From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: Possible networking regression in 3.6.0
Date: Mon, 01 Oct 2012 17:31:38 +0200
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Cc: David Miller <davem@davemloft.net>, netdev@vger.kernel.org,
	gpiez@web.de
To: Chris Clayton <chris2553@googlemail.com>
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On Mon, 2012-10-01 at 16:13 +0100, Chris Clayton wrote:
> 
> On 10/01/12 10:15, Eric Dumazet wrote:
> > On Mon, 2012-10-01 at 09:36 +0100, Chris Clayton wrote:
> >>
> >
> >>       0 ICMP messages received
> >>       0 input ICMP message failed.
> >>       ICMP input histogram:
> >>       0 ICMP messages sent
> >>       0 ICMP messages failed
> >>       ICMP output histogram:
> >
> >>
> >> After:
> >>
> >> $ netstat -s
> >> Icmp:
> >>       4 ICMP messages received
> >>       4 input ICMP message failed.
> >>       ICMP input histogram:
> >>           echo replies: 4
> >
> > So icmp replies come back and are delivered to host instead of being
> > forwarded.
> >
> > I wonder if MASQUERADE broke...
> >
> > Could you send
> >
> > iptables -t -nat -nvL
> 
> $ iptables -t -nat -nvL
> iptables v1.4.15: can't initialize iptables table `-nat': Table does not 
> exist (do you need to insmod?)
> Perhaps iptables or your kernel needs to be upgraded.
> 
> > conntrack -L   # while ping is running from guest
> 
> $ conntrack -L
> conntrack v1.2.2 (conntrack-tools): Operation failed: invalid parameters
> 

Thats not expected, you described you used MASQUERADE target, so
"iptables -t nat -nvL" should display something.


> Forgive me for asking, but why is the problem not down to the change 
> that I identified by bisecting? The title of the patch is "ipv4: Cache 
> local output routes" and, although I'm a million miles from being an 
> expert here, to me it does make it look a good candidate. 
> http://marc.info/?l=linux-netdev&m=134797809611847&w=2

Because I cant reproduce your problem at all, using your setup.