[HTTP/2] Throw meaningful exception if we get GOAWAY while reading response body

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http2Connection.cs

@@ -72,6 +72,8 @@ internal sealed partial class Http2Connection : HttpConnectionBase
         // _shutdown above is true, and requests in flight have been (or are being) failed.
         private Exception? _abortException;
 
+        private Http2ProtocolErrorCode? _goAwayErrorCode;
+
         private const int MaxStreamId = int.MaxValue;
 
         // Temporary workaround for request burst handling on connection start.
@@ -410,7 +412,11 @@ private async ValueTask<FrameHeader> ReadFrameAsync(bool initialFrame = false)
                     _incomingBuffer.Commit(bytesRead);
                     if (bytesRead == 0)
                     {
-                        if (_incomingBuffer.ActiveLength == 0)
+                        if (_goAwayErrorCode is not null)
+                        {
+                            ThrowProtocolError(_goAwayErrorCode.Value, SR.net_http_http2_connection_close);
+                        }
+                        else if (_incomingBuffer.ActiveLength == 0)
                         {
                             ThrowMissingFrame();
                         }
@@ -1070,6 +1076,7 @@ private void ProcessGoAwayFrame(FrameHeader frameHeader)
 
             Debug.Assert(lastStreamId >= 0);
             Exception resetException = HttpProtocolException.CreateHttp2ConnectionException(errorCode, SR.net_http_http2_connection_close);
+            _goAwayErrorCode = errorCode;
 
             // There is no point sending more PING frames for RTT estimation:
             _rttEstimator.OnGoAwayReceived();

src/libraries/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTest.Http2.cs

@@ -1051,6 +1051,36 @@ public async Task GoAwayFrame_RequestWithBody_ServerDisconnect_AbortStreamsAndTh
             }
         }
 
+        [ConditionalFact(nameof(SupportsAlpn))]
+        public async Task GoAwayFrame_RequestServerDisconnects_ThrowsHttpProtocolExceptionWithProperErrorCode()
+        {
+            await Http2LoopbackServer.CreateClientAndServerAsync(async uri =>
+            {
+                // Client starts an HTTP/2 request and awaits response headers
+                using HttpClient client = CreateHttpClient();
+                HttpResponseMessage response = await client.GetAsync(uri, HttpCompletionOption.ResponseHeadersRead);
+
+                // Client reads from response stream
+                using Stream responseStream = await response.Content.ReadAsStreamAsync();
+                Memory<byte> buffer = new byte[1024];
+                HttpProtocolException exception = await Assert.ThrowsAsync<HttpProtocolException>(() => responseStream.ReadAsync(buffer).AsTask());
+                Assert.Equal(ProtocolErrors.ENHANCE_YOUR_CALM, (ProtocolErrors) exception.ErrorCode);
+                Assert.Contains("The HTTP/2 server closed the connection.", exception.Message);
+
+            },
+            async server =>
+            {
+                // Server returns response headers
+                await using Http2LoopbackConnection connection = await server.EstablishConnectionAsync();
+                int streamId = await connection.ReadRequestHeaderAsync();
+                await connection.SendDefaultResponseHeadersAsync(streamId);
+
+                // Server sends GOAWAY frame
+                await connection.SendGoAway(streamId, ProtocolErrors.ENHANCE_YOUR_CALM);
+                connection.ShutdownSend();
+            });
+        }
+
         [ConditionalFact(nameof(SupportsAlpn))]
         public async Task GoAwayFrame_UnprocessedStreamFirstRequestFinishedFirst_RequestRestarted()
         {