inet: fix a UFO regression

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@stressinduktion.org>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

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);