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From: Nicolas Cannasse <>
Subject: Re: poll() blocked / packets not received ?
Date: Mon, 20 Oct 2008 12:46:56 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

>> We have Shorewall installed and enabled, but what seems strange is that 
>> the problem depends on multithreading. It also occurs much more often on 
>> the 4 core machines than on a 2 core ones (both with Hyperthreading 
>> activated). We're using kernel 2.6.20-15-server (#2 SMP) provided by Ubuntu.
>> Any tip on we could fix that or investigate further would be 
>> appreciated. After one month of debugging we're really out of solution now.
>> Best,
>> Nicolas
> Your usage pattern is a very common one, I highly doubt you are experiencing
> a kernel bug here or many people (including myself) would be complaining.
> Shorewall sounds like it might be suspect, are FIN's not coming in when the
> remote closes?  You can look in the output of netstat to see what state the
> TCP is in, still ESTABLISHED?

Yes, it's still ESTABLISHED, but we can't see the corresponding 
connection on the other machine while running netstat. I'm not a TCP 
expert, so I'm not sure in which case this can occur.

I agree with your comment in general, except that we have been running 
the same application in single-thread environment for years without 
running into this very specific problem.

The only logs we get in the dmesg are the following :

either (a few everyday) :

[10742708.006350] TCP: Treason uncloaked! Peer 
shrinks window 4049064122:4049064123. Repaired.

Or (more often) :

[10755036.856217] Shorewall:net2all:DROP:IN=eth0 OUT= 
DST=XX.XX.XX.43 LEN=404 TOS=0x00 PREC=0x00 TTL=114 ID=12366 PROTO=UDP 
SPT=1057 DPT=1434 LEN=384

Both SRC/DST IPs does not correspond to the connections that are 
stalled, since they occur on the local network.


  reply	other threads:[~2008-10-20 10:47 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-20  8:25 Nicolas Cannasse
2008-10-20 10:15 ` swivel
2008-10-20 10:46   ` Nicolas Cannasse [this message]
2008-10-20 11:39     ` swivel
2008-10-20 12:13       ` Nicolas Cannasse
2008-10-20 12:39       ` Nicolas Cannasse
2008-10-20 15:53         ` David Schwartz
2008-10-20 17:24           ` Nicolas Cannasse
2008-10-20 23:21             ` David Schwartz
2008-10-21  5:12             ` Willy Tarreau

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