void ip_natexpire()
ip_natexpire()
void ip_natexpire(){	register struct nat *nat, **natp;	register int i;	MUTEX_ENTER(&ipf_nat);	for (i = 0; i < NAT_SIZE; i++)		for (natp = &nat_table[0][i]; (nat = *natp); ) {			if (nat->nat_age > 0)				nat->nat_age--;			if (!nat->nat_use || !nat->nat_age) {				*natp = nat->nat_next;				if (nat->nat_use)					nat->nat_use--;				if (!nat->nat_use) {					KFREE(nat);					nat_stats.ns_expire++;					nat_inuse--;				}			} else				natp = &nat->nat_next;		}	for (i = 0; i < NAT_SIZE; i++)		for (natp = &nat_table[1][i]; (nat = *natp); ) {			if (nat->nat_age > 0)				nat->nat_age--;			if (!nat->nat_use || !nat->nat_age) {				*natp = nat->nat_next;				if (nat->nat_use)					nat->nat_use--;				if (!nat->nat_use) {					KFREE(nat);					nat_stats.ns_expire++;					nat_inuse--;				}			} else				natp = &nat->nat_next;		}	MUTEX_EXIT(&ipf_nat);}