Re: RSS Hash value returned by the gvnic pmd dpdk driver not matching Toeplitz

[Nagesh Mallappa <mallappanagesh@gmail.com>]

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Hi Stephen,

Thanks for your response,
I have verified that too, but that is not the case.

Thanks,
Nagesh

On Wed, May 15, 2024 at 8:34 PM Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Wed, 15 May 2024 13:50:38 +0530
> Nagesh Mallappa <mallappanagesh@gmail.com> wrote:
>
> > Hi Team,
> >
> > We are using a C3 GCP instance having GVNIC with DPDK enabled.
> > We are using latest version of DPDK ( dpdk-24.03 ) to configure RSS key,
> we
> > understand C3 GCP instance with gvnic supports Toeplitz rss algorithm (
> > Reference -
> >
> https://github.com/google/compute-virtual-ethernet-dpdk/blob/main/gve_ethdev.c
> > ),
> > but we are hitting below issue.
> >
> > *Problem Statement - The RSS Hash value returned by the gvnic driver is
> > different and is not matching the one computed by Toeplitz.*
> >
> > Using below script to compute rss hash value from Toeplitz.
> > (https://gist.github.com/joongh/16867705b03b49e393cbf91da3cb42a7)
> >
> > Consider below data to compute RSS Hash value -
> >
> > Source IP - 79.124.62.122
> > Destination IP - 192.168.7.28
> > Source Port - 49442
> > Destination Port - 55327
> > RSS Key - {0x94e3e97e, 0x4abac401, 0x1e0edbf, 0xe059e1f4, 0xb6e27dff,
> > 0xdf55c916, 0xe9e6e4db, 0x1f9fb82c, 0x1e0edbf, 0xe059e1f4}
> >
> > *Hash Value returned by Toeplitz - 0x8bbafd0f*
> >
> > Gvnic dpdk pmd driver which uses Toeplitz RSS hash algorithm too is
> > expected to compute above RSS Hash value but we see the Hash value stored
> > in dpdk mbuf to be 0xc6a15941 which is not right.
> > From the DPDK side we have ensured RSS offloading configuration is done
> > appropriately, but still we are seeing above mismatch.
> >
> > We request you to please help us understand why this mismatch is
> happening
> > and is this expected behavior of gvnic on C3 instance.
>
> Could you see if it is a driver byte order issue by byteswapping the key?
>

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