netdev - Re: [PATCH v2 net-next] tcp: avoid reusing FIN_WAIT2 when trying to find port in connect() process

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Message-ID: <CAL+tcoCxGMNrcuDW1VBqSCFtsrvCoAGiX+AjnuNkh8Ukyzfaaw@mail.gmail.com>
Date: Tue, 20 Aug 2024 20:54:31 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Paolo Abeni <pabeni@...hat.com>, davem@...emloft.net, kuba@...nel.org, 
	dsahern@...nel.org, ncardwell@...gle.com, kuniyu@...zon.com, 
	netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>, 
	Jade Dong <jadedong@...cent.com>
Subject: Re: [PATCH v2 net-next] tcp: avoid reusing FIN_WAIT2 when trying to
 find port in connect() process

Hello Eric,

On Tue, Aug 20, 2024 at 8:39 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Aug 20, 2024 at 1:04 PM Paolo Abeni <pabeni@...hat.com> wrote:
> >
> > On 8/15/24 13:37, Jason Xing wrote:
> > > From: Jason Xing <kernelxing@...cent.com>
> > >
> > > We found that one close-wait socket was reset by the other side
> > > which is beyond our expectation,
> >
> > I'm unsure if you should instead reconsider your expectation: what if
> > the client application does:
> >
> > shutdown(fd, SHUT_WR)
> > close(fd); // with unread data
> >
>
> Also, I was hoping someone would mention IPv6 at some point.

Thanks for reminding me. I'll dig into the IPv6 logic.

>
> Jason, instead of a lengthy ChatGPT-style changelog, I would prefer a

LOL, but sorry, I manually control the length which makes it look
strange, I'll adjust it.

> packetdrill test exactly showing the issue.

I will try the packetdrill.

After this patch applied in my local kernel, if we have some remote
sockets delaying calling close(), it turns out that the client side
will not reuse the fin_wait2 port like when we disable the tw reuse
feature.

Thanks,
Jason