usbnet: modern method to get random MAC

The driver generates a random MAC once on load
and uses it over and over, including on two devices
needing a random MAC at the same time.

Jakub suggested revamping the driver to the modern
API for setting a random MAC rather than fixing
the old stuff.

The bug is as old as the driver.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Fixes: 1da177e ("Linux-2.6.12-rc2")
Link: https://patch.msgid.link/20240829175201.670718-1-oneukum@suse.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/usb/usbnet.c

@@ -61,9 +61,6 @@
 
 /*-------------------------------------------------------------------------*/
 
-// randomly generated ethernet address
-static u8	node_id [ETH_ALEN];
-
 /* use ethtool to change the level for any given device */
 static int msg_level = -1;
 module_param (msg_level, int, 0);
@@ -1725,7 +1722,6 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 
 	dev->net = net;
 	strscpy(net->name, "usb%d", sizeof(net->name));
-	eth_hw_addr_set(net, node_id);
 
 	/* rx and tx sides can use different message sizes;
 	 * bind() should set rx_urb_size in that case.
@@ -1801,9 +1797,9 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 		goto out4;
 	}
 
-	/* let userspace know we have a random address */
-	if (ether_addr_equal(net->dev_addr, node_id))
-		net->addr_assign_type = NET_ADDR_RANDOM;
+	/* this flags the device for user space */
+	if (!is_valid_ether_addr(net->dev_addr))
+		eth_hw_addr_random(net);
 
 	if ((dev->driver_info->flags & FLAG_WLAN) != 0)
 		SET_NETDEV_DEVTYPE(net, &wlan_type);
@@ -2211,7 +2207,6 @@ static int __init usbnet_init(void)
 	BUILD_BUG_ON(
 		sizeof_field(struct sk_buff, cb) < sizeof(struct skb_data));
 
-	eth_random_addr(node_id);
 	return 0;
 }
 module_init(usbnet_init);