done

Netch/3rd/DNS/Client/RequestResolver/UdpRequestResolver.cs

@@ -0,0 +1,57 @@
+using DNS.Protocol;
+using DNS.Protocol.Utils;
+using System;
+using System.IO;
+using System.Net;
+using System.Net.Sockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace DNS.Client.RequestResolver
+{
+    public class UdpRequestResolver : IRequestResolver
+    {
+        private int timeout;
+        private IRequestResolver fallback;
+        private IPEndPoint dns;
+
+        public UdpRequestResolver(IPEndPoint dns, IRequestResolver fallback, int timeout = 5000)
+        {
+            this.dns = dns;
+            this.fallback = fallback;
+            this.timeout = timeout;
+        }
+
+        public UdpRequestResolver(IPEndPoint dns, int timeout = 5000)
+        {
+            this.dns = dns;
+            this.fallback = new NullRequestResolver();
+            this.timeout = timeout;
+        }
+
+        public async Task<IResponse> Resolve(IRequest request, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            using (UdpClient udp = new UdpClient())
+            {
+                await udp
+                    .SendAsync(request.ToArray(), request.Size, dns)
+                    .WithCancellationTimeout(TimeSpan.FromMilliseconds(timeout), cancellationToken);
+
+                UdpReceiveResult result = await udp
+                    .ReceiveAsync()
+                    .WithCancellationTimeout(TimeSpan.FromMilliseconds(timeout), cancellationToken);
+
+                if (!result.RemoteEndPoint.Equals(dns)) throw new IOException("Remote endpoint mismatch");
+                byte[] buffer = result.Buffer;
+                Response response = Response.FromArray(buffer);
+
+                if (response.Truncated)
+                {
+                    return await fallback.Resolve(request, cancellationToken);
+                }
+
+                return new ClientResponse(request, response, buffer);
+            }
+        }
+    }
+}