Re: [dpdk-dev] [PATCH 1/2] ethdev: add symmetric toeplitz hash support

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 7/31/19 3:30 PM, Adrien Mazarguil wrote:
> On Wed, Jul 31, 2019 at 03:08:19PM +0300, Andrew Rybchenko wrote:
>> On 7/25/19 7:57 AM, simei wrote:
>>> From: Simei Su <simei.su@intel.com>
>>>
>>> Currently, there are DEFAULT,TOEPLITZ and SIMPLE_XOR hash funtion.
>>> To support symmetric hash by rte_flow RSS action, this patch adds
>>> new hash function "Symmetric Toeplitz" which is supported by some hardware.
>> Isn't it a question of key to achieve symmetry?
>> I.e. hash algorithm (function) is still the same - Toeplitz, but
>> hash key makes the result symmetric (i.e. equal for flows in both
>> directions - swap transport ports and IPv4/6 addresses).
> This is only an option when src/dst are known in advance.
>
> When doing RSS, HW implementations (such as Mellanox's) implement a modified
> Toeplitz XOR'ing src with dst resulting in the same hash both ways
> regardless of the key.

OK, I see. But generic symmetric Toeplitz is introduced by the patch.
What is criteria for other vendor to say that it is supported?
What should application expect?
The algorithm should be defined.

Also interesting question is how does it co-exists with the other
patch in the mailing list which introduces way to use source or
destination IP/port only.