netdev - Re: GRE with GRO very slow when forwarding starting with 3.14.24

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Message-ID: <CA+mtBx9SOr5RH7S63S28YbgxR8EwjgfS_dUkS2A4D1W3NzazHQ@mail.gmail.com>
Date:	Mon, 24 Nov 2014 10:16:26 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Wolfgang Walter <linux@...m.de>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Alexander Duyck <alexander.h.duyck@...hat.com>
Subject: Re: GRE with GRO very slow when forwarding starting with 3.14.24

On Mon, Nov 24, 2014 at 8:48 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> 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
> egress.
>
Inner mac header is probably not being set in GRO->GSO GRE path.
Please try this also:

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index bb5947b..51973dd 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -247,6 +247,9 @@ static int gre_gro_complete(struct sk_buff *skb, int nhoff)
                err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);

        rcu_read_unlock();
+
+       skb_set_inner_mac_header(skb, nhoff + grehlen);
+
        return err;
 }


> Can you try to revert :
>
> commit abe640984aa492652232b65d3579361cf6d461f5
> Author: Tom Herbert <therbert@...gle.com>
> 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 <therbert@...gle.com>
>     Acked-by: Alexander Duyck <alexander.h.duyck@...hat.com>
>     Signed-off-by: David S. Miller <davem@...emloft.net>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> 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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