Multifile request proxied leads into exception

[walterancona]

When proxying a request containing more than one file, I have this exception:
System.Net.Http.HttpRequestException: An error occurred while sending the request.
---> System.InvalidOperationException: The inner stream position has changed unexpectedly.
at Microsoft.AspNetCore.Http.ReferenceReadStream.VerifyPosition()
at Microsoft.AspNetCore.Http.ReferenceReadStream.ReadAsync(Memory`1 buffer, CancellationToken cancellationToken)
at System.IO.Stream.g__Core|29_0(Stream source, Stream destination, Int32 bufferSize, CancellationToken cancellationToken)
at System.Net.Http.HttpContent.g__WaitAsync|56_0(ValueTask copyTask)
at System.Net.Http.MultipartContent.SerializeToStreamAsyncCore(Stream stream, TransportContext context, CancellationToken cancellationToken)
at System.Net.Http.HttpContent.g__WaitAsync|56_0(ValueTask copyTask)
at System.Net.Http.HttpConnection.SendRequestContentAsync(HttpRequestMessage request, HttpContentWriteStream stream, Boolean async, CancellationToken cancellationToken)
at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
--- End of inner exception stack trace ---
at System.Net.Http.HttpConnection.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
at System.Net.Http.AuthenticationHelper.SendWithNtAuthAsync(HttpRequestMessage request, Uri authUri, Boolean async, ICredentials credentials, Boolean isProxyAuth, HttpConnection connection, HttpConnectionPool connectionPool, CancellationToken cancellationToken)
at System.Net.Http.HttpConnectionPool.SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
at System.Net.Http.AuthenticationHelper.SendWithAuthAsync(HttpRequestMessage request, Uri authUri, Boolean async, ICredentials credentials, Boolean preAuthenticate, Boolean isProxyAuth, Boolean doRequestAuth, HttpConnectionPool pool, CancellationToken cancellationToken)
at System.Net.Http.DiagnosticsHandler.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
at Microsoft.Extensions.Http.Logging.LoggingHttpMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at Microsoft.Extensions.Http.Logging.LoggingScopeHttpMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
at System.Net.Http.HttpClient.g__Core|83_0(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken)
at AspNetCore.Proxy.HttpExtensions.ExecuteHttpProxyOperationAsync(HttpContext context, HttpProxy httpProxy)

I've seen that there's a PR (#109) that could solve this issue. Is It possible to see if it could be approved?
Thanks

[twitchax]

Hello! I'm happy to take a look soon, but likely won't be able to for a week or so.

I'd really just like to have a validation test for that PR. If you can help with that, I'll get it merged and shipped ASAP.

[walterancona]

Hi, I tried to put the code in that PR in a DLL and test it in my case and it works.
The Api that i am proxying is with a multiform/form-data body with an IFormFileCollection. With the actual release of the dll it sends the error mentioned, while applying the PR it simply works.