Re: [RFC PATCH net-next v6 11/13] net-timestamp: add a new callback in tcp_tx_timestamp()

[Martin KaFai Lau <martin.lau@linux.dev>]

On 1/20/25 5:28 PM, Jason Xing wrote:
> Introduce the callback to correlate tcp_sendmsg timestamp with other
> three points (SND/SW/ACK). We can let bpf trace the beginning of
> tcp_sendmsg_locked() and fetch the socket addr, so that in
> tcp_tx_timestamp() we can correlate the tskey with the socket addr.
> It is accurate since they are under the protect of socket lock.
> More details can be found in the selftest.
> 
> Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
> ---
>   include/uapi/linux/bpf.h       | 3 +++
>   net/ipv4/tcp.c                 | 1 +
>   tools/include/uapi/linux/bpf.h | 3 +++
>   3 files changed, 7 insertions(+)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 3b9bfc88345c..55c74fa18163 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -7042,6 +7042,9 @@ enum {
>   					 * feature is on. It indicates the
>   					 * recorded timestamp.
>   					 */
> +	BPF_SOCK_OPS_TS_TCP_SND_CB,	/* Called when every tcp_sendmsg
> +					 * syscall is triggered
> +					 */

I recall we agreed in v5 to adjust the "TCP_" naming part because it will be 
used in UDP also. Like completely remove the "TCP_" from the name?

>   };
>   
>   /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 0a41006b10d1..49e489c346ea 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -500,6 +500,7 @@ static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
>   		tcb->txstamp_ack_bpf = 1;
>   		shinfo->tx_flags |= SKBTX_BPF;
>   		shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1;
> +		bpf_skops_tx_timestamping(sk, skb, BPF_SOCK_OPS_TS_TCP_SND_CB);
>   	}
>   }
>   
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index b463aa9c27da..38fc04a7ac20 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -7035,6 +7035,9 @@ enum {
>   					 * feature is on. It indicates the
>   					 * recorded timestamp.
>   					 */
> +	BPF_SOCK_OPS_TS_TCP_SND_CB,	/* Called when every tcp_sendmsg
> +					 * syscall is triggered
> +					 */
>   };
>   
>   /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect