dns: implement {ttl: true} for dns.resolve6()

Add an option to retrieve the Time-To-Live of the AAAA record.

PR-URL: https://github.com/nodejs/node/pull/9296
Refs: https://github.com/nodejs/node/issues/5893
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

doc/api/dns.md

@@ -212,7 +212,7 @@ will contain an array of IPv4 addresses (e.g.
     rather than an array of strings.  The TTL is expressed in seconds.
 * `callback` {Function} An `(err, result)` callback function.
 
-## dns.resolve6(hostname, callback)
+## dns.resolve6(hostname[, options], callback)
 <!-- YAML
 added: v0.1.16
 -->
@@ -221,6 +221,13 @@ Uses the DNS protocol to resolve a IPv6 addresses (`AAAA` records) for the
 `hostname`. The `addresses` argument passed to the `callback` function
 will contain an array of IPv6 addresses.
 
+* `hostname` {String} Hostname to resolve.
+* `options` {Object}
+  * `ttl` {Boolean} Retrieve the Time-To-Live value (TTL) of each record.
+    The callback receives an array of `{ address: '0:1:2:3:4:5:6:7', ttl: 60 }`
+    objects rather than an array of strings.  The TTL is expressed in seconds.
+* `callback` {Function} An `(err, result)` callback function.
+
 ## dns.resolveCname(hostname, callback)
 <!-- YAML
 added: v0.3.2

src/cares_wrap.cc

@@ -441,18 +441,27 @@ class QueryAaaaWrap: public QueryWrap {
     HandleScope handle_scope(env()->isolate());
     Context::Scope context_scope(env()->context());
 
-    struct hostent* host;
+    hostent* host;
+    ares_addr6ttl addrttls[256];
+    int naddrttls = arraysize(addrttls);
 
-    int status = ares_parse_aaaa_reply(buf, len, &host, nullptr, nullptr);
+    int status = ares_parse_aaaa_reply(buf, len, &host, addrttls, &naddrttls);
     if (status != ARES_SUCCESS) {
       ParseError(status);
       return;
     }
 
     Local<Array> addresses = HostentToAddresses(env(), host);
+    Local<Array> ttls = Array::New(env()->isolate(), naddrttls);
+
+    auto context = env()->context();
+    for (int i = 0; i < naddrttls; i += 1) {
+      auto value = Integer::New(env()->isolate(), addrttls[i].ttl);
+      ttls->Set(context, i, value).FromJust();
+    }
     ares_free_hostent(host);
 
-    this->CallOnComplete(addresses);
+    CallOnComplete(addresses, ttls);
   }
 };
 

test/internet/test-dns.js

@@ -81,6 +81,27 @@ TEST(function test_resolve4_ttl(done) {
   checkWrap(req);
 });
 
+TEST(function test_resolve6_ttl(done) {
+  const req = dns.resolve6('google.com', { ttl: true }, function(err, result) {
+    assert.ifError(err);
+    assert.ok(result.length > 0);
+
+    for (let i = 0; i < result.length; i++) {
+      const item = result[i];
+      assert.ok(item);
+      assert.strictEqual(typeof item, 'object');
+      assert.strictEqual(typeof item.ttl, 'number');
+      assert.strictEqual(typeof item.address, 'string');
+      assert.ok(item.ttl > 0);
+      assert.ok(isIPv6(item.address));
+    }
+
+    done();
+  });
+
+  checkWrap(req);
+});
+
 TEST(function test_resolveMx(done) {
   const req = dns.resolveMx('gmail.com', function(err, result) {
     if (err) throw err;