linux-kernel - Re: [Intel-wired-lan] [PATCH] igc: Fix HW RX timestamp when passed by ZC XDP

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Message-ID: <320b5101-8c57-4fa0-9f22-99b984c7a48c@intel.com>
Date: Thu, 6 Feb 2025 14:47:16 +0200
From: Mor Bar-Gabay <morx.bar.gabay@...el.com>
To: Zdenek Bouska <zdenek.bouska@...mens.com>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>, "Daniel
 Borkmann" <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>, Vinicius Costa Gomes
	<vinicius.gomes@...el.com>, Florian Bezdeka <florian.bezdeka@...mens.com>,
	Jan Kiszka <jan.kiszka@...mens.com>, Song Yoong Siang
	<yoong.siang.song@...el.com>
CC: <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: Re: [Intel-wired-lan] [PATCH] igc: Fix HW RX timestamp when passed by
 ZC XDP

On 28/01/2025 14:26, Zdenek Bouska wrote:
> Fixes HW RX timestamp in the following scenario:
> - AF_PACKET socket with enabled HW RX timestamps is created
> - AF_XDP socket with enabled zero copy is created
> - frame is forwarded to the BPF program, where the timestamp should
>    still be readable (extracted by igc_xdp_rx_timestamp(), kfunc
>    behind bpf_xdp_metadata_rx_timestamp())
> - the frame got XDP_PASS from BPF program, redirecting to the stack
> - AF_PACKET socket receives the frame with HW RX timestamp
> 
> Moves the skb timestamp setting from igc_dispatch_skb_zc() to
> igc_construct_skb_zc() so that igc_construct_skb_zc() is similar to
> igc_construct_skb().
> 
> This issue can also be reproduced by running:
>   # tools/testing/selftests/bpf/xdp_hw_metadata enp1s0
> When a frame with the wrong port 9092 (instead of 9091) is used:
>   # echo -n xdp | nc -u -q1 192.168.10.9 9092
> then the RX timestamp is missing and xdp_hw_metadata prints:
>   skb hwtstamp is not found!
> 
> With this fix or when copy mode is used:
>   # tools/testing/selftests/bpf/xdp_hw_metadata -c enp1s0
> then RX timestamp is found and xdp_hw_metadata prints:
>   found skb hwtstamp = 1736509937.852786132
> 
> Fixes: 069b142f5819 ("igc: Add support for PTP .getcyclesx64()")
> Signed-off-by: Zdenek Bouska <zdenek.bouska@...mens.com>
> Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> Reviewed-by: Simon Horman <horms@...nel.org>
> Reviewed-by: Florian Bezdeka <florian.bezdeka@...mens.com>
> Reviewed-by: Song Yoong Siang <yoong.siang.song@...el.com>
> ---
>   drivers/net/ethernet/intel/igc/igc_main.c | 21 ++++++++++++---------
>   1 file changed, 12 insertions(+), 9 deletions(-)
> 
Tested-by: Mor Bar-Gabay <morx.bar.gabay@...el.com>