netdev - [PATCH v2 net-next] inet: fix a UFO regression

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Date:	Thu, 07 Nov 2013 18:32:06 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: [PATCH v2 net-next] inet: fix a UFO regression

From: Eric Dumazet <edumazet@...gle.com>

While testing virtio_net and skb_segment() changes, Hannes reported
that UFO was sending wrong frames.

It appears this was introduced by a recent commit :
8c3a897bfab1 ("inet: restore gso for vxlan")

The old condition to perform IP frag was :

tunnel = !!skb->encapsulation;
...
        if (!tunnel && proto == IPPROTO_UDP) {

So the new one should be :

udpfrag = !skb->encapsulation && proto == IPPROTO_UDP;
...
        if (udpfrag) {

Initialization of udpfrag must be done before call
to ops->callbacks.gso_segment(skb, features), as
skb_udp_tunnel_segment() clears skb->encapsulation

(We want udpfrag to be true for UFO, false for VXLAN)

With help from Alexei Starovoitov

Reported-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
---
v2: move the udpfrag init, as spotted by Alexei.

 net/ipv4/af_inet.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 09d78d4a3cff..68af9aac91d0 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1299,6 +1299,9 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 
 	segs = ERR_PTR(-EPROTONOSUPPORT);
 
+	/* Note : following gso_segment() might change skb->encapsulation */
+	udpfrag = !skb->encapsulation && proto == IPPROTO_UDP;
+
 	ops = rcu_dereference(inet_offloads[proto]);
 	if (likely(ops && ops->callbacks.gso_segment))
 		segs = ops->callbacks.gso_segment(skb, features);
@@ -1306,7 +1309,6 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 	if (IS_ERR_OR_NULL(segs))
 		goto out;
 
-	udpfrag = !!skb->encapsulation && proto == IPPROTO_UDP;
 	skb = segs;
 	do {
 		iph = (struct iphdr *)(skb_mac_header(skb) + nhoff);


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