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Date: Wed, 18 Apr 2012 16:54:00 -0400 (EDT)
Message-Id: <20120418.165400.980383816074286216.davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: a.beregalov@gmail.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, marc@merlins.org
Subject: Re: [PATCH] tcp: fix retransmit of partially acked frames
From: David Miller <davem@davemloft.net>
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From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 18 Apr 2012 22:14:23 +0200

> From: Eric Dumazet <edumazet@google.com>
> 
> Alexander Beregalov reported skb_over_panic errors and provided stack
> trace.
> 
> I occurs commit a21d45726aca (tcp: avoid order-1 allocations on wifi and
> tx path) added a regression, when a retransmit is done after a partial
> ACK.
> 
> tcp_retransmit_skb() tries to aggregate several frames if the first one
> has enough available room to hold the following ones payload. This is
> controlled by /proc/sys/net/ipv4/tcp_retrans_collapse tunable (default :
> enabled)
> 
> Problem is we must make sure _pskb_trim_head() doesnt fool
> skb_availroom() when pulling some bytes from skb (this pull is done when
> receiver ACK part of the frame).
> 
> Reported-by: Alexander Beregalov <a.beregalov@gmail.com>
> Cc: Marc MERLIN <marc@merlins.org>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied, thanks.