M_BITS
#define S_FACTOR (2 * M_BITS)
const static int nbits = 8192 << M_BITS;
if_getmtu(ifp) + IEEE80211_MESH_MAXOVERHEAD, rate, 0) << M_BITS;
if_getcounter(ifp, IFCOUNTER_IERRORS)) / 100) << M_BITS)
((1 << S_FACTOR) / ((1 << M_BITS) - errrate));