tcp: add trace event class tcp_event_sk_skb

Introduce event class tcp_event_sk_skb for tcp tracepoints that
have arguments sk and skb.

Existing tracepoint trace_tcp_retransmit_skb() falls into this class.
This patch rewrites the definition of trace_tcp_retransmit_skb() with
tcp_event_sk_skb.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/trace/events/tcp.h

@@ -9,7 +9,13 @@
 #include <linux/tracepoint.h>
 #include <net/ipv6.h>
 
-TRACE_EVENT(tcp_retransmit_skb,
+/*
+ * tcp event with arguments sk and skb
+ *
+ * Note: this class requires a valid sk pointer; while skb pointer could
+ *       be NULL.
+ */
+DECLARE_EVENT_CLASS(tcp_event_sk_skb,
 
 	TP_PROTO(struct sock *sk, struct sk_buff *skb),
 
@@ -64,6 +70,13 @@ TRACE_EVENT(tcp_retransmit_skb,
 		  __entry->saddr_v6, __entry->daddr_v6)
 );
 
+DEFINE_EVENT(tcp_event_sk_skb, tcp_retransmit_skb,
+
+	TP_PROTO(struct sock *sk, struct sk_buff *skb),
+
+	TP_ARGS(sk, skb)
+);
+
 #endif /* _TRACE_TCP_H */
 
 /* This part must be outside protection */