netdev - Re: Fw: [Bug 18822] New: TCP Communications gets blocked, then resetted

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Date:	Tue, 21 Sep 2010 13:18:47 +0300 (EEST)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	dc6iq@....de
cc:	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: Fw: [Bug 18822] New: TCP Communications gets blocked, then
 resetted

Now with the original reported too among the receivers.

On Tue, 21 Sep 2010, Ilpo Järvinen wrote:

> On Mon, 20 Sep 2010, Stephen Hemminger wrote:
> 
> > Begin forwarded message:
> > 
> > Date: Mon, 20 Sep 2010 10:39:47 GMT
> > From: bugzilla-daemon@...zilla.kernel.org
> > To: shemminger@...ux-foundation.org
> > Subject: [Bug 18822] New: TCP Communications gets blocked, then resetted
> > 
> > 
> > https://bugzilla.kernel.org/show_bug.cgi?id=18822
> > 
> >            Summary: TCP Communications gets blocked, then resetted
> >            Product: Networking
> >            Version: 2.5
> >     Kernel Version: 2.6.32-24-generic #43-Ubuntu
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: IPV4
> >         AssignedTo: shemminger@...ux-foundation.org
> >         ReportedBy: dc6iq@....de
> >         Regression: No
> > 
> > 
> > Created an attachment (id=30682)
> >  --> (https://bugzilla.kernel.org/attachment.cgi?id=30682)
> > both machine dumps
> > 
> > having a freshly installed bacula server i could never get a backup from my
> > working machine done to the bacula server.
> > 
> > The Connection transmits approximately 3 GiB, then locks up and resets the
> > connection.
> > 
> > Transmission gets stuck at a certain point, then the bacula server does not
> > reply to retransmitted packets on IPV4 stack. Retry Count on disks machine (my
> > working machine) raises up to 13, then the Connection is gone. bacula server
> > tries to send a Push packet (after KeepAlive timer runs out), and get the final
> > RST packet from disks, because the connection is gone.
> > 
> > In the Attachment you will find the tcpdumps from both machines, actually the
> > sending machine dropped some packets in the dump.
> 
> If you didn't already, try with -w directly into a binary file and then 
> post process to textual input with -r.
> 
> > It might be a possible help: disks is running an 64 bit kernel whereas bacula
> > is running 32 bit. I haven't looked into the option bits very well but it looks
> > like there is a problem hidden:
> > 
> > last ack being ok:
> > 09:32:56.142876 IP bacula.elkenet.bacula-sd > disks.elkenet.50766: Flags [.],
> > ack 2005754588, win 9582, options [nop,nop,TS val 21825875 ecr 4530083], length
> > 0
> > next ack packet:
> > 09:32:56.144763 IP bacula.elkenet.bacula-sd > disks.elkenet.50766: Flags [.],
> > ack 2005773412, win 9308, options [nop,nop,TS val 21825876 ecr
> > 4530083,nop,nop,sack 1 {2005774860:2005776308}], length 0
> 
> ...I fail to understand to what problem you're trying to point here with 
> these two ACKs. Could you elaborate please (if you had something specific 
> in mind)?
> 
> I went throught the logs... I cannot go through all the checking done 
> because tcpdump without enough -v's hides the sequence numbers for pure 
> ACKs (09:32:56.150182 shows only the ack seqno, not the other seqno which 
> also is used by the validator), I think you need at least -vvv to show 
> them nowadays. The last new data segment at 09:32:56.150132 was still 
> received as it is reported in SACK, only the retransmissions that 
> follow are discarded.
> 
> > root@...ks:~# uname -a
> > Linux disks 2.6.32-24-generic #43-Ubuntu SMP Thu Sep 16 14:58:24 UTC 2010
> > x86_64 GNU/Linux
> > 
> > root@...ula:~# uname -a
> > Linux bacula 2.6.32-24-generic-pae #43-Ubuntu SMP Thu Sep 16 15:30:27 UTC 2010
> > i686 GNU/Linux
> > 
> > Doing a 20GB backup on a debian server works fine
> > 
> > server:~# uname -a
> > Linux server 2.6.32-5-486 #1 Sat Sep 18 01:43:00 UTC 2010 i686 GNU/Linux
> > 
> > Doing a 26 GB backup from a 32 bit Ubuntu works fine as well. Maybe its a 64
> > bit issue...
> > 
> > root@...e:~# uname -a
> > Linux elke 2.6.32-24-generic #43-Ubuntu SMP Thu Sep 16 14:17:33 UTC 2010 i686
> > GNU/Linux
> 
> Hmm, some ubuntu magic in these kernels.
> 
> > If any further input is required, just let me know...
> 
> MIBs might immediately tell what caused the segments between 
> 09:32:56.150310 and 09:46:30.970140 to be discarded (e.g., take before 
> and after snapshots of /proc/net/netstat and /proc/net/snmp and see what 
> did increase).
> 
> Any TSO enabled?
> 
> 

-- 
 i.