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

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Message-ID: <5215f88a-bd31-ccdf-25c9-f06ec602295e@ovn.org>
Date: Thu, 11 May 2023 13:59:32 +0200
From: Ilya Maximets <i.maximets@....org>
To: Antoine Tenart <atenart@...nel.org>, davem@...emloft.net,
 kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com
Cc: netdev@...r.kernel.org, i.maximets@....org
Subject: Re: [PATCH net-next 0/4] net: tcp: make txhash use consistent for
 IPv4

On 5/11/23 11:34, Antoine Tenart wrote:
> Hello,
> 
> 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.

FWIW, same also applies to seg6_flowlabel that is used for flowlable
based load balancing, because seg6_make_flowlabel() is using skb hash.

Best regards, Ilya Maximets.

> 
> IMHO the series makes sense in net-next, but we could argue (some)
> commits be seen as fixes and I can resend if necessary.
> 
> Thanks!
> Antoine
> 
> Antoine Tenart (4):
>   net: tcp: make the txhash available in TIME_WAIT sockets for IPv4 too
>   net: ipv4: use consistent txhash in TIME_WAIT and SYN_RECV
>   Documentation: net: net.core.txrehash is not specific to listening
>     sockets
>   net: skbuff: fix l4_hash comment
> 
>  Documentation/admin-guide/sysctl/net.rst |  4 ++--
>  include/linux/skbuff.h                   |  4 ++--
>  include/net/ip.h                         |  2 +-
>  net/ipv4/ip_output.c                     |  4 +++-
>  net/ipv4/tcp_ipv4.c                      | 14 +++++++++-----
>  net/ipv4/tcp_minisocks.c                 |  2 +-
>  6 files changed, 18 insertions(+), 12 deletions(-)
>