netdev - Re: [PATCH net-next 0/4] net: tcp: make txhash use consistent for IPv4

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Date:   Thu, 27 Apr 2023 17:44:06 +0200
From:   Antoine Tenart <atenart@...nel.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/4] net: tcp: make txhash use consistent for IPv4

Quoting Eric Dumazet (2023-04-27 17:15:27)
> On Thu, Apr 27, 2023 at 3:45 PM Antoine Tenart <atenart@...nel.org> wrote:
> >
> > Series is divided in two parts. First two commits make the txhash (used
> > for the skb hash in TCP) to be consistent for all IPv4/TCP packets (IPv6
> > doesn't have the same issue). Last two commits improve doc/comment
> > hash-related parts.
> >
> > One example is when using OvS with dp_hash, which uses skb->hash, to
> > select a path. We'd like packets from the same flow to be consistent, as
> > well as the hash being stable over time when using net.core.txrehash=0.
> > Same applies for kernel ECMP which also can use skb->hash.
> 
> How do you plan to test these patches ?

I did perform manual checks (with net.core.txrehash=0 to make sure the
hash was consistent) using a setup with OvS and dp_hash (~ECMP like) and
looking which path packets took. Not sure if there is a simpler test
that could be automated, we can't use autoflowlabel to make simple
scripts like for IPv6. Anything you'd like to see specifically?

> > IMHO the series makes sense in net-next, but we could argue (some)
> > commits be seen as fixes and I can resend if necessary.
> 
> net-next is closed...

I was convinced to have checked, but well, completely missed it. Sorry
about that... Will resend when appropriate.

Thanks,
Antoine