netdev - Re: [PATCH] net-packet: tx timestamping on tpacket ring

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Date:	Mon, 15 Apr 2013 09:31:14 +0200
From:	Paul Chavent <Paul.Chavent@...ra.fr>
To:	Willem de Bruijn <willemb@...gle.com>
CC:	richardcochran@...il.com, edumazet@...gle.com,
	daniel.borkmann@....ee.ethz.ch, xemul@...allels.com,
	ebiederm@...ssion.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net-packet: tx timestamping on tpacket ring

Hi.

On 04/13/2013 08:56 PM, Willem de Bruijn wrote:
> [...]
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3311,7 +3311,7 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
>   		 * so keep the shared tx_flags and only
>   		 * store software time stamp
>   		 */
> -		skb->tstamp = ktime_get_real();
> +		orig_skb->tstamp = skb->tstamp = ktime_get_real();
>   	}

You said that "the orig_skb is usually freed shortly after
skb_tstamp_tx is called".

So i suppose that if you had coded it, that's because this orig_skb is 
the one that is given to the skb destructor. So when you call 
__packet_set_timestamp, in tpacket_destruct_skb, you get this timestamp 
? Am i right ?

Why we couldn't call
*skb_hwtstamps(orig_skb) = *skb_hwtstamps(skb) = *hwtstamps;
in order to get the hardware timestamping too ?

Thank for your help.

Paul.
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