net: etherdevice: add address inherit helper

Some etherdevices inherit their address from a parent or
master device. The addr_assign_type should be updated along
with the address in these cases.  Adding a helper function
to simplify this.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/etherdevice.h

@@ -198,6 +198,21 @@ static inline void eth_hw_addr_random(struct net_device *dev)
 	eth_random_addr(dev->dev_addr);
 }
 
+/**
+ * eth_hw_addr_inherit - Copy dev_addr from another net_device
+ * @dst: pointer to net_device to copy dev_addr to
+ * @src: pointer to net_device to copy dev_addr from
+ *
+ * Copy the Ethernet address from one net_device to another along with
+ * the address attributes (addr_assign_type).
+ */
+static inline void eth_hw_addr_inherit(struct net_device *dst,
+				       struct net_device *src)
+{
+	dst->addr_assign_type = src->addr_assign_type;
+	memcpy(dst->dev_addr, src->dev_addr, ETH_ALEN);
+}
+
 /**
  * compare_ether_addr - Compare two Ethernet addresses
  * @addr1: Pointer to a six-byte array containing the Ethernet address