dns: add lookup function.

lib/net/dns-browser.js

@@ -29,3 +29,7 @@ exports.resolve = function resolve(host, proxy) {
     });
   });
 };
+
+exports.lookup = function lookup(host, proxy) {
+  return exports.resolve(host, proxy);
+};

lib/net/dns.js

@@ -8,7 +8,13 @@
 
 var dns = require('dns');
 
-exports.resolve = function resolve(host) {
+var options = {
+  family: 4,
+  hints: dns.ADDRCONFIG | dns.V4MAPPED,
+  all: true
+};
+
+exports.resolve = function resolve(host, proxy) {
   return new Promise(function(resolve, reject) {
     dns.resolve(host, 'A', function(err, result) {
       if (err) {
@@ -25,3 +31,29 @@ exports.resolve = function resolve(host) {
     });
   });
 };
+
+exports.lookup = function lookup(host, proxy) {
+  return new Promise(function(resolve, reject) {
+    var addrs = [];
+    var i, addr;
+
+    dns.lookup(host, options, function(err, result) {
+      if (err) {
+        reject(err);
+        return;
+      }
+
+      if (result.length === 0) {
+        reject(new Error('No DNS results.'));
+        return;
+      }
+
+      for (i = 0; i < result.length; i++) {
+        addr = result[i];
+        addrs.push(addr.address);
+      }
+
+      resolve(addrs);
+    });
+  });
+};