[NETNS]: Process inet_confirm_addr in the correct namespace.

inet_confirm_addr can be called with NULL in_dev from arp_ignore iff
scope is RT_SCOPE_LINK.

Lets always pass the device and check for RT_SCOPE_LINK scope inside
inet_confirm_addr. This let us take network namespace from in_device a
need for an additional argument.
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/arp.c

@@ -402,7 +402,6 @@ static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
 	case 3:	/* Do not reply for scope host addresses */
 		sip = 0;
 		scope = RT_SCOPE_LINK;
-		in_dev = NULL;
 		break;
 	case 4:	/* Reserved */
 	case 5:

net/ipv4/devinet.c

@@ -978,13 +978,15 @@ __be32 inet_confirm_addr(struct in_device *in_dev,
 {
 	__be32 addr = 0;
 	struct net_device *dev;
+	struct net *net;
 
-	if (in_dev != NULL)
+	if (scope != RT_SCOPE_LINK)
 		return confirm_addr_indev(in_dev, dst, local, scope);
 
+	net = in_dev->dev->nd_net;
 	read_lock(&dev_base_lock);
 	rcu_read_lock();
-	for_each_netdev(&init_net, dev) {
+	for_each_netdev(net, dev) {
 		if ((in_dev = __in_dev_get_rcu(dev))) {
 			addr = confirm_addr_indev(in_dev, dst, local, scope);
 			if (addr)