netdev - Re: [PATCH v2] geneve: remove use of internal IP header when calling IP_ECN

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Date:	Fri, 18 Sep 2015 19:19:47 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	"John W. Linville" <linville@...driver.com>
Cc:	netdev <netdev@...r.kernel.org>, David Miller <davem@...emloft.net>
Subject: Re: [PATCH v2] geneve: remove use of internal IP header when calling IP_ECN_decapsulate

On Fri, Sep 18, 2015 at 6:36 PM, John W. Linville
<linville@...driver.com> wrote:
> On Fri, Sep 18, 2015 at 02:49:30PM -0700, Jesse Gross wrote:
>> On Fri, Sep 18, 2015 at 1:40 PM, John W. Linville
>> <linville@...driver.com> wrote:
>> > On Fri, Sep 18, 2015 at 01:30:36PM -0700, Jesse Gross wrote:
>> >> On Thu, Sep 17, 2015 at 1:34 PM, John W. Linville
>> >> <linville@...driver.com> wrote:
>> >> > This seems to have been a "thinko".  IP_ECN_decapsulate needs info
>> >> > from both internal and external headers.
>> >> >
>> >> > Signed-off-by: John W. Linville <linville@...driver.com>
>> >>
>> >> This looks good to me although I realized that the transmit path is
>> >> also conditional based on !collect_md metadata. I suppose that means
>> >> that this difference is intentional and I guess I could see arguments
>> >> either way but I still think it is better to be consistent across
>> >> different code paths in this respect.
>> >
>> > I'm happy with the v2 patch if you are. :-)
>>
>> I'm happy with this part of the code path after this patch. However,
>> my concern was that this patch, while correct, will make receive
>> inconsistent with transmit. Presumably we should update the transmit
>> side as well.
>
> Oh, sorry -- I missed your point.  You mean something like this?
>
> @@ -812,19 +815,16 @@ static netdev_tx_t geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev)
>                 if (unlikely(err))
>                         goto err;
>
> -               tos = key->tos;
> +               tos = ip_tunnel_ecn_encap(key->tos, iip, skb);
>                 ttl = key->ttl;
>                 df = key->tun_flags & TUNNEL_DONT_FRAGMENT ? htons(IP_DF) : 0;
>
> Am I understanding now?

Yes, essentially though I think that 'iip' is only defined in the
latter half of the if statement and it might be nice to have the ECN
encapsulation called only once before udp_tunnel_xmit_skb() rather
than independently in each code path.
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