[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/drivers/net/wan/hdlc.c b/drivers/net/wan/hdlc.c
index 65ad2e2..3b57350 100644
--- a/drivers/net/wan/hdlc.c
+++ b/drivers/net/wan/hdlc.c
@@ -36,6 +36,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/notifier.h>
 #include <linux/hdlc.h>
+#include <net/net_namespace.h>
 
 
 static const char* version = "HDLC support module revision 1.21";
@@ -66,6 +67,12 @@
 		    struct packet_type *p, struct net_device *orig_dev)
 {
 	struct hdlc_device_desc *desc = dev_to_desc(dev);
+
+	if (dev->nd_net != &init_net) {
+		kfree_skb(skb);
+		return 0;
+	}
+
 	if (desc->netif_rx)
 		return desc->netif_rx(skb);