[netdevice] Add mechanism for reporting detailed link status codes

Expand the NETDEV_LINK_UP bit into a link_rc status code field,
allowing specific reasons for link failure to be reported via
"ifstat".

Originally-authored-by: Joshua Oreman <oremanj@rwcr.net>

src/hci/strerror.c

 	{ ENOEXEC, "Not an executable image" },
 	{ ENOMEM, "Out of memory" },
 	{ ENOSPC, "No space left on device" },
+	{ ENOTCONN, "Not connected" },
 	{ ENOTSUP, "Not supported" },
 	{ EPERM, "Operation not permitted" },
 	{ ERANGE, "Out of range" },

src/include/gpxe/netdevice.h

 	 * This is the bitwise-OR of zero or more NETDEV_XXX constants.
 	 */
 	unsigned int state;
+	/** Link status code
+	 *
+	 * Zero indicates that the link is up; any other value
+	 * indicates the error preventing link-up.
+	 */
+	int link_rc;
 	/** Maximum packet length
 	 *
 	 * This length includes any link-layer headers.
 /** Network device is open */
 #define NETDEV_OPEN 0x0001
 
-/** Network device has link */
-#define NETDEV_LINK_UP 0x0002
-
 /** Link-layer protocol table */
 #define LL_PROTOCOLS __table ( struct ll_protocol, "ll_protocols" )
 
  */
 static inline __attribute__ (( always_inline )) void
 netdev_link_up ( struct net_device *netdev ) {
-	netdev->state |= NETDEV_LINK_UP;
+	netdev->link_rc = 0;
 }
 
 /**
- * Mark network device as having link down
+ * Mark network device as having link down due to a specific error
  *
  * @v netdev		Network device
+ * @v rc		Link status code
  */
 static inline __attribute__ (( always_inline )) void
-netdev_link_down ( struct net_device *netdev ) {
-	netdev->state &= ~NETDEV_LINK_UP;
+netdev_link_err ( struct net_device *netdev, int rc ) {
+	netdev->link_rc = rc;
 }
 
 /**
  */
 static inline __attribute__ (( always_inline )) int
 netdev_link_ok ( struct net_device *netdev ) {
-	return ( netdev->state & NETDEV_LINK_UP );
+	return ( netdev->link_rc == 0 );
 }
 
+extern void netdev_link_down ( struct net_device *netdev );
 extern int netdev_tx ( struct net_device *netdev, struct io_buffer *iobuf );
 extern void netdev_tx_complete_err ( struct net_device *netdev,
 				 struct io_buffer *iobuf, int rc );

src/net/netdevice.c

 #include <gpxe/process.h>
 #include <gpxe/init.h>
 #include <gpxe/device.h>
+#include <gpxe/errortab.h>
 #include <gpxe/netdevice.h>
 
 /** @file
 /** List of open network devices, in reverse order of opening */
 struct list_head open_net_devices = LIST_HEAD_INIT ( open_net_devices );
 
+/** Default link status code */
+#define EUNKNOWN_LINK_STATUS EINPROGRESS
+
+/** Human-readable message for the default link status */
+struct errortab netdev_errors[] __errortab = {
+	{ EUNKNOWN_LINK_STATUS, "Unknown" },
+};
+
+/**
+ * Mark network device as having link down
+ *
+ * @v netdev		Network device
+ */
+void netdev_link_down ( struct net_device *netdev ) {
+
+	switch ( netdev->link_rc ) {
+	case 0:
+	case -EUNKNOWN_LINK_STATUS:
+		netdev->link_rc = -ENOTCONN;
+		break;
+	default:
+		/* Avoid clobbering a more detailed link status code,
+		 * if one is already set.
+		 */
+		break;
+	}
+}
+
 /**
  * Record network device statistic
  *
 	netdev = zalloc ( total_len );
 	if ( netdev ) {
 		netdev->refcnt.free = free_netdev;
+		netdev->link_rc = -EUNKNOWN_LINK_STATUS;
 		INIT_LIST_HEAD ( &netdev->tx_queue );
 		INIT_LIST_HEAD ( &netdev->rx_queue );
 		netdev_settings_init ( netdev );

src/usr/ifmgmt.c

 		 ( netdev_link_ok ( netdev ) ? "up" : "down" ),
 		 netdev->tx_stats.good, netdev->tx_stats.bad,
 		 netdev->rx_stats.good, netdev->rx_stats.bad );
+	if ( ! netdev_link_ok ( netdev ) ) {
+		printf ( "  [Link status: %s]\n",
+			 strerror ( netdev->link_rc ) );
+	}
 	ifstat_errors ( &netdev->tx_stats, "TXE" );
 	ifstat_errors ( &netdev->rx_stats, "RXE" );
 }