Re: [virtio-dev] Re: [virtio-comment] Re: [virtio-dev] Re: [virtio-comment] [PATCH v13] virtio-net: support inner header hash

[Heng Qi <hengqi@linux.alibaba.com>]

在 2023/5/5 下午10:56, Michael S. Tsirkin 写道:
> On Fri, May 05, 2023 at 09:51:15PM +0800, Heng Qi wrote:
>> On Thu, Apr 27, 2023 at 01:13:29PM -0400, Michael S. Tsirkin wrote:
>>> On Thu, Apr 27, 2023 at 10:28:29AM +0800, Heng Qi wrote:
>>>>
>>>> 在 2023/4/26 下午10:48, Michael S. Tsirkin 写道:
>>>>> On Wed, Apr 26, 2023 at 10:14:30PM +0800, Heng Qi wrote:
>>>>>> This does not mean that every device needs to implement and support all of
>>>>>> these, they can choose to support some protocols they want.
>>>>>>
>>>>>> I add these because we have scale application scenarios for modern protocols
>>>>>> VXLAN-GPE/GENEVE:
>>>>>>
>>>>>> +\item In scenarios where the same flow passing through different tunnels is expected to be received in the same queue,
>>>>>> +      warm caches, lessing locking, etc. are optimized to obtain receiving performance.
>>>>>>
>>>>>>
>>>>>> Maybe the legacy GRE, VXLAN-GPE and GENEVE? But it has a little crossover.
>>>>>>
>>>>>> Thanks.
>>>>> But VXLAN-GPE/GENEVE can use source port for entropy.
>>>>>
>>>>> 	It is recommended that the UDP source port number
>>>>> 	 be calculated using a hash of fields from the inner packet
>>>>>
>>>>> That is best because
>>>>> it allows end to end control and is protocol agnostic.
>>>> Yes. I agree with this, I don't think we have an argument on this point
>>>> right now.:)
>>>>
>>>> For VXLAN-GPE/GENEVE or other modern tunneling protocols, we have to deal
>>>> with
>>>> scenarios where the same flow passes through different tunnels.
>>>>
>>>> Having them hashed to the same rx queue, is hard to do via outer headers.
>>>>> All that is missing is symmetric Toepliz and all is well?
>>>> The scenarios above or in the commit log also require inner headers.
>>> Hmm I am not sure I get it 100%.
>>> Could you show an example with inner header hash in the port #,
>>> hash is symmetric, and you still have trouble?
>>>
>>>
>>> It kinds of sounds like not enough entropy is not the problem
>>> at this point.
>> Sorry for the late reply. :)
>>
>> For modern tunneling protocols, yes.
>>
>>> You now want to drop everything from the header
>>> except the UDP source port. Is that a fair summary?
>>>
>> For example, for the same flow passing through different VXLAN tunnels,
>> packets in this flow have the same inner header and different outer
>> headers. Sometimes these packets of the flow need to be hashed to the
>> same rxq, then we can use the inner header as the hash input.
>>
>> Thanks!
> So, they will have the same source port yes?

Yes. The outer source port can be calculated using the 5-tuple of the 
original packet,
and the outer ports are the same but the outer IPs are different after 
different directions of the same flow pass through different tunnels.

> Any way to use that

We use it in monitoring, firewall and other scenarios.

> so we don't depend on a specific protocol?

Yes, selected tunneling protocols can be used in this scenario like this.

Thanks.



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