Re: [dpdk-dev] [PATCH v5] ethdev: extend flow metadata

[Olivier Matz <olivier.matz@6wind.com>]

Hi,

On Wed, Oct 30, 2019 at 02:46:06PM +0000, Slava Ovsiienko wrote:
> > -----Original Message-----
> > From: Slava Ovsiienko
> > Sent: Wednesday, October 30, 2019 16:41
> > To: Andrew Rybchenko <arybchenko@solarflare.com>; dev@dpdk.org
> > Cc: Matan Azrad <matan@mellanox.com>; Raslan Darawsheh
> > <rasland@mellanox.com>; Thomas Monjalon <thomas@monjalon.net>;
> > olivier.matz@6wind.com
> > Subject: RE: [PATCH v5] ethdev: extend flow metadata
> > 
> > > -----Original Message-----
> > > From: Andrew Rybchenko <arybchenko@solarflare.com>
> > > Sent: Wednesday, October 30, 2019 10:02
> > > To: Slava Ovsiienko <viacheslavo@mellanox.com>; dev@dpdk.org
> > > Cc: Matan Azrad <matan@mellanox.com>; Raslan Darawsheh
> > > <rasland@mellanox.com>; Thomas Monjalon <thomas@monjalon.net>;
> > > olivier.matz@6wind.com; Yongseok Koh <yskoh@mellanox.com>
> > > Subject: Re: [PATCH v5] ethdev: extend flow metadata
> > >
> > > On 10/29/19 10:31 PM, Viacheslav Ovsiienko wrote:
> > > > Currently, metadata can be set on egress path via mbuf tx_metadata
> > > > field with PKT_TX_METADATA flag and RTE_FLOW_ITEM_TYPE_META
> > > matches metadata.
> > > >
> > > > This patch extends the metadata feature usability.
> > > >
> > > > 1) RTE_FLOW_ACTION_TYPE_SET_META
> > > >
> > > > When supporting multiple tables, Tx metadata can also be set by a
> > > > rule and matched by another rule. This new action allows metadata to
> > > > be set as a result of flow match.
> > > >
> > > > 2) Metadata on ingress
> > > >
> > > > There's also need to support metadata on ingress. Metadata can be
> > > > set by SET_META action and matched by META item like Tx. The final
> > > > value set by the action will be delivered to application via
> > > > metadata dynamic field of mbuf which can be accessed by
> > > > RTE_FLOW_DYNF_METADATA() macro or with
> > > > rte_flow_dynf_metadata_set() and rte_flow_dynf_metadata_get() helper
> > > > routines. PKT_RX_DYNF_METADATA flag will be set along with the data.
> > 
> > We have a problem with PKT_RX_DYNF_METADATA/
> > PKT_TX_DYNF_METADATA.
> > These ones are referencing to global variable
> > "rte_flow_dynf_metadata_mask".
> > And there are routines in rte_mbuf.c  (rte_get_rx_ol_flag_list) which show
> > the names of flags. It is not good if rte_mbuf.c would require including of
> > rte_flow.h and  linking rte_flow.c (not all apps use rte_flow or even ethdev).
> > 
> > What do you think? Should we rename rte_flow_dynf_xxxxx variables to
> > rte_mbuf_dynf_flow_metadata_xxxx and put ones into the  rte_mbuf_dyn.c?
> > The same about PKT_RX_DYNF_METADATA definition, is it candidate to
> > move to rte_mbuf_dyn.h ? It would allow not to link or include rte_flow.c/h
> > into rte_mbuf.c
> > 

In rte_mbuf_dyn.c, we maintain a list of registered flags. I think it
wouldn't be too difficult to introduce the equivalent of
rte_get_*_ol_flag_list() and *rte_get_*_ol_flag_name() for dynamic
flags. There is already a dump function (which does both fields and
flags), and a lookup by name function.

Maybe we could split the dump into fields and flags, and add a lookup by
offset/bitnum. Would it work for your use-case?

> It is interesting to note that despite metadata field looks to be related to rte_flow,
> there is no any reference to this field or flags inside rte_flow API implementation.
> Only datapath references this field. Metadata is gateway between flow HW space and datapath,
> it tends to be mostly on datapath side not on rte_flow.

Yes, only the registration of the field is related to rte_flow. But I
don't get where are you going with this. Is it a problem?