Use interned headernames for known headers not in the preallocated block

Author: benaadams

src/Http/Headers/src/HeaderNames.cs

@@ -65,7 +65,7 @@ public static class HeaderNames
         public static readonly string Authorization = "Authorization";
 
         /// <summary>Gets the <c>baggage</c> HTTP header name.</summary>
-        public static readonly string Baggage = "baggage";
+        public static readonly string Baggage = "Baggage";
 
         /// <summary>Gets the <c>Cache-Control</c> HTTP header name.</summary>
         public static readonly string CacheControl = "Cache-Control";
@@ -166,6 +166,9 @@ public static class HeaderNames
         /// <summary>Gets the <c>Last-Modified</c> HTTP header name.</summary>
         public static readonly string LastModified = "Last-Modified";
 
+        /// <summary>Gets the <c>Link</c> HTTP header name.</summary>
+        public static readonly string Link = "Link";
+
         /// <summary>Gets the <c>Location</c> HTTP header name.</summary>
         public static readonly string Location = "Location";
 
@@ -245,10 +248,10 @@ public static class HeaderNames
         public static readonly string Translate = "Translate";
 
         /// <summary>Gets the <c>traceparent</c> HTTP header name.</summary>
-        public static readonly string TraceParent = "traceparent";
+        public static readonly string TraceParent = "TraceParent";
 
         /// <summary>Gets the <c>tracestate</c> HTTP header name.</summary>
-        public static readonly string TraceState = "tracestate";
+        public static readonly string TraceState = "TraceState";
 
         /// <summary>Gets the <c>Upgrade</c> HTTP header name.</summary>
         public static readonly string Upgrade = "Upgrade";
@@ -274,10 +277,16 @@ public static class HeaderNames
         /// <summary>Gets the <c>WWW-Authenticate</c> HTTP header name.</summary>
         public static readonly string WWWAuthenticate = "WWW-Authenticate";
 
+        /// <summary>Gets the <c>X-Content-Type-Options</c> HTTP header name.</summary>
+        public static readonly string XContentTypeOptions = "X-Content-Type-Options";
+
         /// <summary>Gets the <c>X-Frame-Options</c> HTTP header name.</summary>
         public static readonly string XFrameOptions = "X-Frame-Options";
 
         /// <summary>Gets the <c>X-Requested-With</c> HTTP header name.</summary>
         public static readonly string XRequestedWith = "X-Requested-With";
+
+        /// <summary>Gets the <c>X-XSS-Protection</c> HTTP header name.</summary>
+        public static readonly string XXssProtection = "X-XSS-Protection";
     }
 }

src/Http/Headers/src/PublicAPI.Unshipped.txt

@@ -3,4 +3,7 @@
 Microsoft.Net.Http.Headers.MediaTypeHeaderValue.MatchesMediaType(Microsoft.Extensions.Primitives.StringSegment otherMediaType) -> bool
 Microsoft.Net.Http.Headers.RangeConditionHeaderValue.RangeConditionHeaderValue(Microsoft.Net.Http.Headers.EntityTagHeaderValue! entityTag) -> void
 static readonly Microsoft.Net.Http.Headers.HeaderNames.Baggage -> string!
+static readonly Microsoft.Net.Http.Headers.HeaderNames.Link -> string!
 static readonly Microsoft.Net.Http.Headers.HeaderNames.ProxyConnection -> string!
+static readonly Microsoft.Net.Http.Headers.HeaderNames.XContentTypeOptions -> string!
+static readonly Microsoft.Net.Http.Headers.HeaderNames.XXssProtection -> string!

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

@@ -99,6 +99,106 @@ internal enum KnownHeaderType
         WWWAuthenticate,
     }
 
+    internal partial class HttpHeaders
+    {
+        protected readonly static HashSet<string> s_internedHeaderNames = new HashSet<string>(93, StringComparer.OrdinalIgnoreCase)
+        {
+            HeaderNames.Accept,
+            HeaderNames.AcceptCharset,
+            HeaderNames.AcceptEncoding,
+            HeaderNames.AcceptLanguage,
+            HeaderNames.AcceptRanges,
+            HeaderNames.AccessControlAllowCredentials,
+            HeaderNames.AccessControlAllowHeaders,
+            HeaderNames.AccessControlAllowMethods,
+            HeaderNames.AccessControlAllowOrigin,
+            HeaderNames.AccessControlExposeHeaders,
+            HeaderNames.AccessControlMaxAge,
+            HeaderNames.AccessControlRequestHeaders,
+            HeaderNames.AccessControlRequestMethod,
+            HeaderNames.Age,
+            HeaderNames.Allow,
+            HeaderNames.AltSvc,
+            HeaderNames.Authority,
+            HeaderNames.Authorization,
+            HeaderNames.Baggage,
+            HeaderNames.CacheControl,
+            HeaderNames.Connection,
+            HeaderNames.ContentDisposition,
+            HeaderNames.ContentEncoding,
+            HeaderNames.ContentLanguage,
+            HeaderNames.ContentLength,
+            HeaderNames.ContentLocation,
+            HeaderNames.ContentMD5,
+            HeaderNames.ContentRange,
+            HeaderNames.ContentSecurityPolicy,
+            HeaderNames.ContentSecurityPolicyReportOnly,
+            HeaderNames.ContentType,
+            HeaderNames.CorrelationContext,
+            HeaderNames.Cookie,
+            HeaderNames.Date,
+            HeaderNames.DNT,
+            HeaderNames.ETag,
+            HeaderNames.Expires,
+            HeaderNames.Expect,
+            HeaderNames.From,
+            HeaderNames.GrpcAcceptEncoding,
+            HeaderNames.GrpcEncoding,
+            HeaderNames.GrpcMessage,
+            HeaderNames.GrpcStatus,
+            HeaderNames.GrpcTimeout,
+            HeaderNames.Host,
+            HeaderNames.KeepAlive,
+            HeaderNames.IfMatch,
+            HeaderNames.IfModifiedSince,
+            HeaderNames.IfNoneMatch,
+            HeaderNames.IfRange,
+            HeaderNames.IfUnmodifiedSince,
+            HeaderNames.LastModified,
+            HeaderNames.Link,
+            HeaderNames.Location,
+            HeaderNames.MaxForwards,
+            HeaderNames.Method,
+            HeaderNames.Origin,
+            HeaderNames.Path,
+            HeaderNames.Pragma,
+            HeaderNames.ProxyAuthenticate,
+            HeaderNames.ProxyAuthorization,
+            HeaderNames.ProxyConnection,
+            HeaderNames.Range,
+            HeaderNames.Referer,
+            HeaderNames.RetryAfter,
+            HeaderNames.RequestId,
+            HeaderNames.Scheme,
+            HeaderNames.SecWebSocketAccept,
+            HeaderNames.SecWebSocketKey,
+            HeaderNames.SecWebSocketProtocol,
+            HeaderNames.SecWebSocketVersion,
+            HeaderNames.Server,
+            HeaderNames.SetCookie,
+            HeaderNames.Status,
+            HeaderNames.StrictTransportSecurity,
+            HeaderNames.TE,
+            HeaderNames.Trailer,
+            HeaderNames.TransferEncoding,
+            HeaderNames.Translate,
+            HeaderNames.TraceParent,
+            HeaderNames.TraceState,
+            HeaderNames.Upgrade,
+            HeaderNames.UpgradeInsecureRequests,
+            HeaderNames.UserAgent,
+            HeaderNames.Vary,
+            HeaderNames.Via,
+            HeaderNames.Warning,
+            HeaderNames.WebSocketSubProtocols,
+            HeaderNames.WWWAuthenticate,
+            HeaderNames.XContentTypeOptions,
+            HeaderNames.XFrameOptions,
+            HeaderNames.XRequestedWith,
+            HeaderNames.XXssProtection,
+        };
+    }
+
     internal partial class HttpRequestHeaders
     {
         private HeaderReferences _headers;

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

@@ -15,13 +15,13 @@
 
 namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 {
-    internal abstract class HttpHeaders : IHeaderDictionary
+    internal abstract partial class HttpHeaders : IHeaderDictionary
     {
         protected long _bits = 0;
         protected long? _contentLength;
         protected bool _isReadOnly;
         protected Dictionary<string, StringValues>? MaybeUnknown;
-        protected Dictionary<string, StringValues> Unknown => MaybeUnknown ?? (MaybeUnknown = new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase));
+        protected Dictionary<string, StringValues> Unknown => MaybeUnknown ??= new Dictionary<string, StringValues>(StringComparer.OrdinalIgnoreCase);
 
         public long? ContentLength
         {
@@ -126,6 +126,18 @@ public void Reset()
             ClearFast();
         }
 
+        protected static string GetInternedHeaderName(string name)
+        {
+            // Some headers can be very long lived; for example those on a WebSocket connection
+            // so we exchange these for the preallocated strings predefined in HeaderNames
+            if (s_internedHeaderNames.TryGetValue(name, out var internedName))
+            {
+                return internedName;
+            }
+
+            return name;
+        }
+
         [MethodImpl(MethodImplOptions.NoInlining)]
         protected static StringValues AppendValue(StringValues existing, string append)
         {

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

@@ -121,20 +121,21 @@ private void AppendContentLengthCustomEncoding(ReadOnlySpan<byte> value, Encodin
         [MethodImpl(MethodImplOptions.NoInlining)]
         private void SetValueUnknown(string key, StringValues value)
         {
-            Unknown[key] = value;
+            Unknown[GetInternedHeaderName(key)] = value;
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         private bool AddValueUnknown(string key, StringValues value)
         {
-            Unknown.Add(key, value);
+            Unknown.Add(GetInternedHeaderName(key), value);
             // Return true, above will throw and exit for false
             return true;
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         private unsafe void AppendUnknownHeaders(string name, string valueString)
         {
+            name = GetInternedHeaderName(name);
             Unknown.TryGetValue(name, out var existing);
             Unknown[name] = AppendValue(existing, valueString);
         }

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

@@ -76,14 +76,14 @@ private static void ThrowInvalidContentLengthException(string value)
         private void SetValueUnknown(string key, StringValues value)
         {
             ValidateHeaderNameCharacters(key);
-            Unknown[key] = value;
+            Unknown[GetInternedHeaderName(key)] = value;
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         private bool AddValueUnknown(string key, StringValues value)
         {
             ValidateHeaderNameCharacters(key);
-            Unknown.Add(key, value);
+            Unknown.Add(GetInternedHeaderName(key), value);
             // Return true, above will throw and exit for false
             return true;
         }

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

@@ -25,14 +25,14 @@ protected override IEnumerator<KeyValuePair<string, StringValues>> GetEnumerator
         private void SetValueUnknown(string key, StringValues value)
         {
             ValidateHeaderNameCharacters(key);
-            Unknown[key] = value;
+            Unknown[GetInternedHeaderName(key)] = value;
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         private bool AddValueUnknown(string key, StringValues value)
         {
             ValidateHeaderNameCharacters(key);
-            Unknown.Add(key, value);
+            Unknown.Add(GetInternedHeaderName(key), value);
             // Return true, above will throw and exit for false
             return true;
         }