6lowpan: fix segmentation fault caused by mlme request

Add nescesary mlme callbacks to satisfy "iz list" request from user space.
Due to 6lowpan device doesn't have its own phy, mlme implemented as a pipe
to a real phy to which 6lowpan is attached.
Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/6lowpan.c

@@ -1044,6 +1044,24 @@ static void lowpan_dev_free(struct net_device *dev)
 	free_netdev(dev);
 }
 
+static struct wpan_phy *lowpan_get_phy(const struct net_device *dev)
+{
+	struct net_device *real_dev = lowpan_dev_info(dev)->real_dev;
+	return ieee802154_mlme_ops(real_dev)->get_phy(real_dev);
+}
+
+static u16 lowpan_get_pan_id(const struct net_device *dev)
+{
+	struct net_device *real_dev = lowpan_dev_info(dev)->real_dev;
+	return ieee802154_mlme_ops(real_dev)->get_pan_id(real_dev);
+}
+
+static u16 lowpan_get_short_addr(const struct net_device *dev)
+{
+	struct net_device *real_dev = lowpan_dev_info(dev)->real_dev;
+	return ieee802154_mlme_ops(real_dev)->get_short_addr(real_dev);
+}
+
 static struct header_ops lowpan_header_ops = {
 	.create	= lowpan_header_create,
 };
@@ -1053,6 +1071,12 @@ static const struct net_device_ops lowpan_netdev_ops = {
 	.ndo_set_mac_address	= eth_mac_addr,
 };
 
+static struct ieee802154_mlme_ops lowpan_mlme = {
+	.get_pan_id = lowpan_get_pan_id,
+	.get_phy = lowpan_get_phy,
+	.get_short_addr = lowpan_get_short_addr,
+};
+
 static void lowpan_setup(struct net_device *dev)
 {
 	pr_debug("(%s)\n", __func__);
@@ -1070,6 +1094,7 @@ static void lowpan_setup(struct net_device *dev)
 
 	dev->netdev_ops		= &lowpan_netdev_ops;
 	dev->header_ops		= &lowpan_header_ops;
+	dev->ml_priv		= &lowpan_mlme;
 	dev->destructor		= lowpan_dev_free;
 }