ethdev: extend flow metadata

ethdev: extend flow metadata

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.

The mbuf dynamic field must be registered by calling
rte_flow_dynf_metadata_register() prior to use SET_META action.

The availability of dynamic mbuf metadata field can be checked
with rte_flow_dynf_metadata_avail() routine.

If application is going to engage the metadata feature it registers
the metadata  dynamic fields, then PMD checks the metadata field
availability and handles the appropriate fields in datapath.

For loopback/hairpin packet, metadata set on Rx/Tx may or may not be
propagated to the other path depending on hardware capability.

MARK and METADATA look similar and might operate in similar way,
but not interacting.

Initially, there were proposed two metadata related actions:

- RTE_FLOW_ACTION_TYPE_FLAG
- RTE_FLOW_ACTION_TYPE_MARK

These actions set the special flag in the packet metadata, MARK action
stores some specified value in the metadata storage, and, on the packet
receiving PMD puts the flag and value to the mbuf and applications can
see the packet was threated inside flow engine according to the appropriate
RTE flow(s). MARK and FLAG are like some kind of gateway to transfer some
per-packet information from the flow engine to the application via
receiving datapath. Also, there is the item of type RTE_FLOW_ITEM_TYPE_MARK
provided. It allows us to extend the flow match pattern with the capability
to match the metadata values set by MARK/FLAG actions on other flows.

From the datapath point of view, the MARK and FLAG are related to the
receiving side only. It would useful to have the same gateway on the
transmitting side and there was the feature of type RTE_FLOW_ITEM_TYPE_META
was proposed. The application can fill the field in mbuf and this value
will be transferred to some field in the packet metadata inside the flow
engine. It did not matter whether these metadata fields are shared because
of MARK and META items belonged to different domains (receiving and
transmitting) and could be vendor-specific.

So far, so good, DPDK proposes some entities to control metadata inside
the flow engine and gateways to exchange these values on a per-packet basis
via datapaths.

As we can see, the MARK and META means are not symmetric, there is absent
action which would allow us to set META value on the transmitting path.
So, the action of type:

- RTE_FLOW_ACTION_TYPE_SET_META was proposed.

The next, applications raise the new requirements for packet metadata.
The flow ngines are getting more complex, internal switches are introduced,
multiple ports might be supported within the same flow engine namespace.
From the DPDK points of view, it means the packets might be sent on one
eth_dev port and received on the other one, and the packet path inside
the flow engine entirely belongs to the same hardware device. The simplest
example is SR-IOV with PF, VFs and the representors. And there is a
brilliant opportunity to provide some out-of-band channel to transfer
some extra data from one port to another one, besides the packet data
itself. And applications would like to use this opportunity.

It is supposed for application to use trials (with rte_flow_validate)
to detect which metadata features (FLAG, MARK, META) actually supported
by PMD and underlying hardware. It might depend on PMD configuration,
system software, hardware settings, etc., and should be detected
in run time.

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Ori Kam <orika@mellanox.com>