With CentOS 6 and LXC, “ifconfig” is unable to see network interface (but busybox “ifconfig” works fine)

Question

I've just started working with LXC under CentOS 6 (via the libvirt adapter). If I create an LXC container, I'm unable to see any network interfaces when using the native system tools:

# ifconfig -a
#

The behavior is very odd; specifying an interface by names yields neither the expected output nor an error message. This is true even for clearly invalid interface names, like this:

# ifconfig foo
#

The ip command exhibits the same behavior.

On the other hand, if I use "ifconfig" provided by busybox, everything works as expected:

# busybox ifconfig -a

eth0      Link encap:Ethernet  HWaddr 52:54:00:E0:12:C8  
          inet6 addr: fe80::5054:ff:fee0:12c8/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:268 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:17814 (17.3 KiB)  TX bytes:552 (552.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

So...what does busybox know that the native tools don't? The libvirt config for this environment is pretty standard; the network definition looks like this:

<interface type='network'>
  <mac address='52:54:00:e0:12:c8'/>
  <source network='default'/>
  <target dev='veth0'/>
</interface>

The full configuration is here if you think it might help.

I'm running:

• lxc-0.7.2-2.el6.x86_64
• kernel-2.6.32-71.29.1.el6.x86_64

EDIT

Weirder and weirder...it's a display issue, not a functionality issue. I can see the output of ifconfig if I pipe it into anything, so for example:

# ifconfig eth0 | cat
eth0      Link encap:Ethernet  HWaddr 52:54:00:E0:12:C8  
          inet addr:192.168.10.10  Bcast:192.168.10.255  Mask:255.255.255.0
          inet6 addr: fe80::5054:ff:fee0:12c8/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:573 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:37914 (37.0 KiB)  TX bytes:552 (552.0 b)

And in fact even when not piping the output, strace shows that ifconfig is in fact writing the output to file descriptor 1 (aka stdout), so it's not clear why no output is actually showing up. This could be either an LXC or a virsh issue, I guess.