netdev - Re: [PATCH v2] tracepoint: add new `tcp:tcp_ca

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Date: Tue, 8 Aug 2023 10:48:21 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Manjusaka <me@...jusaka.me>
Cc: ncardwell@...gle.com, bpf@...r.kernel.org, davem@...emloft.net, 
	dsahern@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, mhiramat@...nel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, rostedt@...dmis.org
Subject: Re: [PATCH v2] tracepoint: add new `tcp:tcp_ca_event` trace event

On Tue, Aug 8, 2023 at 10:46 AM Manjusaka <me@...jusaka.me> wrote:
>
>
>
> On 2023/8/8 16:26, Eric Dumazet wrote:
> > On Tue, Aug 8, 2023 at 7:59 AM Manjusaka <me@...jusaka.me> wrote:
> >>
> >> In normal use case, the tcp_ca_event would be changed in high frequency.
> >>
> >> It's a good indicator to represent the network quanlity.
> >
> > quality ?
> >
> > Honestly, it is more about TCP stack tracing than 'network quality'
> >
> >>
> >> So I propose to add a `tcp:tcp_ca_event` trace event
> >> like `tcp:tcp_cong_state_set` to help the people to
> >> trace the TCP connection status
> >>
> >> Signed-off-by: Manjusaka <me@...jusaka.me>
> >> ---
> >>  include/net/tcp.h          |  9 ++------
> >>  include/trace/events/tcp.h | 45 ++++++++++++++++++++++++++++++++++++++
> >>  net/ipv4/tcp_cong.c        | 10 +++++++++
> >>  3 files changed, 57 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/include/net/tcp.h b/include/net/tcp.h
> >> index 0ca972ebd3dd..a68c5b61889c 100644
> >> --- a/include/net/tcp.h
> >> +++ b/include/net/tcp.h
> >> @@ -1154,13 +1154,8 @@ static inline bool tcp_ca_needs_ecn(const struct sock *sk)
> >>         return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
> >>  }
> >>
> >> -static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
> >> -{
> >> -       const struct inet_connection_sock *icsk = inet_csk(sk);
> >> -
> >> -       if (icsk->icsk_ca_ops->cwnd_event)
> >> -               icsk->icsk_ca_ops->cwnd_event(sk, event);
> >> -}
> >> +/* from tcp_cong.c */
> >> +void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event);
> >>
> >>  /* From tcp_cong.c */
> >>  void tcp_set_ca_state(struct sock *sk, const u8 ca_state);
> >> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> >> index bf06db8d2046..b374eb636af9 100644
> >> --- a/include/trace/events/tcp.h
> >> +++ b/include/trace/events/tcp.h
> >> @@ -416,6 +416,51 @@ TRACE_EVENT(tcp_cong_state_set,
> >>                   __entry->cong_state)
> >>  );
> >>
> >> +TRACE_EVENT(tcp_ca_event,
> >> +
> >> +       TP_PROTO(struct sock *sk, const u8 ca_event),
> >> +
> >> +       TP_ARGS(sk, ca_event),
> >> +
> >> +       TP_STRUCT__entry(
> >> +               __field(const void *, skaddr)
> >> +               __field(__u16, sport)
> >> +               __field(__u16, dport)
> >> +               __array(__u8, saddr, 4)
> >> +               __array(__u8, daddr, 4)
> >> +               __array(__u8, saddr_v6, 16)
> >> +               __array(__u8, daddr_v6, 16)
> >> +               __field(__u8, ca_event)
> >> +       ),
> >> +
> >
> > Please add the family (look at commit 3dd344ea84e1 ("net: tracepoint:
> > exposing sk_family in all tcp:tracepoints"))
> >
> >
> >
> >> +       TP_fast_assign(
> >> +               struct inet_sock *inet = inet_sk(sk);
> >> +               __be32 *p32;
> >> +
> >> +               __entry->skaddr = sk;
> >> +
> >> +               __entry->sport = ntohs(inet->inet_sport);
> >> +               __entry->dport = ntohs(inet->inet_dport);
> >> +
> >> +               p32 = (__be32 *) __entry->saddr;
> >> +               *p32 = inet->inet_saddr;
> >> +
> >> +               p32 = (__be32 *) __entry->daddr;
> >> +               *p32 =  inet->inet_daddr;
> >
> > We keep copying IPv4 addresses that might contain garbage for IPv6 sockets :/
> >
> >> +
> >> +               TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr,
> >> +                          sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
> >
> > I will send a cleanup, because IP_STORE_ADDRS() should really take
> > care of all details.
> >
> >
> >> +
> >> +               __entry->ca_event = ca_event;
> >> +       ),
> >> +
> >> +       TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c ca_event=%u",
> >> +                 __entry->sport, __entry->dport,
> >> +                 __entry->saddr, __entry->daddr,
> >> +                 __entry->saddr_v6, __entry->daddr_v6,
> >> +                 __entry->ca_event)
> >
> > Please print the symbol instead of numeric ca_event.
> >
> > Look at show_tcp_state_name() for instance.
>
> Thanks for the kindness code review, I still get some issue here(Sorry for the first time to contribute):
>
> 1. > We keep copying IPv4 addresses that might contain garbage for IPv6 sockets :/
>
> I'm not getting your means, would you mean that we should only save the IPv4 Address here?
>
> 2. > I will send a cleanup, because IP_STORE_ADDRS() should really take care of all details.
>
> I think you will make the address assignment code in TP_fast_assign as a new function.
>
> Should I submit the new change until you send the cleanup patch or I can make this in my patch(cleanup the address assignment)
>

Wait a bit, I am sending fixes today, so that no more copy/paste
duplicates the issues.