This is an iptables module and it can match Caller-Station-Id attribute from PDP Create Context request. It also implements whitelisting by Station-Id ranges.
pdp match options for PDP Create Context requests:
--pdp-any Match any request
--pdp-reserved Match hardcoded list of station ids
--pdp-station-id num Match particular Calling-Station-ID
iptables -A INPUT -m pdp --pdp-reserved -j ACCEPT
iptables -A INPUT -m pdp --pdp-station-id 111111111111 -j ACCEPT
iptables -A INPUT -m pdp --pdp-any -j DROP
You should edit whitelist.c to change harcoded list of Station-Id ranges