BSD_OVHD
rptr += BSD_OVHD;
db->comp_bytes += ilen + BSD_OVHD;
db->comp_bytes += ilen + BSD_OVHD;
if (wptr == NULL || olen + PPP_HDRLEN + BSD_OVHD >= maxolen) {
db->comp_bytes += olen + BSD_OVHD;
return (olen + PPP_HDRLEN + BSD_OVHD);