feat(ServiceDiscovery): option to move additional records into answers

src/ServiceDiscovery.cs

@@ -60,6 +60,20 @@ public ServiceDiscovery(MulticastService mdns)
         /// </value>
         public MulticastService Mdns { get; private set; }
 
+        /// <summary>
+        ///   Add the additional records into the answers.
+        /// </summary>
+        /// <value>
+        ///   Defaults to <b>false</b>.
+        /// </value>
+        /// <remarks>
+        ///   Some malformed systems, such as js-ipfs and go-ipfs, only examine
+        ///   the <see cref="Message.Answers"/> and not the <see cref="Message.AdditionalRecords"/>.
+        ///   Setting this to <b>true</b>, will move the additional records
+        ///   into the answers.
+        /// </remarks>
+        public bool AnswersContainsAdditionalRecords { get; set; }
+
         /// <summary>
         ///   Gets the name server.
         /// </summary>
@@ -193,6 +207,12 @@ void OnQuery(object sender, MessageEventArgs e)
                     response.AdditionalRecords.Clear();
                 }
 
+                if (AnswersContainsAdditionalRecords)
+                {
+                    response.Answers.AddRange(response.AdditionalRecords);
+                    response.AdditionalRecords.Clear();
+                }
+
                 Mdns.SendAnswer(response);
                 if (log.IsDebugEnabled)
                     log.Debug($"sent answer {response.Answers[0]}");

test/ServiceDiscoveryTest.cs

@@ -189,5 +189,45 @@ public void Discover_ServiceInstance()
             }
         }
 
+        [TestMethod]
+        public void Discover_ServiceInstance_WithAnswersContainingAdditionRecords()
+        {
+            var service = new ServiceProfile("y", "_sdtest-2._udp", 1024);
+            var done = new ManualResetEvent(false);
+            var mdns = new MulticastService();
+            var sd = new ServiceDiscovery(mdns)
+            {
+                AnswersContainsAdditionalRecords = true
+            };
+            Message discovered = null;
+            mdns.NetworkInterfaceDiscovered += (s, e) =>
+            {
+                sd.QueryServiceInstances(service.ServiceName);
+            };
+
+            sd.ServiceInstanceDiscovered += (s, e) =>
+            {
+                if (e.ServiceInstanceName == service.FullyQualifiedName)
+                {
+                    Assert.IsNotNull(e.Message);
+                    discovered = e.Message;
+                    done.Set();
+                }
+            };
+            try
+            {
+                sd.Advertise(service);
+                mdns.Start();
+                Assert.IsTrue(done.WaitOne(TimeSpan.FromSeconds(1)), "instance not found");
+                Assert.AreEqual(0, discovered.AdditionalRecords.Count);
+                Assert.IsTrue(discovered.Answers.Count > 1);
+            }
+            finally
+            {
+                sd.Dispose();
+                mdns.Stop();
+            }
+        }
+
     }
 }