netdev - Re: [PATCH net-next v5 11/15] net-timestamp: support export skb to the userspace

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Message-ID: <8b9b9206-86ce-4d03-86b4-82f378fd0dc0@linux.dev>
Date: Wed, 15 Jan 2025 15:05:04 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, dsahern@...nel.org, willemdebruijn.kernel@...il.com,
 willemb@...gle.com, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev,
 john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, jolsa@...nel.org, horms@...nel.org, bpf@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net-next v5 11/15] net-timestamp: support export skb to
 the userspace

On 1/12/25 3:37 AM, Jason Xing wrote:
> People can follow these three steps as below to fetch the shared info
> from the exported skb in the bpf prog:
> 1. skops_kern = bpf_cast_to_kern_ctx(skops);
> 2. skb = skops_kern->skb;
> 3. shinfo = bpf_core_cast(skb->head + skb->end, struct skb_shared_info);
> 
> It's worth to highlight we will be able to fetch the hwstamp, tskey
> and more key information extracted from the skb.
> 
> More details can be seen in the last selftest patch of the series.
> 
> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> ---
>   net/core/sock.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index dbb9326ae9d1..2f54e60a50d4 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -958,6 +958,7 @@ void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op)
>   	if (sk_is_tcp(sk) && sk_fullsock(sk))
>   		sock_ops.is_fullsock = 1;
>   	sock_ops.sk = sk;
> +	bpf_skops_init_skb(&sock_ops, skb, 0);

nit. This change can fold into patch 1.

>   	sock_ops.timestamp_used = 1;
>   	__cgroup_bpf_run_filter_sock_ops(sk, &sock_ops, CGROUP_SOCK_OPS);
>   }