Re: [RFC] Generic flow director/filtering/classification API

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Tue, Jul 05, 2016 at 08:16:46PM +0200, Adrien Mazarguil wrote:

Hi Adrien,

Overall this proposal looks very good. I could easily map to the
classification hardware engines I am familiar with.


> Priorities
> ~~~~~~~~~~
> 
> A priority can be assigned to a matching pattern.
> 
> The default priority level is 0 and is also the highest. Support for more
> than a single priority level in hardware is not guaranteed.
> 
> If a packet is matched by several filters at a given priority level, the
> outcome is undefined. It can take any path and can even be duplicated.

In some cases fatal unrecoverable error too

> 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       |
> +---+------------+

How about enumerating as "Inner-IPV6" flow type to avoid any confusion. Though spec
can be same for both IPv6 and Inner-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.

It would be good if the common code can give it as Ethernet, IPV6, UDP
to PMD(to avoid common code duplication across PMDs)

> 
> 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.

a separate flow type enumeration may fix that problem. like "Inner-IPV6"
mentioned above.

> 
> +---------------------+
> | 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.
> 

> ``SIGNATURE``
> ^^^^^^^^^^^^^
> 
> Requests hash-based signature dispatching for this rule.
> 
> Considering this is a global setting on devices that support it, all
> subsequent filter rules may have to be created with it as well.

Can you describe the use case for this and how its different from
existing rte_eth devel RSS settings.

> 
> - Only ``spec`` needs to be defined, ``mask`` is ignored.
> 
> +--------------------+
> | SIGNATURE          |
> +==========+=========+
> | ``spec`` | TBD     |
> +----------+---------+
> | ``mask`` | ignored |
> +----------+---------+
> 

> 
> ``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, innermost first. For each one:
> 
>  - ``tpid``: Tag protocol identifier.
>  - ``tci``: Tag control information.

Find below the other L2 layer attributes are useful in HW classification,

- HiGig headers
- DSA Headers
- MPLS

May be we need to intrdouce a separate flow type with spec to add the support. Right?

Jerin