Imported Upstream version 4.2.1.60

Former-commit-id: 05052d1d7a3a94b0d9ee70461d62b6591e5ab5bc

mcs/class/System.Net.Http/System.Net.Http/HttpClientHandler.cs

@@ -276,6 +276,14 @@ namespace System.Net.Http
 			var headers = wr.Headers;
 			foreach (var header in request.Headers) {
 				var values = header.Value;
+				if (header.Key == "Host") {
+					//
+					// Host must be explicitly set for HttpWebRequest
+					//
+					wr.Host = request.Headers.Host;
+					continue;
+				}
+
 				if (header.Key == "Transfer-Encoding") {
 					// Chunked Transfer-Encoding is never set for HttpWebRequest. It's detected
 					// from ContentLength by HttpWebRequest

mcs/class/System.Net.Http/Test/System.Net.Http/HttpClientTest.cs

@@ -606,6 +606,39 @@ namespace MonoTests.System.Net.Http
 			}
 		}
 
+		[Test]
+		public void Send_Complete_CustomHeaders_Host ()
+		{
+			bool? failed = null;
+			var listener = CreateListener (l => {
+				var request = l.Request;
+
+				try {
+					Assert.AreEqual ("customhost", request.Headers["Host"], "#1");
+					failed = false;
+				} catch {
+					failed = true;
+				}
+			});
+
+			try {
+				var client = new HttpClient ();
+
+				client.DefaultRequestHeaders.Add("Host", "customhost");
+
+				var request = new HttpRequestMessage (HttpMethod.Get, LocalServer);
+
+				var response = client.SendAsync (request, HttpCompletionOption.ResponseHeadersRead).Result;
+
+				Assert.AreEqual ("", response.Content.ReadAsStringAsync ().Result, "#100");
+				Assert.AreEqual (HttpStatusCode.OK, response.StatusCode, "#101");
+				Assert.AreEqual (false, failed, "#102");
+			} finally {
+				listener.Abort ();
+				listener.Close ();
+			}
+		}
+
 		[Test]
 		public void Send_Transfer_Encoding_Chunked ()
 		{