[dpdk-dev] [RFC v2] Generic flow director/filtering/classification API

[Adrien Mazarguil]

Hi All,

Thanks to many for the positive and constructive feedback I've received so
far. Here is the updated specification (v0.7) at last.

I've attempted to address as many comments as possible but could not
process them all just yet. A new section "Future evolutions" has been
added for the remaining topics.

This series adds rte_flow.h to the DPDK tree. Next time I will attempt to
convert the specification as a documentation commit part of the patchset
and actually implement API functions.

I think including the entire document here makes it easier to annotate on
the ML, apologies in advance for the resulting traffic.

Finally I'm off for the next two weeks, do not expect replies from me in
the meantime.

Updates are also available online:

HTML version:
 https://rawgit.com/6WIND/rte_flow/master/rte_flow.html

PDF version:
 https://rawgit.com/6WIND/rte_flow/master/rte_flow.pdf                          

Related draft header file (also in the next patch):
 https://raw.githubusercontent.com/6WIND/rte_flow/master/rte_flow.h

Git tree:
 https://github.com/6WIND/rte_flow

Changes from v1:

 Specification:

 - Settled on [generic] "flow interface" / "flow API" as the name of this
   framework, matches the rte_flow prefix better.
 - Minor wording changes in several places.
 - Partially added egress (TX) support.
 - Added "unrecoverable errors" as another consequence of overlapping
   rules.
 - Described flow rules groups and their interaction with flow rule
   priorities.
 - Fully described PF and VF meta pattern items so they are not open to
   interpretation anymore.
 - Removed the SIGNATURE meta pattern item as its description was too
   vague, may be re-added later if necessary.
 - Added the PORT pattern item to apply rules to non-default physical
   ports.
 - Entirely redefined the RAW pattern item.
 - Fixed tag error in the ETH item definition.
 - Updated protocol definitions (IPV4, IPV6, ICMP, UDP).
 - Added missing protocols (SCTP, VXLAN).
 - Converted ID action to MARK and FLAG actions, described interaction
   with the RSS hash result in mbufs.
 - Updated COUNT query structure to retrieve the number of bytes.
 - Updated VF action.
 - Documented negative item and action types, those will be used for
   dynamic types generated at run-time.
 - Added blurb about IPv4 options and IPv6 extension headers matching.
 - Updated function definitions.
 - Documented a flush method to remove all rules on a given port at once.
 - Documented the verbose error reporting interface.
 - Documented how the private interface for PMD use will work.
 - Documented expected behavior between successive port initializations.
 - Documented expected behavior for ports not under DPDK control.
 - Updated API migration section.
 - Added future evolutions section.

 Header file:
 
 - Not a draft anymore and can be used as-is for preliminary
   implementations.
 - Flow rule attributes (group, priority, etc) now have their own
   structure provided separately to API functions (struct rte_flow_attr).
 - Group and priority interactions have been documented.
 - Added PORT item.
 - Removed SIGNATURE item.
 - Defined ICMP, SCTP and VXLAN items.
 - Redefined PF, VF, RAW, IPV4, IPV6, UDP and TCP items.
 - Fixed tag error in the ETH item definition.
 - Converted ID action to MARK and FLAG actions.
   hash result in mbufs.
 - Updated COUNT query structure.
 - Updated VF action.
 - Added verbose errors interface.
 - Updated function prototypes according to the above.
 - Defined rte_flow_flush().

--------

======================
Generic flow interface
======================

.. footer::

   v0.7

.. contents::
.. sectnum::
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Overview
========

DPDK provides several competing interfaces added over time to perform packet
matching and related actions such as filtering and classification.

They must be extended to implement the features supported by newer devices
in order to expose them to applications, however the current design has
several drawbacks:

- Complicated filter combinations which have not been hard-coded cannot be
  expressed.
- Prone to API/ABI breakage when new features must be added to an existing
  filter type, which frequently happens.

>From an application point of view:

- Having disparate interfaces, all optional and lacking in features does not
  make this API easy to use.
- Seemingly arbitrary built-in limitations of filter types based on the
  device they were initially designed for.
- Undefined relationship between different filter types.
- High complexity, considerable undocumented and/or undefined behavior.

Considering the growing number of devices supported by DPDK, adding a new
filter type each time a new feature must be implemented is not sustainable
in the long term. Applications not written to target a specific device
cannot really benefit from such an API.

For these reasons, this document defines an extensible unified API that
encompasses and supersedes these legacy filter types.

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Current API
===========

Rationale
---------

The reason several competing (and mostly overlapping) filtering APIs are
present in DPDK is due to its nature as a thin layer between hardware and
software.

Each subsequent interface has been added to better match the capabilities
and limitations of the latest supported device, which usually happened to
need an incompatible configuration approach. Because of this, many ended up
device-centric and not usable by applications that were not written for that
particular device.

This document is not the first attempt to address this proliferation issue,
in fact a lot of work has already been done both to create a more generic
interface while somewhat keeping compatibility with legacy ones through a
common call interface (``rte_eth_dev_filter_ctrl()`` with the
``.filter_ctrl`` PMD callback in ``rte_ethdev.h``).

Today, these previously incompatible interfaces are known as filter types
(``RTE_ETH_FILTER_*`` from ``enum rte_filter_type`` in ``rte_eth_ctrl.h``).

However while trivial to extend with new types, it only shifted the
underlying problem as applications still need to be written for one kind of
filter type, which, as described in the following sections, is not
necessarily implemented by all PMDs that support filtering.

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Filter types
------------

This section summarizes the capabilities of each filter type.

Although the following list is exhaustive, the description of individual
types may contain inaccuracies due to the lack of documentation or usage
examples.

Note: names are prefixed with ``RTE_ETH_FILTER_``.

``MACVLAN``
~~~~~~~~~~~

Matching:

- L2 source/destination addresses.
- Optional 802.1Q VLAN ID.
- Masking individual fields on a rule basis is not supported.

Action:

- Packets are redirected either to a given VF device using its ID or to the
  PF.

``ETHERTYPE``
~~~~~~~~~~~~~

Matching:

- L2 source/destination addresses (optional).
- Ethertype (no VLAN ID?).
- Masking individual fields on a rule basis is not supported.

Action:

- Receive packets on a given queue.
- Drop packets.

``FLEXIBLE``
~~~~~~~~~~~~

Matching:

- At most 128 consecutive bytes anywhere in packets.
- Masking is supported with byte granularity.
- Priorities are supported (relative to this filter type, undefined
  otherwise).

Action:

- Receive packets on a given queue.

``SYN``
~~~~~~~

Matching:

- TCP SYN packets only.
- One high priority bit can be set to give the highest possible priority to
  this type when other filters with different types are configured.

Action:

- Receive packets on a given queue.

``NTUPLE``
~~~~~~~~~~

Matching:

- Source/destination IPv4 addresses (optional in 2-tuple mode).
- Source/destination TCP/UDP port (mandatory in 2 and 5-tuple modes).
- L4 protocol (2 and 5-tuple modes).
- Masking individual fields is supported.
- TCP flags.
- Up to 7 levels of priority relative to this filter type, undefined
  otherwise.
- No IPv6.

Action:

- Receive packets on a given queue.

``TUNNEL``
~~~~~~~~~~

Matching:

- Outer L2 source/destination addresses.
- Inner L2 source/destination addresses.
- Inner VLAN ID.
- IPv4/IPv6 source (destination?) address.
- Tunnel type to match (VXLAN, GENEVE, TEREDO, NVGRE, IP over GRE, 802.1BR
  E-Tag).
- Tenant ID for tunneling protocols that have one.
- Any combination of the above can be specified.
- Masking individual fields on a rule basis is not supported.

Action:

- Receive packets on a given queue.

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``FDIR``
~~~~~~~~

Queries:

- Device capabilities and limitations.
- Device statistics about configured filters (resource usage, collisions).
- Device configuration (matching input set and masks)

Matching:

- Device mode of operation: none (to disable filtering), signature
  (hash-based dispatching from masked fields) or perfect (either MAC VLAN or
  tunnel).
- L2 Ethertype.
- Outer L2 destination address (MAC VLAN mode).
- Inner L2 destination address, tunnel type (NVGRE, VXLAN) and tunnel ID
  (tunnel mode).
- IPv4 source/destination addresses, ToS, TTL and protocol fields.
- IPv6 source/destination addresses, TC, protocol and hop limits fields.
- UDP source/destination IPv4/IPv6 and ports.
- TCP source/destination IPv4/IPv6 and ports.
- SCTP source/destination IPv4/IPv6, ports and verification tag field.
- Note, only one protocol type at once (either only L2 Ethertype, basic
  IPv6, IPv4+UDP, IPv4+TCP and so on).
- VLAN TCI (extended API).
- At most 16 bytes to match in payload (extended API). A global device
  look-up table specifies for each possible protocol layer (unknown, raw,
  L2, L3, L4) the offset to use for each byte (they do not need to be
  contiguous) and the related bit-mask.
- Whether packet is addressed to PF or VF, in that case its ID can be
  matched as well (extended API).
- Masking most of the above fields is supported, but simultaneously affects
  all filters configured on a device.
- Input set can be modified in a similar fashion for a given device to
  ignore individual fields of filters (i.e. do not match the destination
  address in a IPv4 filter, refer to **RTE_ETH_INPUT_SET_**
  macros). Configuring this also affects RSS processing on **i40e**.
- Filters can also provide 32 bits of arbitrary data to return as part of
  matched packets.

Action:

- **RTE_ETH_FDIR_ACCEPT**: receive (accept) packet on a given queue.
- **RTE_ETH_FDIR_REJECT**: drop packet immediately.
- **RTE_ETH_FDIR_PASSTHRU**: similar to accept for the last filter in list,
  otherwise process it with subsequent filters.
- For accepted packets and if requested by filter, either 32 bits of
  arbitrary data and four bytes of matched payload (only in case of flex
  bytes matching), or eight bytes of matched payload (flex also) are added
  to meta data.

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``HASH``
~~~~~~~~

Not an actual filter type. Provides and retrieves the global device
configuration (per port or entire NIC) for hash functions and their
properties.

Hash function selection: "default" (keep current), XOR or Toeplitz.

This function can be configured per flow type (**RTE_ETH_FLOW_**
definitions), supported types are:

- Unknown.
- Raw.
- Fragmented or non-fragmented IPv4.
- Non-fragmented IPv4 with L4 (TCP, UDP, SCTP or other).
- Fragmented or non-fragmented IPv6.
- Non-fragmented IPv6 with L4 (TCP, UDP, SCTP or other).
- L2 payload.
- IPv6 with extensions.
- IPv6 with L4 (TCP, UDP) and extensions.

``L2_TUNNEL``
~~~~~~~~~~~~~

Matching:

- All packets received on a given port.

Action:

- Add tunnel encapsulation (VXLAN, GENEVE, TEREDO, NVGRE, IP over GRE,
  802.1BR E-Tag) using the provided Ethertype and tunnel ID (only E-Tag
  is implemented at the moment).
- VF ID to use for tag insertion (currently unused).
- Destination pool for tag based forwarding (pools are IDs that can be
  affected to ports, duplication occurs if the same ID is shared by several
  ports of the same NIC).

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Driver support
--------------

======== ======= ========= ======== === ====== ====== ==== ==== =========
Driver   MACVLAN ETHERTYPE FLEXIBLE SYN NTUPLE TUNNEL FDIR HASH L2_TUNNEL
======== ======= ========= ======== === ====== ====== ==== ==== =========
bnx2x
cxgbe
e1000            yes       yes      yes yes
ena
enic                                                  yes
fm10k
i40e     yes     yes                           yes    yes  yes
ixgbe            yes                yes yes           yes       yes
mlx4
mlx5                                                  yes
szedata2
======== ======= ========= ======== === ====== ====== ==== ==== =========

Flow director
-------------

Flow director (FDIR) is the name of the most capable filter type, which
covers most features offered by others. As such, it is the most widespread
in PMDs that support filtering (i.e. all of them besides **e1000**).

It is also the only type that allows an arbitrary 32 bits value provided by
applications to be attached to a filter and returned with matching packets
instead of relying on the destination queue to recognize flows.

Unfortunately, even FDIR requires applications to be aware of low-level
capabilities and limitations (most of which come directly from **ixgbe** and
**i40e**):

- Bit-masks are set globally per device (port?), not per filter.
- Configuration state is not expected to be saved by the driver, and
  stopping/restarting a port requires the application to perform it again
  (API documentation is also unclear about this).
- Monolithic approach with ABI issues as soon as a new kind of flow or
  combination needs to be supported.
- Cryptic global statistics/counters.
- Unclear about how priorities are managed; filters seem to be arranged as a
  linked list in hardware (possibly related to configuration order).

Packet alteration
-----------------

One interesting feature is that the L2 tunnel filter type implements the
ability to alter incoming packets through a filter (in this case to
encapsulate them), thus the **mlx5** flow encap/decap features are not a
foreign concept.

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Proposed API
============

Terminology
-----------

- **Flow API**: overall framework affecting the fate of selected packets,
  covers everything described in this document.
- **Filtering API**: an alias for *Flow API*.
- **Matching pattern**: properties to look for in packets, a combination of
  any number of items.
- **Pattern item**: part of a pattern that either matches packet data
  (protocol header, payload or derived information), or specifies properties
  of the pattern itself.
- **Actions**: what needs to be done when a packet is matched by a pattern.
- **Flow rule**: this is the result of combining a *matching pattern* with
  *actions*.
- **Filter rule**: a less generic term than *flow rule*, can otherwise be
  used interchangeably.
- **Hit**: a flow rule is said to be *hit* when processing a matching
  packet.

Requirements
------------

As described in the previous section, there is a growing need for a common
method to configure filtering and related actions in a hardware independent
fashion.

The flow API should not disallow any filter combination by design and must
remain as simple as possible to use. It can simply be defined as a method to
perform one or several actions on selected packets.

PMDs are aware of the capabilities of the device they manage and should be
responsible for preventing unsupported or conflicting combinations.

This approach is fundamentally different as it places most of the burden on
the software side of the PMD instead of having device capabilities directly
mapped to API functions, then expecting applications to work around ensuing
compatibility issues.

Requirements for a new API:

- Flexible and extensible without causing API/ABI problems for existing
  applications.
- Should be unambiguous and easy to use.
- Support existing filtering features and actions listed in `Filter types`_.
- Support packet alteration.
- In case of overlapping filters, their priority should be well documented.
- Support filter queries (for example to retrieve counters).
- Support egress (TX) matching and specific actions.

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High level design
-----------------

The chosen approach to make filtering as generic as possible is by
expressing matching patterns through lists of items instead of the flat
structures used in DPDK today, enabling combinations that are not predefined
and thus being more versatile.

Flow rules can have several distinct actions (such as counting,
encapsulating, decapsulating before redirecting packets to a particular
queue, etc.), instead of relying on several rules to achieve this and having
applications deal with hardware implementation details regarding their
order.

Support for different priority levels on a rule basis is provided, for
example in order to force a more specific rule come before a more generic
one for packets matched by both, however hardware support for more than a
single priority level cannot be guaranteed. When supported, the number of
available priority levels is usually low, which is why they can also be
implemented in software by PMDs (e.g. missing priority levels may be
emulated by reordering rules).

In order to remain as hardware agnostic as possible, by default all rules
are considered to have the same priority, which means that the order between
overlapping rules (when a packet is matched by several filters) is
undefined, packet duplication or unrecoverable errors may even occur as a
result.

PMDs may refuse to create overlapping rules at a given priority level when
they can be detected (e.g. if a pattern matches an existing filter).

Thus predictable results for a given priority level can only be achieved
with non-overlapping rules, using perfect matching on all protocol layers.

Flow rules can also be grouped, the flow rule priority is specific to the
group they belong to. All flow rules in a given group are thus processed
either before or after another group.

Support for multiple actions per rule may be implemented internally on top
of non-default hardware priorities, as a result both features may not be
simultaneously available to applications.

Considering that allowed pattern/actions combinations cannot be known in
advance and would result in an unpractically large number of capabilities to
expose, a method is provided to validate a given rule from the current
device configuration state without actually adding it (akin to a "dry run"
mode).

This enables applications to check if the rule types they need is supported
at initialization time, before starting their data path. This method can be
used anytime, its only requirement being that the resources needed by a rule
must exist (e.g. a target RX queue must be configured first).

Each defined rule is associated with an opaque handle managed by the PMD,
applications are responsible for keeping it. These can be used for queries
and rules management, such as retrieving counters or other data and
destroying them.

To avoid resource leaks on the PMD side, handles must be explicitly
destroyed by the application before releasing associated resources such as
queues and ports.

Integration
-----------

To avoid ABI breakage, this new interface will be implemented through the
existing filtering control framework (``rte_eth_dev_filter_ctrl()``) using
**RTE_ETH_FILTER_GENERIC** as a new filter type.

However a public front-end API described in `Rules management`_ will
be added as the preferred method to use it.

Once discussions with the community have converged to a definite API, legacy
filter types should be deprecated and a deadline defined to remove their
support entirely.

PMDs will have to be gradually converted to **RTE_ETH_FILTER_GENERIC** or
drop filtering support entirely. Less maintained PMDs for older hardware may
lose support at this point.

The notion of filter type will then be deprecated and subsequently dropped
to avoid confusion between both frameworks.

Implementation details
======================

Flow rule
---------

A flow rule is the combination a matching pattern with a list of actions,
and is the basis of this API.

They also have several other attributes described in the following sections.

Groups
~~~~~~

Flow rules can be grouped by assigning them a common group number. Lower
values have higher priority. Group 0 has the highest priority.

Although optional, applications are encouraged to group similar rules as
much as possible to fully take advantage of hardware capabilities
(e.g. optimized matching) and work around limitations (e.g. a single pattern
type possibly allowed in a given group).

Note that support for more than a single group is not guaranteed.

Priorities
~~~~~~~~~~

A priority level can be assigned to a flow rule. Like groups, lower values
denote higher priority, with 0 as the maximum.

A rule with priority 0 in group 8 is always matched after a rule with
priority 8 in group 0.

Group and priority levels are arbitrary and up to the application, they do
not need to be contiguous nor start from 0, however the maximum number
varies between devices and may be affected by existing flow rules.

If a packet is matched by several rules of a given group for a given
priority level, the outcome is undefined. It can take any path, may be
duplicated or even cause unrecoverable errors.

Note that support for more than a single priority level is not guaranteed.

Traffic direction
~~~~~~~~~~~~~~~~~

Flow rules can apply to inbound and/or outbound traffic (ingress/egress).

Several pattern items and actions are valid and can be used in both
directions. Those valid for only one direction are described as such.

Specifying both directions at once is not recommended but may be valid in
some cases, such as incrementing the same counter twice.

Not specifying any direction is currently an error.

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Matching pattern
~~~~~~~~~~~~~~~~

A matching pattern comprises any number of items of various types.

Items are arranged in a list to form a matching pattern for packets. They
fall in two categories:

- Protocol matching (ANY, RAW, ETH, IPV4, IPV6, ICMP, UDP, TCP, SCTP, VXLAN
  and so on), usually associated with a specification structure. These must
  be stacked in the same order as the protocol layers to match, starting
  from L2.

- Affecting how the pattern is processed (END, VOID, INVERT, PF, VF, PORT
  and so on), often without a specification structure. Since they are meta
  data that does not match packet contents, these can be specified anywhere
  within item lists without affecting the protocol matching items.

Most item specifications can be optionally paired with a mask to narrow the
specific fields or bits to be matched.

- Items are defined with ``struct rte_flow_item``.
- Patterns are defined with ``struct rte_flow_pattern``.

Example of an item specification matching an Ethernet header:

+-----------------------------------------+
| Ethernet                                |
+==========+=========+====================+
| ``spec`` | ``src`` | ``00:01:02:03:04`` |
|          +---------+--------------------+
|          | ``dst`` | ``00:2a:66:00:01`` |
+----------+---------+--------------------+
| ``mask`` | ``src`` | ``00:ff:ff:ff:00`` |
|          +---------+--------------------+
|          | ``dst`` | ``00:00:00:00:ff`` |
+----------+---------+--------------------+

Non-masked bits stand for any value, Ethernet headers with the following
properties are thus matched:

- ``src``: ``??:01:02:03:??``
- ``dst``: ``??:??:??:??:01``

Except for meta types that do not need one, ``spec`` must be a valid pointer
to a structure of the related item type. A ``mask`` of the same type can be
provided to tell which bits in ``spec`` are to be matched.

A mask is normally only needed for ``spec`` fields matching packet data,
ignored otherwise. See individual item types for more information.

A ``NULL`` mask pointer is allowed and is similar to matching with a full
mask (all ones) ``spec`` fields supported by hardware, the remaining fields
are ignored (all zeroes), there is thus no error checking for unsupported
fields.

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Matching pattern items for packet data must be naturally stacked (ordered
from lowest to highest protocol layer), as in the following examples:

+--------------+
| TCPv4 as L4  |
+===+==========+
| 0 | Ethernet |
+---+----------+
| 1 | IPv4     |
+---+----------+
| 2 | TCP      |
+---+----------+

+----------------+
| TCPv6 in VXLAN |
+===+============+
| 0 | Ethernet   |
+---+------------+
| 1 | IPv4       |
+---+------------+
| 2 | UDP        |
+---+------------+
| 3 | VXLAN      |
+---+------------+
| 4 | Ethernet   |
+---+------------+
| 5 | IPv6       |
+---+------------+
| 6 | TCP        |
+---+------------+

+-----------------------------+
| TCPv4 as L4 with meta items |
+===+=========================+
| 0 | VOID                    |
+---+-------------------------+
| 1 | Ethernet                |
+---+-------------------------+
| 2 | VOID                    |
+---+-------------------------+
| 3 | IPv4                    |
+---+-------------------------+
| 4 | TCP                     |
+---+-------------------------+
| 5 | VOID                    |
+---+-------------------------+
| 6 | VOID                    |
+---+-------------------------+

The above example shows how meta items do not affect packet data matching
items, as long as those remain stacked properly. The resulting matching
pattern is identical to "TCPv4 as L4".

+----------------+
| UDPv6 anywhere |
+===+============+
| 0 | IPv6       |
+---+------------+
| 1 | UDP        |
+---+------------+

If supported by the PMD, omitting one or several protocol layers at the
bottom of the stack as in the above example (missing an Ethernet
specification) enables hardware to look anywhere in packets.

This is an alias for specifying `ANY`_ with ``min = 0`` and ``max = 0``
properties as the first item.

It is unspecified whether the payload of supported encapsulations
(e.g. VXLAN inner packet) is matched by such a pattern, which may apply to
inner, outer or both packets.

+---------------------+
| Invalid, missing L3 |
+===+=================+
| 0 | Ethernet        |
+---+-----------------+
| 1 | UDP             |
+---+-----------------+

The above pattern is invalid due to a missing L3 specification between L2
and L4. It is only allowed at the bottom and at the top of the stack.

Meta item types
~~~~~~~~~~~~~~~

These do not match packet data but affect how the pattern is processed, most
of them do not need a specification structure. This particularity allows
them to be specified anywhere without affecting other item types.

``END``
^^^^^^^

End marker for item lists. Prevents further processing of items, thereby
ending the pattern.

- Its numeric value is **0** for convenience.
- PMD support is mandatory.
- Both ``spec`` and ``mask`` are ignored.

+--------------------+
| END                |
+==========+=========+
| ``spec`` | ignored |
+----------+---------+
| ``mask`` | ignored |
+----------+---------+

``VOID``
^^^^^^^^

Used as a placeholder for convenience. It is ignored and simply discarded by
PMDs.

- PMD support is mandatory.
- Both ``spec`` and ``mask`` are ignored.

+--------------------+
| VOID               |
+==========+=========+
| ``spec`` | ignored |
+----------+---------+
| ``mask`` | ignored |
+----------+---------+

One usage example for this type is generating rules that share a common
prefix quickly without reallocating memory, only by updating item types:

+------------------------+
| TCP, UDP or ICMP as L4 |
+===+====================+
| 0 | Ethernet           |
+---+--------------------+
| 1 | IPv4               |
+---+------+------+------+
| 2 | UDP  | VOID | VOID |
+---+------+------+------+
| 3 | VOID | TCP  | VOID |
+---+------+------+------+
| 4 | VOID | VOID | ICMP |
+---+------+------+------+

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``INVERT``
^^^^^^^^^^

Inverted matching, i.e. process packets that do not match the pattern.

- Both ``spec`` and ``mask`` are ignored.

+--------------------+
| INVERT             |
+==========+=========+
| ``spec`` | ignored |
+----------+---------+
| ``mask`` | ignored |
+----------+---------+

Usage example in order to match non-TCPv4 packets only:

+--------------------+
| Anything but TCPv4 |
+===+================+
| 0 | INVERT         |
+---+----------------+
| 1 | Ethernet       |
+---+----------------+
| 2 | IPv4           |
+---+----------------+
| 3 | TCP            |
+---+----------------+

``PF``
^^^^^^

Matches packets addressed to the physical function of the device.

If the underlying device function differs from the one that would normally
receive the matched traffic, specifying this item prevents it from reaching
that device unless the flow rule contains a `PF (action)`_. Packets are not
duplicated between device instances by default.

- Likely to return an error or never match any traffic if applied to a VF
  device.
- Can be combined with any number of `VF`_ items to match both PF and VF
  traffic.
- Both ``spec`` and ``mask`` are ignored.

+--------------------+
| PF                 |
+==========+=========+
| ``spec`` | ignored |
+----------+---------+
| ``mask`` | ignored |
+----------+---------+

``VF``
^^^^^^

Matches packets addressed to a virtual function ID of the device.

If the underlying device function differs from the one that would normally
receive the matched traffic, specifying this item prevents it from reaching
that device unless the flow rule contains a `VF (action)`_. Packets are not
duplicated between device instances by default.

- Likely to return an error or never match any traffic if this causes a VF
  device to match traffic addressed to a different VF.
- Can be specified multiple times to match traffic addressed to several VFs.
- Can be combined with a `PF`_ item to match both PF and VF traffic.
- Only ``spec`` needs to be defined, ``mask`` is ignored.

+-------------------------------------------------+
| VF                                              |
+==========+=========+============================+
| ``spec`` | ``any`` | ignore the specified VF ID |
|          +---------+----------------------------+
|          | ``vf``  | destination VF ID          |
+----------+---------+----------------------------+
| ``mask`` | ignored                              |
+----------+--------------------------------------+

``PORT``
^^^^^^^^

Matches packets coming from the specified physical port of the underlying
device.

The first PORT item overrides the physical port normally associated with the
specified DPDK input port (port_id). This item can be provided several times
to match additional physical ports.

Note that physical ports are not necessarily tied to DPDK input ports
(port_id) when those are not under DPDK control. Possible values are
specific to each device, they are not necessarily indexed from zero and may
not be contiguous.

As a device property, the list of allowed values as well as the value
associated with a port_id should be retrieved by other means.

- Only ``spec`` needs to be defined, ``mask`` is ignored.

+--------------------------------------------+
| PORT                                       |
+==========+===========+=====================+
| ``spec`` | ``index`` | physical port index |
+----------+-----------+---------------------+
| ``mask`` | ignored                         |
+----------+---------------------------------+

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Data matching item types
~~~~~~~~~~~~~~~~~~~~~~~~

Most of these are basically protocol header definitions with associated
bit-masks. They must be specified (stacked) from lowest to highest protocol
layer.

The following list is not exhaustive as new protocols will be added in the
future.

``ANY``
^^^^^^^

Matches any protocol in place of the current layer, a single ANY may also
stand for several protocol layers.

This is usually specified as the first pattern item when looking for a
protocol anywhere in a packet.

- A maximum value of **0** requests matching any number of protocol layers
  above or equal to the minimum value, a maximum value lower than the
  minimum one is otherwise invalid.
- Only ``spec`` needs to be defined, ``mask`` is ignored.

+-----------------------------------------------------------------------+
| ANY                                                                   |
+==========+=========+==================================================+
| ``spec`` | ``min`` | minimum number of layers covered                 |
|          +---------+--------------------------------------------------+
|          | ``max`` | maximum number of layers covered, 0 for infinity |
+----------+---------+--------------------------------------------------+
| ``mask`` | ignored                                                    |
+----------+------------------------------------------------------------+

Example for VXLAN TCP payload matching regardless of outer L3 (IPv4 or IPv6)
and L4 (UDP) both matched by the first ANY specification, and inner L3 (IPv4
or IPv6) matched by the second ANY specification:

+----------------------------------+
| TCP in VXLAN with wildcards      |
+===+==============================+
| 0 | Ethernet                     |
+---+-----+----------+---------+---+
| 1 | ANY | ``spec`` | ``min`` | 2 |
|   |     |          +---------+---+
|   |     |          | ``max`` | 2 |
+---+-----+----------+---------+---+
| 2 | VXLAN                        |
+---+------------------------------+
| 3 | Ethernet                     |
+---+-----+----------+---------+---+
| 4 | ANY | ``spec`` | ``min`` | 1 |
|   |     |          +---------+---+
|   |     |          | ``max`` | 1 |
+---+-----+----------+---------+---+
| 5 | TCP                          |
+---+------------------------------+

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``RAW``
^^^^^^^

Matches a byte string of a given length at a given offset.

Offset is either absolute (using the start of the packet) or relative to the
end of the previous matched item in the stack, in which case negative values
are allowed.

If search is enabled, offset is used as the starting point. The search area
can be delimited by setting limit to a nonzero value, which is the maximum
number of bytes after offset where the pattern may start.

Matching a zero-length pattern is allowed, doing so resets the relative
offset for subsequent items.

- ``mask`` only affects the pattern field.

+---------------------------------------------------------------------------+
| RAW                                                                       |
+==========+==============+=================================================+
| ``spec`` | ``relative`` | look for pattern after the previous item        |
|          +--------------+-------------------------------------------------+
|          | ``search``   | search pattern from offset (see also ``limit``) |
|          +--------------+-------------------------------------------------+
|          | ``reserved`` | reserved, must be set to zero                   |
|          +--------------+-------------------------------------------------+
|          | ``offset``   | absolute or relative offset for ``pattern``     |
|          +--------------+-------------------------------------------------+
|          | ``limit``    | search area limit for start of ``pattern``      |
|          +--------------+-------------------------------------------------+
|          | ``length``   | ``pattern`` length                              |
|          +--------------+-------------------------------------------------+
|          | ``pattern``  | byte string to look for                         |
+----------+--------------+-------------------------------------------------+
| ``mask`` | ``relative`` | ignored                                         |
|          +--------------+-------------------------------------------------+
|          | ``search``   | ignored                                         |
|          +--------------+-------------------------------------------------+
|          | ``reserved`` | ignored                                         |
|          +--------------+-------------------------------------------------+
|          | ``offset``   | ignored                                         |
|          +--------------+-------------------------------------------------+
|          | ``limit``    | ignored                                         |
|          +--------------+-------------------------------------------------+
|          | ``length``   | ignored                                         |
|          +--------------+-------------------------------------------------+
|          | ``pattern``  | bit-mask of the same byte length as ``pattern`` |
+----------+--------------+-------------------------------------------------+

Example pattern looking for several strings at various offsets of a UDP
payload, using combined RAW items:

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+-------------------------------------------+
| UDP payload matching                      |
+===+=======================================+
| 0 | Ethernet                              |
+---+---------------------------------------+
| 1 | IPv4                                  |
+---+---------------------------------------+
| 2 | UDP                                   |
+---+-----+----------+--------------+-------+
| 3 | RAW | ``spec`` | ``relative`` | 1     |
|   |     |          +--------------+-------+
|   |     |          | ``search``   | 1     |
|   |     |          +--------------+-------+
|   |     |          | ``offset``   | 10    |
|   |     |          +--------------+-------+
|   |     |          | ``limit``    | 0     |
|   |     |          +--------------+-------+
|   |     |          | ``length``   | 3     |
|   |     |          +--------------+-------+
|   |     |          | ``pattern``  | "foo" |
+---+-----+----------+--------------+-------+
| 4 | RAW | ``spec`` | ``relative`` | 1     |
|   |     |          +--------------+-------+
|   |     |          | ``search``   | 0     |
|   |     |          +--------------+-------+
|   |     |          | ``offset``   | 20    |
|   |     |          +--------------+-------+
|   |     |          | ``limit``    | 0     |
|   |     |          +--------------+-------+
|   |     |          | ``length``   | 3     |
|   |     |          +--------------+-------+
|   |     |          | ``pattern``  | "bar" |
+---+-----+----------+--------------+-------+
| 5 | RAW | ``spec`` | ``relative`` | 1     |
|   |     |          +--------------+-------+
|   |     |          | ``search``   | 0     |
|   |     |          +--------------+-------+
|   |     |          | ``offset``   | -29   |
|   |     |          +--------------+-------+
|   |     |          | ``limit``    | 0     |
|   |     |          +--------------+-------+
|   |     |          | ``length``   | 3     |
|   |     |          +--------------+-------+
|   |     |          | ``pattern``  | "baz" |
+---+-----+----------+--------------+-------+

This translates to:

- Locate "foo" at least 10 bytes deep inside UDP payload.
- Locate "bar" after "foo" plus 20 bytes.
- Locate "baz" after "bar" minus 29 bytes.

Such a packet may be represented as follows (not to scale)::

 0                     >= 10 B           == 20 B
 |                  |<--------->|     |<--------->|
 |                  |           |     |           |
 |-----|------|-----|-----|-----|-----|-----------|-----|------|
 | ETH | IPv4 | UDP | ... | baz | foo | ......... | bar | .... |
 |-----|------|-----|-----|-----|-----|-----------|-----|------|
                          |                             |
                          |<--------------------------->|
                                      == 29 B

Note that matching subsequent pattern items would resume after "baz", not
"bar" since matching is always performed after the previous item of the
stack.

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``ETH``
^^^^^^^

Matches an Ethernet header.

- ``dst``: destination MAC.
- ``src``: source MAC.
- ``type``: EtherType.
- ``tags``: number of 802.1Q/ad tags defined.
- ``tag[]``: 802.1Q/ad tag definitions, outermost first. For each one:

 - ``tpid``: Tag protocol identifier.
 - ``tci``: Tag control information.

``IPV4``
^^^^^^^^

Matches an IPv4 header.

Note: IPv4 options are handled by dedicated pattern items.

- ``hdr``: IPv4 header definition (``rte_ip.h``).

``IPV6``
^^^^^^^^

Matches an IPv6 header.

Note: IPv6 options are handled by dedicated pattern items.

- ``hdr``: IPv6 header definition (``rte_ip.h``).

``ICMP``
^^^^^^^^

Matches an ICMP header.

- ``hdr``: ICMP header definition (``rte_icmp.h``).

``UDP``
^^^^^^^

Matches a UDP header.

- ``hdr``: UDP header definition (``rte_udp.h``).

``TCP``
^^^^^^^

Matches a TCP header.

- ``hdr``: TCP header definition (``rte_tcp.h``).

``SCTP``
^^^^^^^^

Matches a SCTP header.

- ``hdr``: SCTP header definition (``rte_sctp.h``).

``VXLAN``
^^^^^^^^^

Matches a VXLAN header (RFC 7348).

- ``flags``: normally 0x08 (I flag).
- ``rsvd0``: reserved, normally 0x000000.
- ``vni``: VXLAN network identifier.
- ``rsvd1``: reserved, normally 0x00.

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Actions
~~~~~~~

Each possible action is represented by a type. Some have associated
configuration structures. Several actions combined in a list can be affected
to a flow rule. That list is not ordered.

At least one action must be defined in a filter rule in order to do
something with matched packets.

- Actions are defined with ``struct rte_flow_action``.
- A list of actions is defined with ``struct rte_flow_actions``.

They fall in three categories:

- Terminating actions (such as QUEUE, DROP, RSS, PF, VF) that prevent
  processing matched packets by subsequent flow rules, unless overridden
  with PASSTHRU.

- Non terminating actions (PASSTHRU, DUP) that leave matched packets up for
  additional processing by subsequent flow rules.

- Other non terminating meta actions that do not affect the fate of packets
  (END, VOID, MARK, FLAG, COUNT).

When several actions are combined in a flow rule, they should all have
different types (e.g. dropping a packet twice is not possible). The defined
behavior is for PMDs to only take into account the last action of a given
type found in the list. PMDs still perform error checking on the entire
list.

*Note that PASSTHRU is the only action having the ability to override a
terminating rule.*

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Example of an action that redirects packets to queue index 10:

+----------------+
| QUEUE          |
+===========+====+
| ``queue`` | 10 |
+-----------+----+

Action lists examples, their order is not significant, applications must
consider all actions to be performed simultaneously:

+----------------+
| Count and drop |
+=======+========+
| COUNT |        |
+-------+--------+
| DROP  |        |
+-------+--------+

+--------------------------+
| Tag, count and redirect  |
+=======+===========+======+
| MARK  | ``mark``  | 0x2a |
+-------+-----------+------+
| COUNT |                  |
+-------+-----------+------+
| QUEUE | ``queue`` | 10   |
+-------+-----------+------+

+-----------------------+
| Redirect to queue 5   |
+=======+===============+
| DROP  |               |
+-------+-----------+---+
| QUEUE | ``queue`` | 5 |
+-------+-----------+---+

In the above example, considering both actions are performed simultaneously,
its end result is that only QUEUE has any effect.

+-----------------------+
| Redirect to queue 3   |
+=======+===========+===+
| QUEUE | ``queue`` | 5 |
+-------+-----------+---+
| VOID  |               |
+-------+-----------+---+
| QUEUE | ``queue`` | 3 |
+-------+-----------+---+

As previously described, only the last action of a given type found in the
list is taken into account. The above example also shows that VOID is
ignored.

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Action types
~~~~~~~~~~~~

Common action types are described in this section. Like pattern item types,
this list is not exhaustive as new actions will be added in the future.

``END`` (action)
^^^^^^^^^^^^^^^^

End marker for action lists. Prevents further processing of actions, thereby
ending the list.

- Its numeric value is **0** for convenience.
- PMD support is mandatory.
- No configurable property.

+---------------+
| END           |
+===============+
| no properties |
+---------------+

``VOID`` (action)
^^^^^^^^^^^^^^^^^

Used as a placeholder for convenience. It is ignored and simply discarded by
PMDs.

- PMD support is mandatory.
- No configurable property.

+---------------+
| VOID          |
+===============+
| no properties |
+---------------+

``PASSTHRU``
^^^^^^^^^^^^

Leaves packets up for additional processing by subsequent flow rules. This
is the default when a rule does not contain a terminating action, but can be
specified to force a rule to become non-terminating.

- No configurable property.

+---------------+
| PASSTHRU      |
+===============+
| no properties |
+---------------+

Example to copy a packet to a queue and continue processing by subsequent
flow rules:

+--------------------------+
| Copy to queue 8          |
+==========+===============+
| PASSTHRU |               |
+----------+-----------+---+
| QUEUE    | ``queue`` | 8 |
+----------+-----------+---+

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``MARK``
^^^^^^^^

Attaches a 32 bit value to packets.

This value is arbitrary and application-defined. For compatibility with FDIR
it is returned in the ``hash.fdir.hi`` mbuf field. ``PKT_RX_FDIR_ID`` is
also set in ``ol_flags``.

+------------------------------------------------+
| MARK                                           |
+==========+=====================================+
| ``mark`` | 32 bit value to return with packets |
+----------+-------------------------------------+

``FLAG``
^^^^^^^^

Flag packets. Similar to `MARK`_ but only affects ``ol_flags``.

Note: a distinctive flag must be defined for it.

+---------------+
| FLAG          |
+===============+
| no properties |
+---------------+

``QUEUE``
^^^^^^^^^

Assigns packets to a given queue index.

- Terminating by default.

+--------------------------------+
| QUEUE                          |
+===========+====================+
| ``queue`` | queue index to use |
+-----------+--------------------+

``DROP``
^^^^^^^^

Drop packets.

- No configurable property.
- Terminating by default.
- PASSTHRU overrides this action if both are specified.

+---------------+
| DROP          |
+===============+
| no properties |
+---------------+

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``COUNT``
^^^^^^^^^

Enables counters for this rule.

These counters can be retrieved and reset through ``rte_flow_query()``, see
``struct rte_flow_query_count``.

- Counters can be retrieved with ``rte_flow_query()``.
- No configurable property.

+---------------+
| COUNT         |
+===============+
| no properties |
+---------------+

Query structure to retrieve and reset flow rule counters:

+---------------------------------------------------------+
| COUNT query                                             |
+===============+=====+===================================+
| ``reset``     | in  | reset counter after query         |
+---------------+-----+-----------------------------------+
| ``hits_set``  | out | ``hits`` field is set             |
+---------------+-----+-----------------------------------+
| ``bytes_set`` | out | ``bytes`` field is set            |
+---------------+-----+-----------------------------------+
| ``hits``      | out | number of hits for this rule      |
+---------------+-----+-----------------------------------+
| ``bytes``     | out | number of bytes through this rule |
+---------------+-----+-----------------------------------+

``DUP``
^^^^^^^

Duplicates packets to a given queue index.

This is normally combined with QUEUE, however when used alone, it is
actually similar to QUEUE + PASSTHRU.

- Non-terminating by default.

+------------------------------------------------+
| DUP                                            |
+===========+====================================+
| ``queue`` | queue index to duplicate packet to |
+-----------+------------------------------------+

``RSS``
^^^^^^^

Similar to QUEUE, except RSS is additionally performed on packets to spread
them among several queues according to the provided parameters.

Note: RSS hash result is normally stored in the ``hash.rss`` mbuf field,
however it conflicts with the `MARK`_ action as they share the same
space. When both actions are specified, the RSS hash is discarded and
``PKT_RX_RSS_HASH`` is not set in ``ol_flags``. MARK has priority. The mbuf
structure should eventually evolve to store both.

- Terminating by default.

+---------------------------------------------+
| RSS                                         |
+==============+==============================+
| ``rss_conf`` | RSS parameters               |
+--------------+------------------------------+
| ``queues``   | number of entries in queue[] |
+--------------+------------------------------+
| ``queue[]``  | queue indices to use         |
+--------------+------------------------------+

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``PF`` (action)
^^^^^^^^^^^^^^^

Redirects packets to the physical function (PF) of the current device.

- No configurable property.
- Terminating by default.

+---------------+
| PF            |
+===============+
| no properties |
+---------------+

``VF`` (action)
^^^^^^^^^^^^^^^

Redirects packets to a virtual function (VF) of the current device.

Packets matched by a VF pattern item can be redirected to their original VF
ID instead of the specified one. This parameter may not be available and is
not guaranteed to work properly if the VF part is matched by a prior flow
rule or if packets are not addressed to a VF in the first place.

- Terminating by default.

+-----------------------------------------------+
| VF                                            |
+==============+================================+
| ``original`` | use original VF ID if possible |
+--------------+--------------------------------+
| ``vf``       | VF ID to redirect packets to   |
+--------------+--------------------------------+

Negative types
~~~~~~~~~~~~~~

All specified pattern items (``enum rte_flow_item_type``) and actions
(``enum rte_flow_action_type``) use positive identifiers.

The negative space is reserved for dynamic types generated by PMDs during
run-time, PMDs may encounter them as a result but do not have to accept the
negative types they did not generate.

The method to generate them has not been specified yet.

Planned types
~~~~~~~~~~~~~

Pattern item types will be added as new protocols are implemented.

Variable headers support through dedicated pattern items, for example in
order to match specific IPv4 options and IPv6 extension headers, these would
be stacked behind IPv4/IPv6 items.

Other action types are planned but not defined yet. These actions will add
the ability to alter matched packets in several ways, such as performing
encapsulation/decapsulation of tunnel headers on specific flows.

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Rules management
----------------

A simple API with few functions is provided to fully manage flows.

Each created flow rule is associated with an opaque, PMD-specific handle
pointer. The application is responsible for keeping it until the rule is
destroyed.

Flows rules are represented by ``struct rte_flow`` objects.

Validation
~~~~~~~~~~

Given that expressing a definite set of device capabilities with this API is
not practical, a dedicated function is provided to check if a flow rule is
supported and can be created.

::

 int
 rte_flow_validate(uint8_t port_id,
                   const struct rte_flow_attr *attr,
                   const struct rte_flow_pattern *pattern,
                   const struct rte_flow_actions *actions,
                   struct rte_flow_error *error);

While this function has no effect on the target device, the flow rule is
validated against its current configuration state and the returned value
should be considered valid by the caller for that state only.

The returned value is guaranteed to remain valid only as long as no
successful calls to rte_flow_create() or rte_flow_destroy() are made in the
meantime and no device parameter affecting flow rules in any way are
modified, due to possible collisions or resource limitations (although in
such cases ``EINVAL`` should not be returned).

Arguments:

- ``port_id``: port identifier of Ethernet device.
- ``attr``: flow rule attributes.
- ``pattern``: pattern specification.
- ``actions``: actions associated with the flow definition.
- ``error``: perform verbose error reporting if not NULL.

Return value:

- **0** if flow rule is valid and can be created. A negative errno value
  otherwise (``rte_errno`` is also set), the following errors are defined.
- ``-ENOSYS``: underlying device does not support this functionality.
- ``-EINVAL``: unknown or invalid rule specification.
- ``-ENOTSUP``: valid but unsupported rule specification (e.g. partial
  bit-masks are unsupported).
- ``-EEXIST``: collision with an existing rule.
- ``-ENOMEM``: not enough resources.
- ``-EBUSY``: action cannot be performed due to busy device resources, may
  succeed if the affected queues or even the entire port are in a stopped
  state (see ``rte_eth_dev_rx_queue_stop()`` and ``rte_eth_dev_stop()``).

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Creation
~~~~~~~~

Creating a flow rule is similar to validating one, except the rule is
actually created and a handle returned.

::

 struct rte_flow *
 rte_flow_create(uint8_t port_id,
                 const struct rte_flow_attr *attr,
                 const struct rte_flow_pattern *pattern,
                 const struct rte_flow_actions *actions,
                 struct rte_flow_error *error);

Arguments:

- ``port_id``: port identifier of Ethernet device.
- ``attr``: flow rule attributes.
- ``pattern``: pattern specification.
- ``actions``: actions associated with the flow definition.
- ``error``: perform verbose error reporting if not NULL.

Return value:

A valid handle in case of success, NULL otherwise and ``rte_errno`` is set
to the positive version of one of the error codes defined for
``rte_flow_validate()``.

Destruction
~~~~~~~~~~~

Flow rules destruction is not automatic, and a queue or a port should not be
released if any are still attached to them. Applications must take care of
performing this step before releasing resources.

::

 int
 rte_flow_destroy(uint8_t port_id,
                  struct rte_flow *flow,
                  struct rte_flow_error *error);


Failure to destroy a flow rule handle may occur when other flow rules depend
on it, and destroying it would result in an inconsistent state.

This function is only guaranteed to succeed if handles are destroyed in
reverse order of their creation.

Arguments:

- ``port_id``: port identifier of Ethernet device.
- ``flow``: flow rule handle to destroy.
- ``error``: perform verbose error reporting if not NULL.

Return value:

- **0** on success, a negative errno value otherwise and ``rte_errno`` is
  set.

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Flush
~~~~~

Convenience function to destroy all flow rule handles associated with a
port. They are released as with successive calls to ``rte_flow_destroy()``.

::

 int
 rte_flow_flush(uint8_t port_id,
                struct rte_flow_error *error);

In the unlikely event of failure, handles are still considered destroyed and
no longer valid but the port must be assumed to be in an inconsistent state.

Arguments:

- ``port_id``: port identifier of Ethernet device.
- ``error``: perform verbose error reporting if not NULL.

Return value:

- **0** on success, a negative errno value otherwise and ``rte_errno`` is
  set.

Query
~~~~~

Query an existing flow rule.

This function allows retrieving flow-specific data such as counters. Data
is gathered by special actions which must be present in the flow rule
definition.

::

 int
 rte_flow_query(uint8_t port_id,
                struct rte_flow *flow,
                enum rte_flow_action_type action,
                void *data,
                struct rte_flow_error *error);

Arguments:

- ``port_id``: port identifier of Ethernet device.
- ``flow``: flow rule handle to query.
- ``action``: action type to query.
- ``data``: pointer to storage for the associated query data type.
- ``error``: perform verbose error reporting if not NULL.

Return value:

- **0** on success, a negative errno value otherwise and ``rte_errno`` is
  set.

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Verbose error reporting
~~~~~~~~~~~~~~~~~~~~~~~

The defined *errno* values may not be accurate enough for users or
application developers who want to investigate issues related to flow rules
management. A dedicated error object is defined for this purpose::

 enum rte_flow_error_type {
     RTE_FLOW_ERROR_TYPE_NONE, /**< No error. */
     RTE_FLOW_ERROR_TYPE_UNDEFINED, /**< Cause is undefined. */
     RTE_FLOW_ERROR_TYPE_HANDLE, /**< Flow rule (handle). */
     RTE_FLOW_ERROR_TYPE_ATTR_GROUP, /**< Group field. */
     RTE_FLOW_ERROR_TYPE_ATTR_PRIORITY, /**< Priority field. */
     RTE_FLOW_ERROR_TYPE_ATTR_INGRESS, /**< field. */
     RTE_FLOW_ERROR_TYPE_ATTR_EGRESS, /**< field. */
     RTE_FLOW_ERROR_TYPE_ATTR, /**< Attributes structure itself. */
     RTE_FLOW_ERROR_TYPE_PATTERN_MAX, /**< Pattern length (max field). */
     RTE_FLOW_ERROR_TYPE_PATTERN_ITEM, /**< Specific pattern item. */
     RTE_FLOW_ERROR_TYPE_PATTERN, /**< Pattern structure itself. */
     RTE_FLOW_ERROR_TYPE_ACTION_MAX, /**< Number of actions (max field). */
     RTE_FLOW_ERROR_TYPE_ACTION, /**< Specific action. */
     RTE_FLOW_ERROR_TYPE_ACTIONS, /**< Actions structure itself. */
 };

 struct rte_flow_error {
     enum rte_flow_error_type type; /**< Cause field and error types. */
     void *cause; /**< Object responsible for the error. */
     const char *message; /**< Human-readable error message. */
 };

Error type ``RTE_FLOW_ERROR_TYPE_NONE`` stands for no error, in which case
the remaining fields can be ignored. Other error types describe the object
type pointed to by ``cause``.

If non-NULL, ``cause`` points to the object responsible for the error. For a
flow rule, this may be a pattern item or an individual action.

If non-NULL, ``message`` provides a human-readable error message.

This object is normally allocated by applications and set by PMDs, the
message points to a constant string which does not need to be freed by the
application, however its pointer can be considered valid only as long as its
associated DPDK port remains configured. Closing the underlying device or
unloading the PMD invalidates it.

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PMD interface
~~~~~~~~~~~~~

This specification focuses on the public-facing interface, which must be
fully defined from the start to avoid a re-design later as it is subject to
API and ABI versioning constraints.

No such issue exists with the internal interface for use by poll-mode
drivers which can evolve independently, hence this section only outlines how
requests are processed by PMDs.

Public functions are mapped more or less directly to PMD operation
callbacks, thus:

- Public API functions do not process flow rules definitions at all before
  calling PMD callbacks (no basic error checking, no validation
  whatsoever). They only make sure these callbacks are non-NULL or return
  the ``ENOSYS`` (function not supported) error.

- DPDK does not keep track of flow rules definitions or flow rule objects
  automatically. Applications may keep track of the former and must keep
  track of the latter. PMDs may also do it for internal needs, however this
  cannot be relied on by applications.

The private interface will provide helper functions to perform common tasks
such as parsing, validating and keeping track of flow rule specifications to
avoid redundant code in PMDs and ease implementation.

Its contents are currently largely undefined since at least one PMD
implementation is necessary first. PMD maintainers are encouraged to share
as much generic code as possible.

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Caveats
-------

- Flow rules are not maintained between successive port initializations. An
  application exiting without releasing them and restarting must re-create
  them from scratch.

- API operations are synchronous and blocking (``EAGAIN`` cannot be
  returned).

- There is no provision for reentrancy/multi-thread safety, although nothing
  should prevent different devices from being configured at the same
  time. PMDs may protect their control path functions accordingly.

- Stopping the data path (TX/RX) should not be necessary when managing flow
  rules. If this cannot be achieved naturally or with workarounds (such as
  temporarily replacing the burst function pointers), an appropriate error
  code must be returned (``EBUSY``).

- PMDs, not applications, are responsible for maintaining flow rules
  configuration when stopping and restarting a port or performing other
  actions which may affect them. They can only be destroyed explicitly.

For devices exposing multiple ports sharing global settings affected by flow
rules:

- All ports under DPDK control must behave consistently, PMDs are
  responsible for making sure that existing flow rules on a port are not
  affected by other ports.

- Ports not under DPDK control (unaffected or handled by other applications)
  are user's responsibility. They may affect existing flow rules and cause
  undefined behavior. PMDs aware of this may prevent flow rules creation
  altogether in such cases.

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Compatibility
-------------

No known hardware implementation supports all the features described in this
document.

Unsupported features or combinations are not expected to be fully emulated
in software by PMDs for performance reasons. Partially supported features
may be completed in software as long as hardware performs most of the work
(such as queue redirection and packet recognition).

However PMDs are expected to do their best to satisfy application requests
by working around hardware limitations as long as doing so does not affect
the behavior of existing flow rules.

The following sections provide a few examples of such cases, they are based
on limitations built into the previous APIs.

Global bit-masks
~~~~~~~~~~~~~~~~

Each flow rule comes with its own, per-layer bit-masks, while hardware may
support only a single, device-wide bit-mask for a given layer type, so that
two IPv4 rules cannot use different bit-masks.

The expected behavior in this case is that PMDs automatically configure
global bit-masks according to the needs of the first created flow rule.

Subsequent rules are allowed only if their bit-masks match those, the
``EEXIST`` error code should be returned otherwise.

Unsupported layer types
~~~~~~~~~~~~~~~~~~~~~~~

Many protocols can be simulated by crafting patterns with the `RAW`_ type.

PMDs can rely on this capability to simulate support for protocols with
fixed headers not directly recognized by hardware.

``ANY`` pattern item
~~~~~~~~~~~~~~~~~~~~

This pattern item stands for anything, which can be difficult to translate
to something hardware would understand, particularly if followed by more
specific types.

Consider the following pattern:

+---+--------------------------------+
| 0 | ETHER                          |
+---+--------------------------------+
| 1 | ANY (``min`` = 1, ``max`` = 1) |
+---+--------------------------------+
| 2 | TCP                            |
+---+--------------------------------+

Knowing that TCP does not make sense with something other than IPv4 and IPv6
as L3, such a pattern may be translated to two flow rules instead:

+---+--------------------+
| 0 | ETHER              |
+---+--------------------+
| 1 | IPV4 (zeroed mask) |
+---+--------------------+
| 2 | TCP                |
+---+--------------------+

+---+--------------------+
| 0 | ETHER              |
+---+--------------------+
| 1 | IPV6 (zeroed mask) |
+---+--------------------+
| 2 | TCP                |
+---+--------------------+

Note that as soon as a ANY rule covers several layers, this approach may
yield a large number of hidden flow rules. It is thus suggested to only
support the most common scenarios (anything as L2 and/or L3).

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Unsupported actions
~~~~~~~~~~~~~~~~~~~

- When combined with a `QUEUE`_ action, packet counting (`COUNT`_) and
  tagging (`MARK`_ or `FLAG`_) may be implemented in software as long as the
  target queue is used by a single rule.

- A rule specifying both `DUP`_ + `QUEUE`_ may be translated to two hidden
  rules combining `QUEUE`_ and `PASSTHRU`_.

- When a single target queue is provided, `RSS`_ can also be implemented
  through `QUEUE`_.

Flow rules priority
~~~~~~~~~~~~~~~~~~~

While it would naturally make sense, flow rules cannot be assumed to be
processed by hardware in the same order as their creation for several
reasons:

- They may be managed internally as a tree or a hash table instead of a
  list.
- Removing a flow rule before adding another one can either put the new rule
  at the end of the list or reuse a freed entry.
- Duplication may occur when packets are matched by several rules.

For overlapping rules (particularly in order to use the `PASSTHRU`_ action)
predictable behavior is only guaranteed by using different priority levels.

Priority levels are not necessarily implemented in hardware, or may be
severely limited (e.g. a single priority bit).

For these reasons, priority levels may be implemented purely in software by
PMDs.

- For devices expecting flow rules to be added in the correct order, PMDs
  may destroy and re-create existing rules after adding a new one with
  a higher priority.

- A configurable number of dummy or empty rules can be created at
  initialization time to save high priority slots for later.

- In order to save priority levels, PMDs may evaluate whether rules are
  likely to collide and adjust their priority accordingly.

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API migration
=============

Exhaustive list of deprecated filter types and how to convert them to
generic flow rules.

``MACVLAN`` to ``ETH`` → ``VF``, ``PF``
---------------------------------------

`MACVLAN`_ can be translated to a basic `ETH`_ flow rule with a `VF
(action)`_ or `PF (action)`_ terminating action.

+------------------------------------+
| MACVLAN                            |
+--------------------------+---------+
| Pattern                  | Actions |
+===+=====+==========+=====+=========+
| 0 | ETH | ``spec`` | any | VF,     |
|   |     +----------+-----+ PF      |
|   |     | ``mask`` | any |         |
+---+-----+----------+-----+---------+

``ETHERTYPE`` to ``ETH`` → ``QUEUE``, ``DROP``
----------------------------------------------

`ETHERTYPE`_ is basically an `ETH`_ flow rule with `QUEUE`_ or `DROP`_ as
a terminating action.

+------------------------------------+
| ETHERTYPE                          |
+--------------------------+---------+
| Pattern                  | Actions |
+===+=====+==========+=====+=========+
| 0 | ETH | ``spec`` | any | QUEUE,  |
|   |     +----------+-----+ DROP    |
|   |     | ``mask`` | any |         |
+---+-----+----------+-----+---------+

``FLEXIBLE`` to ``RAW`` → ``QUEUE``
-----------------------------------

`FLEXIBLE`_ can be translated to one `RAW`_ pattern with `QUEUE`_ as the
terminating action and a defined priority level.

+------------------------------------+
| FLEXIBLE                           |
+--------------------------+---------+
| Pattern                  | Actions |
+===+=====+==========+=====+=========+
| 0 | RAW | ``spec`` | any | QUEUE   |
|   |     +----------+-----+         |
|   |     | ``mask`` | any |         |
+---+-----+----------+-----+---------+

``SYN`` to ``TCP`` → ``QUEUE``
------------------------------

`SYN`_ is a `TCP`_ rule with only the ``syn`` bit enabled and masked, and
`QUEUE`_ as the terminating action.

Priority level can be set to simulate the high priority bit.

+---------------------------------------------+
| SYN                                         |
+-----------------------------------+---------+
| Pattern                           | Actions |
+===+======+==========+=============+=========+
| 0 | ETH  | ``spec`` | empty       | QUEUE   |
|   |      +----------+-------------+         |
|   |      | ``mask`` | empty       |         |
+---+------+----------+-------------+         |
| 1 | IPV4 | ``spec`` | empty       |         |
|   |      +----------+-------------+         |
|   |      | ``mask`` | empty       |         |
+---+------+----------+-------------+         |
| 2 | TCP  | ``spec`` | ``syn`` = 1 |         |
|   |      +----------+-------------+         |
|   |      | ``mask`` | ``syn`` = 1 |         |
+---+------+----------+-------------+---------+

``NTUPLE`` to ``IPV4``, ``TCP``, ``UDP`` → ``QUEUE``
----------------------------------------------------

`NTUPLE`_ is similar to specifying an empty L2, `IPV4`_ as L3 with `TCP`_ or
`UDP`_ as L4 and `QUEUE`_ as the terminating action.

A priority level can be specified as well.

+---------------------------------------+
| NTUPLE                                |
+-----------------------------+---------+
| Pattern                     | Actions |
+===+======+==========+=======+=========+
| 0 | ETH  | ``spec`` | empty | QUEUE   |
|   |      +----------+-------+         |
|   |      | ``mask`` | empty |         |
+---+------+----------+-------+         |
| 1 | IPV4 | ``spec`` | any   |         |
|   |      +----------+-------+         |
|   |      | ``mask`` | any   |         |
+---+------+----------+-------+         |
| 2 | TCP, | ``spec`` | any   |         |
|   | UDP  +----------+-------+         |
|   |      | ``mask`` | any   |         |
+---+------+----------+-------+---------+

``TUNNEL`` to ``ETH``, ``IPV4``, ``IPV6``, ``VXLAN`` (or other) → ``QUEUE``
---------------------------------------------------------------------------

`TUNNEL`_ matches common IPv4 and IPv6 L3/L4-based tunnel types.

In the following table, `ANY`_ is used to cover the optional L4.

+------------------------------------------------+
| TUNNEL                                         |
+--------------------------------------+---------+
| Pattern                              | Actions |
+===+=========+==========+=============+=========+
| 0 | ETH     | ``spec`` | any         | QUEUE   |
|   |         +----------+-------------+         |
|   |         | ``mask`` | any         |         |
+---+---------+----------+-------------+         |
| 1 | IPV4,   | ``spec`` | any         |         |
|   | IPV6    +----------+-------------+         |
|   |         | ``mask`` | any         |         |
+---+---------+----------+-------------+         |
| 2 | ANY     | ``spec`` | ``min`` = 0 |         |
|   |         |          +-------------+         |
|   |         |          | ``max`` = 0 |         |
|   |         +----------+-------------+         |
|   |         | ``mask`` | N/A         |         |
+---+---------+----------+-------------+         |
| 3 | VXLAN,  | ``spec`` | any         |         |
|   | GENEVE, +----------+-------------+         |
|   | TEREDO, | ``mask`` | any         |         |
|   | NVGRE,  |          |             |         |
|   | GRE,    |          |             |         |
|   | ...     |          |             |         |
+---+---------+----------+-------------+---------+

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``FDIR`` to most item types → ``QUEUE``, ``DROP``, ``PASSTHRU``
---------------------------------------------------------------

`FDIR`_ is more complex than any other type, there are several methods to
emulate its functionality. It is summarized for the most part in the table
below.

A few features are intentionally not supported:

- The ability to configure the matching input set and masks for the entire
  device, PMDs should take care of it automatically according to the
  requested flow rules.

  For example if a device supports only one bit-mask per protocol type,
  source/address IPv4 bit-masks can be made immutable by the first created
  rule. Subsequent IPv4 or TCPv4 rules can only be created if they are
  compatible.

  Note that only protocol bit-masks affected by existing flow rules are
  immutable, others can be changed later. They become mutable again after
  the related flow rules are destroyed.

- Returning four or eight bytes of matched data when using flex bytes
  filtering. Although a specific action could implement it, it conflicts
  with the much more useful 32 bits tagging on devices that support it.

- Side effects on RSS processing of the entire device. Flow rules that
  conflict with the current device configuration should not be
  allowed. Similarly, device configuration should not be allowed when it
  affects existing flow rules.

- Device modes of operation. "none" is unsupported since filtering cannot be
  disabled as long as a flow rule is present.

- "MAC VLAN" or "tunnel" perfect matching modes should be automatically set
  according to the created flow rules.

- Signature mode of operation is not defined but could be handled through a
  specific item type if needed.

+----------------------------------------------+
| FDIR                                         |
+---------------------------------+------------+
| Pattern                         | Actions    |
+===+============+==========+=====+============+
| 0 | ETH,       | ``spec`` | any | QUEUE,     |
|   | RAW        +----------+-----+ DROP,      |
|   |            | ``mask`` | any | PASSTHRU   |
+---+------------+----------+-----+------------+
| 1 | IPV4,      | ``spec`` | any | MARK       |
|   | IPV6       +----------+-----+ (optional) |
|   |            | ``mask`` | any |            |
+---+------------+----------+-----+            |
| 2 | TCP,       | ``spec`` | any |            |
|   | UDP,       +----------+-----+            |
|   | SCTP       | ``mask`` | any |            |
+---+------------+----------+-----+            |
| 3 | VF,        | ``spec`` | any |            |
|   | PF         +----------+-----+            |
|   | (optional) | ``mask`` | any |            |
+---+------------+----------+-----+------------+

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``HASH``
~~~~~~~~

There is no counterpart to this filter type because it translates to a
global device setting instead of a pattern item. Device settings are
automatically set according to the created flow rules.

``L2_TUNNEL`` to ``VOID`` → ``VXLAN`` (or others)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

All packets are matched. This type alters incoming packets to encapsulate
them in a chosen tunnel type, optionally redirect them to a VF as well.

The destination pool for tag based forwarding can be emulated with other
flow rules using `DUP`_ as the action.

+----------------------------------------+
| L2_TUNNEL                              |
+---------------------------+------------+
| Pattern                   | Actions    |
+===+======+==========+=====+============+
| 0 | VOID | ``spec`` | N/A | VXLAN,     |
|   |      |          |     | GENEVE,    |
|   |      |          |     | ...        |
|   |      +----------+-----+------------+
|   |      | ``mask`` | N/A | VF         |
|   |      |          |     | (optional) |
+---+------+----------+-----+------------+

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Future evolutions
=================

- Describing dedicated testpmd commands to control and validate this API.

- A method to optimize generic flow rules with specific pattern items and
  action types generated on the fly by PMDs. DPDK will assign negative
  numbers to these in order to not collide with the existing types. See
  `Negative types`_.

- Adding specific egress pattern items and actions as described in `Traffic
  direction`_.

- Optional software fallback when PMDs are unable to handle requested flow
  rules so applications do not have to implement their own.

- Ranges in addition to bit-masks. Ranges are more generic in many ways as
  they interpret values. For instance only ranges make sense to cover
  several TCP or UDP ports. These will probably be defined on a pattern item
  basis.

--------

Adrien Mazarguil (1):
  ethdev: introduce generic flow API

 lib/librte_ether/Makefile   |   2 +
 lib/librte_ether/rte_flow.h | 941 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 943 insertions(+)
 create mode 100644 lib/librte_ether/rte_flow.h

-- 
2.1.4