Re: [PATCH v3] tracepoint: add new `tcp:tcp_ca_event` trace event

[Steven Rostedt]

On Sun, 13 Aug 2023 04:17:24 +0800
Manjusaka <me@xxxxxxxxxxxx> wrote:

> On 2023/8/13 04:12, Zheao Li wrote:
> > In normal use case, the tcp_ca_event would be changed in high frequency.
> > 
> > The developer can monitor the network quality more easier by tracing
> > TCP stack with this TP event.
> > 
> > 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: Zheao Li <me@xxxxxxxxxxxx>
> > ---
> >  include/net/tcp.h          |  9 ++----
> >  include/trace/events/tcp.h | 60 ++++++++++++++++++++++++++++++++++++++
> >  net/ipv4/tcp_cong.c        | 10 +++++++
> >  3 files changed, 72 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 7b1ddffa3dfc..993eb00403ea 100644
> > --- a/include/trace/events/tcp.h
> > +++ b/include/trace/events/tcp.h
> > @@ -41,6 +41,18 @@
> >  	TP_STORE_V4MAPPED(__entry, saddr, daddr)
> >  #endif
> >  
> > +/* The TCP CA event traced by tcp_ca_event*/
> > +#define tcp_ca_event_names    \
> > +		EM(CA_EVENT_TX_START)     \
> > +		EM(CA_EVENT_CWND_RESTART) \
> > +		EM(CA_EVENT_COMPLETE_CWR) \
> > +		EM(CA_EVENT_LOSS)         \
> > +		EM(CA_EVENT_ECN_NO_CE)    \
> > +		EMe(CA_EVENT_ECN_IS_CE)
> > +
> > +#define show_tcp_ca_event_names(val) \
> > +	__print_symbolic(val, tcp_ca_event_names)
> > +
> >  /*
> >   * tcp event with arguments sk and skb
> >   *
> > @@ -419,6 +431,54 @@ 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)
> > +		__field(__u16, family)
> > +		__array(__u8, saddr, 4)
> > +		__array(__u8, daddr, 4)
> > +		__array(__u8, saddr_v6, 16)
> > +		__array(__u8, daddr_v6, 16)
> > +		__field(__u8, ca_event)
> > +	),
> > +
> > +	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);
> > +		__entry->family = sk->sk_family;
> > +
> > +		p32 = (__be32 *) __entry->saddr;
> > +		*p32 = inet->inet_saddr;
> > +
> > +		p32 = (__be32 *) __entry->daddr;
> > +		*p32 =  inet->inet_daddr;
> > +
> > +		TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr,
> > +			   sk->sk_v6_rcv_saddr, sk->sk_v6_daddr);
> > +
> > +		__entry->ca_event = ca_event;
> > +	),
> > +
> > +	TP_printk("family=%s sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c ca_event=%s",
> > +		  show_family_name(__entry->family),
> > +		  __entry->sport, __entry->dport,
> > +		  __entry->saddr, __entry->daddr,
> > +		  __entry->saddr_v6, __entry->daddr_v6,
> > +		  show_tcp_ca_event_names(__entry->ca_event))
> > +);
> > +
> >  #endif /* _TRACE_TCP_H */
> >  
> >  /* This part must be outside protection */
> > diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
> > index 1b34050a7538..fb7ec6ebbbd0 100644
> > --- a/net/ipv4/tcp_cong.c
> > +++ b/net/ipv4/tcp_cong.c
> > @@ -34,6 +34,16 @@ struct tcp_congestion_ops *tcp_ca_find(const char *name)
> >  	return NULL;
> >  }
> >  
> > +void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
> > +{
> > +	const struct inet_connection_sock *icsk = inet_csk(sk);
> > +
> > +	trace_tcp_ca_event(sk, (u8)event);
> > +
> > +	if (icsk->icsk_ca_ops->cwnd_event)
> > +		icsk->icsk_ca_ops->cwnd_event(sk, event);
> > +}
> > +
> >  void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
> >  {
> >  	struct inet_connection_sock *icsk = inet_csk(sk);  
> 
> For more information, this patch is not passthrough the `./scripts/checkpatch.pl` check 
> with the following error message `Macros with complex values should be enclosed in parentheses`.
> 
> I have no idea because there is no complex expression and the `include/trace/events/sock.h` files 
> also failed in the style check.

Please ignore all checkpatch.pl messages when it comes to the
TRACE_EVENT() macro and pretty much anything it recommends to do with
TRACE_EVENTS() in general.

checkpatch.pl's recommendations on the include/trace code is just
wrong, and makes it worse.

One day I need to add a patch to fix checkpatch.

-- Steve