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

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Date:	Thu, 21 Feb 2013 15:46:02 -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 Thu, Feb 21, 2013 at 2:26 PM, Dmitry Kravkov <dmitry@...adcom.com> wrote:
> On Tue, 2013-02-19 at 15:03 -0800, pravin wrote:
>> 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.
>
>
> Fixes handling when CSUM or SEQ flags are set - via skb_checksum_help()
> ---
> Tested with each mode (separately)
>
>  net/ipv4/ip_gre.c |   14 +++++++++++---
>  1 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
> index 5ef4da7..0de54cd 100644
> --- a/net/ipv4/ip_gre.c
> +++ b/net/ipv4/ip_gre.c
> @@ -735,7 +735,8 @@ drop:
>         return 0;
>  }
>
> -static struct sk_buff *handle_offloads(struct sk_buff *skb)
> +static struct sk_buff *handle_offloads(struct ip_tunnel *tunnel,
> +                                      struct sk_buff *skb)
>  {
>         int err;
>
> @@ -745,8 +746,15 @@ static struct sk_buff *handle_offloads(struct
> sk_buff *skb)
>                         goto error;
>                 skb_shinfo(skb)->gso_type |= SKB_GSO_GRE;
>                 return skb;
> +       } else if (tunnel->parms.o_flags&(GRE_SEQ|GRE_CSUM) &&
> +                  skb->ip_summed == CHECKSUM_PARTIAL) {
> +               err = skb_checksum_help(skb);
> +               if (unlikely(err))
> +                       goto error;
>         }
> -       if (skb->ip_summed != CHECKSUM_PARTIAL)
> +
> +       if (skb->ip_summed != CHECKSUM_PARTIAL ||
> +           tunnel->parms.o_flags&(GRE_SEQ|GRE_CSUM))
>                 skb->ip_summed = CHECKSUM_NONE;
>
We can simplify this by dropping check of o_flags.

>         return skb;
> @@ -776,7 +784,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff
> *skb, struct net_device *dev
>         int    err;
>         int    pkt_len;
>
> -       skb = handle_offloads(skb);
> +       skb = handle_offloads(tunnel, skb);
>         if (IS_ERR(skb)) {
>                 dev->stats.tx_dropped++;
>                 return NETDEV_TX_OK;
> --
> 1.7.7.2
>
>
>> Thanks,
>> Pravin.
>>
>
>
>
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