3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <f...@strlen.de>

[ Upstream commit 6d39d589bb76ee8a1c6cde6822006ae0053decff ]

In case of tcp, gso_size contains the tcpmss.

For UFO (udp fragmentation offloading) skbs, gso_size is the fragment
payload size, i.e. we must not account for udp header size.

Otherwise, when using virtio drivers, a to-be-forwarded UFO GSO packet
will be needlessly fragmented in the forward path, because we think its
individual segments are too large for the outgoing link.

Fixes: fe6cc55f3a9a053 ("net: ip, ipv6: handle gso skbs in forwarding path")
Cc: Eric Dumazet <eric.duma...@gmail.com>
Reported-by: Tobias Brunner <tob...@strongswan.org>
Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/core/skbuff.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3951,12 +3951,14 @@ EXPORT_SYMBOL_GPL(skb_scrub_packet);
 unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
 {
        const struct skb_shared_info *shinfo = skb_shinfo(skb);
-       unsigned int hdr_len;
 
        if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
-               hdr_len = tcp_hdrlen(skb);
-       else
-               hdr_len = sizeof(struct udphdr);
-       return hdr_len + shinfo->gso_size;
+               return tcp_hdrlen(skb) + shinfo->gso_size;
+
+       /* UFO sets gso_size to the size of the fragmentation
+        * payload, i.e. the size of the L4 (UDP) header is already
+        * accounted for.
+        */
+       return shinfo->gso_size;
 }
 EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);


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