uml: improve checking and diagnostics of ethernet MACs

Improve checking and diagnostics for broadcast and multicast Ethernet MAC
addresses, and distinguish between those cases in output; also make sure the
device is assigned a MAC address valid only locally to avoid collisions.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 41 insertions, 9 deletions

diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index 20963f106c34..cd466e30af67 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -283,7 +283,7 @@ void uml_net_user_timer_expire(unsigned long _conn)
 #endif
 }
 
-static void setup_etheraddr(char *str, unsigned char *addr)
+static void setup_etheraddr(char *str, unsigned char *addr, char *name)
 {
         char *end;
         int i;
@@ -302,15 +302,32 @@ static void setup_etheraddr(char *str, unsigned char *addr)
                 }
                 str = end + 1;
         }
-        if(addr[0] & 1){
+        if (is_multicast_ether_addr(addr)) {
                 printk(KERN_ERR
-                       "Attempt to assign a broadcast ethernet address to a "
+                       "Attempt to assign a multicast ethernet address to a "
                        "device disallowed\n");
                 goto random;
         }
+        if (!is_valid_ether_addr(addr)) {
+                printk(KERN_ERR
+                       "Attempt to assign an invalid ethernet address to a "
+                       "device disallowed\n");
+                goto random;
+        }
+        if (!is_local_ether_addr(addr)) {
+                printk(KERN_WARNING
+                       "Warning: attempt to assign a globally valid ethernet address to a "
+                       "device\n");
+                printk(KERN_WARNING "You should better enable the 2nd rightmost bit "
+                      "in the first byte of the MAC, i.e. "
+                      "%02x:%02x:%02x:%02x:%02x:%02x\n",
+                      addr[0] | 0x02, addr[1], addr[2], addr[3], addr[4], addr[5]);
+        }
         return;
 
 random:
+        printk(KERN_INFO
+               "Choosing a random ethernet address for device %s\n", name);
         random_ether_addr(addr);
 }
 
@@ -331,6 +348,7 @@ static void eth_configure(int n, void *init, char *mac,
         struct net_device *dev;
         struct uml_net_private *lp;
         int save, err, size;
+        char name[sizeof(dev->name)];
 
         size = transport->private_size + sizeof(struct uml_net_private) +
                 sizeof(((struct uml_net_private *) 0)->user);
@@ -344,7 +362,13 @@ static void eth_configure(int n, void *init, char *mac,
         INIT_LIST_HEAD(&device->list);
         device->index = n;
 
-        setup_etheraddr(mac, device->mac);
+        /* If this name ends up conflicting with an existing registered
+         * netdevice, that is OK, register_netdev{,ice}() will notice this
+         * and fail.
+         */
+        snprintf(name, sizeof(name), "eth%d", n);
+
+        setup_etheraddr(mac, device->mac, name);
 
         printk(KERN_INFO "Netdevice %d ", n);
         printk("(%02x:%02x:%02x:%02x:%02x:%02x) ",
@@ -375,11 +399,7 @@ static void eth_configure(int n, void *init, char *mac,
                 goto out_free_netdev;
         SET_NETDEV_DEV(dev,&device->pdev.dev);
 
-        /* If this name ends up conflicting with an existing registered
-         * netdevice, that is OK, register_netdev{,ice}() will notice this
-         * and fail.
-         */
-        snprintf(dev->name, sizeof(dev->name), "eth%d", n);
+        strcpy(dev->name, name);
         device->dev = dev;
 
         /*
diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 745c988359c0..071c67abed86 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -71,6 +71,18 @@ static inline int is_multicast_ether_addr(const u8 *addr)
 }
 
 /**
+ * is_local_ether_addr - Determine if the Ethernet address is locally-assigned
+ * one (IEEE 802).
+ * @addr: Pointer to a six-byte array containing the Ethernet address
+ *
+ * Return true if the address is a local address.
+ */
+static inline int is_local_ether_addr(const u8 *addr)
+{
+        return (0x02 & addr[0]);
+}
+
+/**
  * is_broadcast_ether_addr - Determine if the Ethernet address is broadcast
  * @addr: Pointer to a six-byte array containing the Ethernet address
  *