Automatic PPP disconnection

I use a proxy server on a net for Internet on demand   browsing  clients on ISDN lines with one modem (shared) on PPP serial line connection. I need to set active-filter on ppp daemon  together idle option (Debian box with 2.2.17 kernel and CONFIG_FILTER enable, ppp daemon 2

PPP_FILTER

Can I use PPP_FILTER on ppp package ? If the package is in deb format, how can I get that? I have to get source package and compile it ? Can you help me (I have to set package filtering with tcpdump-style _expression_ ma my pppd don't recognize active filter option) Thnk's for service Dan