netdev - Re: [PATCH 1/2] net: Toeplitz library functions

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Message-ID: <1380042143.2736.48.camel@bwh-desktop.uk.level5networks.com>
Date:	Tue, 24 Sep 2013 18:02:23 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Tom Herbert <therbert@...gle.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	David Miller <davem@...emloft.net>,
	"Linux Netdev List" <netdev@...r.kernel.org>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
Subject: Re: [PATCH 1/2] net: Toeplitz library functions

On Tue, 2013-09-24 at 09:46 -0700, Eric Dumazet wrote:
> On Tue, 2013-09-24 at 09:35 -0700, Tom Herbert wrote:
> 
> > We should really be using rxhash for that anyway, eliminate this
> > ehashfn.  This would entail adding rxhash argument in the various
> > udp_lookup functions.
> 
> Nope : Some NICs provide UDP rxhash only using L3  (source IP,
> destination IP), not L4 (adding source & destination ports)

Indeed the Microsoft RSS spec doesn't define an L4 hash for UDP/IP,
since it can't work with fragmented datagrams (which TCP avoids).  Using
the TCP/IP hash function for UDP is a non-standard option - presumably
useful where no fragmentation is expected.

Ben.

> This is again a case where we want our own hashing.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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