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Message-ID: <65e098566b4c3_d40e329486@willemb.c.googlers.com.notmuch>
Date: Thu, 29 Feb 2024 09:44:38 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Abhishek Chauhan <quic_abchauha@...cinc.com>
Cc: kernel@...cinc.com,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
Andrew Halaney <ahalaney@...hat.com>,
Martin KaFai Lau <martin.lau@...nel.org>
Subject: Re: [PATCH net-next v2] net: Modify mono_delivery_time with
clockid_delivery_time
Martin KaFai Lau wrote:
> On 2/28/24 7:53 AM, Willem de Bruijn wrote:
> > Sidenote: with sk_clockid, FQ could detect when skb->tstamp is not
> > set in monotonic (i.e., set by SO_TXTIME) and drop the packet or
> > ignore the embedded timestamp, warn, etc.
>
> Thanks for cc-ing me. Sorry for the late reply. I just catch up to this thread
> and the v1.
>
> I think it is needed to detect if skb->tstamp is monotonic or not in fq. The
> container (with the veth setup) may use sch_etf while the host usually uses fq
> at the physical NIC and expects monotonic skb->tstamp.
>
> During forward (e.g. by bpf_redirect / ip[6]_forward from a veth to a physical
> NIC), skb_clear_tstamp() only forwards the monotonic skb->tstamp now. While
> sch_etf does check sk_clockid first before using skb->tstamp, fq does not check
> that now.
> or fq_packet_beyond_horizon() is enough to catch this clock discrepancy?
Before your patch, I believe FQ had no such guard rails. An skb with
any clockid from SO_TXTIME can arrive at FQ.
With the new clockid field, we could add guard rails in fq_enqueue.
If the bit is set, look up sk_clockid.
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