[PATCH v4 net-next 1/2] tcp: use data length instead of skb->len in tcp_probe

From: Yafang Shao
Date: Tue May 29 2018 - 09:35:39 EST


At this point skb->len is including tcp header length, so it is meaningless
to user. data length could be more helpful, with which we can easily filter
out the packet without payload.

Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>

---
v4: no change on this patch
v3: tcp_hdr() is a little expensive than skb->data, so replace it with
skb->data.

---
include/trace/events/tcp.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
index c1a5284..7ff0446 100644
--- a/include/trace/events/tcp.h
+++ b/include/trace/events/tcp.h
@@ -236,7 +236,7 @@
__field(__u16, sport)
__field(__u16, dport)
__field(__u32, mark)
- __field(__u16, length)
+ __field(__u16, data_len)
__field(__u32, snd_nxt)
__field(__u32, snd_una)
__field(__u32, snd_cwnd)
@@ -250,6 +250,7 @@
TP_fast_assign(
const struct tcp_sock *tp = tcp_sk(sk);
const struct inet_sock *inet = inet_sk(sk);
+ const struct tcphdr *th = (const struct tcphdr *)skb->data;

memset(__entry->saddr, 0, sizeof(struct sockaddr_in6));
memset(__entry->daddr, 0, sizeof(struct sockaddr_in6));
@@ -261,7 +262,7 @@
__entry->dport = ntohs(inet->inet_dport);
__entry->mark = skb->mark;

- __entry->length = skb->len;
+ __entry->data_len = skb->len - __tcp_hdrlen(th);
__entry->snd_nxt = tp->snd_nxt;
__entry->snd_una = tp->snd_una;
__entry->snd_cwnd = tp->snd_cwnd;
@@ -272,9 +273,9 @@
__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->data_len, __entry->snd_nxt, __entry->snd_una,
__entry->snd_cwnd, __entry->ssthresh, __entry->snd_wnd,
__entry->srtt, __entry->rcv_wnd, __entry->sock_cookie)
);
--
1.8.3.1