From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH 1/2 v2] net: Add function to get SW rxhash
Date: Tue, 24 Sep 2013 14:30:03 -0700
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Cc: davem@davemloft.net, netdev@vger.kernel.org
To: Tom Herbert <therbert@google.com>
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On Tue, 2013-09-24 at 13:42 -0700, Tom Herbert wrote:
> Some uses of skb_get_rxhash expect that the function will return
> a consistent value whether it is called on RX or TX paths. On RX
> path, we will use the rxhash if provided by the NIC, so this
> would not normally be the same result computed in TX path would be
> a software calculation.
> 
> This patch adds skb_get_sw_rxhash to explicitly request a hash
> calculated by the stack, disregarding the hash provided by NIC.

As I said, I think this is overhead in network fast path.

This can be done without adding a new skb field.

I suspect tun should not use rxhash but a proper hash, as conntrack or
tcp...