netdev - Re: [PATCH net-next] ipv4: use l4 hash for locally generated multipath flows

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Date:	Thu, 29 Oct 2015 16:00:59 +0100
From:	Paolo Abeni <pabeni@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Peter Nørlund <pch@...bogen.com>,
	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH net-next] ipv4: use l4 hash for locally generated
 multipath flows

On Thu, 2015-10-29 at 07:31 -0700, Eric Dumazet wrote:
> On Wed, 2015-10-28 at 18:39 +0100, Paolo Abeni wrote:
> > This patch changes how the multipath hash is computed for locally
> > generated UDP or TCP flows: now the hash comprises also l4 information
> > (source and destination port).
> > 
> > This allows better utilization of the available paths when the existing
> > flows have the same source IP and the same destination IP: with l3 hash,
> > even when multiple connections are in place simultaneously, a single path
> > will be used, while with l4 hash we can use all the available paths.
> > 
> > Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> 
> Please note that many skb already have a l4 hash. No need to perform yet
> another dissection.

This patch do not add dissection code: it use the information provided
by the available flowi4 structure. Moreover the skb is not available on
the calling site (in __ip_route_output_key_hash) and pushing it all the
way will require a lot of intrusive changes. Do you think it's the
better option ?

Paolo

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