netdev - Re: [PATCH net] net: Clear local_df only if crossing namespace.

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Message-ID: <52FB3FC1.8080603@6wind.com>
Date:	Wed, 12 Feb 2014 10:32:49 +0100
From:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:	Pravin Shelar <pshelar@...ira.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"Templin, Fred L" <Fred.L.Templin@...ing.com>,
	Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: [PATCH net] net: Clear local_df only if crossing namespace.

Le 12/02/2014 05:26, Pravin Shelar a écrit :
> On Mon, Feb 10, 2014 at 6:11 PM, Hannes Frederic Sowa
> <hannes@...essinduktion.org> wrote:
>> On Mon, Feb 10, 2014 at 01:00:14PM -0800, Pravin Shelar wrote:
>>> On Fri, Feb 7, 2014 at 4:58 PM, Hannes Frederic Sowa
>>> <hannes@...essinduktion.org> wrote:
>>>> May I know because of wich vport, vxlan or gre, you did this change?
>>>>
>>> It affects both gre and vxlan.
>>
>> Ok, thanks.
>>
>>>> I am feeling a bit uncomfortable handling remote and local packets that
>>>> differently on lower tunnel output (local_df is mostly set on locally
>>>> originating packets).
>>>
>>> For ip traffic it make sense to turn on local_df only for local
>>> traffic, since for remote case we can send icmp (frag-needed) back to
>>> source. No such thing exist for OVS tunnels. ICMP packet are not
>>> returned to source for the tunnels. That is why to be on safe side,
>>> local_df is turned on for tunnels in OVS.
>>
>> I have a proposal:
>>
>> I don't like it that much because of the many arguments. But I currently
>> don't see another easy solution. Maybe we should make bool xnet an enum and
>> test with bitops?
>>
>> I left the clearing of local_df in skb_scrub_packet as we need it for the
>> dev_forward_skb case and it should be done that in any case.
>>
>> This diff is slightly compile tested. ;)
>>
>> I can test and make proper submit if you agree.
>>
>> What do you think?
>>
>
> I am not sure why the caller can not just set skb->local_df before
> calling iptunnel_xmit() rather than passing extra arg to this
> function?
> There are not that many caller of this function.
The benefit is that it ensures that future callers will think about this point
;-)

Steffen is reworking vti code and will use skb_scrub_packet(), I CC'ed him in
case he has some comment about this change.


Regards,
Nicolas
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