[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/tipc/eth_media.c b/net/tipc/eth_media.c
index 711ca4b..d2ed237 100644
--- a/net/tipc/eth_media.c
+++ b/net/tipc/eth_media.c
@@ -38,6 +38,7 @@
 #include <net/tipc/tipc_bearer.h>
 #include <net/tipc/tipc_msg.h>
 #include <linux/netdevice.h>
+#include <net/net_namespace.h>
 
 #define MAX_ETH_BEARERS		2
 #define ETH_LINK_PRIORITY	TIPC_DEF_LINK_PRI
@@ -100,6 +101,11 @@
 	struct eth_bearer *eb_ptr = (struct eth_bearer *)pt->af_packet_priv;
 	u32 size;
 
+	if (dev->nd_net != &init_net) {
+		kfree_skb(buf);
+		return 0;
+	}
+
 	if (likely(eb_ptr->bearer)) {
 		if (likely(buf->pkt_type <= PACKET_BROADCAST)) {
 			size = msg_size((struct tipc_msg *)buf->data);