[dpdk-dev] [PATCH] doc: clarify implicit filtering in transfer rules

[Ori Kam]

Hi Andrew,

PSB

Thanks,
Ori

> -----Original Message-----
> From: dev <dev-bounces at dpdk.org> On Behalf Of Andrew Rybchenko
> Sent: Wednesday, September 1, 2021 6:11 PM
> 
> As per existing documentation, attribute "transfer", quote, "complements
> the behavior of some pattern items such as
> RTE_FLOW_ITEM_TYPE_PHY_PORT and is meaningless without them". That
> effectively confronts the idea of implicit filtering imposed by port_id
> argument passed by flow create API.
> 
> This bit of documentation is vague, and having no implicit filtering is
> unfriendly to applications which insert flow rules on specific ports based on
> the source port IDs of the (not offloaded) incoming packets.
> 
> In order to address the problem, document the existence of the implicit
> filtering. Use the term "weak" for this filtering as it implies the possibility to
> override it by including explicit traffic source criteria in the flow pattern
> (PORT_ID, PHY_PORT and the likes).
> 
> Signed-off-by: Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>
> ---
> The topic was briefly discussed in mail thread [1].
> 
> I'm not sure if the patch should have "Fixes:" tag. If it is really behaviour
> intended from the very beginning, it should be backported and
> corresponding fixes in drivers should be backported as well.
> 
> [1] https://patches.dpdk.org/project/dpdk/patch/20210601111420.5549-1-
> ivan.malov at oktetlabs.ru/
> 
>  doc/guides/prog_guide/rte_flow.rst   | 17 ++++++++++++++---
>  doc/guides/rel_notes/deprecation.rst |  5 -----
>  2 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/rte_flow.rst
> b/doc/guides/prog_guide/rte_flow.rst
> index 2b42d5ec8c..af54939418 100644
> --- a/doc/guides/prog_guide/rte_flow.rst
> +++ b/doc/guides/prog_guide/rte_flow.rst
> @@ -171,13 +171,24 @@ When supported, this effectively enables an
> application to reroute traffic  not necessarily intended for it (e.g. coming from
> or addressed to different  physical ports, VFs or applications) at the device
> level.
> 
> -It complements the behavior of some pattern items such as `Item:
> PHY_PORT`_ -and is meaningless without them.
> -
>  When transferring flow rules, **ingress** and **egress** attributes
>  (`Attribute: Traffic direction`_) keep their original meaning, as if  processing
> traffic emitted or received by the application.

I know this is original code but what do we mean application?
You assume that the application is the switch?
Or the application is some DPDK application running on the PF?

> 
> +DPDK port used to create transfer rule is important since it implicitly
> +adds filtering by it (similar to `Item: PORT_ID` with ``spec.id`` equal
> +to the port ID and exact match mask) if no other items which specify
> +source are present in the rule pattern (e.g. `Item: PHY_PORT`, `Item:
> +VF` or explicit `Item: PORT_ID`). It means that by default ingress
> +rules apply to traffic which comes from associated upstream switch
> +port, i.e. physical network port for PF DPDK port, VF for VF
> +representor. Egress rules transfer traffic transmitted via
> +corresponding DPDK port, i.e. PF DPDK port or VF representor itself.
> +
To make sure I understand the direction should be defined as follows:
Traffic from  ---> to
Wire --> VF ==> ingress direction.
VF  --> Wire ==> ingress direction.
VF1 --> VF2 ==> ingress direction.
VF 1--> VF2 representor ==> ingress.
VF representor --> wire ==> egress.
VF representor --> VF ==> egress



> +It is still possible to apply transfer rule on a traffic originating
> +from any switch port using wildcard mask in corresponding pattern item
> +if underlying PMD supports it.
> +
>  Pattern item
>  ~~~~~~~~~~~~
> 
> diff --git a/doc/guides/rel_notes/deprecation.rst
> b/doc/guides/rel_notes/deprecation.rst
> index 76a4abfd6b..f1d290a911 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -134,11 +134,6 @@ Deprecation Notices
>    traffic direction to the represented entity or ethdev port itself
>    in DPDK 21.11.
> 
> -* ethdev: Flow API documentation is unclear if ethdev port used to create
> -  a flow rule adds any implicit match criteria in the case of transfer rules.
> -  The semantics will be clarified in DPDK 21.11 and it will require fixes in
> -  drivers and applications which interpret it in a different way.
> -
>  * ethdev: The flow API matching pattern structures, ``struct
> rte_flow_item_*``,
>    should start with relevant protocol header.
>    Some matching pattern structures implements this by duplicating protocol
> header
> --
> 2.30.2