tcp connection is not closed if websocket goes down about cumulocity-remote-access-local-proxy

[toewsar]

First tests were successful. Thank you.

[reubenmiller]

@toewsar do you happen to have an easy way to reproduce it? I’d say the fix will be relatively easy (as some kind of shutdown signal is probably missing), but just finding the right spot might be more difficult.

[toewsar]

@reubenmiller it should possible to reproduce, by restarting the remote-access app in the device while a connection is running.

1. Start the proxy in server mode

host$ c8ylp server ABCD --env-file .env -c ssh --port 22222

2. Open a ssh connection

host$ ssh admin@localhost -p 22222

3. Disconnect the device from websocket (e.g. by pulling the cable)
4. You shoud see in the c8ylp output [c8ylp] INFO WebSocket Connection closed. Status: 1000 (NORMAL)
5. The local ssh is still open, but shoudn't

[switschel]

@reubenmiller I had this implemented in the previous version of c8ylp.

cumulocity-remote-access-local-proxy/c8ylp/websocket_client/ws_client.py

Line 155 in d355b36

if self.tcp_server.is_tcp_socket_available():

I think we can do something similar here:

cumulocity-remote-access-local-proxy/c8ylp/websocket_client/ws_client.py

Line 232 in 4abfc42

def _on_ws_close(self, _ws, close_status, close_reason):

We can use the proxy and call shutdown()? Anything that I'm missing?

[switschel]

It's also a question of expected behavior in server mode. In last version I expected that it runs forever, so on each disconnect of WS it tries to reconnect instead of terminating the whole proxy instance.

[toewsar]

Every protocol that requires a specific handshake at the beginning and does not send keepalive frames won't work if the client doesn't get informed about the connection abort.

[switschel]

For that reason we have to discuss what's the best scenario on web socket disconnect is:

1. Disconnecting the TCP client and shutting down the whole c8ylp instance - tcp-server is shutdown
2. Disconnecting the TCP client and keep the c8ylp alive - tcp-server is accepting new connections

I would prefer the 2. option but only in server mode, so we cannot just run "shutdown" (option 1) but have to implement a new function "disconnect" which disconnects the client but keeps the server alive.

[toewsar]

I would also prefer the 2. option.

[reubenmiller]

@toewsar This should be fixed now in v2.4.1. Please let use know if this is not the case.