It looks like a recent patch to 2.6.5 got rid of CLEAR_BITMAP. diff -Nru a/net/bridge/br_if.c b/net/bridge/br_if.c --- a/net/bridge/br_if.c Wed Apr 14 12:01:21 2004 +++ b/net/bridge/br_if.c Wed Apr 14 12:01:21 2004 @@ -175,7 +175,7 @@ if (!inuse) return -ENOMEM; - CLEAR_BITMAP(inuse, BR_MAX_PORTS); + memset(inuse, 0, BITS_TO_LONGS(BR_MAX_PORTS)*sizeof(unsigned long)); set_bit(0, inuse); /* zero is reserved */ list_for_each_entry(p, &br->port_list, list) { set_bit(p->port_no, inuse);