netdev - Re: [PATCH net-next] tcp: temporarily disable Fast Open on SYN timeout

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Message-Id: <20131029.225122.1012560091000427156.davem@davemloft.net>
Date:	Tue, 29 Oct 2013 22:51:22 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	ycheng@...gle.com
Cc:	ncardwell@...gle.com, edumazet@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tcp: temporarily disable Fast Open on SYN
 timeout

From: Yuchung Cheng <ycheng@...gle.com>
Date: Tue, 29 Oct 2013 10:09:05 -0700

> Fast Open currently has a fall back feature to address SYN-data
> being dropped by but it requires the middle-box to pass on regular
> SYN retry after SYN-data. This is implemented in commit aab487435
> ("net-tcp: Fast Open client - detecting SYN-data drops")
> 
> However some NAT boxes will drop all subsequent packets after first
> SYN-data and blackholes the entire connections.  An example is incommit
> 356d7d8 "netfilter: nf_conntrack: fix tcp_in_window for Fast Open".
> 
> The sender should note such incidents and falls back to use regular
> TCP handshake on subsequent attempt temporarily as well: after the
> second SYN timeouts the original Fast Open SYN is most likely lost.
> When such an event recurs Fast Open is disabled based on the number
> of recurrences exponentially.
> 
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks.
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