netdev - Re: [RFC PATCH net-next 2/2] net: Reset forwarded skb->tstamp before delivering to user space

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Message-ID: <20211208204816.tvwckytomjuei2fz@kafai-mbp.dhcp.thefacebook.com>
Date:   Wed, 8 Dec 2021 12:48:16 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     Eric Dumazet <edumazet@...gle.com>
CC:     Daniel Borkmann <daniel@...earbox.net>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, <Kernel-team@...com>
Subject: Re: [RFC PATCH net-next 2/2] net: Reset forwarded skb->tstamp before
 delivering to user space

On Wed, Dec 08, 2021 at 10:27:51AM -0800, Eric Dumazet wrote:
> On Wed, Dec 8, 2021 at 12:30 AM Martin KaFai Lau <kafai@...com> wrote:
> 
> > For non bpf ingress, hmmm.... yeah, not sure if it is indeed an issue :/
> > may be save the tx tstamp first and then temporarily restamp with __net_timestamp()
> 
> Martin, have you looked at time namespaces (CLONE_NEWTIME) ?
> 
> Perhaps we need to have more than one bit to describe time bases.
My noob understanding is it only affects the time returning
to the user in the syscall.  Could you explain how that
may affect the time in skb->tstamp?