netdev - Re: [PATCH] tcp: bug fix Fast Open client retransmission

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Message-Id: <20121207.144108.1794765164441829140.davem@davemloft.net>
Date:	Fri, 07 Dec 2012 14:41:08 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ncardwell@...gle.com
Cc:	ycheng@...gle.com, nanditad@...gle.com, edumazet@...gle.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] tcp: bug fix Fast Open client retransmission

From: Neal Cardwell <ncardwell@...gle.com>
Date: Thu, 6 Dec 2012 14:50:58 -0500

> On Thu, Dec 6, 2012 at 1:45 PM, Yuchung Cheng <ycheng@...gle.com> wrote:
>> If SYN-ACK partially acks SYN-data, the client retransmits the
>> remaining data by tcp_retransmit_skb(). This increments lost recovery
>> state variables like tp->retrans_out in Open state. If loss recovery
>> happens before the retransmission is acked, it triggers the WARN_ON
>> check in tcp_fastretrans_alert(). For example: the client sends
>> SYN-data, gets SYN-ACK acking only ISN, retransmits data, sends
>> another 4 data packets and get 3 dupacks.
>>
>> Since the retransmission is not caused by network drop it should not
>> update the recovery state variables. Further the server may return a
>> smaller MSS than the cached MSS used for SYN-data, so the retranmission
>> needs a loop. Otherwise some data will not be retransmitted until timeout
>> or other loss recovery events.
>>
>> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
>> ---
> 
> Acked-by: Neal Cardwell <ncardwell@...gle.com>

Applied.
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