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Date: Mon, 10 Nov 2014 17:17:22 +0100
From: Olivier MATZ <olivier.matz@6wind.com>
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To: "Liu, Jijiang" <jijiang.liu@intel.com>
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Subject: Re: [dpdk-dev] [PATCH v8 10/10] app/testpmd:test VxLAN Tx checksum
 offload
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Hi Jijiang,

On 11/10/2014 07:03 AM, Liu, Jijiang wrote:
>> Another thing is surprising me.
>>
>> - if PKT_TX_VXLAN_CKSUM is not set (legacy use case), then the
>>    driver use l2_len and l3_len to offload inner IP/UDP/TCP checksums.
> If the flag is not set, and imply that it is not VXLAN packet, 
>  and do TX checksum offload as regular packet.
> 
>> - if PKT_TX_VXLAN_CKSUM is set, then the driver has to use
>>    inner_l{23}_len instead of l{23}_len for the same operation.
> Your understanding is not fully correct.
> The l{23}_len is still used for TX checksum offload, please refer to i40e_txd_enable_checksum()  implementation.

This fields are part of public mbuf API. You cannot say to refer to
i40e PMD code to understand how to use it.

>> Adding PKT_TX_VXLAN_CKSUM changes the semantic of l2_len and l3_len.
>> To fix this, I suggest to remove the new fields inner_l{23}_len then add
>> outer_l{23}_len instead. Therefore, the semantic of l2_len and l3_len would not
>> change, and a driver would always use the same field for a specific offload.
> Oh...

Does it mean you agree?

>> For my TSO development, I will follow the current semantic.
> For TSO, you still can use l{2,3} _len .
> When I develop tunneling TSO, I will use inner_l3_len/inner_l4_len.

I've just submitted a first version, please feel free to comment it.


Regards,
Olivier