[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/appletalk/ddp.c b/net/appletalk/ddp.c
index fd1d52f..c1f1367 100644
--- a/net/appletalk/ddp.c
+++ b/net/appletalk/ddp.c
@@ -1403,6 +1403,9 @@
 	int origlen;
 	__u16 len_hops;
 
+	if (dev->nd_net != &init_net)
+		goto freeit;
+
 	/* Don't mangle buffer if shared */
 	if (!(skb = skb_share_check(skb, GFP_ATOMIC)))
 		goto out;
@@ -1488,6 +1491,9 @@
 static int ltalk_rcv(struct sk_buff *skb, struct net_device *dev,
 		     struct packet_type *pt, struct net_device *orig_dev)
 {
+	if (dev->nd_net != &init_net)
+		goto freeit;
+
 	/* Expand any short form frames */
 	if (skb_mac_header(skb)[2] == 1) {
 		struct ddpehdr *ddp;