From: Song Liu <songliubraving@fb.com>
Date: Mon, 30 Oct 2017 21:41:35 +0000 (-0700)
Subject: tcp: add tracepoint trace_tcp_retransmit_synack()
X-Git-Tag: v4.15-rc1~84^2~167
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=cf34ce3da1e41579296364509266c7dac573822a;p=linux.git

tcp: add tracepoint trace_tcp_retransmit_synack()

This tracepoint can be used to trace synack retransmits. It maintains
pointer to struct request_sock.

We cannot simply reuse trace_tcp_retransmit_skb() here, because the
sk here is the LISTEN socket. The IP addresses and ports should be
extracted from struct request_sock.

Note that, like many other tracepoints, this patch uses IS_ENABLED
in TP_fast_assign macro, which triggers sparse warning like:

./include/trace/events/tcp.h:274:1: error: directive in argument list
./include/trace/events/tcp.h:281:1: error: directive in argument list

However, there is no good solution to avoid these warnings. To the
best of our knowledge, these warnings are harmless.

Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
index 03699ba71623..07cccca6cbf1 100644
--- a/include/trace/events/tcp.h
+++ b/include/trace/events/tcp.h
@@ -237,6 +237,62 @@ TRACE_EVENT(tcp_set_state,
 		  show_tcp_state_name(__entry->newstate))
 );
 
+TRACE_EVENT(tcp_retransmit_synack,
+
+	TP_PROTO(const struct sock *sk, const struct request_sock *req),
+
+	TP_ARGS(sk, req),
+
+	TP_STRUCT__entry(
+		__field(const void *, skaddr)
+		__field(const void *, req)
+		__field(__u16, sport)
+		__field(__u16, dport)
+		__array(__u8, saddr, 4)
+		__array(__u8, daddr, 4)
+		__array(__u8, saddr_v6, 16)
+		__array(__u8, daddr_v6, 16)
+	),
+
+	TP_fast_assign(
+		struct inet_request_sock *ireq = inet_rsk(req);
+		struct in6_addr *pin6;
+		__be32 *p32;
+
+		__entry->skaddr = sk;
+		__entry->req = req;
+
+		__entry->sport = ireq->ir_num;
+		__entry->dport = ntohs(ireq->ir_rmt_port);
+
+		p32 = (__be32 *) __entry->saddr;
+		*p32 = ireq->ir_loc_addr;
+
+		p32 = (__be32 *) __entry->daddr;
+		*p32 = ireq->ir_rmt_addr;
+
+#if IS_ENABLED(CONFIG_IPV6)
+		if (sk->sk_family == AF_INET6) {
+			pin6 = (struct in6_addr *)__entry->saddr_v6;
+			*pin6 = ireq->ir_v6_loc_addr;
+			pin6 = (struct in6_addr *)__entry->daddr_v6;
+			*pin6 = ireq->ir_v6_rmt_addr;
+		} else
+#endif
+		{
+			pin6 = (struct in6_addr *)__entry->saddr_v6;
+			ipv6_addr_set_v4mapped(ireq->ir_loc_addr, pin6);
+			pin6 = (struct in6_addr *)__entry->daddr_v6;
+			ipv6_addr_set_v4mapped(ireq->ir_rmt_addr, pin6);
+		}
+	),
+
+	TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c",
+		  __entry->sport, __entry->dport,
+		  __entry->saddr, __entry->daddr,
+		  __entry->saddr_v6, __entry->daddr_v6)
+);
+
 #endif /* _TRACE_TCP_H */
 
 /* This part must be outside protection */
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index a85e8a282d17..06a0c89ffe40 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3782,6 +3782,7 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
 		if (unlikely(tcp_passive_fastopen(sk)))
 			tcp_sk(sk)->total_retrans++;
+		trace_tcp_retransmit_synack(sk, req);
 	}
 	return res;
 }