When xfrm is applied to TSO/GSO packets, it follows this path:
    xfrm_output() -> xfrm_output_gso() -> skb_gso_segment()
where skb_gso_segment() relies on skb->protocol to function properly.
This patch sets skb->protocol to ETH_P_IPV6 before dst_output() is called,
fixing a bug where GSO packets sent through an ipip6 tunnel are dropped
when xfrm is involved.
Cc: stable@vger.kernel.org
Signed-off-by: Eli Cooper <elicooper@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
        if (unlikely(!skb))
                return 0;
 
+       skb->protocol = htons(ETH_P_IPV6);
+
        return nf_hook(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
                       net, sk, skb, NULL, skb_dst(skb)->dev,
                       dst_output);