pfil_add_hook
error = pfil_add_hook((void *)pfil4_wrapper, NULL,
error = pfil_add_hook((void *)pfil6_wrapper, NULL,
pfil_add_hook((void *)bridge_ipf, NULL, PFIL_IN|PFIL_OUT,
error = pfil_add_hook(npfos_layer2_handler, npf,
error = pfil_add_hook(npfos_packet_handler, npf,
error = pfil_add_hook(npfos_packet_handler, npf,
int pfil_add_hook(pfil_func_t, void *, int, pfil_head_t *);