netdev - Re: WARNING: at net/ipv4/tcp.c:1301 tcp_cleanup

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Date:	Wed, 23 May 2012 18:36:58 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sergio Correia <lists@...e.net>
Cc:	netdev@...r.kernel.org
Subject: Re: WARNING: at net/ipv4/tcp.c:1301 tcp_cleanup_rbuf+0x4f/0x110()

On Wed, 2012-05-23 at 12:56 -0300, Sergio Correia wrote:
> On Wed, May 23, 2012 at 12:08 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > On Tue, 2012-05-22 at 11:47 -0300, Sergio Correia wrote:
> >> Hi Eric,
> > ...
> >> Yes, it's an Atheros AR9285 adapter.
> >> This morning I did a make mrproper before rebuilding the kernel
> >> (should I always do that?), but the warning has just appeared again.
> >
> > OK, I am taking a look at this problem, thanks.
> >
> 
> Thanks. Let me know if you need additional info. As of now, my dmesg
> basically shows only those warnings.

I believe I found the bug and am testing a fix right now.

By the way, we might have the same problem in tcp collapses.

TCP coalescing (introduced in linux-3.5) triggers the problem faster.

Please test following patch :

 net/ipv4/tcp_input.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cfa2aa1..b224eb8 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4555,6 +4555,11 @@ static bool tcp_try_coalesce(struct sock *sk,
 
 	if (tcp_hdr(from)->fin)
 		return false;
+
+	/* Its possible this segment overlaps with prior segment in queue */
+	if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq)
+		return false;
+
 	if (!skb_try_coalesce(to, from, fragstolen, &delta))
 		return false;
 


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