netdev - Re: [PATCH net-next] net: add a helper to avoid issues with HW TX timestamping and SO

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Message-ID: <87k0qen5vh.fsf@vcostago-mobl2.amr.corp.intel.com>
Date:   Wed, 10 Mar 2021 11:52:34 -0800
From:   Vinicius Costa Gomes <vinicius.gomes@...el.com>
To:     Vladimir Oltean <olteanv@...il.com>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Po Liu <po.liu@....com>,
        Claudiu Manoil <claudiu.manoil@....com>
Cc:     Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH net-next] net: add a helper to avoid issues with HW TX
 timestamping and SO_TXTIME

Vladimir Oltean <olteanv@...il.com> writes:

> As explained in commit 29d98f54a4fe ("net: enetc: allow hardware
> timestamping on TX queues with tc-etf enabled"), hardware TX
> timestamping requires an skb with skb->tstamp = 0. When a packet is sent
> with SO_TXTIME, the skb->skb_mstamp_ns corrupts the value of skb->tstamp,
> so the drivers need to explicitly reset skb->tstamp to zero after
> consuming the TX time.
>
> Create a helper named skb_txtime_consumed() which does just that. All
> drivers which offload TC_SETUP_QDISC_ETF should implement it, and it

nitpick: to my ears, it seems that you meant "call"/"use" instead of
"implement".

> would make it easier to assess during review whether they do the right
> thing in order to be compatible with hardware timestamping or not.
>
> Suggested-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---

Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>


Cheers,
-- 
Vinicius