[dpdk-dev] [PATCH v8 2/3] ethdev: tunnel offload model

[Eli Britstein]

On 3/3/2021 4:03 PM, Ivan Malov wrote:
> Hi,
>
> Could someone please also clarify the meaning (from PMD standpoint and 
> from application's standpoint) of the 64-bit field "tun_id" in 
> "rte_flow_tunnel"? The current comment reads: "Tunnel identification", 
> which is quite ambiguous, not to mention the fact that it simply 
> expands the field's name. Does this ID have anything to do with 
> VXLAN's VNI (which is 24-bit field)?

rte_flow_tunnel struct is the tunnel details communicated between the 
application and PMD when applying flows, and from the PMD to the 
application upon miss.

The fields in it are porting of the kernel's 'struct ip_tunnel_key'. See 
https://elixir.bootlin.com/linux/latest/source/include/net/ip_tunnels.h#L40

Regarding 'tun_id' - yes. In case of VXLAN tunnel it stores the VNI.

>
> As far as I can learn from the testpmd patch series, this field gets 
> printed only if it's non-zero. Hmm. A special value of sorts? Maybe 
> clarify this, too?
>
> Thank you.
>
> On 02/03/2021 12:42, Thomas Monjalon wrote:
>> 02/03/2021 10:22, Ivan Malov:
>>> Hi Gregory, Eli,
>>>
>>> On 16/10/2020 15:51, Gregory Etelson wrote:
>>>   > Applications wishing to offload tunneled traffic are required to 
>>> use
>>>   > the rte_flow primitives, such as group, meta, mark, tag, and 
>>> others to
>>>   > model their high-level objects.  The hardware model design for
>>>
>>> As far as I understand, the model is an abstraction of sorts, and the
>>> quoted lines provide examples of primitives which applications would
>>> have to use if the model did not exist.
>>>
>>> Looking at the implementation, I don't quite discern any means to let
>>> the application query PMD-specific values of "rte_flow_attr". In
>>> example, the PMD may need to enforce "transfer=1" both for the "tunnel
>>> set" rule and for "tunnel match" one. What if "group" and "priority"
>>> values also need to be implicitly controlled by the PMD for the tunnel
>>> offload rules?
>>>
>>> Have you considered adding an abstraction for "rte_flow_attr" in terms
>>> of this model?
>>>
>>>   > The first VXLAN packet that arrives matches the rule in group 0 and
>>>   > jumps to group 3.  In group 3 the packet will miss since there 
>>> is no
>>>
>>> This example considers jumping from group 0 to group 3. First of all,
>>> it's unclear whether this model intentionally lets the application
>>> choose group values freely (see my question above) or simply lacks an
>>> interface to let the application use values enforced by the PMD (if
>>> any). Secondly, given the fact that existing description of
>>> "rte_flow_attr" does not shed any light on how groups are ordered by
>>> default, when no JUMPs are configured (it only explains how priority
>>> levels are ordered within the given group but not how groups are
>>> ordered), it's unclear whether the model intentionally permits the
>>> application to jump between arbitrary groups (in example, from 0 to 3)
>>> and not necessarily between, say, 0 to 1. More to that, it's unclear
>>> whether the model lets the application jump from, say, group 0 to the
>>> very same group, 0 ("recirculation") or not. Or is the "recirculation"
>>> is in fact the main scenario in the model? Could you please 
>>> elaborate on
>>> the model's expectations of groups?
>>>
>>> Thank you.
>>
>> Given the questions, I think the discussion should be concluded
>> (when done) with a patch updating the API description.
>> Thanks for the questions and clarifications to come :)
>>
>>
>>
>