netdev - Re: [PATCH net-next V2 1/3] net: Add GRO support for UDP encapsulating protocols

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Message-ID: <52CD4151.9050100@mellanox.com>
Date:	Wed, 8 Jan 2014 14:15:13 +0200
From:	Or Gerlitz <ogerlitz@...lanox.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Or Gerlitz <or.gerlitz@...il.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next V2 1/3] net: Add GRO support for UDP encapsulating
 protocols

On 08/01/2014 13:58, Eric Dumazet wrote:
> On Wed, 2014-01-08 at 10:04 +0200, Or Gerlitz wrote:
>> On 07/01/2014 23:38, Eric Dumazet wrote:
>>> On Tue, 2014-01-07 at 22:37 +0200, Or Gerlitz wrote:
>>>
>>>> So here's the thing, per my understanding we want to GRO only received
>>>> **encapsulated** packets whose checksum status is != CHECKSUM_NONE
>>>> which means the NIC has some support for doing RX checksum of
>>>> encapsulated packets. Per the current convension, in that case the NIC
>>>> RX code has to set skb->encapsulation see 6a674e9c75b17 "net: Add
>>>> support for hardware-offloaded encapsulation" this convension is
>>>> implemented in the current drivers that have HW offloads for
>>>> encapsulated packets (bnx2x, i40e and mlx4)
>>> I do not think its true.
>>>
>>> Some drivers set CHECKSUM_COMPLETE even for regular UDP frames...
>>>
>>> git grep -n CHECKSUM_COMPLETE -- drivers/net
>>>
>>>
>>>
>> Eric, the point I was trying to make is that as long as the driver set a
>> value which is different from CHECKSUM_NONE
>> for an skb who carry encapsulated packet, we want skb->encapsulation to
>> be set, per the architecture dictated by the above commit.
> Then this point is obviously wrong. Your interpretation is wrong, I am very sorry.
> skb->encapsulation _might_ be set, only if the NIC is performing header
> analysis. CHECKSUM_COMPLETE support doesn't require header analysis.
>
>
>
>
fair enough && thanks for shedding more light on this - so in that 
respect, the gro handler for udp encapsulated packets will not flush skb 
who is either marked with CHECKSUM_COMPLETE or has skb->encapsulation set.

Or.

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