netdev - Re: [PATCH net] tcp: fix indefinite deferral of RTO with SACK reneging

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Date:   Mon, 24 Oct 2022 18:20:18 +0000
From:   patchwork-bot+netdevbpf@...nel.org
To:     Neal Cardwell <ncardwell.kernel@...il.com>
Cc:     kuba@...nel.org, edumazet@...gle.com, davem@...emloft.net,
        netdev@...r.kernel.org, ncardwell@...gle.com, ntspring@...com,
        ycheng@...gle.com
Subject: Re: [PATCH net] tcp: fix indefinite deferral of RTO with SACK reneging

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@...nel.org>:

On Fri, 21 Oct 2022 17:08:21 +0000 you wrote:
> From: Neal Cardwell <ncardwell@...gle.com>
> 
> This commit fixes a bug that can cause a TCP data sender to repeatedly
> defer RTOs when encountering SACK reneging.
> 
> The bug is that when we're in fast recovery in a scenario with SACK
> reneging, every time we get an ACK we call tcp_check_sack_reneging()
> and it can note the apparent SACK reneging and rearm the RTO timer for
> srtt/2 into the future. In some SACK reneging scenarios that can
> happen repeatedly until the receive window fills up, at which point
> the sender can't send any more, the ACKs stop arriving, and the RTO
> fires at srtt/2 after the last ACK. But that can take far too long
> (O(10 secs)), since the connection is stuck in fast recovery with a
> low cwnd that cannot grow beyond ssthresh, even if more bandwidth is
> available.
> 
> [...]

Here is the summary with links:
  - [net] tcp: fix indefinite deferral of RTO with SACK reneging
    https://git.kernel.org/netdev/net/c/3d2af9cce313

You are awesome, thank you!
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