Re: tramp (2.6.0-pre master/1476b0d7a61ca5244eed81161c31d794fbd1e571); (setq tramp-use-ssh-controlmaster-options nil) unexpectedly required

[Michael Albinus]

Malcolm Cook <malcolm.cook@gmail.com> writes:

Hi Malcolm,

> I find in my environment that I must
>
> `(setq tramp-use-ssh-controlmaster-options nil)`
>
> in order for vanilla configuration of tramp to support locally display
> of remote X11
>
> Details:
>
> From my home Windows 10 laptop with Xming running I use `putty` to
> open
> a terminal over VPN with ${hosta} at work running CentOS7 where:
>
> shell: bash.
>
> .ssh/config
> Host *
>   TCPKeepAlive yes
>   ServerAliveInterval 120
>   ForwardAgent yes
>   ForwardX11 yes
>   ForwardX11Trusted yes
>   XAuthLocation /usr/bin/xauth
>
> On ${hosta} I run emacs, and use tramp to connect to another server,
> ${hostb}, on work's LAN, and can successfully open X11 applications
> only if
> tramp-use-ssh-controlmaster-options is nil.
>
> Example:
>
> emacs -Q -eval $'(progn (setq tramp-use-ssh-controlmaster-options nil)
> (find-file \"/ssh:${myUserName}@${hostb}:~/test.sh\") (shell))'
> type: xeyes<enter>
> result: xeyes program displays cartoon eyes
>
> This does not:
> emacs -Q -eval $'(progn  (setq tramp-use-ssh-controlmaster-options t )
> (find-file \"/ssh:${myUserName}@${hostb}:~/test.sh\") (shell))'
> type: xeyes<enter>
> result:
> PuTTY X11 proxy: Authorisation not recognised
> Error: Can't open display: localhost:16.0
>
> Perhaps I am abusing X11/emacs/tramp/ssh, but it seems ill-advised
> that
> such a change to default configuration should be required.
>
> All advice welcome.

The error message "PuTTY X11 proxy: Authorisation not recognised"
indicates, that this is rather a problem in PuTTY. Have you played with
the PuTTY setting "Share SSH connections if possible"? Enabling /
disabling it might make a difference.

Otherwise, I've tested shortly, if PuTTY is not in play, X11 forwarding
works in Tramp with and without enabling ControlMaster. I'm sorry that I
cannot help too much bringing PuTTY to play.

> Malcolm Cook

Best regards, Michel.