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Date:	Tue, 29 Oct 2013 22:51:22 -0400 (EDT)
From:	David Miller <>
Subject: Re: [PATCH net-next] tcp: temporarily disable Fast Open on SYN

From: Yuchung Cheng <>
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 <>
> Signed-off-by: Neal Cardwell <>
> Signed-off-by: Eric Dumazet <>

Applied, thanks.
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