OK, I can see what's happening here. eth0 doesn't detect link-up until
after a few seconds, so when the vlan interface is opened immediately
after eth0 has been opened, it inherits the link-down state. Subsequently
the vlan interface is never properly activated and are thus unable to
transmit any packets.
dev->state bits are not supposed to be manipulated directly. Something
similar is probably needed for the netif_device_present() bit, although
I don't know how this is meant to work for a virtual device.
Signed-off-by: David S. Miller <davem@davemloft.net>
                        if (!vlandev)
                                continue;
 
+                       if (netif_carrier_ok(dev)) {
+                               if (!netif_carrier_ok(vlandev))
+                                       netif_carrier_on(vlandev);
+                       } else {
+                               if (netif_carrier_ok(vlandev))
+                                       netif_carrier_off(vlandev);
+                       }
+
                        if ((vlandev->state & VLAN_LINK_STATE_MASK) != flgs) {
                                vlandev->state = (vlandev->state &~ VLAN_LINK_STATE_MASK) 
                                        | flgs;