Using non-hvm domU networking takes down dom0 external networking

Using non-hvm domU networking takes down dom0 external networking

[Adam Wendt]

Ever since the subarch changeset (8706) and through all the kernel versions
(.12.6, .14, .15, 16-rc1/2)  and up through the latest changeset (8776) when I
start a non-hvm domU and ping outside the xen machine the dom0 can no longer ping
outside the machine (and domU fails from the start).

Here's a step by step:

1. Start machine, start xend, start pinging google from dom0, all is fine, leave
this running
2. Start non-hvm domU, ping its local address, ping the dom0 ip, all is still
fine and dom0 can still ping google.
3. Have domU attempt to ping google, immediatly dom0's ping to google dies and
nothing short of reboot seems to be able to get it back.

I have confirmed this on two separate machines with different network cards and
different motherboards, though both are em64t dual core chips. Changeset 8705 has
no problem but anything after that shows this behavior.

My networking setup is about as stock as it comes, no firewalls, basic eth0 with
default network scripts, generic domU network configuration.

Any ideas?

Adam Wendt
IPCoast, Inc.

Re: Using non-hvm domU networking takes down dom0 external networking

[Travis Cross]

> 3. Have domU attempt to ping google, immediatly dom0's ping to google dies and
> nothing short of reboot seems to be able to get it back.

I was unable to reproduce your results on a Pentium D dual-core box
running xen-unstable near the tip.

You might ensure that IP forwarding is enabled (on dom0) with:

# echo "1" > /proc/sys/net/ipv4/ip_forward

The behavior of my networking was a bit quirky until I remembered to
do this.

Cheers,

-- Travis


Adam Wendt wrote:
> Ever since the subarch changeset (8706) and through all the kernel versions
> (.12.6, .14, .15, 16-rc1/2)  and up through the latest changeset (8776) when I
> start a non-hvm domU and ping outside the xen machine the dom0 can no longer ping
> outside the machine (and domU fails from the start).
> 
> Here's a step by step:
> 
> 1. Start machine, start xend, start pinging google from dom0, all is fine, leave
> this running
> 2. Start non-hvm domU, ping its local address, ping the dom0 ip, all is still
> fine and dom0 can still ping google.
> 3. Have domU attempt to ping google, immediatly dom0's ping to google dies and
> nothing short of reboot seems to be able to get it back.
> 
> I have confirmed this on two separate machines with different network cards and
> different motherboards, though both are em64t dual core chips. Changeset 8705 has
> no problem but anything after that shows this behavior.
> 
> My networking setup is about as stock as it comes, no firewalls, basic eth0 with
> default network scripts, generic domU network configuration.
> 
> Any ideas?
> 
> Adam Wendt
> IPCoast, Inc.
> 
> 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel