GNU bug report logs - #17653
24.3; Tramp doesn't detect ssh ControlMaster

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3; Tramp doesn't detect ssh ControlMaster
Date: Sat, 31 May 2014 16:04:33 +0200

(tramp-detect-ssh-controlmaster)
nil
(call-process "ssh" nil t nil "-o" "ControlMaster")
command-line line 0: missing argument.
255

The issue is that tramp-detect-ssh-controlmaster looks for the fixed
string "Missing ControlMaster argument", while my version of ssh returns
a differently worded error message.

On a related note -- there doesn't seem to be a way of working around that
without resorting to advice, there's no defvar to tweak.

-- Juliusz

Message #8 received at 17653 <at> debbugs.gnu.org (full text, mbox):

From: Michael Albinus <michael.albinus <at> gmx.de>
To: Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr>
Cc: 17653 <at> debbugs.gnu.org
Subject: Re: bug#17653: 24.3; Tramp doesn't detect ssh ControlMaster
Date: Sun, 01 Jun 2014 10:20:24 +0200

Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr> writes:

> (tramp-detect-ssh-controlmaster)
> nil
> (call-process "ssh" nil t nil "-o" "ControlMaster")
> command-line line 0: missing argument.
> 255
>
> The issue is that tramp-detect-ssh-controlmaster looks for the fixed
> string "Missing ControlMaster argument", while my version of ssh returns
> a differently worded error message.

In the current pretest of Emacs 24.4 as well in recent Tramp versions,
the defun `tramp-detect-ssh-controlmaster' is replaced by a defconst
`tramp-ssh-controlmaster-options'. The defcustom
`tramp-use-ssh-controlmaster-options' controls whether you use it.

> On a related note -- there doesn't seem to be a way of working around that
> without resorting to advice, there's no defvar to tweak.

The native way to fix this in Tramp is tweaking `tramp-methods'. Add a
new method "myssh" with your preferred arguments.

Confirmed, `tramp-methods' is under-documented. I could guide you in
case of problems.

> -- Juliusz

Best regards, Michael.

Message #11 received at 17653 <at> debbugs.gnu.org (full text, mbox):

From: Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr>
To: Michael Albinus <michael.albinus <at> gmx.de>
Cc: 17653 <at> debbugs.gnu.org
Subject: Re: bug#17653: 24.3; Tramp doesn't detect ssh ControlMaster
Date: Sun, 01 Jun 2014 13:52:27 +0200

>> The issue is that tramp-detect-ssh-controlmaster looks for the fixed
>> string "Missing ControlMaster argument", while my version of ssh returns
>> a differently worded error message.

> The native way to fix this in Tramp is tweaking `tramp-methods'. Add a
> new method "myssh" with your preferred arguments.

I know I can tweak it -- that's Emacs, I can advise any function -- but
that's not the issue.  I expect Emacs to work optimally out of the box on
an up-to-date Debian testing box, and this is not the case.

Ideally, tramp should use a less fragile method to check for ControlMaster
support; if that's not possible, it should at least use a regexp that's
permissive enough to work on recent OpenSSH.

Please fix Emacs to detect ControlMaster out of the box with recent Debian.

-- Juliusz

Message #14 received at 17653 <at> debbugs.gnu.org (full text, mbox):

From: Michael Albinus <michael.albinus <at> gmx.de>
To: Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr>
Cc: 17653 <at> debbugs.gnu.org
Subject: Re: bug#17653: 24.3; Tramp doesn't detect ssh ControlMaster
Date: Sun, 01 Jun 2014 17:42:06 +0200

Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr> writes:

>> The native way to fix this in Tramp is tweaking `tramp-methods'. Add a
>> new method "myssh" with your preferred arguments.
>
> I know I can tweak it -- that's Emacs, I can advise any function -- but
> that's not the issue.  I expect Emacs to work optimally out of the box on
> an up-to-date Debian testing box, and this is not the case.

I don't speak about advising a function. `tramp-methods' is a variable
intended for configuration.

> Ideally, tramp should use a less fragile method to check for ControlMaster
> support; if that's not possible, it should at least use a regexp that's
> permissive enough to work on recent OpenSSH.
>
> Please fix Emacs to detect ControlMaster out of the box with recent Debian.

Well, in Emacs 24.4 the situation will be more complex, because Tramp
doesn't search for ControlMaster only, but also for ControlPersist. One
regexp alone won't fit.

That's why there exists the defconst `tramp-ssh-controlmaster-options'.
You could change it at your will.

However, I will check whether the situation with Debian could be
enhanced, somehow.

> -- Juliusz

Best regards, Michael.

Message #19 received at 17653-done <at> debbugs.gnu.org (full text, mbox):

From: Michael Albinus <michael.albinus <at> gmx.de>
To: Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr>
Cc: 17653-done <at> debbugs.gnu.org
Subject: Re: bug#17653: 24.3; Tramp doesn't detect ssh ControlMaster
Date: Tue, 03 Jun 2014 09:55:37 +0200

Juliusz Chroboczek <jch <at> pps.univ-paris-diderot.fr> writes:

Hi Juliusz,

>> However, I will check whether the situation with Debian could be
>> enhanced, somehow.
>
> Please do, and thanks.

I've fixed it in the emacs-24 branch, which will become Emacs 24.4. It
is also fixed in the Tramp repository; Tramp 2.2.10 will be released
within one or two weeks.

> -- Juliusz

Best regards, Michael.

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