[netdevice] Allow duplicate MAC addresses

Many laptops now include the ability to specify a "system-specific MAC
address" (also known as "pass-through MAC"), which is supposed to be
used for both the onboard NIC and for any attached docking station or
other USB NIC.  This is intended to simplify interoperability with
software or hardware that relies on a MAC address to recognise an
individual machine: for example, a deployment server may associate the
MAC address with a particular operating system image to be deployed.

This therefore creates legitimate situations in which duplicate MAC
addresses may exist within the same system.  Remove the code that
rejects attempts to register a network device with a duplicate MAC.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/ecm.c

@@ -121,10 +121,9 @@ int ecm_fetch_mac ( struct usb_function *func,
 	}
 
 	/* Apply system-specific MAC address as current link-layer
-	 * address, if present and not already used.
+	 * address, if present.
 	 */
-	if ( ( ( rc = acpi_mac ( amac ) ) == 0 ) &&
-	     ! find_netdev_by_ll_addr ( &ethernet_protocol, amac ) ) {
+	if ( ( rc = acpi_mac ( amac ) ) == 0 ) {
 		memcpy ( netdev->ll_addr, amac, ETH_ALEN );
 		DBGC ( usb, "USB %s using system-specific MAC %s\n",
 		       func->name, eth_ntoa ( netdev->ll_addr ) );

src/include/ipxe/netdevice.h

@@ -729,8 +729,6 @@ extern struct net_device * find_netdev ( const char *name );
 extern struct net_device * find_netdev_by_scope_id ( unsigned int scope_id );
 extern struct net_device * find_netdev_by_location ( unsigned int bus_type,
 						     unsigned int location );
-extern struct net_device *
-find_netdev_by_ll_addr ( struct ll_protocol *ll_protocol, const void *ll_addr );
 extern struct net_device * last_opened_netdev ( void );
 extern int net_tx ( struct io_buffer *iobuf, struct net_device *netdev,
 		    struct net_protocol *net_protocol, const void *ll_dest,

src/net/netdevice.c

@@ -735,18 +735,6 @@ int register_netdev ( struct net_device *netdev ) {
 				ll_protocol->ll_header_len );
 	}
 
-	/* Reject network devices that are already available via a
-	 * different hardware device.
-	 */
-	duplicate = find_netdev_by_ll_addr ( ll_protocol, netdev->ll_addr );
-	if ( duplicate && ( duplicate->dev != netdev->dev ) ) {
-		DBGC ( netdev, "NETDEV rejecting duplicate (phys %s) of %s "
-		       "(phys %s)\n", netdev->dev->name, duplicate->name,
-		       duplicate->dev->name );
-		rc = -EEXIST;
-		goto err_duplicate;
-	}
-
 	/* Reject named network devices that already exist */
 	if ( netdev->name[0] && ( duplicate = find_netdev ( netdev->name ) ) ) {
 		DBGC ( netdev, "NETDEV rejecting duplicate name %s\n",
@@ -1002,27 +990,6 @@ struct net_device * find_netdev_by_location ( unsigned int bus_type,
 	return NULL;	
 }
 
-/**
- * Get network device by link-layer address
- *
- * @v ll_protocol	Link-layer protocol
- * @v ll_addr		Link-layer address
- * @ret netdev		Network device, or NULL
- */
-struct net_device * find_netdev_by_ll_addr ( struct ll_protocol *ll_protocol,
-					     const void *ll_addr ) {
-	struct net_device *netdev;
-
-	list_for_each_entry ( netdev, &net_devices, list ) {
-		if ( ( netdev->ll_protocol == ll_protocol ) &&
-		     ( memcmp ( netdev->ll_addr, ll_addr,
-				ll_protocol->ll_addr_len ) == 0 ) )
-			return netdev;
-	}
-
-	return NULL;
-}
-
 /**
  * Get most recently opened network device
  *