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

[Adrien Mazarguil]

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 at 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.

-- 
Adrien Mazarguil
6WIND