netdev - Re: RFC: VETH patch to zero timestamp.

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Date:	Thu, 16 Jul 2009 17:01:43 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Ben Greear <greearb@...delatech.com>
Cc:	NetDev <netdev@...r.kernel.org>, xemul@...nvz.org,
	Linux Containers <containers@...ts.osdl.org>
Subject: Re: RFC:  VETH patch to zero timestamp.

Ben Greear <greearb@...delatech.com> writes:

> The patch below helps when using VETH and bridge(s)
> This makes sure that the pkt timestamp is properly (re)calculated on
> receiving the packet on the peer veth device.
>
> I'm sure this patch is white-space damaged.  If this looks
> useful, I'll generate a clean patch and send as attachment.

We reset everything else that needs to be reset.  So we might as well
reset the timestamps as well.  Unless there is a big performance
impact by doing so.

> Signed-off-by:  Ben Greear<greearb@...delatech.com>
>
>
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 1097c72..e9136af 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -170,7 +173,12 @@ static int veth_xmit(struct sk_buff *skb, struct net_device *dev)
>
>         if (skb->len > (rcv->mtu + MTU_PAD))
>                 goto rx_drop;
> -
> +
> +       /* Zero out the time-stamp so that receiving code is forced
> +        * to recalculate it.
> +        */
> +       skb->tstamp.tv64 = 0;
> +
>         skb->pkt_type = PACKET_HOST;
>         skb->protocol = eth_type_trans(skb, rcv);
>         if (dev->features & NETIF_F_NO_CSUM)
>
>
> Thanks,
> Ben
>
> -- 
> Ben Greear <greearb@...delatech.com>
> Candela Technologies Inc  http://www.candelatech.com
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