bridge: forwarding table information for >256 devices

The forwarding table binary interface (my bad choice), only exposes
the port number of the first 8 bits. The bridge code was limited to
256 ports at the time, but now the kernel supports up 1024 ports, so
the upper bits are lost when doing:

   brctl showmacs

The fix is to squeeze the extra bits into small hole left in data
structure, to maintain binary compatiablity.

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

include/linux/if_bridge.h

@@ -97,7 +97,9 @@ struct __fdb_entry
 	__u8 port_no;
 	__u8 is_local;
 	__u32 ageing_timer_value;
-	__u32 unused;
+	__u8 port_hi;
+	__u8 pad0;
+	__u16 unused;
 };
 
 #ifdef __KERNEL__

net/bridge/br_fdb.c

@@ -285,7 +285,11 @@ int br_fdb_fillbuf(struct net_bridge *br, void *buf,
 
 			/* convert from internal format to API */
 			memcpy(fe->mac_addr, f->addr.addr, ETH_ALEN);
+
+			/* due to ABI compat need to split into hi/lo */
 			fe->port_no = f->dst->port_no;
+			fe->port_hi = f->dst->port_no >> 8;
+
 			fe->is_local = f->is_local;
 			if (!f->is_static)
 				fe->ageing_timer_value = jiffies_to_clock_t(jiffies - f->ageing_timer);