From: Eric Dumazet <eric.dumazet@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: netdev@vger.kernel.org, bugzilla-daemon@bugzilla.kernel.org,
bugme-daemon@bugzilla.kernel.org, roysjosh@gmail.com
Subject: Re: [Bugme-new] [Bug 15507] New: kernel misses 3rd part of tcp handshake (ACK), stays in SYN_RECV state
Date: Fri, 19 Mar 2010 00:12:31 +0100 [thread overview]
Message-ID: <1268953951.2894.194.camel@edumazet-laptop> (raw)
In-Reply-To: <20100318160103.cc28c367.akpm@linux-foundation.org>
Le jeudi 18 mars 2010 à 16:01 -0700, Andrew Morton a écrit :
> (switched to email. Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
>
> On Wed, 10 Mar 2010 14:50:51 GMT
> bugzilla-daemon@bugzilla.kernel.org wrote:
>
> > http://bugzilla.kernel.org/show_bug.cgi?id=15507
> >
> > Summary: kernel misses 3rd part of tcp handshake (ACK), stays
> > in SYN_RECV state
> > Product: Networking
> > Version: 2.5
> > Kernel Version: 2.6.32.9-67.fc12
> > Platform: All
> > OS/Version: Linux
> > Tree: Fedora
> > Status: NEW
> > Severity: normal
> > Priority: P1
> > Component: IPV4
> > AssignedTo: shemminger@linux-foundation.org
> > ReportedBy: roysjosh@gmail.com
> > Regression: Yes
> >
> >
> > Created an attachment (id=25450)
> > --> (http://bugzilla.kernel.org/attachment.cgi?id=25450)
> > tcpdump from virtual guest over ::1 showing dup synacks
> >
> > Setup:
> > 64-bit dual-core, latest F12. (I've experienced this on .31 and .32 kernels.)
> >
> > I have also experienced this on 2 other machines, all 64-bit. One was a
> > single-core virtual guest.
> >
> > 1. Install httpd.
> > 2. Start it. Don't bother configuring anything unless you need to.
> > 3. tcpdump .....
> > 4. connect from localhost or (possibly) a nearby host. I'm not sure if this is
> > timing related yet.
> > 5. note duplicate SYN-ACKs sent out at the exponential backoff. Some setups
> > exhibit this more/worse than others, and will actually time out the connection.
> > (Others will only send one or two duplicate SYN-ACKs, and then enter the
> > ESTABLISHED state.) However, if any data is sent the kernel enters
> > ESTABLISHED.
> >
> > Note that this isn't ipv4 specific. I have seen it under ipv4 and ipv6 (via
> > loopback).
> >
>
> --
I would say this is expected if httpd server set DEFER_ACCEPT socket
option.
next prev parent reply other threads:[~2010-03-18 23:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-15507-10286@http.bugzilla.kernel.org/>
2010-03-18 23:01 ` [Bugme-new] [Bug 15507] New: kernel misses 3rd part of tcp handshake (ACK), stays in SYN_RECV state Andrew Morton
2010-03-18 23:12 ` Eric Dumazet [this message]
2010-03-19 11:53 ` Joshua Roys
2010-03-19 13:42 ` Eric Dumazet
2010-03-19 14:46 ` Eric Dumazet
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