linux-kernel - Re: [PATCH net-next] tcp: use data length instead of skb->len in tcp

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Message-ID: <630ED9AE-A932-4B6A-8236-D133CE3E0726@fb.com>
Date:   Thu, 24 May 2018 17:44:46 +0000
From:   Song Liu <songliubraving@...com>
To:     Yafang Shao <laoar.shao@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] tcp: use data length instead of skb->len in
 tcp_probe



> On May 24, 2018, at 5:48 AM, Yafang Shao <laoar.shao@...il.com> wrote:
> 
> skb->len is meaningless to user.
> data length could be more helpful, with which we can easily filter out
> the packet without payload.
> 
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> ---
> include/trace/events/tcp.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> index c1a5284..259b991 100644
> --- a/include/trace/events/tcp.h
> +++ b/include/trace/events/tcp.h
> @@ -261,7 +261,7 @@
> 		__entry->dport = ntohs(inet->inet_dport);
> 		__entry->mark = skb->mark;
> 
> -		__entry->length = skb->len;
> +		__entry->length = skb->len - tcp_hdrlen(skb);

We should also rename __entry->length to __entry->data_len, so that whoever
using this field will notice the change. 

Thanks,
Song


> 		__entry->snd_nxt = tp->snd_nxt;
> 		__entry->snd_una = tp->snd_una;
> 		__entry->snd_cwnd = tp->snd_cwnd;
> @@ -272,7 +272,7 @@
> 		__entry->sock_cookie = sock_gen_cookie(sk);
> 	),
> 
> -	TP_printk("src=%pISpc dest=%pISpc mark=%#x length=%d snd_nxt=%#x snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u rcv_wnd=%u sock_cookie=%llx",
> +	TP_printk("src=%pISpc dest=%pISpc mark=%#x data_len=%d snd_nxt=%#x snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u rcv_wnd=%u sock_cookie=%llx",
> 		  __entry->saddr, __entry->daddr, __entry->mark,
> 		  __entry->length, __entry->snd_nxt, __entry->snd_una,
> 		  __entry->snd_cwnd, __entry->ssthresh, __entry->snd_wnd,
> -- 
> 1.8.3.1
>