[mosh-users] Problems with mosh-server and pselect syscall, fixed

[Alexander Chernyakhovsky]

Hi Ingo,

To add to Keith's explanation that this happens with Xen, I believe it primarily happens when the VM is booted with a different kernel image than the one that is installed on the disk. My understanding is that Amazon does this for EC2, to guarantee that the kernel is compatible with their Xen, but as you found, this causes confusion with userspace. I would suggest checking the output of "uname -a" against whatever is the distribution-installed kernel.

Sincerely,
-Alex
________________________________________
From: mosh-users-bounces at MIT.EDU [mosh-users-bounces at MIT.EDU] on behalf of Keith Winstein [keithw at MIT.EDU]
Sent: Friday, January 04, 2013 5:44 PM
To: Ingo Blechschmidt
Cc: mosh-users at mit.edu
Subject: Re: [mosh-users] Problems with mosh-server and pselect syscall,        fixed

Hello Ingo,

We think this problem happens when you have a userspace glibc that
doesn't match your kernel. (Because glibc would emulate the pselect()
call if it knew the kernel was before 2.6.16 and didn't support it
directly.) We've heard of this happening in Xen installations but I'm
not sure exactly how you are supposed to install Xen so this doesn't
happen. Thanks for the report and maybe somebody else knows better.

Best regards,
Keith

On Tue, Jan 1, 2013 at 1:01 PM, Ingo Blechschmidt <iblech at web.de> wrote:
> Hello,
>
> I experienced the following problem with mosh-1.2.3 on a virtual Debian
> Linux box (using Xen): mosh-server terminated itself instantly after
> starting. Using
>
>     $ mosh-server new -v
>
> revealed the error message
>
>     "select: Function not implemented".
>
> Looking into src/frontend/mosh-server.cc, src/util/select.h and
> experimenting with the example provided by the select(2) manpage, it
> seemed that the pselect syscall was not supported on my particular
> system; but I did not dig further to find out why.
>
> As a quick and dirty workaround, I modified src/util/select.h to use
> select() instead of pselect(), see attached patch. This resulted in a
> working and usable mosh-server, but I suspect this might very well cause
> some undesirable consequences; use at your own risk.
>
> To the developers: I'd be happy to provide additional information to fix
> this properly.
>
> Thanks!
> Ingo
>
> _______________________________________________
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> mosh-users at mit.edu
> http://mailman.mit.edu/mailman/listinfo/mosh-users
>
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