ip_is_idle_packet
m0 = ip_is_idle_packet(m0, &is_idle);
m0 = ip_is_idle_packet(m0, &is_idle);
struct mbuf *ip_is_idle_packet (struct mbuf *, int *);
if (ppp->timeout_sec > 0 && !ip_is_idle_packet(pip, lbuf))
if (ppp->timeout_sec > 0 && !ip_is_idle_packet(iphdr, lpktp))
int ip_is_idle_packet (const struct ip *, int);