ppp_recv_config
ppp_recv_config(0, framemax, (u_int32_t) 0, 0, 0);
ppp_recv_config(f->unit, mru,
ppp_recv_config(f->unit, (PPP_MRU > absmax_mru ? absmax_mru : PPP_MRU),
ppp_recv_config(unit, mru, (lax_recv? 0: 0xffffffff),
extern void ppp_recv_config __P((int, int, u_int32_t, int, int));