[dpdk-dev] [PATCH] ethdev: introduce generic copy rte flow action

[Ori Kam]

Hi Jerin,

> -----Original Message-----
> From: Jerin Jacob <jerinjacobk at gmail.com>
> Sent: Thursday, January 14, 2021 4:00 PM
> Subject: Re: [dpdk-dev] [PATCH] ethdev: introduce generic copy rte flow action
> 
> On Fri, Jan 8, 2021 at 12:02 PM Alexander Kozyrev <akozyrev at nvidia.com>
> wrote:
> >
> > Implement a generic copy flow API to allow copying of an arbitrary
> > header field (as well as mark, metadata or tag) to another item.
> >
> > This generic copy mechanism removes the necessity to implement a
> > separate RTE Flow action every time we need to modify a new packet
> > field in the future. A user-provided value can be used from a
> > specified tag/metadata or directly copied from other packet field.
> >
> > The number of bits to copy as well as the offset to start from can
> > be specified to allow a partial copy or copy into an arbitrary
> > place in a packet for greater flexibility.
> >
> > RFC:
> https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpatches.d
> pdk.org%2Fpatch%2F85384%2F&data=04%7C01%7Corika%40nvidia.com%
> 7C62ab41b9ed5948d056c308d8b894af02%7C43083d15727340c1b7db39efd9cc
> c17a%7C0%7C0%7C637462296023413253%7CUnknown%7CTWFpbGZsb3d8eyJ
> WIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C
> 1000&sdata=ovpEss3%2B7TgZRYFiDkrvuMFW52747Gno5oOIeDLwrBQ%3D
> &reserved=0
> >
> > Signed-off-by: Alexander Kozyrev <akozyrev at nvidia.com>
> > ---
> 
> >
> > +Action: ``COPY_ITEM``
> > +^^^^^^^^^^^^^^^^^^^^^
> > +
> > +Copy ``width`` bits from ``src`` item to ``dst`` item.
> > +
> > +An arbitrary header field (as well as mark, metadata or tag values)
> > +can be used as both source and destination items as set by ``item``.
> > +
> > +Inner packet header fields can be accessed using the ``index`` and
> > +it is possible to start the copy from the ``offset`` bits in an item.
> > +
> > +.. _table_rte_flow_action_copy_item:
> > +
> > +.. table:: COPY_ITEM
> > +
> > +   +-----------------------------------------+
> > +   | Field         | Value                   |
> > +   +===============+=========================+
> > +   | ``dst``       | destination item        |
> > +   | ``src``       | source item             |
> > +   | ``width``     | number of bits to copy  |
> 
> 
> 
> Overall it is a good improvement.
> 
> I think, if we add transform "op" here then it can be more generic. In
> other words, A generic packet transform and copy operation is just one
> of the operations.
> ie.. making it as rte_flow_action_xform_item and introduce COPY, ADD,
> SUB, etc transform along with existing rte_flow_action_copy_item
> fields.
> 
> It may useful for expressing P4 packet transforms to rte_flow.
> 
> The current generation of Marvell HW does not have COPY transform so I
> am leaving suggestions to vendors with this HW capablity.
> 
> 

+1 
Lest have dst, src, width, op members,
and change the action name to rte_flow_action_modify_field()

also lest add new field name immediate  so the copy can be used as set.
(copy of an immediate value is a set)

Possible op = copy / add / sub

> > +   +---------------+-------------------------+
> 
> 
> 
> 
> > +
> > +.. _table_rte_flow_action_copy_data:
> > +
> > +.. table:: destination/source item definition
> > +
> > +   +----------------------------------------------------------+
> > +   | Field         | Value                                    |
> > +   +===============+==========================================+
> > +   | ``item``      | ID of a packet field/mark/metadata/tag   |
> > +   | ``index``     | index of outer/inner header or tag array |
> > +   | ``offset``    | number of bits to skip during the copy   |
> > +   +---------------+------------------------------------------+
> > +