au>

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 9a4a6c9..041d41d 100644
--- 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;

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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