[BRIDGE]: allow show/store of group multicast address

Bridge's communicate with each other using Spanning Tree Protocol
over a standard multicast address. There are times when testing or
layering bridges over existing topologies or tunnels, when it is
useful to use alternative multicast addresses for STP packets.

The 802.1d standard has some unused addresses, that can be used for this.
This patch is restrictive in that it only allows one of the possible
addresses in the standard.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index dad409489753..a9feb2015425 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -19,7 +19,8 @@
 #include <linux/netfilter_bridge.h>
 #include "br_private.h"
 
-const unsigned char bridge_ula[6] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
+/* Bridge group multicast address 802.1d (pg 51). */
+const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
 
 static void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
 {
@@ -108,9 +109,9 @@ static int br_handle_local_finish(struct sk_buff *skb)
 /* Does address match the link local multicast address.
  * 01:80:c2:00:00:0X
  */
-static inline int is_link_local(const unsigned char *dest)
+static inline int is_link_local(const const unsigned char *dest)
 {
-        return memcmp(dest, bridge_ula, 5) == 0 && (dest[5] & 0xf0) == 0;
+        return memcmp(dest, br_group_address, 5) == 0 && (dest[5] & 0xf0) == 0;
 }
 
 /*