netdev - Re: [PATCH stable-5.4 4/4] tcp: avoid too many retransmit packets

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Message-ID: <CAL+tcoDVJK_J+ZGs=b94=A+3ci0uD4foZ4JQRmVa8+44udeUxA@mail.gmail.com>
Date: Tue, 16 Jul 2024 20:40:40 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: gregkh@...uxfoundation.org, edumazet@...gle.com, davem@...emloft.net, 
	eric.dumazet@...il.com, jmaxwell37@...il.com, kuba@...nel.org, 
	kuniyu@...zon.com, ncardwell@...gle.com, netdev@...r.kernel.org, 
	pabeni@...hat.com
Subject: Re: [PATCH stable-5.4 4/4] tcp: avoid too many retransmit packets

On Tue, Jul 16, 2024 at 7:10 PM Miguel Ojeda <ojeda@...nel.org> wrote:
>
> Hi Greg, Eric, all,
>
> I noticed this in stable-rc/queue and stable-rc/linux- for 6.1 and 6.6:
>
>     net/ipv4/tcp_timer.c:472:7: error: variable 'rtx_delta' is uninitialized when used here [-Werror,-Wuninitialized]
>                     if (rtx_delta > user_timeout)
>                         ^~~~~~~~~
>     net/ipv4/tcp_timer.c:464:15: note: initialize the variable 'rtx_delta' to silence this warning
>             u32 rtx_delta;
>                         ^
>                         = 0
>
> I hope that helps!

Thanks for the report!

I think it missed one small snippet of code from [1] compared to the
latest kernel. We can init this part before using it, something like
this:

+       rtx_delta = (u32)msecs_to_jiffies(tcp_time_stamp(tp) -
+                       (tp->retrans_stamp ?: tcp_skb_timestamp(skb)));

Note: fully untested.

Since Eric is very busy, I decided to check and provide some useful
information here.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=614e8316aa4cafba3e204cb8ee48bd12b92f3d93
>
> Cheers,
> Miguel