netdev - Re: [Intel-wired-lan] [PATCH net-next v4 1/6] net: ethtool: allow symmetric-xor RSS hash for any flow type

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Date: Fri, 20 Oct 2023 17:14:11 -0600
From: Ahmed Zaki <ahmed.zaki@...el.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: <mkubecek@...e.cz>, <andrew@...n.ch>, <willemdebruijn.kernel@...il.com>,
	Wojciech Drewek <wojciech.drewek@...el.com>, <corbet@....net>,
	<netdev@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<jesse.brandeburg@...el.com>, <edumazet@...gle.com>,
	<anthony.l.nguyen@...el.com>, <horms@...nel.org>, <vladimir.oltean@....com>,
	Jacob Keller <jacob.e.keller@...el.com>, <intel-wired-lan@...ts.osuosl.org>,
	<pabeni@...hat.com>, <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [PATCH net-next v4 1/6] net: ethtool: allow
 symmetric-xor RSS hash for any flow type



On 2023-10-20 16:33, Jakub Kicinski wrote:
> On Fri, 20 Oct 2023 15:24:41 -0600 Ahmed Zaki wrote:
>>> IMO fat warning in the documentation and ethtool man saying that this
>>> makes the algo (any / all) vulnerable to attack would be enough.
>>> Willem?
>>
>> Please advise on the next step. Should I send a new version with the Doc
>> warning, or will you use v5?
> 
> Not just the doc changes:
> 
> | We can use one of the reserved fields of struct ethtool_rxfh to carry
> | this extension. I think I asked for this at some point, but there's
> | only so much repeated feedback one can send in a day :(
> 
> https://lore.kernel.org/all/20231016163059.23799429@kernel.org/

I replied to that here:

https://lore.kernel.org/all/afb4a06f-cfba-47ba-adb3-09bea7cb5f00@intel.com/

I am kind of confused now so please bear with me. ethtool either sends 
"ethtool_rxfh" or "ethtool_rxnfc". AFAIK "ethtool_rxfh" is the interface 
for "ethtool -X" which is used to set the RSS algorithm. But we kind of 
agreed to go with "ethtool -U|-N" for symmetric-xor, and that uses 
"ethtool_rxnfc" (as implemented in this series).

Do you mean use "ethtool_rxfh" instead of "ethtool_rxnfc"? how would 
that work on the ethtool user interface?

Finally, a note on Alex's comment:
 >It doesn't make sense to place it in the input flags and will just
 > cause quick congestion as things get added there. This is an algorithm
 > change so it makes more sense to place it there.

the "ethtool_rxnfc->data" is 64 bits and we are only using 8 bits so far.

Thank you.