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>

2 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index 58e43e566457..950e13d09e06 100644
--- a/include/linux/if_bridge.h
+++ b/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__
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 9326c377822e..72c5976a5ce3 100644
--- a/net/bridge/br_fdb.c
+++ b/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);