WIP - cleaner MTU change

src/drivers/net/netvsc.c

@@ -852,16 +852,9 @@ static int netvsc_reset ( struct vmbus_device *vmdev ) {
 	struct net_device *netdev = rndis->netdev;
 	int rc;
 
-	/* A closed device holds no NetVSC (or RNDIS) state, so there
+	/* Reset network device */
-	 * is nothing to reset.
+	if ( ( rc = netdev_reset ( netdev ) ) != 0 ) {
-	 */
+		DBGC ( netvsc, "NETVSC %s could not reset: %s\n",
-	if ( ! netdev_is_open ( netdev ) )
-		return 0;
-
-	/* Close and reopen device to reset any stale state */
-	netdev_close ( netdev );
-	if ( ( rc = netdev_open ( netdev ) ) != 0 ) {
-		DBGC ( netvsc, "NETVSC %s could not reopen: %s\n",
 		       netvsc->name, strerror ( rc ) );
 		return rc;
 	}

src/include/ipxe/netdevice.h

@@ -723,6 +723,7 @@ extern struct net_device * alloc_netdev ( size_t priv_size );
 extern int register_netdev ( struct net_device *netdev );
 extern int netdev_open ( struct net_device *netdev );
 extern void netdev_close ( struct net_device *netdev );
+extern int netdev_reset ( struct net_device *netdev );
 extern void unregister_netdev ( struct net_device *netdev );
 extern void netdev_irq ( struct net_device *netdev, int enable );
 extern struct net_device * find_netdev ( const char *name );

src/net/netdev_settings.c

@@ -453,11 +453,10 @@ static int apply_netdev_settings ( void ) {
 			       netdev->name, mtu );
 		}
 
-		/* Close and reopen network device if MTU has increased */
+		/* Reset network device if MTU has increased */
 		if ( netdev_is_open ( netdev ) && ( mtu > old_mtu ) ) {
-			netdev_close ( netdev );
+			if ( ( rc = netdev_reset ( netdev ) ) != 0 ) {
-			if ( ( rc = netdev_open ( netdev ) ) != 0 ) {
+				DBGC ( netdev, "NETDEV %s could not reset: "
-				DBGC ( netdev, "NETDEV %s could not reopen: "
 				       "%s\n", netdev->name, strerror ( rc ) );
 				return rc;
 			}

src/net/netdevice.c

@@ -612,6 +612,23 @@ static void netdev_rx_flush ( struct net_device *netdev ) {
 	}
 }
 
+/**
+ * Flush device's transmit and receive queues
+ *
+ * @v netdev		Network device
+ */
+static void netdev_flush ( struct net_device *netdev ) {
+
+	/* Sanity check */
+	assert ( ! ( netdev->state & NETDEV_OPEN ) );
+
+	/* Flush TX queue */
+	netdev_tx_flush ( netdev );
+
+	/* Flush RX queue */
+	netdev_rx_flush ( netdev );
+}
+
 /**
  * Finish network device configuration
  *
@@ -657,8 +674,7 @@ static void free_netdev ( struct refcnt *refcnt ) {
 		container_of ( refcnt, struct net_device, refcnt );
 
 	stop_timer ( &netdev->link_block );
-	netdev_tx_flush ( netdev );
+	netdev_flush ( netdev );
-	netdev_rx_flush ( netdev );
 	clear_settings ( netdev_settings ( netdev ) );
 	free ( netdev );
 }
@@ -880,8 +896,47 @@ void netdev_close ( struct net_device *netdev ) {
 	netdev->op->close ( netdev );
 
 	/* Flush TX and RX queues */
-	netdev_tx_flush ( netdev );
+	netdev_flush ( netdev );
-	netdev_rx_flush ( netdev );
+}
+
+/**
+ * Reset transmit and receive queues
+ *
+ * @v netdev		Network device
+ * @ret rc		Return status code
+ */
+int netdev_reset ( struct net_device *netdev ) {
+	int rc;
+
+	/* Do nothing unless device is open */
+	if ( ! ( netdev->state & NETDEV_OPEN ) )
+		return 0;
+
+	DBGC ( netdev, "NETDEV %s resetting\n", netdev->name );
+
+	/* Mark as closed */
+	netdev->state &= ~NETDEV_OPEN;
+
+	/* Close the device */
+	netdev->op->close ( netdev );
+
+	/* Flush TX and RX queues */
+	netdev_flush ( netdev );
+
+	/* Mark as opened */
+	netdev->state |= NETDEV_OPEN;
+
+	/* Reopen device */
+	if ( ( rc = netdev->op->open ( netdev ) ) != 0 )
+		goto err;
+
+	return 0;
+
+ err:
+	netdev->state &= ~NETDEV_OPEN;
+	list_del ( &netdev->open_list );
+	netdev_notify ( netdev );
+	return rc;
 }
 
 /**