Re: [PATCH] net/tcp: introduce TRACE_EVENT for TCP/IPv4 state transition

Song Liu
2017-11-09T18:34:08Z

> On Nov 9, 2017, at 10:18 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Thu, 9 Nov 2017 15:43:29 +0900
> Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
>
>>> +TRACE_EVENT(tcp_set_state,
>>> + TP_PROTO(struct sock *sk, int oldstate, int newstate),
>>> + TP_ARGS(sk, oldstate, newstate),
>>> +
>>> + TP_STRUCT__entry(
>>> + __field(__be32, dst)
>>> + __field(__be32, src)
>>> + __field(__u16, dport)
>>> + __field(__u16, sport)
>>> + __field(int, oldstate)
>>> + __field(int, newstate)
>>> + ),
>>> +
>>> + TP_fast_assign(
>>> + if (oldstate == TCP_TIME_WAIT) {
>>> + __entry->dst = inet_twsk(sk)->tw_daddr;
>>> + __entry->src = inet_twsk(sk)->tw_rcv_saddr;
>>> + __entry->dport = ntohs(inet_twsk(sk)->tw_dport);
>>> + __entry->sport = ntohs(inet_twsk(sk)->tw_sport);
>>> + } else if (oldstate == TCP_NEW_SYN_RECV) {
>>> + __entry->dst = inet_rsk(inet_reqsk(sk))->ir_rmt_addr;
>>> + __entry->src = inet_rsk(inet_reqsk(sk))->ir_loc_addr;
>>> + __entry->dport =
>>> + ntohs(inet_rsk(inet_reqsk(sk))->ir_rmt_port);
>>> + __entry->sport = inet_rsk(inet_reqsk(sk))->ir_num;
>>> + } else {
>>> + __entry->dst = inet_sk(sk)->inet_daddr;
>>> + __entry->src = inet_sk(sk)->inet_rcv_saddr;
>>> + __entry->dport = ntohs(inet_sk(sk)->inet_dport);
>>> + __entry->sport = ntohs(inet_sk(sk)->inet_sport);
>>> + }
>>> +
>>> + __entry->oldstate = oldstate;
>>> + __entry->newstate = newstate;
>>> + ),
>>> +
>>> + TP_printk("%08X:%04X %08X:%04X, %02x %02x",
>>> + __entry->src, __entry->sport, __entry->dst, __entry->dport,
>>> + __entry->oldstate, __entry->newstate)
>>
>> direct %x of state is not allowed.
>> This has to use show_tcp_state_name() like it's done in trace_tcp_set_state
>
> Hmm, I need to look at trace_tcp_set_state. I'm guessing it is in
> net-next too?

Yes, in net-next. There are 6 tracepoints under tcp group:

tcp_destroy_sock
tcp_receive_reset
tcp_retransmit_skb
tcp_retransmit_synack
tcp_send_reset
tcp_set_state

They are all added recently.

>
>>
>> Also I'm missing the reason to introduce another tracepoint
>> that looks just like trace_tcp_set_state.
>
> I want to make sure that perf and trace-cmd can parse the TP_printk(),
> if it is having helper functions like that in the TP_printk() part,
> then the libtraceevent needs to be aware of that.
>

tcp_set_state uses __print_symbolic to show state in text format. I found
trace-cmd cannot parse that part:

[011] 147338.660560: tcp_set_state: sport=16262 dport=48346 \
saddr=127.0.0.6 daddr=127.0.0.6 saddrv6=2401:db00:30:317e:face:0:1f:0 \
daddrv6=2401:db00:30:31e5:face:0:7f:0 oldstate= newstate=

Other parts of the output looks good to me.

Thanks,
Song