From 98d09a1e0372226bdea46f7dc8ce7f0cae98f08c Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@ipxe.org>
Date: Wed, 30 Jul 2014 18:11:20 +0100
Subject: [PATCH] [netdevice] Avoid registering duplicate network devices

Reject network devices which appear to be duplicates of those already
available via a different underlying hardware device.  On a Xen PV-HVM
system, this allows us to filter out the emulated PCI NICs (which
would otherwise appear alongside the netfront NICs).

Note that we cannot use the Xen facility to "unplug" the emulated PCI
NICs, since there is no guarantee that the OS we subsequently load
will have a native netfront driver.

We permit devices with the same MAC address if they are attached to
the same underlying hardware device (e.g. VLAN devices).

Inspired-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/include/ipxe/netdevice.h |  2 ++
 src/net/netdevice.c          | 45 ++++++++++++++++++++++++++++++++----
 2 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/src/include/ipxe/netdevice.h b/src/include/ipxe/netdevice.h
index 6ef9cb1e..95ad1cf1 100644
--- a/src/include/ipxe/netdevice.h
+++ b/src/include/ipxe/netdevice.h
@@ -685,6 +685,8 @@ extern struct net_device * find_netdev ( const char *name );
 extern struct net_device * find_netdev_by_index ( unsigned int index );
 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,
diff --git a/src/net/netdevice.c b/src/net/netdevice.c
index 2350256f..a8020858 100644
--- a/src/net/netdevice.c
+++ b/src/net/netdevice.c
@@ -602,9 +602,27 @@ struct net_device * alloc_netdev ( size_t priv_len ) {
 int register_netdev ( struct net_device *netdev ) {
 	struct ll_protocol *ll_protocol = netdev->ll_protocol;
 	struct net_driver *driver;
+	struct net_device *duplicate;
 	uint32_t seed;
 	int rc;
 
+	/* Set initial link-layer address, if not already set */
+	if ( ! netdev_has_ll_addr ( netdev ) ) {
+		ll_protocol->init_addr ( netdev->hw_addr, netdev->ll_addr );
+	}
+
+	/* 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;
+	}
+
 	/* Record device index and create device name */
 	netdev->index = netdev_index++;
 	if ( netdev->name[0] == '\0' ) {
@@ -612,11 +630,6 @@ int register_netdev ( struct net_device *netdev ) {
 			   netdev->index );
 	}
 
-	/* Set initial link-layer address, if not already set */
-	if ( ! netdev_has_ll_addr ( netdev ) ) {
-		ll_protocol->init_addr ( netdev->hw_addr, netdev->ll_addr );
-	}
-
 	/* Use least significant bits of the link-layer address to
 	 * improve the randomness of the (non-cryptographic) random
 	 * number generator.
@@ -660,6 +673,7 @@ int register_netdev ( struct net_device *netdev ) {
 	clear_settings ( netdev_settings ( netdev ) );
 	unregister_settings ( netdev_settings ( netdev ) );
  err_register_settings:
+ err_duplicate:
 	return rc;
 }
 
@@ -852,6 +866,27 @@ 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
  *