linux-kernel - Re: [PATCH v1] tcp: fix connection reset due to tw hashdance race.

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Message-ID: <A280D6B1-6CAE-4255-9542-21268D9F8997@baidu.com>
Date:   Wed, 7 Jun 2023 12:01:23 +0000
From:   "Duan,Muquan" <duanmuquan@...du.com>
To:     Simon Horman <simon.horman@...igine.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "dsahern@...nel.org" <dsahern@...nel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] tcp: fix connection reset due to tw hashdance race.

Hi, Simon,

Thank you for pointing out the error, I will correct it in next patch.

Best Regards!
Duan

> 2023年6月6日 下午4:57，Simon Horman <simon.horman@...igine.com> 写道：
> 
> On Mon, Jun 05, 2023 at 11:51:40AM +0800, Duan Muquan wrote:
> 
> ...
> 
>> Brief of the scenario:
>> 
>> 1. Server runs on CPU 0 and Client runs on CPU 1. Server closes
>> connection actively and sends a FIN to client. The lookback's driver
>> enqueues the FIN segment to backlog queue of CPU 0 via
>> loopback_xmit()->netif_rx(), one of the conditions for non-delay ack
>> meets in __tcp_ack_snd_check(), and the ACK is sent immediately.
>> 
>> 2. On loopback interface, the ACK is received and processed on CPU 0,
>> the 'dance' from original sock to tw sock will perfrom, tw sock will
> 
> Hi Duan Muquan,
> 
> a minor nit from my side: perfrom -> perform
> 
>> be inserted to ehash table, then the original sock will be removed.
> 
> ...