netdev - Re: [RFC] vxlan: use ether header as fallback hash

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Date:	Thu, 4 Oct 2012 09:27:14 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [RFC] vxlan: use ether header as fallback hash

On Wed, Oct 3, 2012 at 9:39 PM, Stephen Hemminger <shemminger@...tta.com> wrote:
> VXLAN bases source UDP port based on flow to help the
> receiver to be able to load balance based on outer header
> contents.
>
> This patches changes the algorithm to better handle packets
> that can not be categorized by the rxhash() function.
> It adds a fallback to use jhash on the Ether header.
>
> It also fixes a bug where the old code could assign 0 as a port
> value.
>
>
> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>
> ---
> RFC for now, compile tested only
>
> --- a/drivers/net/vxlan.c       2012-10-03 21:25:43.747968165 -0700
> +++ b/drivers/net/vxlan.c       2012-10-03 21:36:10.213805422 -0700
> @@ -622,12 +622,30 @@ static inline u8 vxlan_ecn_encap(u8 tos,
>         return INET_ECN_encapsulate(tos, inner);
>  }
>
> +/* Compute hash to use for source port
> + *   first choice to use L4 flow hash since it will spread
> + *     better and maybe available from hardware
> + *   secondary choice is to use jhash on the Ethernet header
> + * Always returns non-zero value
> + */
> +static u16 vxlan_flow_hash(struct sk_buff *skb)
> +{
> +       u16 hash = skb_get_rxhash(skb);
> +
> +       if (!hash)
> +               hash = jhash(skb->data, 3, skb->protocol);

Shouldn't this be jhash2 for words?
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