[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/aarp.c b/net/appletalk/aarp.c
index 80b5414..9267f48 100644
--- a/net/appletalk/aarp.c
+++ b/net/appletalk/aarp.c
@@ -713,6 +713,9 @@
 	struct atalk_addr sa, *ma, da;
 	struct atalk_iface *ifa;
 
+	if (dev->nd_net != &init_net)
+		goto out0;
+
 	/* We only do Ethernet SNAP AARP. */
 	if (dev->type != ARPHRD_ETHER)
 		goto out0;