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Date:	Mon, 24 Nov 2014 08:48:16 -0800
From:	Eric Dumazet <>
To:	Wolfgang Walter <>
Cc:, Tom Herbert <>,
	Alexander Duyck <>
Subject: Re: GRE with GRO very slow when forwarding starting with 3.14.24

On Mon, 2014-11-24 at 17:13 +0100, Wolfgang Walter wrote:
> Hello,
> starting with 3.14.24 GRE with GRO on is very slow. To be more specific:
> yyyy <--> GRO_endpoint <-_> .... <--> |eth0<->GRO-endpoint | eth1 |<-> xxxx
> routing (IPv4) between xxxx and yyyy is very slow when GRO is enabled on eth0 
> and/or eth1 starting with stable kernel 3.14.24
> Regards,

tcpdump might help, but I presume GSO is no longer working properly on

Can you try to revert :

commit abe640984aa492652232b65d3579361cf6d461f5
Author: Tom Herbert <>
Date:   Thu Oct 30 08:40:56 2014 -0700

    gre: Use inner mac length when computing tunnel length
    [ Upstream commit 14051f0452a2c26a3f4791e6ad6a435e8f1945ff ]
    Currently, skb_inner_network_header is used but this does not account
    for Ethernet header for ETH_P_TEB. Use skb_inner_mac_header which
    handles TEB and also should work with IP encapsulation in which case
    inner mac and inner network headers are the same.
    Tested: Ran TCP_STREAM over GRE, worked as expected.
    Signed-off-by: Tom Herbert <>
    Acked-by: Alexander Duyck <>
    Signed-off-by: David S. Miller <>
    Signed-off-by: Greg Kroah-Hartman <>

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 2d24f293f977..8c8493ea6b1c 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -50,7 +50,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
        greh = (struct gre_base_hdr *)skb_transport_header(skb);
-       ghl = skb_inner_network_header(skb) - skb_transport_header(skb);
+       ghl = skb_inner_mac_header(skb) - skb_transport_header(skb);
        if (unlikely(ghl < sizeof(*greh)))
                goto out;

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