Race Condition in Agent may lead to first data message to arrive at server before channel open confirmation

[obiltschnig]

Server Log excerpt:

2023-01-19 15:09:40.930 [Debug] PortReflector<27>: Adding client connection for target bac45e53-7c19-4bf1-921b-15f241f9a756, port 5900
2023-01-19 15:09:40.930 [Debug] PortReflector<27>: Close timeout for channel 2 to target bac45e53-7c19-4bf1-921b-15f241f9a756.
2023-01-19 15:09:40.930 [Debug] PortReflector<27>: Now 2 channels to target bac45e53-7c19-4bf1-921b-15f241f9a756.
2023-01-19 15:09:40.978 [Debug] PortReflector<27>: Opening channel 4 to target bac45e53-7c19-4bf1-921b-15f241f9a756, port 5900.
2023-01-19 15:09:40.978 [Information] Security<27>: Successful WebTunnel client access by user '820b9535-52fb-418b-9f72-30e3e16b2896_1044' to device 'bac45e53-7c19-4bf1-921b-15f241f9a756'.
2023-01-19 15:09:40.978 [Information] osp.web.access<27>: GET /my-devices/websockify?port=5900 HTTP/1.1
2023-01-19 15:09:41.127 [Error] PortReflector<15>: Received unexpected data message for channel 4 on target bac45e53-7c19-4bf1-921b-15f241f9a756
2023-01-19 15:09:41.127 [Debug] PortReflector<15>: Channel 4 to target bac45e53-7c19-4bf1-921b-15f241f9a756 opened.

The responsible code is in RemotePortForwarder::openChannel(). The socket is added to the socket dispatcher before the WT_OP_OPEN_CONFIRM message is sent.