Add sample DANE usage

samples/dane/client.lua

@@ -0,0 +1,40 @@
+
+local socket = require "socket";
+local ssl = require "ssl";
+
+local dns = require "lunbound".new();
+
+
+local cfg = {
+	protocol = "tlsv1_2",
+	mode = "client",
+	ciphers = "DEFAULT",
+	capath = "/etc/ssl/certs",
+	verify = "peer",
+	dane = true,
+};
+
+local function daneconnect(host, port)
+   port = port or "443";
+	local conn = ssl.wrap(socket.connect(host, port), cfg);
+
+	local tlsa = dns:resolve("_" .. port .. "._tcp." .. host, 52);
+	assert(tlsa.secure, "Insecure DNS");
+
+	assert(conn:setdane(host));
+	for i = 1, tlsa.n do
+		local usage, selector, mtype = tlsa[i] :byte(1, 3);
+		assert(conn:settlsa(usage, selector, mtype, tlsa[i] :sub(4, - 1)));
+	end
+
+	assert(conn:dohandshake());
+	return conn;
+end
+
+if not ... then
+   print("Usage: client.lua example.com [port]");
+   return os.exit(1);
+end
+local conn = daneconnect(...);
+
+print(conn:getpeerverification());