Re: [PATCH v4 1/2] ethdev: add random item support

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 12/14/2023 1:43 PM, Michael Baum wrote:
> 
> On 12/14/2023 2:18 PM, Ferruh Yigit wrote: 
>>
>> On 12/14/2023 10:58 AM, Michael Baum wrote:
>>> Add support for a new item type "RTE_FLOW_ITEM_TYPE_RANDOM".
>>> This item enables to match on some random value as a part of flow rule.
>>>
> 
> ...
> 
>>>
>>> +Item: ``RANDOM``
>>> +^^^^^^^^^^^^^^^^
>>> +
>>> +Matches a random value.
>>> +
>>> +A random unsigned integer (at most 32-bit) is generated for each
>>> +packet during flow rule processing, by either HW, SW or some external source.
>>> +Application can match on either exact value or range of values.
>>> +This value is not based on the packet data/headers.
>>> +Application shouldn't assume that this value is kept during the
>>> +lifetime of the packet.
>>> +
>>> +- ``value``: Specific value to match.
>>> +
>>
>>
>> Hi Michael,
>>
>> What is the usecase for the 'random' flow item?
> I can think about 2 different use cases:
> 1. Sampling - when application wants to sample certain percentage of the flow, it can match random value for getting it.
> 2. Distribution - when application wants to distribute the traffic between ports/queues, it can match all random value range with send to port/queue actions.
> 
>>
>> Is it to match some kind of metadata generated by HW?
> It can be generated by either HW, SW or some external source.
> Each PMD supporting random item responds to have a generator for that.
> 
>> Or is it a way to sampling traffic?
> It can be both. The PMD can use random value generated by HW while user match on it for sampling traffic.
> 
>>
>> And how random 'random' item is, is it configured/set in HW or random per packet?
> From API perspective, it is pure random not packet oriented. Same packet can get different values during the pipeline.
> I mentioned it in documentation:
> "This value is not based on the packet data/headers.
> Application shouldn't assume that this value is kept during the lifetime of the packet."
>

Thanks Michael, for clarification.

I was thinking if this can be used together with external (to DPDK) flow
steering configuration.
Like external tool can set values to match for specific pattern,
tcp --> 100
udp --> 200
Later these values can be used by DPDK application and this filtering item.

Can you please confirm this is not the "use case"/intention, if so we
may need to rename the rte flow item.


Also there will be driver implementation in this release, right?