Re: [PATCH v3 0/3] enhance TX checksum command and csum forwarding engine

Hi Jijiang,

On 01/21/2015 09:01 AM, Liu, Jijiang wrote:

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I still don't understand why you are so eager to 'forbid' it.
Yes we support it for FVL, but no one forces you to use it.

Well, how would you describe this 2 ways of doing the same thing in the
offload API? Would you talk about the i40e registers? It's not because i40e
has 2 ways to do the same operation that the DPDK should do the same.

How will you explain to a user how to choose between these 2 cases?

Talk about B method in http://dpdk.org/ml/archives/dev/2014-December/009213.html again.

DPDK Never supports a  NIC that can recognize tunneling packet for TX side before 1.8, right?

When you say "recognize tunnel", if you mean offlading checksum of
tunnel headers, I agree.

If you mean recognizing a tunnel packet in rx, I also agree
it's new to dpdk-1.8, but I think it's unrelated to what we
are talking about, which is tx checksum. A DPDK application
is able to generate tunnel packets by itself and offload the
checksums to the NIC.

So when we need to support TX checksum offload for tunneling packet,  and we have to choose B.2.

I don't see why we should choose either B.1 or B.2 (I guess you want
to say B.1 here, right?).

The m->lX_len are not filled in rx today. If one day they are, it won't
prevent the application to configure the lX_len fields and offload
flags according to the API.

After introducing i40e(FVL),  FVL is able to recognize tunneling packet and  support outer IP, or inner IP or outer IP and inner IP TX checksum for tunneling packet.
And you agree on "outer and inner at the same time", why do you object "only inner"?

Actually, B.2 method is a software workaround using L2 length when NIC can't recognize tunneling packet.
When NIC is able to recognize tunneling packet, I think you shouldn't take B.2 as a standard to 'forbid' other method.

Again, I'm not sure there is a link between "recognizing tunneling
packets" and tx checksum offload of tunnels.

Regards,
Olivier