netdev - Re: [PATCH bpf-next v12 12/12] selftests/bpf: add simple bpf tests in the tx path for timestamping feature

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Message-ID: <67b49848ec47c_10d6a329425@willemb.c.googlers.com.notmuch>
Date: Tue, 18 Feb 2025 09:25:12 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jason Xing <kerneljasonxing@...il.com>, 
 davem@...emloft.net, 
 edumazet@...gle.com, 
 kuba@...nel.org, 
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 martin.lau@...ux.dev, 
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Cc: bpf@...r.kernel.org, 
 netdev@...r.kernel.org, 
 Jason Xing <kerneljasonxing@...il.com>
Subject: Re: [PATCH bpf-next v12 12/12] selftests/bpf: add simple bpf tests in
 the tx path for timestamping feature

Jason Xing wrote:
> BPF program calculates a couple of latency deltas between each tx
> timestamping callbacks. It can be used in the real world to diagnose
> the kernel behaviour in the tx path.
> 
> Check the safety issues by accessing a few bpf calls in
> bpf_test_access_bpf_calls() which are implemented in the patch 3 and 4.
> 
> Check if the bpf timestamping can co-exist with socket timestamping.
> 
> There remains a few realistic things[1][2] to highlight:
> 1. in general a packet may pass through multiple qdiscs. For instance
> with bonding or tunnel virtual devices in the egress path.
> 2. packets may be resent, in which case an ACK might precede a repeat
> SCHED and SND.
> 3. erroneous or malicious peers may also just never send an ACK.
> 
> [1]: https://lore.kernel.org/all/67a389af981b0_14e0832949d@willemb.c.googlers.com.notmuch/
> [2]: https://lore.kernel.org/all/c329a0c1-239b-4ca1-91f2-cb30b8dd2f6a@linux.dev/
> 
> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>