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 03699ba716230882db91bf8d2bbc11d12099accd..07cccca6cbf1762684152146372e35e1cd758338 100644 (file)
--- 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 a85e8a282d173983e35a2a1e3135ca2a63f1699e..06a0c89ffe408b58ee17bdafd81bb08c3eb2e3fd 100644 (file)
--- 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;
 }