Put request trailers in a separate collection (#10410)

src/Http/Http.Abstractions/ref/Microsoft.AspNetCore.Http.Abstractions.netcoreapp3.0.cs

@@ -373,6 +373,13 @@ namespace Microsoft.AspNetCore.Http
         public string ToUriComponent() { throw null; }
     }
     public delegate System.Threading.Tasks.Task RequestDelegate(Microsoft.AspNetCore.Http.HttpContext context);
+    public static partial class RequestTrailerExtensions
+    {
+        public static bool CheckTrailersAvailable(this Microsoft.AspNetCore.Http.HttpRequest request) { throw null; }
+        public static Microsoft.Extensions.Primitives.StringValues GetDeclaredTrailers(this Microsoft.AspNetCore.Http.HttpRequest request) { throw null; }
+        public static Microsoft.Extensions.Primitives.StringValues GetTrailer(this Microsoft.AspNetCore.Http.HttpRequest request, string trailerName) { throw null; }
+        public static bool SupportsTrailers(this Microsoft.AspNetCore.Http.HttpRequest request) { throw null; }
+    }
     public static partial class ResponseTrailerExtensions
     {
         public static void AppendTrailer(this Microsoft.AspNetCore.Http.HttpResponse response, string trailerName, Microsoft.Extensions.Primitives.StringValues trailerValues) { }

src/Http/Http.Abstractions/src/Extensions/RequestTrailerExtensions.cs

@@ -0,0 +1,65 @@
+// 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 Microsoft.AspNetCore.Http.Features;
+using Microsoft.Extensions.Primitives;
+using Microsoft.Net.Http.Headers;
+
+namespace Microsoft.AspNetCore.Http
+{
+    /// <summary>
+    /// HttpRequest extensions for working with request trailing headers.
+    /// </summary>
+    public static class RequestTrailerExtensions
+    {
+        /// <summary>
+        /// Gets the request "Trailer" header that lists which trailers to expect after the body.
+        /// </summary>
+        /// <param name="request"></param>
+        /// <returns></returns>
+        public static StringValues GetDeclaredTrailers(this HttpRequest request)
+        {
+            return request.Headers.GetCommaSeparatedValues(HeaderNames.Trailer);
+        }
+
+        /// <summary>
+        /// Indicates if the request supports receiving trailer headers.
+        /// </summary>
+        /// <param name="request"></param>
+        /// <returns></returns>
+        public static bool SupportsTrailers(this HttpRequest request)
+        {
+            return request.HttpContext.Features.Get<IHttpRequestTrailersFeature>() != null;
+        }
+
+        /// <summary>
+        /// Checks if the request supports trailers and they are available to be read now.
+        /// This does not mean that there are any trailers to read.
+        /// </summary>
+        /// <param name="request"></param>
+        /// <returns></returns>
+        public static bool CheckTrailersAvailable(this HttpRequest request)
+        {
+            return request.HttpContext.Features.Get<IHttpRequestTrailersFeature>()?.Available == true;
+        }
+
+        /// <summary>
+        /// Gets the requested trailing header from the response. Check <see cref="SupportsTrailers"/>
+        /// or a NotSupportedException may be thrown.
+        /// Check <see cref="CheckTrailersAvailable" /> or an InvalidOperationException may be thrown.
+        /// </summary>
+        /// <param name="request"></param>
+        /// <param name="trailerName"></param>
+        public static StringValues GetTrailer(this HttpRequest request, string trailerName)
+        {
+            var feature = request.HttpContext.Features.Get<IHttpRequestTrailersFeature>();
+            if (feature == null)
+            {
+                throw new NotSupportedException("This request does not support trailers.");
+            }
+
+            return feature.Trailers[trailerName];
+        }
+    }
+}

src/Http/Http.Features/ref/Microsoft.AspNetCore.Http.Features.netstandard2.0.cs

@@ -195,6 +195,11 @@ namespace Microsoft.AspNetCore.Http.Features
         System.Threading.CancellationToken RequestAborted { get; set; }
         void Abort();
     }
+    public partial interface IHttpRequestTrailersFeature
+    {
+        bool Available { get; }
+        Microsoft.AspNetCore.Http.IHeaderDictionary Trailers { get; }
+    }
     public partial interface IHttpResponseFeature
     {
         System.IO.Stream Body { get; set; }

src/Http/Http.Features/src/IHttpRequestTrailersFeature.cs

@@ -0,0 +1,26 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Http.Features
+{
+    /// <summary>
+    /// This feature exposes HTTP request trailer headers, either for HTTP/1.1 chunked bodies or HTTP/2 trailing headers.
+    /// </summary>
+    public interface IHttpRequestTrailersFeature
+    {
+        /// <summary>
+        /// Indicates if the <see cref="Trailers"/> are available yet. They may not be available until the
+        /// request body is fully read.
+        /// </summary>
+        bool Available { get; }
+
+        /// <summary>
+        /// The trailing headers received. This will throw <see cref="InvalidOperationException"/> if <see cref="Available"/>
+        /// returns false. They may not be available until the request body is fully read. If there are no trailers this will
+        /// return an empty collection.
+        /// </summary>
+        IHeaderDictionary Trailers { get; }
+    }
+}

src/Servers/Kestrel/Core/ref/Microsoft.AspNetCore.Server.Kestrel.Core.netcoreapp3.0.cs

@@ -276,6 +276,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure
         public static string GetAsciiOrUTF8StringNonNullCharacters(this System.Span<byte> span) { throw null; }
         public static string GetAsciiStringEscaped(this System.Span<byte> span, int maxChars) { throw null; }
         public static string GetAsciiStringNonNullCharacters(this System.Span<byte> span) { throw null; }
+        public static string GetHeaderName(this System.Span<byte> span) { throw null; }
         [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]public static bool GetKnownHttpScheme(this System.Span<byte> span, out Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpScheme knownScheme) { throw null; }
         [System.Runtime.CompilerServices.MethodImpl(System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]public static bool GetKnownMethod(this System.Span<byte> span, out Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpMethod method, out int length) { throw null; }
         public static Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpMethod GetKnownMethod(string value) { throw null; }

src/Servers/Kestrel/Core/src/CoreStrings.resx

@@ -602,4 +602,7 @@ For more information on configuring HTTPS see https://go.microsoft.com/fwlink/?l
   <data name="Http2MinDataRateNotSupported" xml:space="preserve">
     <value>This feature is not supported for HTTP/2 requests except to disable it entirely by setting the rate to null.</value>
   </data>
+  <data name="RequestTrailersNotAvailable" xml:space="preserve">
+    <value>The request trailers are not available yet. They may not be available until the full request body is read.</value>
+  </data>
 </root>

src/Servers/Kestrel/Core/src/Internal/Http/Http1ChunkedEncodingMessageBody.cs

@@ -35,7 +35,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             : base(context)
         {
             RequestKeepAlive = keepAlive;
-
             _requestBodyPipe = CreateRequestBodyPipe(context);
         }
 
@@ -301,7 +300,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             // _consumedBytes aren't tracked for trailer headers, since headers have separate limits.
             if (_mode == Mode.TrailerHeaders)
             {
-                if (_context.TakeMessageHeaders(readableBuffer, out consumed, out examined))
+                if (_context.TakeMessageHeaders(readableBuffer, trailers: true, out consumed, out examined))
                 {
                     _mode = Mode.Complete;
                 }
@@ -489,6 +488,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 consumed = trailerBuffer.End;
                 AddAndCheckConsumedBytes(2);
                 _mode = Mode.Complete;
+                // No trailers
+                _context.OnTrailersComplete();
             }
             else
             {

src/Servers/Kestrel/Core/src/Internal/Http/Http1Connection.cs

@@ -163,7 +163,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                         break;
                     }
                 case RequestProcessingStatus.ParsingHeaders:
-                    if (TakeMessageHeaders(buffer, out consumed, out examined))
+                    if (TakeMessageHeaders(buffer, trailers: false, out consumed, out examined))
                     {
                         _requestProcessingStatus = RequestProcessingStatus.AppStarted;
                     }
@@ -189,7 +189,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             return result;
         }
 
-        public bool TakeMessageHeaders(ReadOnlySequence<byte> buffer, out SequencePosition consumed, out SequencePosition examined)
+        public bool TakeMessageHeaders(ReadOnlySequence<byte> buffer, bool trailers, out SequencePosition consumed, out SequencePosition examined)
         {
             // Make sure the buffer is limited
             bool overLength = false;
@@ -202,7 +202,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 overLength = true;
             }
 
-            var result = _parser.ParseHeaders(new Http1ParsingHandler(this), buffer, out consumed, out examined, out var consumedBytes);
+            var result = _parser.ParseHeaders(new Http1ParsingHandler(this, trailers), buffer, out consumed, out examined, out var consumedBytes);
             _remainingRequestHeadersBytesAllowed -= consumedBytes;
 
             if (!result && overLength)

src/Servers/Kestrel/Core/src/Internal/Http/Http1ContentLengthMessageBody.cs

@@ -212,6 +212,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 {
                     _context.Input.AdvanceTo(consumed);
                     _finalAdvanceCalled = true;
+                    _context.OnTrailersComplete();
                 }
 
                 return;

src/Servers/Kestrel/Core/src/Internal/Http/Http1MessageBody.cs

@@ -129,6 +129,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                     BadHttpRequestException.Throw(RequestRejectionReason.UpgradeRequestCannotHavePayload);
                 }
 
+                context.OnTrailersComplete(); // No trailers for these.
                 return new Http1UpgradeMessageBody(context);
             }
 
@@ -173,6 +174,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 BadHttpRequestException.Throw(requestRejectionReason, context.Method);
             }
 
+            context.OnTrailersComplete(); // No trailers for these.
             return keepAlive ? MessageBody.ZeroContentLengthKeepAlive : MessageBody.ZeroContentLengthClose;
         }
     }

src/Servers/Kestrel/Core/src/Internal/Http/Http1ParsingHandler.cs

@@ -8,17 +8,43 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
     internal readonly struct Http1ParsingHandler : IHttpRequestLineHandler, IHttpHeadersHandler
     {
         public readonly Http1Connection Connection;
+        public readonly bool Trailers;
 
         public Http1ParsingHandler(Http1Connection connection)
         {
             Connection = connection;
+            Trailers = false;
+        }
+
+        public Http1ParsingHandler(Http1Connection connection, bool trailers)
+        {
+            Connection = connection;
+            Trailers = trailers;
         }
 
         public void OnHeader(Span<byte> name, Span<byte> value)
-            => Connection.OnHeader(name, value);
+        {
+            if (Trailers)
+            {
+                Connection.OnTrailer(name, value);
+            }
+            else
+            {
+                Connection.OnHeader(name, value);
+            }
+        }
 
         public void OnHeadersComplete()
-            => Connection.OnHeadersComplete();
+        {
+            if (Trailers)
+            {
+                Connection.OnTrailersComplete();
+            }
+            else
+            {
+                Connection.OnHeadersComplete();
+            }
+        }
 
         public void OnStartLine(HttpMethod method, HttpVersion version, Span<byte> target, Span<byte> path, Span<byte> query, Span<byte> customMethod, bool pathEncoded)
             => Connection.OnStartLine(method, version, target, path, query, customMethod, pathEncoded);

src/Servers/Kestrel/Core/src/Internal/Http/HttpProtocol.FeatureCollection.cs

@@ -26,6 +26,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                                           IHttpConnectionFeature,
                                           IHttpRequestLifetimeFeature,
                                           IHttpRequestIdentifierFeature,
+                                          IHttpRequestTrailersFeature,
                                           IHttpBodyControlFeature,
                                           IHttpMaxRequestBodySizeFeature,
                                           IHttpResponseStartFeature,
@@ -133,6 +134,20 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             }
         }
 
+        bool IHttpRequestTrailersFeature.Available => RequestTrailersAvailable;
+
+        IHeaderDictionary IHttpRequestTrailersFeature.Trailers
+        {
+            get
+            {
+                if (!RequestTrailersAvailable)
+                {
+                    throw new InvalidOperationException(CoreStrings.RequestTrailersNotAvailable);
+                }
+                return RequestTrailers;
+            }
+        }
+
         int IHttpResponseFeature.StatusCode
         {
             get => StatusCode;

src/Servers/Kestrel/Core/src/Internal/Http/HttpProtocol.Generated.cs

@@ -24,6 +24,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         private static readonly Type IRouteValuesFeatureType = typeof(IRouteValuesFeature);
         private static readonly Type IEndpointFeatureType = typeof(IEndpointFeature);
         private static readonly Type IHttpAuthenticationFeatureType = typeof(IHttpAuthenticationFeature);
+        private static readonly Type IHttpRequestTrailersFeatureType = typeof(IHttpRequestTrailersFeature);
         private static readonly Type IQueryFeatureType = typeof(IQueryFeature);
         private static readonly Type IFormFeatureType = typeof(IFormFeature);
         private static readonly Type IHttpUpgradeFeatureType = typeof(IHttpUpgradeFeature);
@@ -52,6 +53,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         private object _currentIRouteValuesFeature;
         private object _currentIEndpointFeature;
         private object _currentIHttpAuthenticationFeature;
+        private object _currentIHttpRequestTrailersFeature;
         private object _currentIQueryFeature;
         private object _currentIFormFeature;
         private object _currentIHttpUpgradeFeature;
@@ -82,6 +84,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             _currentIHttpUpgradeFeature = this;
             _currentIHttpRequestIdentifierFeature = this;
             _currentIHttpRequestLifetimeFeature = this;
+            _currentIHttpRequestTrailersFeature = this;
             _currentIHttpConnectionFeature = this;
             _currentIHttpMaxRequestBodySizeFeature = this;
             _currentIHttpMinRequestBodyDataRateFeature = this;
@@ -201,6 +204,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 {
                     feature = _currentIHttpAuthenticationFeature;
                 }
+                else if (key == IHttpRequestTrailersFeatureType)
+                {
+                    feature = _currentIHttpRequestTrailersFeature;
+                }
                 else if (key == IQueryFeatureType)
                 {
                     feature = _currentIQueryFeature;
@@ -321,6 +328,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 {
                     _currentIHttpAuthenticationFeature = value;
                 }
+                else if (key == IHttpRequestTrailersFeatureType)
+                {
+                    _currentIHttpRequestTrailersFeature = value;
+                }
                 else if (key == IQueryFeatureType)
                 {
                     _currentIQueryFeature = value;
@@ -439,6 +450,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             {
                 feature = (TFeature)_currentIHttpAuthenticationFeature;
             }
+            else if (typeof(TFeature) == typeof(IHttpRequestTrailersFeature))
+            {
+                feature = (TFeature)_currentIHttpRequestTrailersFeature;
+            }
             else if (typeof(TFeature) == typeof(IQueryFeature))
             {
                 feature = (TFeature)_currentIQueryFeature;
@@ -563,6 +578,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             {
                 _currentIHttpAuthenticationFeature = feature;
             }
+            else if (typeof(TFeature) == typeof(IHttpRequestTrailersFeature))
+            {
+                _currentIHttpRequestTrailersFeature = feature;
+            }
             else if (typeof(TFeature) == typeof(IQueryFeature))
             {
                 _currentIQueryFeature = feature;
@@ -679,6 +698,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             {
                 yield return new KeyValuePair<Type, object>(IHttpAuthenticationFeatureType, _currentIHttpAuthenticationFeature);
             }
+            if (_currentIHttpRequestTrailersFeature != null)
+            {
+                yield return new KeyValuePair<Type, object>(IHttpRequestTrailersFeatureType, _currentIHttpRequestTrailersFeature);
+            }
             if (_currentIQueryFeature != null)
             {
                 yield return new KeyValuePair<Type, object>(IQueryFeatureType, _currentIQueryFeature);

src/Servers/Kestrel/Core/src/Internal/Http/HttpProtocol.cs

@@ -206,6 +206,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         }
 
         public IHeaderDictionary RequestHeaders { get; set; }
+        public IHeaderDictionary RequestTrailers { get; } = new HeaderDictionary();
+        public bool RequestTrailersAvailable { get; set; }
         public Stream RequestBody { get; set; }
         public PipeReader RequestBodyPipeReader { get; set; }
 
@@ -369,6 +371,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             HttpResponseHeaders.Reset();
             RequestHeaders = HttpRequestHeaders;
             ResponseHeaders = HttpResponseHeaders;
+            RequestTrailers.Clear();
+            RequestTrailersAvailable = false;
 
             _isLeasedMemoryInvalid = true;
             _hasAdvanced = false;
@@ -524,11 +528,30 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
             HttpRequestHeaders.Append(name, value);
         }
 
+        public void OnTrailer(Span<byte> name, Span<byte> value)
+        {
+            // Trailers still count towards the limit.
+            _requestHeadersParsed++;
+            if (_requestHeadersParsed > ServerOptions.Limits.MaxRequestHeaderCount)
+            {
+                BadHttpRequestException.Throw(RequestRejectionReason.TooManyHeaders);
+            }
+
+            string key = name.GetHeaderName();
+            var valueStr = value.GetAsciiOrUTF8StringNonNullCharacters();
+            RequestTrailers.Append(key, valueStr);
+        }
+
         public void OnHeadersComplete()
         {
             HttpRequestHeaders.OnHeadersComplete();
         }
 
+        public void OnTrailersComplete()
+        {
+            RequestTrailersAvailable = true;
+        }
+
         public async Task ProcessRequestsAsync<TContext>(IHttpApplication<TContext> application)
         {
             try

src/Servers/Kestrel/Core/src/Internal/Http/HttpRequestHeaders.cs

@@ -103,16 +103,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         [MethodImpl(MethodImplOptions.NoInlining)]
         private unsafe void AppendUnknownHeaders(Span<byte> name, string valueString)
         {
-            string key = new string('\0', name.Length);
-            fixed (byte* pKeyBytes = name)
-            fixed (char* keyBuffer = key)
-            {
-                if (!StringUtilities.TryGetAsciiString(pKeyBytes, keyBuffer, name.Length))
-                {
-                    BadHttpRequestException.Throw(RequestRejectionReason.InvalidCharactersInHeaderName);
-                }
-            }
-
+            string key = name.GetHeaderName();
             Unknown.TryGetValue(key, out var existing);
             Unknown[key] = AppendValue(existing, valueString);
         }

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Connection.cs

@@ -1073,9 +1073,11 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
             ValidateHeader(name, value);
             try
             {
-                // Drop trailers for now. Adding them to the request headers is not thread safe.
-                // https://github.com/aspnet/KestrelHttpServer/issues/2051
-                if (_requestHeaderParsingState != RequestHeaderParsingState.Trailers)
+                if (_requestHeaderParsingState == RequestHeaderParsingState.Trailers)
+                {
+                    _currentHeadersStream.OnTrailer(name, value);
+                }
+                else
                 {
                     // Throws BadRequest for header count limit breaches.
                     // Throws InvalidOperation for bad encoding.

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Stream.cs

@@ -403,6 +403,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http2
                 }
             }
 
+            OnTrailersComplete();
             RequestBodyPipe.Writer.Complete();
 
             _inputFlowControl.StopWindowUpdates();

src/Servers/Kestrel/Core/src/Internal/Infrastructure/HttpUtilities.cs

@@ -84,6 +84,30 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure
             }
         }
 
+        // The same as GetAsciiStringNonNullCharacters but throws BadRequest
+        public static unsafe string GetHeaderName(this Span<byte> span)
+        {
+            if (span.IsEmpty)
+            {
+                return string.Empty;
+            }
+
+            var asciiString = new string('\0', span.Length);
+
+            fixed (char* output = asciiString)
+            fixed (byte* buffer = span)
+            {
+                // This version if AsciiUtilities returns null if there are any null (0 byte) characters
+                // in the string
+                if (!StringUtilities.TryGetAsciiString(buffer, output, span.Length))
+                {
+                    BadHttpRequestException.Throw(RequestRejectionReason.InvalidCharactersInHeaderName);
+                }
+            }
+
+            return asciiString;
+        }
+
         public static unsafe string GetAsciiStringNonNullCharacters(this Span<byte> span)
         {
             if (span.IsEmpty)

src/Servers/Kestrel/Core/src/Properties/CoreStrings.Designer.cs

@@ -2268,6 +2268,20 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
         internal static string FormatHttp2MinDataRateNotSupported()
             => GetString("Http2MinDataRateNotSupported");
 
+        /// <summary>
+        /// The request trailers are not available yet. They may not be available until the full request body is read.
+        /// </summary>
+        internal static string RequestTrailersNotAvailable
+        {
+            get => GetString("RequestTrailersNotAvailable");
+        }
+
+        /// <summary>
+        /// The request trailers are not available yet. They may not be available until the full request body is read.
+        /// </summary>
+        internal static string FormatRequestTrailersNotAvailable()
+            => GetString("RequestTrailersNotAvailable");
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

src/Servers/Kestrel/Core/test/Http1ConnectionTests.cs

@@ -97,7 +97,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             await _application.Output.WriteAsync(Encoding.UTF8.GetBytes("\r\n\r\n"));
             var readableBuffer = (await _transport.Input.ReadAsync()).Buffer;
 
-            _http1Connection.TakeMessageHeaders(readableBuffer, out _consumed, out _examined);
+            _http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out _consumed, out _examined);
             _transport.Input.AdvanceTo(_consumed, _examined);
 
             Assert.Equal(headerValue, _http1Connection.RequestHeaders[headerName]);
@@ -116,7 +116,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             await _application.Output.WriteAsync(extendedAsciiEncoding.GetBytes("\r\n\r\n"));
             var readableBuffer = (await _transport.Input.ReadAsync()).Buffer;
 
-            var exception = Assert.Throws<InvalidOperationException>(() => _http1Connection.TakeMessageHeaders(readableBuffer, out _consumed, out _examined));
+            var exception = Assert.Throws<InvalidOperationException>(() => _http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out _consumed, out _examined));
         }
 
         [Fact]
@@ -129,7 +129,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             await _application.Output.WriteAsync(Encoding.ASCII.GetBytes($"{headerLine}\r\n"));
             var readableBuffer = (await _transport.Input.ReadAsync()).Buffer;
 
-            var exception = Assert.Throws<BadHttpRequestException>(() => _http1Connection.TakeMessageHeaders(readableBuffer, out _consumed, out _examined));
+            var exception = Assert.Throws<BadHttpRequestException>(() => _http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out _consumed, out _examined));
             _transport.Input.AdvanceTo(_consumed, _examined);
 
             Assert.Equal(CoreStrings.BadRequest_HeadersExceedMaxTotalSize, exception.Message);
@@ -145,7 +145,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             await _application.Output.WriteAsync(Encoding.ASCII.GetBytes($"{headerLines}\r\n"));
             var readableBuffer = (await _transport.Input.ReadAsync()).Buffer;
 
-            var exception = Assert.Throws<BadHttpRequestException>(() => _http1Connection.TakeMessageHeaders(readableBuffer, out _consumed, out _examined));
+            var exception = Assert.Throws<BadHttpRequestException>(() => _http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out _consumed, out _examined));
             _transport.Input.AdvanceTo(_consumed, _examined);
 
             Assert.Equal(CoreStrings.BadRequest_TooManyHeaders, exception.Message);
@@ -250,7 +250,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             await _application.Output.WriteAsync(Encoding.ASCII.GetBytes($"{headerLine1}\r\n"));
             var readableBuffer = (await _transport.Input.ReadAsync()).Buffer;
 
-            var takeMessageHeaders = _http1Connection.TakeMessageHeaders(readableBuffer, out _consumed, out _examined);
+            var takeMessageHeaders = _http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out _consumed, out _examined);
             _transport.Input.AdvanceTo(_consumed, _examined);
 
             Assert.True(takeMessageHeaders);
@@ -262,7 +262,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             await _application.Output.WriteAsync(Encoding.ASCII.GetBytes($"{headerLine2}\r\n"));
             readableBuffer = (await _transport.Input.ReadAsync()).Buffer;
 
-            takeMessageHeaders = _http1Connection.TakeMessageHeaders(readableBuffer, out _consumed, out _examined);
+            takeMessageHeaders = _http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out _consumed, out _examined);
             _transport.Input.AdvanceTo(_consumed, _examined);
 
             Assert.True(takeMessageHeaders);

src/Servers/Kestrel/Core/test/HttpProtocolFeatureCollectionTests.cs

@@ -121,6 +121,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             _collection[typeof(IRequestBodyPipeFeature)] = CreateHttp1Connection();
             _collection[typeof(IHttpRequestIdentifierFeature)] = CreateHttp1Connection();
             _collection[typeof(IHttpRequestLifetimeFeature)] = CreateHttp1Connection();
+            _collection[typeof(IHttpRequestTrailersFeature)] = CreateHttp1Connection();
             _collection[typeof(IHttpConnectionFeature)] = CreateHttp1Connection();
             _collection[typeof(IHttpMaxRequestBodySizeFeature)] = CreateHttp1Connection();
             _collection[typeof(IHttpMinRequestBodyDataRateFeature)] = CreateHttp1Connection();
@@ -144,6 +145,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             _collection.Set<IRequestBodyPipeFeature>(CreateHttp1Connection());
             _collection.Set<IHttpRequestIdentifierFeature>(CreateHttp1Connection());
             _collection.Set<IHttpRequestLifetimeFeature>(CreateHttp1Connection());
+            _collection.Set<IHttpRequestTrailersFeature>(CreateHttp1Connection());
             _collection.Set<IHttpConnectionFeature>(CreateHttp1Connection());
             _collection.Set<IHttpMaxRequestBodySizeFeature>(CreateHttp1Connection());
             _collection.Set<IHttpMinRequestBodyDataRateFeature>(CreateHttp1Connection());

src/Servers/Kestrel/perf/Kestrel.Performance/Http1ConnectionParsingOverheadBenchmark.cs

@@ -83,7 +83,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Performance
                 ErrorUtilities.ThrowInvalidRequestLine();
             }
 
-            if (!_http1Connection.TakeMessageHeaders(_buffer, out consumed, out examined))
+            if (!_http1Connection.TakeMessageHeaders(_buffer, trailers: false, out consumed, out examined))
             {
                 ErrorUtilities.ThrowInvalidRequestHeaders();
             }
@@ -103,7 +103,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Performance
         {
             _http1Connection.Reset();
 
-            if (!_http1Connection.TakeMessageHeaders(_buffer, out var consumed, out var examined))
+            if (!_http1Connection.TakeMessageHeaders(_buffer, trailers: false, out var consumed, out var examined))
             {
                 ErrorUtilities.ThrowInvalidRequestHeaders();
             }

src/Servers/Kestrel/perf/Kestrel.Performance/RequestParsingBenchmark.cs

@@ -159,7 +159,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Performance
 
                 readableBuffer = readableBuffer.Slice(consumed);
 
-                if (!Http1Connection.TakeMessageHeaders(readableBuffer, out consumed, out examined))
+                if (!Http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out consumed, out examined))
                 {
                     ErrorUtilities.ThrowInvalidRequestHeaders();
                 }
@@ -196,7 +196,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Performance
                 result = Pipe.Reader.ReadAsync().GetAwaiter().GetResult();
                 readableBuffer = result.Buffer;
 
-                if (!Http1Connection.TakeMessageHeaders(readableBuffer, out consumed, out examined))
+                if (!Http1Connection.TakeMessageHeaders(readableBuffer, trailers: false, out consumed, out examined))
                 {
                     ErrorUtilities.ThrowInvalidRequestHeaders();
                 }

src/Servers/Kestrel/test/InMemory.FunctionalTests/ChunkedRequestTests.cs

@@ -232,18 +232,59 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
 
                 var buffer = new byte[200];
 
+                // The first request is chunked with no trailers.
+                if (requestsReceived == 0)
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.False(request.CheckTrailersAvailable(), "CheckTrailersAvailable"); // Not yet
+                    Assert.Throws<InvalidOperationException>(() => request.GetTrailer("X-Trailer-Header"));  // Not yet
+                }
+                // The middle requests are chunked with trailers.
+                else if (requestsReceived < requestCount)
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.False(request.CheckTrailersAvailable(), "CheckTrailersAvailable"); // Not yet
+                    Assert.Throws<InvalidOperationException>(() => request.GetTrailer("X-Trailer-Header"));  // Not yet
+                    Assert.Equal("X-Trailer-Header", request.GetDeclaredTrailers().ToString());
+                }
+                // The last request is content-length with no trailers.
+                else
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.False(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Throws<InvalidOperationException>(() => request.GetTrailer("X-Trailer-Header"));
+                }
+
                 while (await request.Body.ReadAsync(buffer, 0, buffer.Length) != 0)
                 {
                     ;// read to end
                 }
 
-                if (requestsReceived < requestCount)
+                Assert.False(request.Headers.ContainsKey("X-Trailer-Header"));
+
+                // The first request is chunked with no trailers.
+                if (requestsReceived == 0)
                 {
-                    Assert.Equal(new string('a', requestsReceived), request.Headers["X-Trailer-Header"].ToString());
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.True(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Equal(string.Empty, request.GetDeclaredTrailers().ToString());
+                    Assert.Equal(string.Empty, request.GetTrailer("X-Trailer-Header").ToString());
                 }
+                // The middle requests are chunked with trailers.
+                else if (requestsReceived < requestCount)
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.True(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Equal("X-Trailer-Header", request.GetDeclaredTrailers().ToString());
+                    Assert.Equal(new string('a', requestsReceived), request.GetTrailer("X-Trailer-Header").ToString());
+                }
+                // The last request is content-length with no trailers.
                 else
                 {
-                    Assert.True(string.IsNullOrEmpty(request.Headers["X-Trailer-Header"]));
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.True(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Equal(string.Empty, request.GetDeclaredTrailers().ToString());
+                    Assert.Equal(string.Empty, request.GetTrailer("X-Trailer-Header").ToString());
                 }
 
                 requestsReceived++;
@@ -278,6 +319,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
                         "POST / HTTP/1.1",
                         "Host:",
                         "Transfer-Encoding: chunked",
+                        "Trailer: X-Trailer-Header",
                         "",
                         "C",
                         $"HelloChunk{i:00}",
@@ -315,6 +357,29 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
                 var response = httpContext.Response;
                 var request = httpContext.Request;
 
+                // The first request is chunked with no trailers.
+                if (requestsReceived == 0)
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.False(request.CheckTrailersAvailable(), "CheckTrailersAvailable"); // Not yet
+                    Assert.Throws<InvalidOperationException>(() => request.GetTrailer("X-Trailer-Header"));  // Not yet
+                }
+                // The middle requests are chunked with trailers.
+                else if (requestsReceived < requestCount)
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.False(request.CheckTrailersAvailable(), "CheckTrailersAvailable"); // Not yet
+                    Assert.Throws<InvalidOperationException>(() => request.GetTrailer("X-Trailer-Header"));  // Not yet
+                    Assert.Equal("X-Trailer-Header", request.GetDeclaredTrailers().ToString());
+                }
+                // The last request is content-length with no trailers.
+                else
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.False(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Throws<InvalidOperationException>(() => request.GetTrailer("X-Trailer-Header"));
+                }
+
                 while (true)
                 {
                     var result = await request.BodyReader.ReadAsync();
@@ -325,13 +390,31 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
                     }
                 }
 
-                if (requestsReceived < requestCount)
+                Assert.False(request.Headers.ContainsKey("X-Trailer-Header"));
+
+                // The first request is chunked with no trailers.
+                if (requestsReceived == 0)
                 {
-                    Assert.Equal(new string('a', requestsReceived), request.Headers["X-Trailer-Header"].ToString());
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.True(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Equal(string.Empty, request.GetDeclaredTrailers().ToString());
+                    Assert.Equal(string.Empty, request.GetTrailer("X-Trailer-Header").ToString());
                 }
+                // The middle requests are chunked with trailers.
+                else if (requestsReceived < requestCount)
+                {
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.True(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Equal("X-Trailer-Header", request.GetDeclaredTrailers().ToString());
+                    Assert.Equal(new string('a', requestsReceived), request.GetTrailer("X-Trailer-Header").ToString());
+                }
+                // The last request is content-length with no trailers.
                 else
                 {
-                    Assert.True(string.IsNullOrEmpty(request.Headers["X-Trailer-Header"]));
+                    Assert.True(request.SupportsTrailers(), "SupportsTrailers");
+                    Assert.True(request.CheckTrailersAvailable(), "CheckTrailersAvailable");
+                    Assert.Equal(string.Empty, request.GetDeclaredTrailers().ToString());
+                    Assert.Equal(string.Empty, request.GetTrailer("X-Trailer-Header").ToString());
                 }
 
                 requestsReceived++;
@@ -366,6 +449,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
                         "POST / HTTP/1.1",
                         "Host:",
                         "Transfer-Encoding: chunked",
+                        "Trailer: X-Trailer-Header",
                         "",
                         "C",
                         $"HelloChunk{i:00}",
@@ -495,13 +579,11 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
                     ;// read to end
                 }
 
+                Assert.True(string.IsNullOrEmpty(request.Headers["X-Trailer-Header"]));
+
                 if (requestsReceived < requestCount)
                 {
-                    Assert.Equal(new string('a', requestsReceived), request.Headers["X-Trailer-Header"].ToString());
-                }
-                else
-                {
-                    Assert.True(string.IsNullOrEmpty(request.Headers["X-Trailer-Header"]));
+                    Assert.Equal(new string('a', requestsReceived), request.GetTrailer("X-Trailer-Header").ToString());
                 }
 
                 requestsReceived++;

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http2/Http2ConnectionTests.cs

@@ -1174,7 +1174,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
         [Theory]
         [InlineData(true)]
         [InlineData(false)]
-        public async Task HEADERS_Received_WithTrailers_Discarded(bool sendData)
+        public async Task HEADERS_Received_WithTrailers_Available(bool sendData)
         {
             await InitializeConnectionAsync(_readTrailersApplication);
 
@@ -1206,10 +1206,12 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
 
             VerifyDecodedRequestHeaders(_browserRequestHeaders);
 
-            // Make sure the trailers are missing. https://github.com/aspnet/KestrelHttpServer/issues/2630
+            // Make sure the trailers are in the trailers collection.
             foreach (var header in _requestTrailers)
             {
                 Assert.False(_receivedHeaders.ContainsKey(header.Key));
+                Assert.True(_receivedTrailers.ContainsKey(header.Key));
+                Assert.Equal(header.Value, _receivedTrailers[header.Key]);
             }
 
             await StopConnectionAsync(expectedLastStreamId: 3, ignoreNonGoAwayFrames: false);
@@ -3288,7 +3290,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
         [Theory]
         [InlineData(true)]
         [InlineData(false)]
-        public async Task CONTINUATION_Received_WithTrailers_Discarded(bool sendData)
+        public async Task CONTINUATION_Received_WithTrailers_Available(bool sendData)
         {
             await InitializeConnectionAsync(_readTrailersApplication);
 
@@ -3331,9 +3333,13 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
 
             VerifyDecodedRequestHeaders(_browserRequestHeaders);
 
-            // Make sure the trailers are missing. https://github.com/aspnet/KestrelHttpServer/issues/2630
+            // Make sure the trailers are in the trailers collection.
             Assert.False(_receivedHeaders.ContainsKey("trailer-1"));
             Assert.False(_receivedHeaders.ContainsKey("trailer-2"));
+            Assert.True(_receivedTrailers.ContainsKey("trailer-1"));
+            Assert.True(_receivedTrailers.ContainsKey("trailer-2"));
+            Assert.Equal("1", _receivedTrailers["trailer-1"]);
+            Assert.Equal("2", _receivedTrailers["trailer-2"]);
 
             await StopConnectionAsync(expectedLastStreamId: 3, ignoreNonGoAwayFrames: false);
         }

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http2/Http2TestBase.cs

@@ -130,6 +130,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
 
         protected readonly ConcurrentDictionary<int, TaskCompletionSource<object>> _runningStreams = new ConcurrentDictionary<int, TaskCompletionSource<object>>();
         protected readonly Dictionary<string, string> _receivedHeaders = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+        protected readonly Dictionary<string, string> _receivedTrailers = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
         protected readonly Dictionary<string, string> _decodedHeaders = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
         protected readonly HashSet<int> _abortedStreamIds = new HashSet<int>();
         protected readonly object _abortedStreamIdsLock = new object();
@@ -199,16 +200,29 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
 
             _readTrailersApplication = async context =>
             {
+                Assert.True(context.Request.SupportsTrailers(), "SupportsTrailers");
+                Assert.False(context.Request.CheckTrailersAvailable(), "SupportsTrailers");
+
                 using (var ms = new MemoryStream())
                 {
                     // Consuming the entire request body guarantees trailers will be available
                     await context.Request.Body.CopyToAsync(ms);
                 }
 
+                Assert.True(context.Request.SupportsTrailers(), "SupportsTrailers");
+                Assert.True(context.Request.CheckTrailersAvailable(), "SupportsTrailers");
+
                 foreach (var header in context.Request.Headers)
                 {
                     _receivedHeaders[header.Key] = header.Value.ToString();
                 }
+
+                var trailers = context.Features.Get<IHttpRequestTrailersFeature>().Trailers;
+
+                foreach (var header in trailers)
+                {
+                    _receivedTrailers[header.Key] = header.Value.ToString();
+                }
             };
 
             _bufferingApplication = async context =>

src/Servers/Kestrel/test/InMemory.FunctionalTests/MaxRequestBodySizeTests.cs

@@ -5,6 +5,7 @@ using System;
 using System.IO;
 using System.Text;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Server.Kestrel.Core;
 using Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests.TestTransport;
@@ -360,7 +361,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests
                 } while (count != 0);
 
                 Assert.Equal("Hello World", Encoding.ASCII.GetString(buffer));
-                Assert.Equal("trailing-value", context.Request.Headers["Trailing-Header"].ToString());
+                Assert.Equal("trailing-value", context.Request.GetTrailer("Trailing-Header").ToString());
             },
             new TestServiceContext(LoggerFactory) { ServerOptions = { Limits = { MaxRequestBodySize = globalMaxRequestBodySize } } }))
             {

src/Servers/Kestrel/tools/CodeGenerator/HttpProtocolFeatureCollection.cs

@@ -26,6 +26,7 @@ namespace CodeGenerator
             var commonFeatures = new[]
             {
                 "IHttpAuthenticationFeature",
+                "IHttpRequestTrailersFeature",
                 "IQueryFeature",
                 "IFormFeature",
             };
@@ -69,6 +70,7 @@ namespace CodeGenerator
                 "IHttpUpgradeFeature",
                 "IHttpRequestIdentifierFeature",
                 "IHttpRequestLifetimeFeature",
+                "IHttpRequestTrailersFeature",
                 "IHttpConnectionFeature",
                 "IHttpMaxRequestBodySizeFeature",
                 "IHttpMinRequestBodyDataRateFeature",