SocketTransport: FIN handling

[tmds]

If a client sends a request and then sends a FIN to indicate it won't send anymore data, this should

• not be treated as an exception
• not cause the server to stop sending a reply.

[davidfowl]

not be treated as an exception

It's an exception because we want application code to fail reading the body. Though we're adding a new pipe for the body reading so we can split app and transport behavior if we found that valuable.

not cause the server to stop sending a reply.

We could make this code only stop the input if the output ended, today it does both things (which happens either way but it's a responsibility question).

Either way, when a fin is received, kestrel will complete the output so the net effect will be the same.

[tmds]

It is valid for an http client to do this:

socket.write(request);
socket.shutdown(SHUT_WR);
response = socket.read();

This won't work well with the Socket Transport. The libuv Transport handles this fine.

[davidfowl]

You may not get the response though. When you send the FIN Kestrel will kill the output potentially before the client gets a chance to read the response. Before we make the sockets transport the default, we'll make sure it has equivalent behavior to the libuv transport.

[davidfowl]

Sent a PR to fix it.

[davidfowl]

The exception case is interesting because libuv doesn't always close with an exception it seems but I think that was an assumption we made.

/cc @CesarBS @halter73

[tmds]

The libuv transport does the proper thing.
When the client sends a FIN, it completes the input without an exception.
When the reading is stopped due to output completing, it completes the input with an exception.

[davidfowl]

When the reading is stopped due to output completing, it completes the input with an exception.

How did you verify that? When does the read callback get triggered with a failure?

[tmds]

I didn't verify it, but I assume this is working code.

Input.Complete(new TaskCanceledException("The request was aborted"));

[davidfowl]

I guess this is only no null for a random UV error or a connection reset.

KestrelHttpServer/src/Microsoft.AspNetCore.Server.Kestrel.Transport.Libuv/Internal/LibuvConnection.cs

Line 183 in c2f15fc

Input.Complete(error);