netdev - Re: [PATCH net-next] tcp/dccp: drop SYN packets if accept queue is full

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Message-Id: <20161029.150948.1138589874373025111.davem@davemloft.net>
Date:   Sat, 29 Oct 2016 15:09:48 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org, ycheng@...gle.com, ncardwell@...gle.com
Subject: Re: [PATCH net-next] tcp/dccp: drop SYN packets if accept queue is
 full

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 26 Oct 2016 09:27:57 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Per listen(fd, backlog) rules, there is really no point accepting a SYN,
> sending a SYNACK, and dropping the following ACK packet if accept queue
> is full, because application is not draining accept queue fast enough.
> 
> This behavior is fooling TCP clients that believe they established a
> flow, while there is nothing at server side. They might then send about
> 10 MSS (if using IW10) that will be dropped anyway while server is under
> stress.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied.