Include Server and Date in the initial response header dictionary

src/Microsoft.AspNet.Server.Kestrel.GeneratedCode/KnownHeaders.cs

@@ -170,7 +170,20 @@ using System;
 using System.Collections.Generic;
 
 namespace Microsoft.AspNet.Server.Kestrel.Http 
-{{{Each(loops, loop => $@"
+{{
+    public partial class FrameResponseHeaders
+    {{
+        public FrameResponseHeaders()
+        {{
+            _Server = new[] {{ ""Kestrel"" }};
+            _Date = new[] {{ DateTime.UtcNow.ToString(""r"") }};
+            _bits = {
+                1L << responseHeaders.First(header => header.Name == "Server").Index |
+                1L << responseHeaders.First(header => header.Name == "Date").Index
+            }L;
+        }}
+    }}
+{Each(loops, loop => $@"
     public partial class {loop.ClassName} 
     {{
         long _bits = 0;

src/Microsoft.AspNet.Server.Kestrel/Http/Frame.cs

@@ -338,7 +338,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Http
                     // the app func has failed. https://github.com/aspnet/KestrelHttpServer/issues/43
                     _onStarting = null;
 
-                    ResponseHeaders.Clear();
+                    ResponseHeaders = new FrameResponseHeaders();
                     ResponseHeaders["Content-Length"] = new[] { "0" };
                 }
             }

src/Microsoft.AspNet.Server.Kestrel/Http/FrameHeaders.Generated.cs

@@ -4,6 +4,16 @@ using System.Collections.Generic;
 
 namespace Microsoft.AspNet.Server.Kestrel.Http 
 {
+    public partial class FrameResponseHeaders
+    {
+        public FrameResponseHeaders()
+        {
+            _Server = new[] { "Kestrel" };
+            _Date = new[] { DateTime.UtcNow.ToString("r") };
+            _bits = 67108868L;
+        }
+    }
+
     public partial class FrameRequestHeaders 
     {
         long _bits = 0;

test/Microsoft.AspNet.Server.KestrelTests/EngineTests.cs

@@ -22,6 +22,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
     {
         private async Task App(Frame frame)
         {
+            frame.ResponseHeaders.Clear();
             for (; ;)
             {
                 var buffer = new byte[8192];
@@ -59,6 +60,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
 
         private async Task AppChunked(Frame frame)
         {
+            frame.ResponseHeaders.Clear();
             var data = new MemoryStream();
             for (; ;)
             {
@@ -358,6 +360,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                 }, null);
 
                 // Anything added to the ResponseHeaders dictionary is ignored
+                frame.ResponseHeaders.Clear();
                 frame.ResponseHeaders["Content-Length"] = new[] { "11" };
                 throw new Exception();
             }))
@@ -371,12 +374,20 @@ namespace Microsoft.AspNet.Server.KestrelTests
                         "Connection: close",
                         "",
                         "");
-                    await connection.ReceiveEnd(
+                    await connection.Receive(
                         "HTTP/1.1 500 Internal Server Error",
+                        "");
+                    await connection.ReceiveStartsWith("Date:");
+                    await connection.Receive(
                         "Content-Length: 0",
+                        "Server: Kestrel",
                         "",
                         "HTTP/1.1 500 Internal Server Error",
+                        "");
+                    await connection.ReceiveStartsWith("Date:");
+                    await connection.ReceiveEnd(
                         "Content-Length: 0",
+                        "Server: Kestrel",
                         "Connection: close",
                         "",
                         "");
@@ -399,6 +410,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                     return Task.FromResult<object>(null);
                 }, null);
 
+                frame.ResponseHeaders.Clear();
                 frame.ResponseHeaders["Content-Length"] = new[] { "11" };
                 await frame.ResponseBody.WriteAsync(Encoding.ASCII.GetBytes("Hello World"), 0, 11);
                 throw new Exception();
@@ -434,6 +446,7 @@ namespace Microsoft.AspNet.Server.KestrelTests
                     return Task.FromResult<object>(null);
                 }, null);
 
+                frame.ResponseHeaders.Clear();
                 frame.ResponseHeaders["Content-Length"] = new[] { "11" };
                 await frame.ResponseBody.WriteAsync(Encoding.ASCII.GetBytes("Hello"), 0, 5);
                 throw new Exception();

test/Microsoft.AspNet.Server.KestrelTests/FrameResponseHeadersTests.cs

@@ -0,0 +1,47 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using Microsoft.AspNet.Server.Kestrel.Http;
+using Xunit;
+
+namespace Microsoft.AspNet.Server.KestrelTests
+{
+    public class FrameResponseHeadersTests
+    {
+        [Fact]
+        public void InitialDictionaryContainsServerAndDate()
+        {
+            IDictionary<string, string[]> headers = new FrameResponseHeaders();
+
+            Assert.Equal(2, headers.Count);
+
+            string[] serverHeader;
+            Assert.True(headers.TryGetValue("Server", out serverHeader));
+            Assert.Equal(1, serverHeader.Length);
+            Assert.Equal("Kestrel", serverHeader[0]);
+
+            string[] dateHeader;
+            DateTime date;
+            Assert.True(headers.TryGetValue("Date", out dateHeader));
+            Assert.Equal(1, dateHeader.Length);
+            Assert.True(DateTime.TryParse(dateHeader[0], out date));
+            Assert.True(DateTime.Now - date <= TimeSpan.FromMinutes(1));
+
+            Assert.False(headers.IsReadOnly);
+        }
+
+        [Fact]
+        public void InitialEntriesCanBeCleared()
+        {
+            IDictionary<string, string[]> headers = new FrameResponseHeaders();
+
+            headers.Clear();
+
+            Assert.Equal(0, headers.Count);
+            Assert.False(headers.ContainsKey("Server"));
+            Assert.False(headers.ContainsKey("Date"));
+        }
+    }
+}

test/Microsoft.AspNet.Server.KestrelTests/TestConnection.cs

@@ -84,6 +84,38 @@ namespace Microsoft.AspNet.Server.KestrelTests
             Assert.Equal(expected, new String(actual, 0, offset));
         }
 
+        public async Task ReceiveStartsWith(string prefix, int maxLineLength = 1024)
+        {
+            var actual = new char[maxLineLength];
+            var offset = 0;
+
+            while (offset < maxLineLength)
+            {
+                // Read one char at a time so we don't read past the end of the line.
+                var task = _reader.ReadAsync(actual, offset, 1);
+                if (!Debugger.IsAttached)
+                {
+                    Assert.True(task.Wait(1000), "timeout");
+                }
+                var count = await task;
+                if (count == 0)
+                {
+                    break;
+                }
+
+                Assert.True(count == 1);
+                offset++;
+
+                if (actual[offset - 1] == '\n')
+                {
+                    break;
+                }
+            }
+
+            var actualLine = new string(actual, 0, offset);
+            Assert.StartsWith(prefix, actualLine);
+        }
+
         public async Task ReceiveEnd(params string[] lines)
         {
             await Receive(lines);