Steps to reproduce: $ cat ~/.ssh/config ControlMaster auto ControlPath ~/.ssh/connections/%r@%h:%p ControlPersist 1 Host workstation HostName remote.example.com HostKeyAlias workstation ForwardX11 yes ForwardX11Timeout 10h AddKeysToAgent yes ForwardAgent yes With two local terminal sessions A and B. A: ssh workstation B: ssh workstation A: logout The ssh connection to workstation is immediately completed but stderr gets an extra message Shared connection to remote.example.com closed. This is problematic for two reasons: (1) The message is incorrect. The shared connection is in fact still running because connection in terminal B is still using it. The message should say "Disconnected from shared connection to %s". (2) The whole message is only suitable for debugging and should not be emitted in normal cases. I understand that it would be nice with `-v`. The problematic code is at https://github.com/openssh/openssh-portable/blob/396d32f3a1a16e54df2a76b2a9b237868580dcbe/mux.c#L2081 Note that all the other mux related messages are emitted with debug1: ssh -v workstation ... debug1: Authentication succeeded (publickey). Authenticated to remote.example.com ([1.2.3.4]:22). debug1: setting up multiplex master socket debug1: channel 0: new [/home/USER/.ssh/connections/USER@remote.example.com:22] debug1: control_persist_detach: backgrounding master process debug1: forking to background debug1: Entering interactive session. debug1: pledge: id debug1: multiplexing control connection debug1: channel 1: new [mux-control] debug1: channel 2: new [client-session] debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0 debug1: Requesting X11 forwarding with authentication spoofing. debug1: Requesting authentication agent forwarding. debug1: Sending environment. ... debug1: mux_client_request_session: master session id: 2 As a result, I would suggest that the above code should be fixed to emit the message at level debug1 only AND the actual message content should be fixed, too. Note that the actual verbose output already says during disconnect ... debug1: client_input_channel_req: channel 2 rtype exit-status reply 0 debug1: client_input_channel_req: channel 2 rtype eow@openssh.com reply 0 debug1: channel 2: free: client-session, nchannels 3 debug1: channel 1: free: mux-control, nchannels 2 Shared connection to remote.example.com closed. USER@LOCALDOMAIN:~ $ debug1: ControlPersist timeout expired debug1: channel 0: free: /home/USER/.ssh/connections/USER@remote.example.com:22, nchannels 1 Transferred: sent 3684, received 3904 bytes, in 158.6 seconds Bytes per second: sent 23.2, received 24.6 debug1: Exit status -1 Note how the message in question is emitted and ssh process ends (local prompt is displayed) before ControlPersist timout actually happens.
See also: https://unix.stackexchange.com/a/203346/20336
I'm not seeing a problem here. The message is sent to stderr, IMO accurate and can be suppressed using -q/Loglevel=quiet
> I'm not seeing a problem here. [About issue (2):] All the other messages related to mux handling are debug1: debug1: setting up multiplex master socket debug1: control_persist_detach: backgrounding master process debug1: forking to background Why does this one specific message should be silenced only with Loglevel=quiet? I'd expect stderr (literally "standard error stream") to stay quiet by *default* unless there is at least one error. If I use verbose log level, then sure, emit these messages. > The message is sent to stderr, IMO accurate [...] [About issue (1):] Did you understand that that the shared connection *is not closed* despite the fact that the message says so? The process emitting that message is detaching from the shared connection but the shared connection is active and will not be closed because of process "B" in the example still using it. My point is that (1) the message is incorrect and (2) the message is not worth emitting unless verbose log is requested. With the current log level, even if you disable all warnings, errors and fatal errors(!), this message is still emitted. If you disagree with either (1) or (2), could you elaborate your reasoning?