[PATCH] [RFC PATCH] tcp event: add new tcp:tcp_cwnd_restart event

[Manjusaka]

The tcp_cwnd_restart function would be called if the user has enabled the
tcp_slow_start_after_idle configuration and would be triggered when the
connection is idle (like LONG RTO etc.). I think it would be great to
add a new trace event named 'tcp:tcp_cwnd_reset'; it would help people
to monitor the TCP state in a complicated network environment(like
overlay/underlay SDN in Kubernetes, etc)

Signed-off-by: Manjusaka <me@xxxxxxxxxxxx>
---
 include/trace/events/tcp.h | 7 +++++++
 net/ipv4/tcp_output.c      | 1 +
 2 files changed, 8 insertions(+)

diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
index bf06db8d2046..fa44191cc609 100644
--- a/include/trace/events/tcp.h
+++ b/include/trace/events/tcp.h
@@ -187,6 +187,13 @@ DEFINE_EVENT(tcp_event_sk, tcp_rcv_space_adjust,
 	TP_ARGS(sk)
 );
 
+DEFINE_EVENT(tcp_event_sk, tcp_cwnd_restart,
+
+	TP_PROTO(struct sock *sk),
+
+	TP_ARGS(sk)
+);
+
 TRACE_EVENT(tcp_retransmit_synack,
 
 	TP_PROTO(const struct sock *sk, const struct request_sock *req),
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 51d8638d4b4c..e902fa74303d 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -141,6 +141,7 @@ static __u16 tcp_advertise_mss(struct sock *sk)
  */
 void tcp_cwnd_restart(struct sock *sk, s32 delta)
 {
+	trace_tcp_cwnd_restart(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
 	u32 cwnd = tcp_snd_cwnd(tp);
-- 
2.34.1