bridge: Prepare for forwarding another bridge group addresses

If a bridge is an 802.1ad bridge, it must forward another bridge group
addresses (the Nearest Customer Bridge group addresses).
(For details, see IEEE 802.1Q-2011 8.6.3.)

As user might not want group_fwd_mask to be modified by enabling 802.1ad,
introduce a new mask, group_fwd_mask_required, which indicates addresses
the bridge wants to forward. This will be set by enabling 802.1ad.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 13e570e..4eba348 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -35,6 +35,8 @@
 #define BR_GROUPFWD_DEFAULT	0
 /* Don't allow forwarding control protocols like STP and LLDP */
 #define BR_GROUPFWD_RESTRICTED	0x4007u
+/* The Nearest Customer Bridge Group Address, 01-80-C2-00-00-[00,0B,0C,0D,0F] */
+#define BR_GROUPFWD_8021AD	0xB801u
 
 /* Path to usermode spanning tree program */
 #define BR_STP_PROG	"/sbin/bridge-stp"
@@ -226,6 +228,7 @@
 	bool				nf_call_arptables;
 #endif
 	u16				group_fwd_mask;
+	u16				group_fwd_mask_required;
 
 	/* STP */
 	bridge_id			designated_root;