ChannelCredentials.Insecure + corporate proxy = Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled.

What version of gRPC and what language are you using?

• Grpc.Net.Client - 2.38.0

What operating system (Linux, Windows,…) and version?

• Windows 20H2 (10.0.19042)

What runtime / compiler are you using (e.g. .NET Core SDK version dotnet --info)

• 5.0.400

What did you do?

Scenario a) Secure Connection

var uri = new Uri($"https://{options.Host}:{options.Port}");
rpcChannel = GrpcChannel.ForAddress(uri);

Case 1: Circumvent the corporate proxy (=direct connection to the service)

To circumvent the corporate proxy, I set it to HTTPS_PROXY=:

HTTPS_PROXY= ./Client.exe

The gPRC connection works. ✓

Case 2: Use the corporate proxy

HTTPS_PROXY=http://corporate-proxy ./Client.exe

The gPRC connection works. ✓

Scenario b) Insecure Connection

var uri = new Uri($"http://{options.Host}:{options.Port}");
var grpcChannelOptions = new GrpcChannelOptions
{
    Credentials = ChannelCredentials.Insecure
};
GrpcChannel grpcChannel = GrpcChannel.ForAddress(uri, grpcChannelOptions);
[...]

Case 3: Circumvent the corporate proxy (=direct connection to the service)

HTTP_PROXY= ./Client.exe

The gPRC connection works. ✓

Case 4: Use the corporate proxy

HTTP_PROXY=http://corporate-proxy ./Client.exe

The gPRC connection does not work. I get the following exception: System.Net.Http.HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled. The connection occus immediately, it does not even try to connect (nothing can be seen in Wireshark).

System.AggregateException: One or more errors occurred. (Status(StatusCode="Internal", Detail="Error starting gRPC call. HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled.", DebugException="System.Net.Http.HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled.
   at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at Grpc.Net.Client.Internal.GrpcCall`2.RunCall(HttpRequestMessage request, Nullable`1 timeout)"))
 ---> Grpc.Core.RpcException: Status(StatusCode="Internal", Detail="Error starting gRPC call. HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled.", DebugException="System.Net.Http.HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while HTTP/2 is not enabled.
   at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at Grpc.Net.Client.Internal.GrpcCall`2.RunCall(HttpRequestMessage request, Nullable`1 timeout)")
   at Grpc.Net.Client.Internal.HttpClientCallInvoker.BlockingUnaryCall[TRequest,TResponse](Method`2 method, String host, CallOptions options, TRequest request)
   at Grpc.Core.Interceptors.InterceptingCallInvoker.<BlockingUnaryCall>b__3_0[TRequest,TResponse](TRequest req, ClientInterceptorContext`2 ctx)

What did you expect to see?

Case 4 should connect with a proxy as well.

What did you see instead?

See Case 4.

[JamesNK]

I haven’t seen this situation before, but my guess is your HTTP_PROXY server supports HTTP/1.1 and HTTP/2.

TLS (aka HTTPS) is required to negotiate an HTTP/2 connection when a server supports multiple. Because you’re using HTTP, the connection is falling back to HTTP/1.1.

I’ll double-check this with some experts. The error message is unclear.

[JamesNK]

I don’t know. You should create an issue at dotnet/runtime to talk to the experts who work on the underlying client networking.

This isn’t an issue in gRPC or something that we can fix here.