[PATCH net-next v2 0/2] tcp: add tcp_warn_once() common helper

[PATCH net-next v2 0/2] tcp: add tcp_warn_once() common helper

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

Paolo Abeni suggested we can introduce a new helper to cover more cases
in the future for better debug.

Jason Xing (2):
  tcp: add a common helper to debug the underlying issue
  tcp: add more warn of socket in tcp_send_loss_probe()

 include/net/tcp.h     | 27 ++++++++++++++++-----------
 net/ipv4/tcp_output.c |  4 +---
 2 files changed, 17 insertions(+), 14 deletions(-)

-- 
2.37.3

[PATCH net-next v2 1/2] tcp: add a common helper to debug the underlying issue

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

Following the commit c8770db2d544 ("tcp: check skb is non-NULL
in tcp_rto_delta_us()"), we decided to add a helper so that it's
easier to get verbose warning on either cases.

Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Cc: Neal Cardwell <ncardwell@google.com>
---
v2
Link: https://lore.kernel.org/all/38811a75-ae98-48e7-96c0-bb1a39a0d722@kernel.org/
1. fix "break quoted strings at a space character" warning (David Ahern)
---
 include/net/tcp.h | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 739a9fb83d0c..8b8d94bb1746 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2430,6 +2430,19 @@ void tcp_plb_update_state(const struct sock *sk, struct tcp_plb_state *plb,
 void tcp_plb_check_rehash(struct sock *sk, struct tcp_plb_state *plb);
 void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
 
+static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
+{
+	WARN_ONCE(cond,
+		  "%sout:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
+		  str,
+		  tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
+		  tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
+		  tcp_sk(sk)->tlp_high_seq, sk->sk_state,
+		  inet_csk(sk)->icsk_ca_state,
+		  tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
+		  inet_csk(sk)->icsk_pmtu_cookie);
+}
+
 /* At how many usecs into the future should the RTO fire? */
 static inline s64 tcp_rto_delta_us(const struct sock *sk)
 {
@@ -2441,17 +2454,7 @@ static inline s64 tcp_rto_delta_us(const struct sock *sk)
 
 		return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
 	} else {
-		WARN_ONCE(1,
-			"rtx queue empty: "
-			"out:%u sacked:%u lost:%u retrans:%u "
-			"tlp_high_seq:%u sk_state:%u ca_state:%u "
-			"advmss:%u mss_cache:%u pmtu:%u\n",
-			tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
-			tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
-			tcp_sk(sk)->tlp_high_seq, sk->sk_state,
-			inet_csk(sk)->icsk_ca_state,
-			tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
-			inet_csk(sk)->icsk_pmtu_cookie);
+		tcp_warn_once(sk, 1, "rtx queue empty: ");
 		return jiffies_to_usecs(rto);
 	}
 
-- 
2.37.3

[PATCH net-next v2 2/2] tcp: add more warn of socket in tcp_send_loss_probe()

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

Add two fields to print in the helper which here covers tcp_send_loss_probe().

Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Cc: Neal Cardwell <ncardwell@google.com>
--
v2
Link:https://lore.kernel.org/all/CAL+tcoAr7RHhaZGV12wYDcPPPaubAqdxMCmy7Jujtr8b3+bY=w@mail.gmail.com/
1. use "" instead of NULL in tcp_send_loss_probe()
---
 include/net/tcp.h     | 4 +++-
 net/ipv4/tcp_output.c | 4 +---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 8b8d94bb1746..78158169e944 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2433,12 +2433,14 @@ void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
 static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
 {
 	WARN_ONCE(cond,
-		  "%sout:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
+		  "%scwn:%u out:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u mss:%u advmss:%u mss_cache:%u pmtu:%u\n",
 		  str,
+		  tcp_snd_cwnd(tcp_sk(sk)),
 		  tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
 		  tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
 		  tcp_sk(sk)->tlp_high_seq, sk->sk_state,
 		  inet_csk(sk)->icsk_ca_state,
+		  tcp_current_mss((struct sock *)sk),
 		  tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
 		  inet_csk(sk)->icsk_pmtu_cookie);
 }
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 054244ce5117..36562b5fe290 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2954,9 +2954,7 @@ void tcp_send_loss_probe(struct sock *sk)
 	}
 	skb = skb_rb_last(&sk->tcp_rtx_queue);
 	if (unlikely(!skb)) {
-		WARN_ONCE(tp->packets_out,
-			  "invalid inflight: %u state %u cwnd %u mss %d\n",
-			  tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);
+		tcp_warn_once(sk, tp->packets_out, "");
 		smp_store_release(&inet_csk(sk)->icsk_pending, 0);
 		return;
 	}
-- 
2.37.3

Re: [PATCH net-next v2 1/2] tcp: add a common helper to debug the underlying issue

[David Ahern]

On 10/21/24 9:52 AM, Jason Xing wrote:
> From: Jason Xing <kernelxing@tencent.com>
> 
> Following the commit c8770db2d544 ("tcp: check skb is non-NULL
> in tcp_rto_delta_us()"), we decided to add a helper so that it's
> easier to get verbose warning on either cases.
> 
> Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
> Suggested-by: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> ---
> v2
> Link: https://lore.kernel.org/all/38811a75-ae98-48e7-96c0-bb1a39a0d722@kernel.org/
> 1. fix "break quoted strings at a space character" warning (David Ahern)
> ---
>  include/net/tcp.h | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>

Re: [PATCH net-next v2 2/2] tcp: add more warn of socket in tcp_send_loss_probe()

[David Ahern]

On 10/21/24 9:52 AM, Jason Xing wrote:
> From: Jason Xing <kernelxing@tencent.com>
> 
> Add two fields to print in the helper which here covers tcp_send_loss_probe().
> 
> Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
> Suggested-by: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> --
> v2
> Link:https://lore.kernel.org/all/CAL+tcoAr7RHhaZGV12wYDcPPPaubAqdxMCmy7Jujtr8b3+bY=w@mail.gmail.com/
> 1. use "" instead of NULL in tcp_send_loss_probe()
> ---
>  include/net/tcp.h     | 4 +++-
>  net/ipv4/tcp_output.c | 4 +---
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 8b8d94bb1746..78158169e944 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -2433,12 +2433,14 @@ void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
>  static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
>  {
>  	WARN_ONCE(cond,
> -		  "%sout:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
> +		  "%scwn:%u out:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u mss:%u advmss:%u mss_cache:%u pmtu:%u\n",
>  		  str,
> +		  tcp_snd_cwnd(tcp_sk(sk)),
>  		  tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
>  		  tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
>  		  tcp_sk(sk)->tlp_high_seq, sk->sk_state,
>  		  inet_csk(sk)->icsk_ca_state,
> +		  tcp_current_mss((struct sock *)sk),
>  		  tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
>  		  inet_csk(sk)->icsk_pmtu_cookie);
>  }
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 054244ce5117..36562b5fe290 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2954,9 +2954,7 @@ void tcp_send_loss_probe(struct sock *sk)
>  	}
>  	skb = skb_rb_last(&sk->tcp_rtx_queue);
>  	if (unlikely(!skb)) {
> -		WARN_ONCE(tp->packets_out,
> -			  "invalid inflight: %u state %u cwnd %u mss %d\n",
> -			  tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);
> +		tcp_warn_once(sk, tp->packets_out, "");

you dropped the "invalid inflight: " string for context.

>  		smp_store_release(&inet_csk(sk)->icsk_pending, 0);
>  		return;
>  	}

Besides the nit:
Reviewed-by: David Ahern <dsahern@kernel.org>

Re: [PATCH net-next v2 2/2] tcp: add more warn of socket in tcp_send_loss_probe()

[Jason Xing]

On Tue, Oct 22, 2024 at 1:51 AM David Ahern <dsahern@kernel.org> wrote:
>
> On 10/21/24 9:52 AM, Jason Xing wrote:
> > From: Jason Xing <kernelxing@tencent.com>
> >
> > Add two fields to print in the helper which here covers tcp_send_loss_probe().
> >
> > Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
> > Suggested-by: Paolo Abeni <pabeni@redhat.com>
> > Signed-off-by: Jason Xing <kernelxing@tencent.com>
> > Cc: Neal Cardwell <ncardwell@google.com>
> > --
> > v2
> > Link:https://lore.kernel.org/all/CAL+tcoAr7RHhaZGV12wYDcPPPaubAqdxMCmy7Jujtr8b3+bY=w@mail.gmail.com/
> > 1. use "" instead of NULL in tcp_send_loss_probe()
> > ---
> >  include/net/tcp.h     | 4 +++-
> >  net/ipv4/tcp_output.c | 4 +---
> >  2 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/net/tcp.h b/include/net/tcp.h
> > index 8b8d94bb1746..78158169e944 100644
> > --- a/include/net/tcp.h
> > +++ b/include/net/tcp.h
> > @@ -2433,12 +2433,14 @@ void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
> >  static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
> >  {
> >       WARN_ONCE(cond,
> > -               "%sout:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
> > +               "%scwn:%u out:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u mss:%u advmss:%u mss_cache:%u pmtu:%u\n",
> >                 str,
> > +               tcp_snd_cwnd(tcp_sk(sk)),
> >                 tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
> >                 tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
> >                 tcp_sk(sk)->tlp_high_seq, sk->sk_state,
> >                 inet_csk(sk)->icsk_ca_state,
> > +               tcp_current_mss((struct sock *)sk),
> >                 tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
> >                 inet_csk(sk)->icsk_pmtu_cookie);
> >  }
> > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> > index 054244ce5117..36562b5fe290 100644
> > --- a/net/ipv4/tcp_output.c
> > +++ b/net/ipv4/tcp_output.c
> > @@ -2954,9 +2954,7 @@ void tcp_send_loss_probe(struct sock *sk)
> >       }
> >       skb = skb_rb_last(&sk->tcp_rtx_queue);
> >       if (unlikely(!skb)) {
> > -             WARN_ONCE(tp->packets_out,
> > -                       "invalid inflight: %u state %u cwnd %u mss %d\n",
> > -                       tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);
> > +             tcp_warn_once(sk, tp->packets_out, "");
>
> you dropped the "invalid inflight: " string for context.

Well, sorry, let me add it back.

>
> >               smp_store_release(&inet_csk(sk)->icsk_pending, 0);
> >               return;
> >       }
>
> Besides the nit:
> Reviewed-by: David Ahern <dsahern@kernel.org>

Thanks.

Re: [PATCH net-next v2 2/2] tcp: add more warn of socket in tcp_send_loss_probe()

[Eric Dumazet]

On Mon, Oct 21, 2024 at 5:53 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> From: Jason Xing <kernelxing@tencent.com>
>
> Add two fields to print in the helper which here covers tcp_send_loss_probe().
>
> Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
> Suggested-by: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> --
> v2
> Link:https://lore.kernel.org/all/CAL+tcoAr7RHhaZGV12wYDcPPPaubAqdxMCmy7Jujtr8b3+bY=w@mail.gmail.com/
> 1. use "" instead of NULL in tcp_send_loss_probe()
> ---
>  include/net/tcp.h     | 4 +++-
>  net/ipv4/tcp_output.c | 4 +---
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 8b8d94bb1746..78158169e944 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -2433,12 +2433,14 @@ void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
>  static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
>  {
>         WARN_ONCE(cond,
> -                 "%sout:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
> +                 "%scwn:%u out:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u mss:%u advmss:%u mss_cache:%u pmtu:%u\n",
>                   str,
> +                 tcp_snd_cwnd(tcp_sk(sk)),
>                   tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
>                   tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
>                   tcp_sk(sk)->tlp_high_seq, sk->sk_state,
>                   inet_csk(sk)->icsk_ca_state,
> +                 tcp_current_mss((struct sock *)sk),

You can not promote to non const, because tcp_current_mss() might
change socket state.

If a debug helper changes the socket state, then it is no longer a debug helper.

>                   tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,

This was already reported btw.

>                   inet_csk(sk)->icsk_pmtu_cookie);
>  }
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 054244ce5117..36562b5fe290 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2954,9 +2954,7 @@ void tcp_send_loss_probe(struct sock *sk)
>         }
>         skb = skb_rb_last(&sk->tcp_rtx_queue);
>         if (unlikely(!skb)) {
> -               WARN_ONCE(tp->packets_out,
> -                         "invalid inflight: %u state %u cwnd %u mss %d\n",
> -                         tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);
> +               tcp_warn_once(sk, tp->packets_out, "");
>                 smp_store_release(&inet_csk(sk)->icsk_pending, 0);
>                 return;
>         }
> --
> 2.37.3
>

Re: [PATCH net-next v2 2/2] tcp: add more warn of socket in tcp_send_loss_probe()

[Jason Xing]

On Tue, Oct 22, 2024 at 4:00 PM Eric Dumazet <edumazet@google.com> wrote:
>
> On Mon, Oct 21, 2024 at 5:53 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
> >
> > From: Jason Xing <kernelxing@tencent.com>
> >
> > Add two fields to print in the helper which here covers tcp_send_loss_probe().
> >
> > Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
> > Suggested-by: Paolo Abeni <pabeni@redhat.com>
> > Signed-off-by: Jason Xing <kernelxing@tencent.com>
> > Cc: Neal Cardwell <ncardwell@google.com>
> > --
> > v2
> > Link:https://lore.kernel.org/all/CAL+tcoAr7RHhaZGV12wYDcPPPaubAqdxMCmy7Jujtr8b3+bY=w@mail.gmail.com/
> > 1. use "" instead of NULL in tcp_send_loss_probe()
> > ---
> >  include/net/tcp.h     | 4 +++-
> >  net/ipv4/tcp_output.c | 4 +---
> >  2 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/net/tcp.h b/include/net/tcp.h
> > index 8b8d94bb1746..78158169e944 100644
> > --- a/include/net/tcp.h
> > +++ b/include/net/tcp.h
> > @@ -2433,12 +2433,14 @@ void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
> >  static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
> >  {
> >         WARN_ONCE(cond,
> > -                 "%sout:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
> > +                 "%scwn:%u out:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u mss:%u advmss:%u mss_cache:%u pmtu:%u\n",
> >                   str,
> > +                 tcp_snd_cwnd(tcp_sk(sk)),
> >                   tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
> >                   tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
> >                   tcp_sk(sk)->tlp_high_seq, sk->sk_state,
> >                   inet_csk(sk)->icsk_ca_state,
> > +                 tcp_current_mss((struct sock *)sk),
>
> You can not promote to non const, because tcp_current_mss() might
> change socket state.
>
> If a debug helper changes the socket state, then it is no longer a debug helper.

It does make sense. Thanks.

>
> >                   tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
>
> This was already reported btw.

So I'm going to remove this tcp_current_mss() line.

Thanks,
Jason