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

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

[Yafang Shao]

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@gmail.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);
 		__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

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

[Song Liu]

> On May 24, 2018, at 5:48 AM, Yafang Shao <laoar.shao@gmail.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@gmail.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
> 

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

[David Miller]

From: Song Liu <songliubraving@fb.com>
Date: Thu, 24 May 2018 17:44:46 +0000

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

Agreed.