WebSockets over HTTP/2

[Tratcher]

We've heard some interest express for WebSockets support over HTTP/2 in YARP. This would require support in ASP.NET Core (Kestrel) and HttpClient. The protocol is quite different from original WebSockets.

RFC: https://datatracker.ietf.org/doc/html/rfc8441
Kestrel: dotnet/aspnetcore#7801
HttpClient: dotnet/runtime#69669

We'd also need to worry about protocol upgrades/downgrades between front-end and back-end.

[karelz]

Triage: We have interested partner team, but not yet committed. It helps with COGS.
We would need feature work in .NET Runtime (7.0+).

Forwarding is directly through SocketsHttpHandler, so the API pattern might be different from current ClientWebSocket.

[adityamandaleeka]

This should be happening for .NET 7 on both the server and client side, so let's make YARP take advantage of that in 2.0

[Tratcher]

@greenEkatherine as the first step here, can you test YARP 1.1 on .NET 7 with an Http/2 WebSocket client and capture the error here in this issue? It's expected to fail since Kestrel will accept the H2 WS request but YARP won't know what to do with it. We just want to document what that failure looks like.

[serpent5]

I'm running YARP 1.1 with .NET 7, attempting to proxy the Angular CLI development server's WebSocket connection. Here's some information that might be helpful:

Request Headers:

{
  "method": "GET",
  "url": "wss://localhost:5001/ng-cli-ws",
  "httpVersion": "",
  "headers": [
    {
      "name": "Pragma",
      "value": "no-cache"
    },
    {
      "name": "Origin",
      "value": "https://localhost:5001"
    },
    {
      "name": "Accept-Encoding",
      "value": "gzip, deflate, br"
    },
    {
      "name": "Host",
      "value": "localhost:5001"
    },
    {
      "name": "Accept-Language",
      "value": "en-GB,en-US;q=0.9,en;q=0.8"
    },
    {
      "name": "User-Agent",
      "value": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36 Edg/107.0.1418.42"
    },
    {
      "name": "Upgrade",
      "value": "websocket"
    },
    {
      "name": "Cache-Control",
      "value": "no-cache"
    },
    {
      "name": "Connection",
      "value": "Upgrade"
    },
    {
      "name": "Sec-WebSocket-Version",
      "value": "13"
    },
    {
      "name": "Sec-WebSocket-Extensions",
      "value": "permessage-deflate; client_max_window_bits"
    }
  ]
}

Here's the request as logged in ASP.NET Core:

[09:44:51 INF] Request starting HTTP/2 CONNECT https://localhost:5001/ng-cli-ws

Here's a stack-trace from YARP:

System.NotSupportedException: Unsupported request method 'CONNECT'.
   at Yarp.ReverseProxy.Forwarder.RequestUtilities.GetHttpMethod(String method)
   at Yarp.ReverseProxy.Forwarder.HttpForwarder.CreateRequestMessageAsync(HttpContext context, String destinationPrefix, HttpTransformer transformer, ForwarderRequestConfig requestConfig, Boolean isStreamingRequest, ActivityCancellationTokenSource activityToken)
   at Yarp.ReverseProxy.Forwarder.HttpForwarder.SendAsync(HttpContext context, String destinationPrefix, HttpMessageInvoker httpClient, ForwarderRequestConfig requestConfig, HttpTransformer transformer)

Let me know if I can provide more information. If I've misunderstood and this isn't what you're after, I can delete this comment.