pfSense

function filter_nat_rules_automatic_tonathosts() {

	global $config, $FilterIflist, $GatewaysList;

	$tonathosts = array("127.0.0.0/8", "0.0.0.0");

	foreach (get_staticroutes() as $route) {

		$netip = explode("/", $route['network']);

		if (isset($GatewaysList[$route['gateway']])) {

			$gateway =& $GatewaysList[$route['gateway']];

			if(!interface_has_gateway($gateway['interface']) && is_private_ip($netip[0]))

				$tonathosts[] = $route['network'];

		}

	}

	/* create outbound nat entries for all local networks */

	foreach($FilterIflist as $ocname => $oc) {

		if(interface_has_gateway($ocname))

			continue;

		if(is_ipaddr($oc['alias-address']))

			$tonathosts[] = "{$oc['alias-address']}/{$oc['alias-subnet']}";

		if($oc['sa'])

			$tonathosts[] = "{$oc['sa']}/{$oc['sn']}";

	}

	/* PPTP subnet */

	if(($config['pptpd']['mode'] == "server" ) && is_private_ip($config['pptpd']['remoteip'])) {

		if (isset($config['pptpd']['n_pptp_units']) && is_numeric($config['pptpd']['n_pptp_units']))

			$pptp_subnets = ip_range_to_subnet_array($config['pptpd']['remoteip'],

				long2ip32(ip2long($config['pptpd']['remoteip'])+($config['pptpd']['n_pptp_units']-1)));

		else

			$pptp_subnets = ip_range_to_subnet_array($config['pptpd']['remoteip'],

				long2ip32(ip2long($config['pptpd']['remoteip'])));

		$tonathosts = array_merge($tonathosts, $pptp_subnets);

	}

	/* PPPoE subnet */

	if (is_array($FilterIflist['pppoe']))

		foreach ($FilterIflist['pppoe'] as $pppoe)

			if(is_private_ip($pppoe['ip']))

				$tonathosts[] = "{$pppoe['sa']}/{$pppoe['sn']}";

	/* L2TP subnet */

	if(isset($FilterIflist['l2tp']) && $FilterIflist['l2tp']['mode'] == "server") {

		$l2tp_sa = $FilterIflist['l2tp']['sa'];

		$l2tp_sn = $FilterIflist['l2tp']['sn'];

		if(is_private_ip($l2tp_sa) && !empty($l2tp_sn))

			$tonathosts[] = "{$l2tp_sa}/{$l2tp_sn}";

	}

	/* add openvpn interfaces */

	if(is_array($config['openvpn']['openvpn-server']))

		foreach ($config['openvpn']['openvpn-server'] as $ovpnsrv)

			if (!empty($ovpnsrv['tunnel_network']))

				$tonathosts[] = $ovpnsrv['tunnel_network'];

	if(is_array($config['openvpn']['openvpn-client']))

		foreach ($config['openvpn']['openvpn-client'] as $ovpncli)

			if (!empty($ovpncli['tunnel_network']))

				$tonathosts[] = $ovpncli['tunnel_network'];

	/* IPsec mode_cfg subnet */

	if (isset($config['ipsec']['client']['enable']) &&

	    !empty($config['ipsec']['client']['pool_address']) &&

	    !empty($config['ipsec']['client']['pool_netbits']))

		$tonathosts[] = "{$config['ipsec']['client']['pool_address']}/{$config['ipsec']['client']['pool_netbits']}";

	return $tonathosts;

}

function filter_nat_rules_outbound_automatic($src) {

	global $config, $FilterIflist;

	$rules = array();

	foreach ($FilterIflist as $if => $ifcfg) {

		if (substr($ifcfg['if'], 0, 4) == "ovpn")

			continue;

		if (!interface_has_gateway($if))

			continue;

		$natent = array();

		$natent['interface'] = $if;

		$natent['source']['network'] = $src;

		$natent['dstport'] = "500";

		$natent['target'] = $ifcfg['ip'];

		$natent['destination']['any'] = true;

		$natent['staticnatport'] = true;

		$natent['descr'] = gettext('Auto created rule for ISAKMP');

		$rules[] = $natent;

		$natent = array();

		$natent['interface'] = $if;

		$natent['source']['network'] = $src;

		$natent['sourceport'] = "";

		$natent['target'] = $ifcfg['ip'];

		$natent['destination']['any'] = true;

		$natent['natport'] = "";

		$natent['descr'] = gettext('Auto created rule');

		if (isset($ifcfg['nonat']))

			$natent['nonat'] = true;

		$rules[] = $natent;

	}

	return $rules;

}

		$tonathosts_array = filter_nat_rules_automatic_tonathosts();

		$tonathosts = implode(" ", $tonathosts_array);

		$numberofnathosts = count($tonathosts_array);

		if ($numberofnathosts > 0) {

			update_filter_reload_status(gettext('Creating automatic outbound rules'));

			if ($numberofnathosts > 4) {

				$natrules .= "table <tonatsubnets> { {$tonathosts} }\n";

				$macroortable = "<tonatsubnets>";

			} else {

				$natrules .= "tonatsubnets	= \"{ {$tonathosts} }\"\n";

				$macroortable = "\$tonatsubnets";

			}

			$a_outs = filter_nat_rules_outbound_automatic($macroortable);

			foreach ($a_outs as $a_out) {

				$natrules .= filter_nat_rules_generate_if($a_out['interface'],

					$a_out['source']['network'],

					$a_out['sourceport'],

					$a_out['destination']['address'],

					$a_out['dstport'],

					$a_out['target'],

					$a_out['natport'],

					isset($a_out['nonat']),

					isset($a_out['staticnatport']));

		unset($tonathosts, $tonathosts_array, $numberofnathosts);