netdev - Re: [PATCH net-next v2 1/2] ip_gre: allow CSUM capable devices to handle packets

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Date:	Tue, 19 Feb 2013 15:03:45 -0800
From:	pravin <pravin.shelar@...il.com>
To:	Dmitry Kravkov <dmitry@...adcom.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v2 1/2] ip_gre: allow CSUM capable devices to
 handle packets

On Tue, Feb 19, 2013 at 11:20 AM, Dmitry Kravkov <dmitry@...adcom.com> wrote:
>
>> -----Original Message-----
>> From: pravin [mailto:pravin.shelar@...il.com]
>> Sent: Tuesday, February 19, 2013 8:28 PM
>> To: Dmitry Kravkov
>> Cc: davem@...emloft.net; netdev@...r.kernel.org
>> Subject: Re: [PATCH net-next v2 1/2] ip_gre: allow CSUM capable devices to
>> handle packets
>>
>> On Mon, Feb 18, 2013 at 11:50 AM, Dmitry Kravkov <dmitry@...adcom.com>
>> wrote:
>> > If device is not able to handle checksumming it will
>> > be handled in dev_xmit
>> >
>> > Signed-off-by: Dmitry Kravkov <dmitry@...adcom.com>
>> > ---
>> > Changes from v1: fixed email address
>> >
>> >  net/ipv4/ip_gre.c |    7 ++-----
>> >  1 files changed, 2 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
>> > index a56f118..cdc31ac 100644
>> > --- a/net/ipv4/ip_gre.c
>> > +++ b/net/ipv4/ip_gre.c
>> > @@ -745,12 +745,9 @@ static struct sk_buff *handle_offloads(struct sk_buff
>> *skb)
>> >                         goto error;
>> >                 skb_shinfo(skb)->gso_type |= SKB_GSO_GRE;
>> >                 return skb;
>> > -       } else if (skb->ip_summed == CHECKSUM_PARTIAL) {
>> > -               err = skb_checksum_help(skb);
>> > -               if (unlikely(err))
>> > -                       goto error;
>> >         }
>> > -       skb->ip_summed = CHECKSUM_NONE;
>> > +       if (skb->ip_summed != CHECKSUM_PARTIAL)
>> > +               skb->ip_summed = CHECKSUM_NONE;
>> >
>> >         return skb;
>> >
>> > --
>> > 1.7.7.2
>> >
>> >
>>
>> This patch breaks GRE tunnel with GRE_CSUM. since GRE_CSUM need
>> complete IP packet to checksum entire GRE payload.
>
> Testing for o_flags&GRE_CSUM does not look too hurt here, since it will be used in ipgre_tunnel_xmit() later on
> This is the only problematic case, right?
>

It does not work for me. I have GRE device with csum on. Ping works
fine but Netperf is not working.
Looking at code, I am not sure how tcp will work if inner packet TCP
checksum is calculated after GRE_CSUM calculation.

Thanks,
Pravin.
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