linux-kernel - Re: Unexpected Acknowledgement / Stalled Connections

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Date:	Sun, 4 Feb 2007 17:56:55 -0500
From:	"Parag Warudkar" <parag.warudkar@...il.com>
To:	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Unexpected Acknowledgement / Stalled Connections

On 2/4/07, Parag Warudkar <parag.warudkar@...il.com> wrote:
> I am running 2.6.20 and have trouble with stalled connections. For
> instance, if I try to download a debian ISO image using wget, the
> connection runs fine for few seconds and then stalls for ever.
>
> In my router logs I see a ton of messages like the below -
>
> [INFO] Sun Feb 04 17:22:03 2007 Blocked incoming TCP packet from
> 192.168.0.174:34090 to 130.239.18.138:80 with unexpected
> acknowledgement 3269301836 (expected 3269343453 to 3269408989)
>
> Where 192.168.0.174 is my laptop running FC6 and kernel 2.6.20 and
> 130.239.18.138 is whatever cdimage.debian.org resolves to atm.
>
> What's going on here? Any TCP/IP tunable that I can set/turn on/off to
> prevent this from happening?

Turning tcp_sack off seems to cure it. Turning it on again makes the
connections stall. Seems like the D-Link router doesn't like the SACKs
linux sends?

Parag
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