netdev - Re: After many hours all outbound connections get stuck in SYN

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Date:	Wed, 19 Dec 2007 18:58:57 +0100 (CET)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	James Nichols <jamesnichols3@...il.com>
cc:	Eric Dumazet <dada1@...mosbay.com>, linux-kernel@...r.kernel.org,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: After many hours all outbound connections get stuck in SYN_SENT


On Dec 19 2007 12:43, James Nichols wrote:
>On 12/19/07, Eric Dumazet <dada1@...mosbay.com> wrote:
>> James Nichols a écrit :
>> >> So you see outgoing SYN packets, but no SYN replies coming from the remote
>> >> peer ?  (you mention ACKS, but the first packet received from the remote
>> >>  peer should be a SYN+ACK),
>> >
>> > Right, I meant to say SYN+ACK.  I don't see them coming back.
>>
>> So... Really unlikely a linux problem, but ...
>
>I don't know how you can be so sure.  Turning tcp_sack off instantly
>resovles the problem and all connections are succesful.  I can't
>imagine even the most far-fetched scenario where a router or every
>single remote endpoints would suddenly stop causing the problem just
>by removing a single TCP option.

The router could be sooo crappy that it drops all packets from
TCP streams that have SACK enabled and the client has opened
200+ SACK connections previously... something like that?

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