netdev - Re: [PATCH bpf-next v7 10/13] net-timestamp: make TCP tx timestamp bpf extension work

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Message-ID: <e7364435-caaa-481a-9fee-83e5c915ed07@linux.dev>
Date: Mon, 3 Feb 2025 17:03:08 -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 bpf-next v7 10/13] net-timestamp: make TCP tx timestamp
 bpf extension work

On 1/28/25 12:46 AM, Jason Xing wrote:
> Make partial of the feature work finally. After this, user can

If it is "partial"-ly done, what is still missing?

My understanding is after this patch, the BPF program can fully support the TX 
timestamping in TCP.

> fully use the bpf prog to trace the tx path for TCP type.
> 
> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> ---
>   net/ipv4/tcp.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 0d704bda6c41..0a41006b10d1 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -492,6 +492,15 @@ static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
>   		if (tsflags & SOF_TIMESTAMPING_TX_RECORD_MASK)
>   			shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
>   	}
> +
> +	if (SK_BPF_CB_FLAG_TEST(sk, SK_BPF_CB_TX_TIMESTAMPING) && skb) {
> +		struct skb_shared_info *shinfo = skb_shinfo(skb);
> +		struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
> +
> +		tcb->txstamp_ack_bpf = 1;
> +		shinfo->tx_flags |= SKBTX_BPF;
> +		shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
> +	}
>   }
>   
>   static bool tcp_stream_is_readable(struct sock *sk, int target)