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

[Ivan Malov <Ivan.Malov@oktetlabs.ru>]

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.

-- 
Ivan M