[PATCH v4] tracepoint: add new `tcp:tcp_ca_event` trace event

[Zheao Li]

Hello 

This the 4th version of the patch, the previous discusstion is here

https://lore.kernel.org/linux-trace-kernel/20230807183308.9015-1-me@xxxxxxxxxxxx/

In this version of the code, here's some different:

1. The event name has been changed from `tcp_ca_event_set` to
`tcp_ca_event`

2. Output the current protocol family in TP_printk

3. Show the ca_event symbol instead of the original number

But the `./scripts/checkpatch.pl` has been failed to check this patch,
because we sill have some code error in ./scripts/checkpatch.pl(in
another world, the test would be failed when we use the 
scripts/checkpatch.pl to check the events/tcp.h

Feel free to ask me if you have have any issues and ideas.

Thanks

---

In normal use case, the tcp_ca_event would be changed in high frequency.

The developer can monitor the network quality more easier by tracing
TCP stack with this TP event.

So I propose to add a `tcp:tcp_ca_event` trace event
like `tcp:tcp_cong_state_set` to help the people to
trace the TCP connection status

Signed-off-by: Zheao Li <me@xxxxxxxxxxxx>
---
 include/net/tcp.h          |  9 ++----
 include/trace/events/tcp.h | 60 ++++++++++++++++++++++++++++++++++++++
 net/ipv4/tcp_cong.c        | 10 +++++++
 3 files changed, 72 insertions(+), 7 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0ca972ebd3dd..a68c5b61889c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1154,13 +1154,8 @@ static inline bool tcp_ca_needs_ecn(const struct sock *sk)
 	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
 }
 
-static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
-{
-	const struct inet_connection_sock *icsk = inet_csk(sk);
-
-	if (icsk->icsk_ca_ops->cwnd_event)
-		icsk->icsk_ca_ops->cwnd_event(sk, event);
-}
+/* from tcp_cong.c */
+void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event);
 
 /* From tcp_cong.c */
 void tcp_set_ca_state(struct sock *sk, const u8 ca_state);
diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
index 7b1ddffa3dfc..993eb00403ea 100644
--- a/include/trace/events/tcp.h
+++ b/include/trace/events/tcp.h
@@ -41,6 +41,18 @@
 	TP_STORE_V4MAPPED(__entry, saddr, daddr)
 #endif
 
+/* The TCP CA event traced by tcp_ca_event*/
+#define tcp_ca_event_names    \
+		EM(CA_EVENT_TX_START)     \
+		EM(CA_EVENT_CWND_RESTART) \
+		EM(CA_EVENT_COMPLETE_CWR) \
+		EM(CA_EVENT_LOSS)         \
+		EM(CA_EVENT_ECN_NO_CE)    \
+		EMe(CA_EVENT_ECN_IS_CE)
+
+#define show_tcp_ca_event_names(val) \
+	__print_symbolic(val, tcp_ca_event_names)
+
 /*
  * tcp event with arguments sk and skb
  *
@@ -419,6 +431,54 @@ TRACE_EVENT(tcp_cong_state_set,
 		  __entry->cong_state)
 );
 
+TRACE_EVENT(tcp_ca_event,
+
+	TP_PROTO(struct sock *sk, const u8 ca_event),
+
+	TP_ARGS(sk, ca_event),
+
+	TP_STRUCT__entry(
+		__field(const void *, skaddr)
+		__field(__u16, sport)
+		__field(__u16, dport)
+		__field(__u16, family)
+		__array(__u8, saddr, 4)
+		__array(__u8, daddr, 4)
+		__array(__u8, saddr_v6, 16)
+		__array(__u8, daddr_v6, 16)
+		__field(__u8, ca_event)
+	),
+
+	TP_fast_assign(
+		struct inet_sock *inet = inet_sk(sk);
+		__be32 *p32;
+
+		__entry->skaddr = sk;
+
+		__entry->sport = ntohs(inet->inet_sport);
+		__entry->dport = ntohs(inet->inet_dport);
+		__entry->family = sk->sk_family;
+
+		p32 = (__be32 *) __entry->saddr;
+		*p32 = inet->inet_saddr;
+
+		p32 = (__be32 *) __entry->daddr;
+		*p32 =  inet->inet_daddr;
+
+		TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr,
+			   sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
+
+		__entry->ca_event = ca_event;
+	),
+
+	TP_printk("family=%s sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c ca_event=%s",
+		  show_family_name(__entry->family),
+		  __entry->sport, __entry->dport,
+		  __entry->saddr, __entry->daddr,
+		  __entry->saddr_v6, __entry->daddr_v6,
+		  show_tcp_ca_event_names(__entry->ca_event))
+);
+
 #endif /* _TRACE_TCP_H */
 
 /* This part must be outside protection */
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 1b34050a7538..fb7ec6ebbbd0 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -34,6 +34,16 @@ struct tcp_congestion_ops *tcp_ca_find(const char *name)
 	return NULL;
 }
 
+void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
+{
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+
+	trace_tcp_ca_event(sk, (u8)event);
+
+	if (icsk->icsk_ca_ops->cwnd_event)
+		icsk->icsk_ca_ops->cwnd_event(sk, event);
+}
+
 void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
-- 
2.34.1