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

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Message-ID: <504C9EFCA2D0054393414C9CB605C37F1C019F1F@SJEXCHMB06.corp.ad.broadcom.com>
Date:	Wed, 20 Feb 2013 14:45:30 +0000
From:	"Dmitry Kravkov" <dmitry@...adcom.com>
To:	pravin <pravin.shelar@...il.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

> -----Original Message-----
> From: pravin [mailto:pravin.shelar@...il.com]
> Sent: Wednesday, February 20, 2013 1:04 AM
> 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 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.

I will test this mode also  ...

> Looking at code, I am not sure how tcp will work if inner packet TCP
> checksum is calculated after GRE_CSUM calculation.

Not sure if there is HW that supports it today

> Thanks,
> Pravin.


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