netdev - Re: [PATCH net-next] tcp: avoid spurious loopback retransmit

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Message-ID: <20210609084504.GP53857@linux.alibaba.com>
Date:   Wed, 9 Jun 2021 16:45:04 +0800
From:   "dust.li" <dust.li@...ux.alibaba.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Tony Lu <tonylu@...ux.alibaba.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH net-next] tcp: avoid spurious loopback retransmit

On Wed, Jun 09, 2021 at 09:03:14AM +0200, Eric Dumazet wrote:
>On Wed, Jun 9, 2021 at 2:25 AM dust.li <dust.li@...ux.alibaba.com> wrote:
>>
>
>> Normal RTO and fast retransmits are rarely triggerred.
>> But for TLP timers, it is easy since its timeout is usally only 2ms.
>>
>
>OK, by definition rtx timers can fire too early, so I think we will
>leave the code as it is.
>(ie not try to do special things for 'special' interfaces like loopback)
>
>We want to be generic as much as possible.
Totally understand!

After talking to you, I also rethinked this a bit more.
The original patch is bad and not generic, my original intention is
also to discuss with the community.

Through the patch is bad, I still think the problem is generic.
Devices like loopback/veth/ifb and maybe some others as well,
who depend on netif_rx() or tasklet to receive packets from CPU
backlog should all have this problem.

But I really didn't find a general way to gracefully solve this.

Thanks.