Re: [PATCH v3] ethdev: deprecate header fields and metadata flow actions

[Thomas Monjalon <thomas@monjalon.net>]

25/11/2021 12:53, Ferruh Yigit:
> On 11/24/2021 3:37 PM, Viacheslav Ovsiienko wrote:
> > The generic RTE_FLOW_ACTION_TYPE_MODIFY_FIELD action was
> > introduced by [1]. This action provides an unified way
> > to perform various arithmetic and transfer operations over
> > packet network header fields and packet metadata.
> > 
> > [1] commit 641dbe4fb053 ("net/mlx5: support modify field flow action")
> > 
> > On other side there are a bunch of multiple legacy actions,
> > that can be superseded by the generic modify field action:
> > 
> > RTE_FLOW_ACTION_TYPE_OF_SET_MPLS_TTL
> > RTE_FLOW_ACTION_TYPE_OF_DEC_MPLS_TTL
> > RTE_FLOW_ACTION_TYPE_OF_SET_NW_TTL
> > RTE_FLOW_ACTION_TYPE_OF_DEC_NW_TTL      sfc
> > RTE_FLOW_ACTION_TYPE_OF_COPY_TTL_OUT
> > RTE_FLOW_ACTION_TYPE_OF_COPY_TTL_IN
> > RTE_FLOW_ACTION_TYPE_SET_IPV4_SRC       bnxt, cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_SET_IPV4_DST       bnxt, cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_SET_IPV6_SRC       cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_SET_IPV6_DST       cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_SET_TP_SRC         cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_SET_TP_DST         cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_DEC_TTL            mlx5, sfc
> > RTE_FLOW_ACTION_TYPE_SET_TTL            mlx5
> > RTE_FLOW_ACTION_TYPE_SET_MAC_SRC        cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_SET_MAC_DST        cxgbe, mlx5
> > RTE_FLOW_ACTION_TYPE_INC_TCP_SEQ        mlx5
> > RTE_FLOW_ACTION_TYPE_DEC_TCP_SEQ        mlx5
> > RTE_FLOW_ACTION_TYPE_INC_TCP_ACK        mlx5
> > RTE_FLOW_ACTION_TYPE_DEC_TCP_ACK        mlx5
> > RTE_FLOW_ACTION_TYPE_SET_IPV4_DSCP      mlx5
> > RTE_FLOW_ACTION_TYPE_SET_IPV6_DSCP      mlx5
> > RTE_FLOW_ACTION_TYPE_OF_SET_VLAN_VID    bnxt, cnxk, cxgbe, enic,
> >                                          mlx5, octeontx2, sfc
> > RTE_FLOW_ACTION_TYPE_OF_SET_VLAN_PCP    bnxt, cnxk, cxgbe, enic,
> >                                          mlx5, octeontx2, sfc
> > RTE_FLOW_ACTION_TYPE_SET_TAG            mlx5
> > RTE_FLOW_ACTION_TYPE_SET_META           mlx5
> > 
> > This note deprecates the following RTE Flow actions:
> > 1. As not supported by any of PMDs:
> > 
> > RTE_FLOW_ACTION_TYPE_OF_SET_MPLS_TTL
> > RTE_FLOW_ACTION_TYPE_OF_DEC_MPLS_TTL
> > RTE_FLOW_ACTION_TYPE_OF_SET_NW_TTL
> > RTE_FLOW_ACTION_TYPE_OF_COPY_TTL_OUT
> > RTE_FLOW_ACTION_TYPE_OF_COPY_TTL_IN
> > 
> > 2. As supposed to be replaced by generig field modify action:
> > RTE_FLOW_ACTION_TYPE_OF_DEC_NW_TTL
> > RTE_FLOW_ACTION_TYPE_SET_IPV4_SRC
> > RTE_FLOW_ACTION_TYPE_SET_IPV4_DST
> > RTE_FLOW_ACTION_TYPE_SET_IPV6_SRC
> > RTE_FLOW_ACTION_TYPE_SET_IPV6_DST
> > RTE_FLOW_ACTION_TYPE_SET_TP_SRC
> > RTE_FLOW_ACTION_TYPE_SET_TP_DST
> > RTE_FLOW_ACTION_TYPE_DEC_TTL
> > RTE_FLOW_ACTION_TYPE_SET_TTL
> > RTE_FLOW_ACTION_TYPE_SET_MAC_SRC
> > RTE_FLOW_ACTION_TYPE_SET_MAC_DST
> > RTE_FLOW_ACTION_TYPE_INC_TCP_SEQ
> > RTE_FLOW_ACTION_TYPE_DEC_TCP_SEQ
> > RTE_FLOW_ACTION_TYPE_INC_TCP_ACK
> > RTE_FLOW_ACTION_TYPE_DEC_TCP_ACK
> > RTE_FLOW_ACTION_TYPE_SET_IPV4_DSCP
> > RTE_FLOW_ACTION_TYPE_SET_IPV6_DSCP
> > RTE_FLOW_ACTION_TYPE_SET_TAG
> > RTE_FLOW_ACTION_TYPE_SET_META
> > 
> > The VLAN set actions are interrelated to VLAN header insertion/removal
> > and supported by multiple PMDs and supposed to be just deprecated but
> > not be removed in 22.11.
> > 
> 
> Why not remove them for v22.11? Do you think PMDs can't change the
> existing implementation until 22.11?
> 
> > Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
> > 
> > --
> > v2  - deprecation.rst is updated
> > v3  - doc comments addressed
> >      - commit message comments addressed
> >      - SET_VLAN_VID and SET_VLAN_PCP actions deprecated, but will not
> >        be removed in 22.11
> 
> Deprecated symbols are to prevent new code using them, but for this case
> there is no alternative, since PMDs still don't support
> 'RTE_FLOW_ACTION_TYPE_MODIFY_FIELD' yet.

This patch is not preventing new code using old actions,
there are just comments to point to the new direction.

> This patch is forcing users to use deprecated actions (except from mlx).

I don't get it.
It is encouraging to use the new generic action,
which is supported only by mlx5 for now.


> What about a slight change:
> 1- In this release, update header/document as 'RTE_FLOW_ACTION_TYPE_MODIFY_FIELD'
>     is preferred way if supported. Instead of deprecating old ones.

Deprecation is just a comment, clearly showing that it may be removed in future.
In my opinion, it makes the message simple and clear.


> 2- Have an agreement with PMD maintainers to switch to new action before v22.11,
>     and don't accept old action implementation in PMDs anymore.
>     Based on agreement update 'deprecation.rst' in this release to note that
>     old actions will be removed on v22.11.
>     (It would be good to have a check to prevent old actions merged during that time.)

Not sure I get it.
You want to remove VLAN actions? I think it is premature.

> 3- In v22.11, remove old actions, the PMDs that don't support MODIFY_FIELD
>     action will lose the feature.

The VLAN actions are probably already used a lot in the field.
I would consider removing them only if it becomes a burden to maintain.