Re: KVM induced panic on 2.6.38[2367] & 2.6.39

From: Brad Campbell
Date: Tue Jun 07 2011 - 20:24:55 EST

On 07/06/11 23:35, Patrick McHardy wrote:

The main suspects would be NAT and TCPMSS. Did you also try whether
the crash occurs with only one of these these rules?

To be honest I'm actually having trouble finding where TCPMSS is actually set in that ruleset. This is a production machine so I can only take it down after about 9PM at night. I'll have another crack at it tonight.

I've just compiled out CONFIG_BRIDGE_NETFILTER and can no longer access
the address the way I was doing it, so that's a no-go for me.

That's really weird since you're apparently not using any bridge
netfilter features. It shouldn't have any effect besides changing
at which point ip_tables is invoked. How are your network devices
configured (specifically any bridges)?

I have one bridge with all my virtual machines on it.

In this particular instance the packets leave VM A destined for the IP address of ppp0 (the external interface). This is intercepted by the DNAT PREROUTING rule above and shunted back to VM B.

The VM's are on br1 and the external address is ppp0. Without CONFIG_BRIDGE_NETFILTER compiled in I can see the traffic entering and leaving VM B with tcpdump, but the packets never seem to get back to VM A.

VM A is XP 32 bit, VM B is Linux. I have some other Linux VM's, so I'll do some more testing tonight between those to see where the packets are going without CONFIG_BRIDGE_NETFILTER set.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at