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

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Message-ID: <Pine.LNX.4.64.0712192209470.26514@kivilampi-30.cs.helsinki.fi>
Date:	Wed, 19 Dec 2007 23:27:45 +0200 (EET)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	James Nichols <jamesnichols3@...il.com>
cc:	Jan Engelhardt <jengelh@...putergmbh.de>,
	Eric Dumazet <dada1@...mosbay.com>,
	LKML <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 Wed, 19 Dec 2007, Eric Dumazet wrote:

> James Nichols a écrit :
> > 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.

You could also check if you can pull same trick off by touching 
tcp_timestamps. It affects the TCP header as well.



-- 
 i.