uspot/spotfilter: implement captive generate

For basic uspot setups, this commit implements a 'generate' verb to
uspot /usr/bin/captive that takes a config uspot section name, and
parses the following extra options to generate the relevant spotfilter
config:

  option generate_spotfilter (bool) # if unset/false, generate is a NOP
  option interface 'name' # config/network interface name to redirect to
  option client_autoremove (bool) # if set/true, sets client_autoremove
  list wl_hosts '*.example.com' # optional list of whitelist hostnames
  list wl_addrs '1.2.3.4' # optional list of whitelist IPs

"captive generate" is called in spotfilter.init to optionally (depending
on 'generate_spotfilter') create the required spotfilter-XXX.json before
starting spotfilter.

Signed-off-by: Thibaut VARÈNE <hacks@slashdirt.org>

feeds/ucentral/spotfilter/files/spotfilter.init

@@ -7,7 +7,12 @@ USE_PROCD=1
 PROG=/usr/sbin/spotfilter
 
 add_interface() {
-	ubus call spotfilter interface_add "$(cat /tmp/spotfilter-$1.json)"
+	local cfg="$1"
+	local enabled
+
+	config_get_bool enabled "$cfg" "configure_spotfilter" 0
+	[ $enabled -eq 0 ] || /usr/bin/captive generate "$cfg" > /tmp/spotfilter-$cfg.json
+	ubus call spotfilter interface_add "$(cat /tmp/spotfilter-$cfg.json)"
 }
 
 reload_service() {

feeds/ucentral/uspot/files/usr/bin/captive

@@ -17,6 +17,68 @@ function interfaces() {
 	return uniq(interfaces);
 }
 
+function generate_spotfilter(name) {
+	function parse_bool(val) {
+		if (val == "1" || val == "on" || val == "true" || val == "yes")
+			return true;
+		else if (val == "0" || val == "off" || val == "false" || val == "no")
+			return false;
+		else
+			return null;
+	}
+	function fail(msg) {
+		warn(msg + '\n');
+		exit(1);
+	}
+
+	if (!parse_bool(uci.get('uspot', name, 'configure_spotfilter')))
+		exit(0);
+
+	let uspot = uci.get_all('uspot', name);
+	if (!uspot)
+		fail('Cannot load uspot config for "' + name);
+
+	let device_macaddr = uci.get('network', uspot.interface, 'device');
+	if (!device_macaddr)
+		fail('Cannot find target network interface');
+	if (uspot.wl_hosts && type(uspot.wl_hosts) != "array")
+		fail('Expecting list for wl_hosts');
+	if (uspot.wl_addrs && type(uspot.wl_addrs) != "array")
+		fail('Expecting list for wl_addrs');
+
+	let class = [
+		{
+			index: 0,
+			device_macaddr,
+			fwmark: 1,
+			fwmark_mask: 127
+		}, {
+			index: 1,
+			fwmark: 2,
+			fwmark_mask: 127
+		}
+	];
+
+	let whitelist = [{
+		class: 1,
+		hosts: uspot.wl_hosts || [],
+		address: uspot.wl_addrs || [],
+	}];
+
+	let conf = {
+		name,
+		devices: type(uspot.ifname) == "array" ? uspot.ifname : [ uspot.ifname ],
+		config: {
+			default_class: 0,
+			default_dns_class: 1,
+			client_autoremove: !!parse_bool(uspot.client_autoremove),
+			class,
+			whitelist
+		}
+	};
+	printf('%.J\n', conf);
+}
+
 switch(ARGV[0]) {
 case 'dump':
 	for (let interface in interfaces()) {
@@ -58,6 +120,9 @@ case 'debugoff':
 	uci.commit();
 	restart();
 	break;
+case 'generate':
+	generate_spotfilter(ARGV[1]);
+	break;
 default:
 	break;
 }