[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/packet/af_packet.c b/net/packet/af_packet.c
index 766b5fa..cae1ee4 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -252,6 +252,9 @@
 	struct sock *sk;
 	struct sockaddr_pkt *spkt;
 
+	if (dev->nd_net != &init_net)
+		goto out;
+
 	/*
 	 *	When we registered the protocol we saved the socket in the data
 	 *	field for just this event.
@@ -452,6 +455,9 @@
 	int skb_len = skb->len;
 	unsigned int snaplen, res;
 
+	if (dev->nd_net != &init_net)
+		goto drop;
+
 	if (skb->pkt_type == PACKET_LOOPBACK)
 		goto drop;
 
@@ -568,6 +574,9 @@
 	struct sk_buff *copy_skb = NULL;
 	struct timeval tv;
 
+	if (dev->nd_net != &init_net)
+		goto drop;
+
 	if (skb->pkt_type == PACKET_LOOPBACK)
 		goto drop;