net: constify netdev->dev_addr

Commit 406f42f ("net-next: When a bond have a massive amount
of VLANs...") introduced a rbtree for faster Ethernet address look
up. We converted all users to make modifications via appropriate
helpers, make netdev->dev_addr const.

The update helpers need to upcast from the buffer to
struct netdev_hw_addr.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdevice.h

@@ -2117,7 +2117,7 @@ struct net_device {
  * Cache lines mostly used on receive path (including eth_type_trans())
  */
 	/* Interface address info used in eth_type_trans() */
-	unsigned char		*dev_addr;
+	const unsigned char	*dev_addr;
 
 	struct netdev_rx_queue	*_rx;
 	unsigned int		num_rx_queues;
@@ -4268,24 +4268,20 @@ void __hw_addr_unsync_dev(struct netdev_hw_addr_list *list,
 void __hw_addr_init(struct netdev_hw_addr_list *list);
 
 /* Functions used for device addresses handling */
+void dev_addr_mod(struct net_device *dev, unsigned int offset,
+		  const void *addr, size_t len);
+
 static inline void
 __dev_addr_set(struct net_device *dev, const void *addr, size_t len)
 {
-	memcpy(dev->dev_addr, addr, len);
+	dev_addr_mod(dev, 0, addr, len);
 }
 
 static inline void dev_addr_set(struct net_device *dev, const u8 *addr)
 {
 	__dev_addr_set(dev, addr, dev->addr_len);
 }
 
-static inline void
-dev_addr_mod(struct net_device *dev, unsigned int offset,
-	     const void *addr, size_t len)
-{
-	memcpy(&dev->dev_addr[offset], addr, len);
-}
-
 int dev_addr_add(struct net_device *dev, const unsigned char *addr,
 		 unsigned char addr_type);
 int dev_addr_del(struct net_device *dev, const unsigned char *addr,

net/core/dev_addr_lists.c

@@ -549,6 +549,16 @@ int dev_addr_init(struct net_device *dev)
 }
 EXPORT_SYMBOL(dev_addr_init);
 
+void dev_addr_mod(struct net_device *dev, unsigned int offset,
+		  const void *addr, size_t len)
+{
+	struct netdev_hw_addr *ha;
+
+	ha = container_of(dev->dev_addr, struct netdev_hw_addr, addr[0]);
+	memcpy(&ha->addr[offset], addr, len);
+}
+EXPORT_SYMBOL(dev_addr_mod);
+
 /**
  *	dev_addr_add - Add a device address
  *	@dev: device