[PATCH v2 net-next] tcp: expose sk_state in tcp_retransmit_skb tracepoint

[Yafang Shao]

After sk_state exposed, we can get in which state this retransmission
occurs. That could give us more detail for dignostic.
For example, if this retransmission occurs in SYN_SENT state, it may
also indicates that the syn packet may be dropped on the remote peer due
to syn backlog queue full and then we could check the remote peer.

BTW,SYNACK retransmission is traced in tcp_retransmit_synack tracepoint.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 include/trace/events/tcp.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
index ac55b32..2bc9960 100644
--- a/include/trace/events/tcp.h
+++ b/include/trace/events/tcp.h
@@ -56,6 +56,7 @@
 	TP_STRUCT__entry(
 		__field(const void *, skbaddr)
 		__field(const void *, skaddr)
+		__field(int, state)
 		__field(__u16, sport)
 		__field(__u16, dport)
 		__array(__u8, saddr, 4)
@@ -70,6 +71,7 @@
 
 		__entry->skbaddr = skb;
 		__entry->skaddr = sk;
+		__entry->state = sk->sk_state;
 
 		__entry->sport = ntohs(inet->inet_sport);
 		__entry->dport = ntohs(inet->inet_dport);
@@ -84,9 +86,10 @@
 			      sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
 	),
 
-	TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c",
+	TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c state=%s\n",
 		  __entry->sport, __entry->dport, __entry->saddr, __entry->daddr,
-		  __entry->saddr_v6, __entry->daddr_v6)
+		  __entry->saddr_v6, __entry->daddr_v6,
+		  show_tcp_state_name(__entry->state))
 );
 
 DEFINE_EVENT(tcp_event_sk_skb, tcp_retransmit_skb,
-- 
1.8.3.1