bug#21727: Tramp hangs in Windows

bug#21727: Tramp hangs in Windows

[Arni Magnusson]

The official Windows builds of Emacs 24.4 and 24.5 hang when I run

   M-x load-library tramp [RET]

Earlier Emacs versions (24.3, 24.2, 24.1, 23.4) do not have this problem. 
To get Emacs out of the frozen state, I can either kill some cmd.exe 
subprocesses or kill Emacs itself.

I get the same behavior on Windows XP and Windows 7, and I'm invoking 
Emacs with -Q factory settings. Some changes between 24.3 and 24.4 are 
probably causing the problem I'm having.

What I'm after is not to get Tramp functionality in Windows, but simply to 
run Emacs commands that do some Tramp checks. These functions run fine on 
the Linux side but hang in Windows. As far as I can tell, load-library 
tramp is intended to run in Emacs in Windows, like in earlier versions. My 
WinXP and Win7 machines are quite differently configured from each other, 
so I hope this problem is reproducible.

Thanks,

Arni

bug#21727: Tramp hangs in Windows

[Michael Albinus]

Arni Magnusson <arnima@hafro.is> writes:

Hi Arni,

> The official Windows builds of Emacs 24.4 and 24.5 hang when I run
>
>   M-x load-library tramp [RET]
>
> Earlier Emacs versions (24.3, 24.2, 24.1, 23.4) do not have this
> problem. To get Emacs out of the frozen state, I can either kill some
> cmd.exe subprocesses or kill Emacs itself.

There were bug reports 20015 and 21504, which have reported similar
problems. The problem was improper DNS setting on the local host.

Could it be, that you suffer from the same problem?

> Thanks,
>
> Arni

Best regards, Michael.

bug#21727: Tramp hangs in Windows

[Arni Magnusson]

Thank you for looking into this, Michael.

You are right, this problem is machine-specific. I tried loading Tramp in 
Emacs 24.5 on my colleague's Windows 7 laptop (next door office) and it 
works.

Alas, I'm not able to determine what is improper about my DNS settings, if 
that is the case. All settings seem to be set to default (obtain DNS 
server addresss automatically) and no network-related applications show 
any symptoms of improper DNS settings. They all work smoothly (Putty, 
wget, Firefox, Skype, etc.), both on the wireless at home and the ethernet 
at work. As a simple test, I tried unplugging the ethernet cable to go 
offline, but Tramp still hangs.

My best workaround at present is to use Emacs 24.3, but that's not a very 
good long-term solution...

The Linux commands in bug thread 20015 do not apply to diagnose the 
problem in native Windows. Can you suggest some test I can run to analyze 
what is causing the problem?

Thanks,

Arni



On Thu, 22 Oct 2015, Michael Albinus wrote:

> Arni Magnusson <arnima@hafro.is> writes:
>
> Hi Arni,
>
>> The official Windows builds of Emacs 24.4 and 24.5 hang when I run
>>
>>   M-x load-library tramp [RET]
>>
>> Earlier Emacs versions (24.3, 24.2, 24.1, 23.4) do not have this 
>> problem. To get Emacs out of the frozen state, I can either kill some 
>> cmd.exe subprocesses or kill Emacs itself.
>
> There were bug reports 20015 and 21504, which have reported similar 
> problems. The problem was improper DNS setting on the local host.
>
> Could it be, that you suffer from the same problem?
>
>> Thanks,
>>
>> Arni
>
> Best regards, Michael.
>

bug#21727: Tramp hangs in Windows

[Eli Zaretskii]

> Date: Wed, 21 Oct 2015 18:24:22 +0000 (UTC)
> From: Arni Magnusson <arnima@hafro.is>
> 
> The official Windows builds of Emacs 24.4 and 24.5 hang when I run
> 
>    M-x load-library tramp [RET]

It doesn't hang for me when I try that here.

bug#21727: Tramp hangs in Windows

[Michael Albinus]

Arni Magnusson <arnima@hafro.is> writes:

Hi Arni,

> Thank you for looking into this, Michael.
>
> You are right, this problem is machine-specific. I tried loading Tramp
> in Emacs 24.5 on my colleague's Windows 7 laptop (next door office)
> and it works.

Good to know.

> Alas, I'm not able to determine what is improper about my DNS
> settings, if that is the case. All settings seem to be set to default
> (obtain DNS server addresss automatically) and no network-related
> applications show any symptoms of improper DNS settings. They all work
> smoothly (Putty, wget, Firefox, Skype, etc.), both on the wireless at
> home and the ethernet at work. As a simple test, I tried unplugging
> the ethernet cable to go offline, but Tramp still hangs.

No, that's not the point. Tramp wants to check some ssh arguments, and
tries to contact an *inalid* host name on purpose. If DNS is configured
properly, there will be an immediate reaction that this is an invalid FQDN.

> The Linux commands in bug thread 20015 do not apply to diagnose the
> problem in native Windows. Can you suggest some test I can run to
> analyze what is causing the problem?

Well, I don't run Windows personally, so my advice might be wrong. But
you could open a cmd.exe window, and try

# ssh -o ControlPath=%C host.does.not.exist

Likely, it will hang for you.

An alternative could be to install Emacs 25.0.50. This works pretty
stable, and Tramp has changed its test to be used w/o DNS. You find
weekly snapshots at <https://sourceforge.net/projects/emacs-bin/>.

> Thanks,
>
> Arni

Best regards, Michael.

bug#21727: Tramp hangs in Windows

[Arni Magnusson]

>> Alas, I'm not able to determine what is improper about my DNS settings, 
>> if that is the case.

Okay, after more experiments I have found out that the problem is not 
related to DNS settings, after all.


> Well, I don't run Windows personally, so my advice might be wrong. But 
> you could open a cmd.exe window, and try
>
> # ssh -o ControlPath=%C host.does.not.exist
>
> Likely, it will hang for you.

Yes, indeed, that was a useful test. The problem is that Windows XP and 
Windows 7 do not have a built-in ssh command.

What happens when I type ssh on my Windows machines is that it invokes 
some random ssh program that happens to be on my machines, but doesn't 
support the options that Linux users might expect. In other words, calling 
'ssh' on a Windows machine with some options will result in an undefined 
and unpredictable behavior - in my case, hanging.


> An alternative could be to install Emacs 25.0.50. This works pretty 
> stable, and Tramp has changed its test to be used w/o DNS. You find 
> weekly snapshots at <https://sourceforge.net/projects/emacs-bin/>.

That's it. Emacs 25 loads Tramp without getting tangled up in the random 
ssh program that's installed on my machines. I'm sold.


Thanks for your help in identifying and solving the problem,

Arni

bug#21727: Tramp hangs in Windows

[Michael Albinus]

tags 21727 notabug

Arni Magnusson <arnima@hafro.is> writes:

> What happens when I type ssh on my Windows machines is that it invokes
> some random ssh program that happens to be on my machines, but doesn't
> support the options that Linux users might expect. In other words,
> calling 'ssh' on a Windows machine with some options will result in an
> undefined and unpredictable behavior - in my case, hanging.
>
>> An alternative could be to install Emacs 25.0.50. This works pretty
>> stable, and Tramp has changed its test to be used w/o DNS. You find
>> weekly snapshots at <https://sourceforge.net/projects/emacs-bin/>.
>
> That's it. Emacs 25 loads Tramp without getting tangled up in the
> random ssh program that's installed on my machines. I'm sold.

Thanks for your tests, so it isn't a Tramp bug. I'm closing this report.

> Thanks for your help in identifying and solving the problem,
>
> Arni

Best regards, Michael.