netdev - Re: [PATCH net-next] tcp: tcp_transmit

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Message-Id: <20131012.010605.1320162777840311015.davem@davemloft.net>
Date:	Sat, 12 Oct 2013 01:06:05 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, fitz@...yale.edu, ycheng@...gle.com,
	ncardwell@...gle.com
Subject: Re: [PATCH net-next] tcp: tcp_transmit_skb() optimizations

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 11 Oct 2013 18:20:19 -0700

> On Fri, 2013-10-11 at 15:43 -0700, Eric Dumazet wrote:
>> On Fri, 2013-10-11 at 17:48 -0400, David Miller wrote:
>> 
>> > This patch is correct, so I've applied it, but it points out a bug.
>> > 
>> > The __tcp_retransmit_skb() code that does a __pskb_copy() to handle
>> > NET_IP_ALIGN violations and skb_headroom() overflows is buggy because
>> > it needs to store a congestion control timestamp in the original 'skb'
>> > since that's what we'll look at in the retransmit queue.
>> 
>> Yes, I saw that, indeed.
>> 
>> I added it as low priority bug for the moment, as the default congestion
>> module do not really care, and this case is really unlikely ;)
>> 
> 
> Ah, I remember now that the conclusion was :
> the timestamp is not taken into account for retransmits.
> 
> ( FLAG_RETRANS_DATA_ACKED )

Great, thanks for the clarification.
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