linux-kernel - Re: [PATCH net v3] tcp: check skb is non-NULL in tcp_rto_delta

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Message-ID: <CAL+tcoBCsfK0qkDe_CehmYzUzNk58UjiVj8Kk0qZGQT6gbvRxA@mail.gmail.com>
Date: Sat, 12 Oct 2024 08:17:17 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Josh Hunt <johunt@...mai.com>
Cc: Paolo Abeni <pabeni@...hat.com>, edumazet@...gle.com, davem@...emloft.net, 
	kuba@...nel.org, netdev@...r.kernel.org, ncardwell@...gle.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3] tcp: check skb is non-NULL in tcp_rto_delta_us()

On Wed, Sep 25, 2024 at 2:16 AM Josh Hunt <johunt@...mai.com> wrote:
>
> On 9/19/24 2:05 AM, Paolo Abeni wrote:
> > !-------------------------------------------------------------------|
> >   This Message Is From an External Sender
> >   This message came from outside your organization.
> > |-------------------------------------------------------------------!
> >
> > On 9/10/24 21:08, Josh Hunt wrote:
> >> diff --git a/include/net/tcp.h b/include/net/tcp.h
> >> index 2aac11e7e1cc..196c148fce8a 100644
> >> --- a/include/net/tcp.h
> >> +++ b/include/net/tcp.h
> >> @@ -2434,9 +2434,26 @@ static inline s64 tcp_rto_delta_us(const struct
> >> sock *sk)
> >>   {
> >>       const struct sk_buff *skb = tcp_rtx_queue_head(sk);
> >>       u32 rto = inet_csk(sk)->icsk_rto;
> >> -    u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) +
> >> jiffies_to_usecs(rto);
> >> -    return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
> >> +    if (likely(skb)) {
> >> +        u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) +
> >> jiffies_to_usecs(rto);
> >> +
> >> +        return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
> >> +    } else {
> >> +        WARN_ONCE(1,
> >> +            "rtx queue emtpy: "
> >> +            "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);
> >
> > As the underlying issue here share the same root cause as the one
> > covered by the WARN_ONCE() in tcp_send_loss_probe(), I'm wondering if it
> > would make sense do move the info dumping in a common helper, so that we
> > get the verbose warning on either cases.
> >
> > Thanks,
> >
> > Paolo
>
> Thanks for the review Paolo. Sorry for the delay in replying I was OOO.
> I can send a follow-up commit to create a common helper.

I nearly forgot this helper.

Josh, please go ahead. Thanks!