[netdevice] Add a generic concept of a "blocked link"

When Spanning Tree Protocol (STP) is used, there may be a substantial
delay (tens of seconds) from the time that the link goes up to the
time that the port starts forwarding packets.

Add a generic concept of a "blocked link" (i.e. a link which is up but
which is not expected to communicate successfully), and allow "ifstat"
to indicate when a link is blocked.

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

src/include/ipxe/netdevice.h

@@ -15,6 +15,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <ipxe/refcnt.h>
 #include <ipxe/settings.h>
 #include <ipxe/interface.h>
+#include <ipxe/retry.h>
 
 struct io_buffer;
 struct net_device;
@@ -392,6 +393,8 @@ struct net_device {
 	 * indicates the error preventing link-up.
 	 */
 	int link_rc;
+	/** Link block timer */
+	struct retry_timer link_block;
 	/** Maximum packet length
 	 *
 	 * This length includes any link-layer headers.
@@ -613,6 +616,17 @@ netdev_link_ok ( struct net_device *netdev ) {
 	return ( netdev->link_rc == 0 );
 }
 
+/**
+ * Check link block state of network device
+ *
+ * @v netdev		Network device
+ * @ret link_blocked	Link is blocked
+ */
+static inline __attribute__ (( always_inline )) int
+netdev_link_blocked ( struct net_device *netdev ) {
+	return ( timer_running ( &netdev->link_block ) );
+}
+
 /**
  * Check whether or not network device is open
  *
@@ -661,6 +675,9 @@ extern void netdev_rx_freeze ( struct net_device *netdev );
 extern void netdev_rx_unfreeze ( struct net_device *netdev );
 extern void netdev_link_err ( struct net_device *netdev, int rc );
 extern void netdev_link_down ( struct net_device *netdev );
+extern void netdev_link_block ( struct net_device *netdev,
+				unsigned long timeout );
+extern void netdev_link_unblock ( struct net_device *netdev );
 extern int netdev_tx ( struct net_device *netdev, struct io_buffer *iobuf );
 extern void netdev_tx_defer ( struct net_device *netdev,
 			      struct io_buffer *iobuf );

src/net/netdevice.c

@@ -161,6 +161,9 @@ void netdev_rx_unfreeze ( struct net_device *netdev ) {
  */
 void netdev_link_err ( struct net_device *netdev, int rc ) {
 
+	/* Stop link block timer */
+	stop_timer ( &netdev->link_block );
+
 	/* Record link state */
 	netdev->link_rc = rc;
 	if ( netdev->link_rc == 0 ) {
@@ -190,6 +193,50 @@ void netdev_link_down ( struct net_device *netdev ) {
 	}
 }
 
+/**
+ * Mark network device link as being blocked
+ *
+ * @v netdev		Network device
+ * @v timeout		Timeout (in ticks)
+ */
+void netdev_link_block ( struct net_device *netdev, unsigned long timeout ) {
+
+	/* Start link block timer */
+	if ( ! netdev_link_blocked ( netdev ) ) {
+		DBGC ( netdev, "NETDEV %s link blocked for %ld ticks\n",
+		       netdev->name, timeout );
+	}
+	start_timer_fixed ( &netdev->link_block, timeout );
+}
+
+/**
+ * Mark network device link as being unblocked
+ *
+ * @v netdev		Network device
+ */
+void netdev_link_unblock ( struct net_device *netdev ) {
+
+	/* Stop link block timer */
+	if ( netdev_link_blocked ( netdev ) )
+		DBGC ( netdev, "NETDEV %s link unblocked\n", netdev->name );
+	stop_timer ( &netdev->link_block );
+}
+
+/**
+ * Handle network device link block timer expiry
+ *
+ * @v timer		Link block timer
+ * @v fail		Failure indicator
+ */
+static void netdev_link_block_expired ( struct retry_timer *timer,
+					int fail __unused ) {
+	struct net_device *netdev =
+		container_of ( timer, struct net_device, link_block );
+
+	/* Assume link is no longer blocked */
+	DBGC ( netdev, "NETDEV %s link block expired\n", netdev->name );
+}
+
 /**
  * Record network device statistic
  *
@@ -545,7 +592,8 @@ static struct interface_descriptor netdev_config_desc =
 static void free_netdev ( struct refcnt *refcnt ) {
 	struct net_device *netdev =
 		container_of ( refcnt, struct net_device, refcnt );
-	
+
+	stop_timer ( &netdev->link_block );
 	netdev_tx_flush ( netdev );
 	netdev_rx_flush ( netdev );
 	clear_settings ( netdev_settings ( netdev ) );
@@ -575,6 +623,8 @@ struct net_device * alloc_netdev ( size_t priv_len ) {
 	if ( netdev ) {
 		ref_init ( &netdev->refcnt, free_netdev );
 		netdev->link_rc = -EUNKNOWN_LINK_STATUS;
+		timer_init ( &netdev->link_block, netdev_link_block_expired,
+			     &netdev->refcnt );
 		INIT_LIST_HEAD ( &netdev->tx_queue );
 		INIT_LIST_HEAD ( &netdev->tx_deferred );
 		INIT_LIST_HEAD ( &netdev->rx_queue );

src/usr/ifmgmt.c

@@ -103,11 +103,12 @@ static void ifstat_errors ( struct net_device_stats *stats,
  */
 void ifstat ( struct net_device *netdev ) {
 	printf ( "%s: %s using %s on %s (%s)\n"
-		 "  [Link:%s, TX:%d TXE:%d RX:%d RXE:%d]\n",
+		 "  [Link:%s%s, TX:%d TXE:%d RX:%d RXE:%d]\n",
 		 netdev->name, netdev_addr ( netdev ),
 		 netdev->dev->driver_name, netdev->dev->name,
 		 ( netdev_is_open ( netdev ) ? "open" : "closed" ),
 		 ( netdev_link_ok ( netdev ) ? "up" : "down" ),
+		 ( netdev_link_blocked ( netdev ) ? " (blocked)" : "" ),
 		 netdev->tx_stats.good, netdev->tx_stats.bad,
 		 netdev->rx_stats.good, netdev->rx_stats.bad );
 	if ( ! netdev_link_ok ( netdev ) ) {