netdev - Re: [RFC PATCH v3 net-next 0/4] Preserve mono delivery time (EDT) in skb->tstamp

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Date:   Sat, 22 Jan 2022 13:05:22 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
CC:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, <kernel-team@...com>
Subject: Re: [RFC PATCH v3 net-next 0/4] Preserve mono delivery time (EDT) in
 skb->tstamp

On Sat, Jan 22, 2022 at 10:43:57AM -0500, Willem de Bruijn wrote:
> This overall looks great to me.
> 
> The only effect on timestamping is slightly delayed receive timestamp
> for packets arriving over a virtual loop (loopback, veth, ..)
> interface, as the timestamp is now captured at the network protocol
> input.
> 
> Actually, while writing that: timestamping is a socket level option,
> not specific to IP. Might this break receive timestamping over such
> interfaces for other protocols?
The EDT (and the skb->mono_delivery_time bit) is only set for TCP
which is IP only.  For other non IP skb->protocol, that bit is
not set, so the skb->tstamp should have been cleared as before.

Thanks for the review !