linux-kernel - Re: [PATCH] tcp: fix retransmission in repair mode

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Date:	Thu, 15 Nov 2012 07:03:04 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrey Vagin <avagin@...nvz.org>
Cc:	netdev@...r.kernel.org, criu@...nvz.org,
	linux-kernel@...r.kernel.org,
	Pavel Emelyanov <xemul@...allels.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH] tcp: fix retransmission in repair mode

On Thu, 2012-11-15 at 18:03 +0400, Andrey Vagin wrote:
> From: Andrew Vagin <avagin@...nvz.org>
> 
> Currently if a socket was repaired with a few packet in a write queue,
> a kernel bug may be triggered:
> 
> kernel BUG at net/ipv4/tcp_output.c:2330!
> RIP: 0010:[<ffffffff8155784f>] tcp_retransmit_skb+0x5ff/0x610
> 
> According to the initial realization v3.4-rc2-963-gc0e88ff,
> all skb-s should look like already posted. This patch fixes code
> according with this sentence.
> 
> Here are three points, which were not done in the initial patch:
> 1. A tcp send head should not be changed
> 2. Initialize TSO state of a skb
> 3. Reset the retransmission time
> 
> This patch moves logic from tcp_sendmsg to tcp_write_xmit. A packet
> passes the ussual way, but isn't sent to network. This patch solves
> all described problems and handles tcp_sendpages.
> 
> Cc: Pavel Emelyanov <xemul@...allels.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Alexey Kuznetsov <kuznet@....inr.ac.ru>
> Cc: James Morris <jmorris@...ei.org>
> Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
> Cc: Patrick McHardy <kaber@...sh.net>
> Signed-off-by: Andrey Vagin <avagin@...nvz.org>

Any chance these tcp repair hacks could be done outside of tcp fast
path ?



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