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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>
This commit is contained in:
Song Liu 2017-10-30 14:41:35 -07:00 committed by David S. Miller
parent 47d3d7ac65
commit cf34ce3da1
2 changed files with 57 additions and 0 deletions
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56
include/trace/events/tcp.h
View File

@ -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 */

1
net/ipv4/tcp_output.c
View File

@ -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;
}