linux-kernel - Re: [bug] stuck localhost TCP connections, v2.6.26-rc3+

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Message-ID: <a01a16b50805311325w7f58ca69h93d02af9bc28d2ea@mail.gmail.com>
Date:	Sat, 31 May 2008 22:25:22 +0200
From:	"Håkon Løvdal" <hlovdal@...il.com>
To:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Netdev <netdev@...r.kernel.org>, "Ingo Molnar" <mingo@...e.hu>,
	"David S. Miller" <davem@...emloft.net>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [bug] stuck localhost TCP connections, v2.6.26-rc3+

2008/5/31 Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>:
> Ok, like you said, this is not exactly the same, though it might be due to
> the same bug. In Ingo's case both endpoints were doing pretty healtily,
> with periodic window probes as expected. In your case TCP is not doing
> window probes but got that interesting RTO value.
>
> So you had that '-' earlier and you checked at that time but the
> connection is now already dead?

This is only from checking after the connection was dead. By the way,
I just had to remotely reboot the new machine because the window
manager locked up, however the old PC are still listing the defunct
connections after this.

> :-(, I would some much liked to see what they were doing.

I can of course keep on copying for testing purposes, but then I would like to
be able to dump only that single tcp connection, any tips of how to do that?
I found nothing specific in the manuals of wireshark and tcpdump. Of course
it is possible to capture everything and filter afterwards, but since I will be
transferring lots of data the logs will get huge and I would not like to have
even additional traffic inside...

> These 7C/D... certainly seem strange values. Which TCP variant you have in
> use (cat /proc/sys/net/ipv4/tcp_congestion_control)? It seems that vegas,
> veno and yeah at least contain 0x7fffffff there for some rtt, which could
> perhaps somehow leak.

I have not done any specific selection myself. On old_pc: bic, new_pc: cubic.

BR Håkon Løvdal