[NET]: Make packet reception network namespace safe

This patch modifies every packet receive function
registered with dev_add_pack() to drop packets if they
are not from the initial network namespace.

This should ensure that the various network stacks do
not receive packets in a anything but the initial network
namespace until the code has been converted and is ready
for them.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 328759c..6644e8f 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -122,6 +122,11 @@
 	unsigned short vlan_TCI;
 	__be16 proto;
 
+	if (dev->nd_net != &init_net) {
+		kfree_skb(skb);
+		return -1;
+	}
+
 	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
 		return -1;