[BRIDGE]: allow setting hardware address of bridge pseudo-dev

Some people are using bridging to hide multiple machines from an ISP
that restricts by MAC address. So in that case allow the bridge mac
address to be set to any of the existing interfaces.  I don't want to
allow any arbitrary value and confuse STP.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index f564ee9..f7a66ab 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -15,7 +15,8 @@
 
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
-#include <linux/module.h>
+#include <linux/etherdevice.h>
+
 #include <asm/uaccess.h>
 #include "br_private.h"
 
@@ -82,6 +83,29 @@
 	return 0;
 }
 
+/* Allow setting mac address of pseudo-bridge to be same as
+ * any of the bound interfaces
+ */
+static int br_set_mac_address(struct net_device *dev, void *p)
+{
+	struct net_bridge *br = netdev_priv(dev);
+	struct sockaddr *addr = p;
+	struct net_bridge_port *port;
+	int err = -EADDRNOTAVAIL;
+
+	spin_lock_bh(&br->lock);
+	list_for_each_entry(port, &br->port_list, list) {
+		if (!compare_ether_addr(port->dev->dev_addr, addr->sa_data)) {
+			br_stp_change_bridge_id(br, addr->sa_data);
+			err = 0;
+			break;
+		}
+	}
+	spin_unlock_bh(&br->lock);
+
+	return err;
+}
+
 void br_dev_setup(struct net_device *dev)
 {
 	memset(dev->dev_addr, 0, ETH_ALEN);
@@ -98,6 +122,6 @@
 	SET_MODULE_OWNER(dev);
 	dev->stop = br_dev_stop;
 	dev->tx_queue_len = 0;
-	dev->set_mac_address = NULL;
+	dev->set_mac_address = br_set_mac_address;
 	dev->priv_flags = IFF_EBRIDGE;
 }