[Qemu-devel] pty/tty functions for BSD too

[Qemu-devel] pty/tty functions for BSD too

[Samuel Thibault]

Hello,

In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
them in upstream qemu too, as patched below?

Samuel

Index: vl.c
===================================================================
--- vl.c	(révision 5022)
+++ vl.c	(copie de travail)
@@ -2466,7 +2466,7 @@
 }
 #endif
 
-#if defined(__linux__) || defined(__sun__)
+#if defined(__linux__) || defined(__sun__) || defined(__NetBSD__) || defined(__OpenBSD__)
 
 typedef struct {
     int fd;
@@ -3816,7 +3816,7 @@
         return qemu_chr_open_pp(filename);
     } else
 #endif
-#if defined(__linux__) || defined(__sun__)
+#if defined(__linux__) || defined(__sun__) || defined(__NetBSD__) || defined(__OpenBSD__)
     if (strstart(filename, "/dev/", NULL)) {
         return qemu_chr_open_tty(filename);
     } else

Re: [Qemu-devel] pty/tty functions for BSD too

[Anthony Liguori]

Samuel Thibault wrote:
> Hello,
>
> In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
> them in upstream qemu too, as patched below?
>   

And you're sure that these functions compile/work on NetBSD/OpenBSD?  If 
so, we can enable them.

Regards,

Anthony Liguori

> Samuel
>
> Index: vl.c
> ===================================================================
> --- vl.c	(révision 5022)
> +++ vl.c	(copie de travail)
> @@ -2466,7 +2466,7 @@
>  }
>  #endif
>  
> -#if defined(__linux__) || defined(__sun__)
> +#if defined(__linux__) || defined(__sun__) || defined(__NetBSD__) || defined(__OpenBSD__)
>  
>  typedef struct {
>      int fd;
> @@ -3816,7 +3816,7 @@
>          return qemu_chr_open_pp(filename);
>      } else
>  #endif
> -#if defined(__linux__) || defined(__sun__)
> +#if defined(__linux__) || defined(__sun__) || defined(__NetBSD__) || defined(__OpenBSD__)
>      if (strstart(filename, "/dev/", NULL)) {
>          return qemu_chr_open_tty(filename);
>      } else
>
>
>   

Re: [Qemu-devel] pty/tty functions for BSD too

[Samuel Thibault]

Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
> Samuel Thibault wrote:
> >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
> >them in upstream qemu too, as patched below?
> >  
> 
> And you're sure that these functions compile/work on NetBSD/OpenBSD?

The defines are explicit in Xen, so I guess somebody tested it.  I
haven't myself.  I wonder why there is no FreeBSD however.

Samuel

Re: [Qemu-devel] pty/tty functions for BSD too

[Warner Losh]

From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: Re: [Qemu-devel] pty/tty functions for BSD too
Date: Mon, 18 Aug 2008 15:23:33 +0100

> Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
> > Samuel Thibault wrote:
> > >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
> > >them in upstream qemu too, as patched below?
> > >  
> > 
> > And you're sure that these functions compile/work on NetBSD/OpenBSD?
> 
> The defines are explicit in Xen, so I guess somebody tested it.  I
> haven't myself.  I wonder why there is no FreeBSD however.

The TTY/PTY code is 4.2BSD, so everybdoy has it...  Not sure about why
no FreeBSD.  I haven't looked at the code, but I thought there was a
different fork it took..

I've noticed many times in the past that the #ifdef sun and/or #ifdef
linux code works great on FreeBSD.

Warner

Re: [Qemu-devel] pty/tty functions for BSD too

[Anthony Liguori]

Warner Losh wrote:
> From: Samuel Thibault <samuel.thibault@ens-lyon.org>
> Subject: Re: [Qemu-devel] pty/tty functions for BSD too
> Date: Mon, 18 Aug 2008 15:23:33 +0100
>
>   
>> Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
>>     
>>> Samuel Thibault wrote:
>>>       
>>>> In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
>>>> them in upstream qemu too, as patched below?
>>>>  
>>>>         
>>> And you're sure that these functions compile/work on NetBSD/OpenBSD?
>>>       
>> The defines are explicit in Xen, so I guess somebody tested it.  I
>> haven't myself.  I wonder why there is no FreeBSD however.
>>     
>
> The TTY/PTY code is 4.2BSD, so everybdoy has it...  Not sure about why
> no FreeBSD.  I haven't looked at the code, but I thought there was a
> different fork it took..
>
> I've noticed many times in the past that the #ifdef sun and/or #ifdef
> linux code works great on FreeBSD.
>   

I hate to admit it, but autoconf really has it right here.

Instead of doing:

#if defined(__linux__) || defined(__FreeBSD__) || ...
fd = openpty();
#endif

we should have:

#ifdef HAVE_openpty
fd = openpty();
#endif

and do a configure check to see if there is a usable openpty.  It makes 
the code easier to maintain and you don't have to deal with all of this 
black magic wrt what individual OSes support.

Regards,

Anthony Liguori

> Warner
>
>
>   

Re: [Qemu-devel] pty/tty functions for BSD too

[Blue Swirl]

[-- Attachment #1: Type: text/plain, Size: 685 bytes --]

On 8/18/08, Samuel Thibault <samuel.thibault@ens-lyon.org> wrote:
> Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
>
> > Samuel Thibault wrote:
>  > >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
>  > >them in upstream qemu too, as patched below?
>  > >
>  >
>  > And you're sure that these functions compile/work on NetBSD/OpenBSD?
>
>
> The defines are explicit in Xen, so I guess somebody tested it.  I
>  haven't myself.  I wonder why there is no FreeBSD however.

The patch does not work on OpenBSD, because while openpty() is
available, ptsname() isn't.

I tested the attached version on OpenBSD and Linux, pty name is
printed correctly.

[-- Attachment #2: obsd_enable_pty_code.diff --]
[-- Type: plain/text, Size: 1605 bytes --]

Re: [Qemu-devel] pty/tty functions for BSD too

[Daniel P. Berrange]

On Mon, Aug 18, 2008 at 07:16:36PM +0300, Blue Swirl wrote:
> On 8/18/08, Samuel Thibault <samuel.thibault@ens-lyon.org> wrote:
> > Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
> >
> > > Samuel Thibault wrote:
> >  > >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
> >  > >them in upstream qemu too, as patched below?
> >  > >
> >  >
> >  > And you're sure that these functions compile/work on NetBSD/OpenBSD?
> >
> >
> > The defines are explicit in Xen, so I guess somebody tested it.  I
> >  haven't myself.  I wonder why there is no FreeBSD however.
> 
> The patch does not work on OpenBSD, because while openpty() is
> available, ptsname() isn't.
> 
> I tested the attached version on OpenBSD and Linux, pty name is
> printed correctly.

Passing a non-NULL value to openpty()'s name parameter is not safe

[quote openpty(1)]
BUGS
       Nobody knows how much space should be reserved for name.  So, call-
       ing openpty() or forkpty() with non-NULL name may not be secure.
[/quote]

If BSD has no other way to determine the PTY name, then at least it
should be conditionalized so that systems with ptsname() use it, only
falling back to using the 'name' arg to openpty() for OS lacking ptsname

Regards,
Daniel
-- 
|: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
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Re: [Qemu-devel] pty/tty functions for BSD too

[Blue Swirl]

On 8/18/08, Daniel P. Berrange <berrange@redhat.com> wrote:
> On Mon, Aug 18, 2008 at 07:16:36PM +0300, Blue Swirl wrote:
>  > On 8/18/08, Samuel Thibault <samuel.thibault@ens-lyon.org> wrote:
>  > > Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
>  > >
>  > > > Samuel Thibault wrote:
>  > >  > >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
>  > >  > >them in upstream qemu too, as patched below?
>  > >  > >
>  > >  >
>  > >  > And you're sure that these functions compile/work on NetBSD/OpenBSD?
>  > >
>  > >
>  > > The defines are explicit in Xen, so I guess somebody tested it.  I
>  > >  haven't myself.  I wonder why there is no FreeBSD however.
>  >
>  > The patch does not work on OpenBSD, because while openpty() is
>  > available, ptsname() isn't.
>  >
>  > I tested the attached version on OpenBSD and Linux, pty name is
>  > printed correctly.
>
>
> Passing a non-NULL value to openpty()'s name parameter is not safe
>
>  [quote openpty(1)]
>  BUGS
>        Nobody knows how much space should be reserved for name.  So, call-
>        ing openpty() or forkpty() with non-NULL name may not be secure.
>  [/quote]

Maybe in theory, but in practice the name will be
/dev/pty[0-9a-z][a-z] or /dev/pts/[0-9]* or something similar. Even if
they are not, PATH_MAX should be enough.

>  If BSD has no other way to determine the PTY name, then at least it
>  should be conditionalized so that systems with ptsname() use it, only
>  falling back to using the 'name' arg to openpty() for OS lacking ptsname

I'm not convinced (yet?) this will be worth it.

Re: [Qemu-devel] pty/tty functions for BSD too

[Blue Swirl]

On 8/18/08, Blue Swirl <blauwirbel@gmail.com> wrote:
> On 8/18/08, Daniel P. Berrange <berrange@redhat.com> wrote:
>  > On Mon, Aug 18, 2008 at 07:16:36PM +0300, Blue Swirl wrote:
>  >  > On 8/18/08, Samuel Thibault <samuel.thibault@ens-lyon.org> wrote:
>  >  > > Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a écrit :
>  >  > >
>  >  > > > Samuel Thibault wrote:
>  >  > >  > >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
>  >  > >  > >them in upstream qemu too, as patched below?
>  >  > >  > >
>  >  > >  >
>  >  > >  > And you're sure that these functions compile/work on NetBSD/OpenBSD?
>  >  > >
>  >  > >
>  >  > > The defines are explicit in Xen, so I guess somebody tested it.  I
>  >  > >  haven't myself.  I wonder why there is no FreeBSD however.
>  >  >
>  >  > The patch does not work on OpenBSD, because while openpty() is
>  >  > available, ptsname() isn't.
>  >  >
>  >  > I tested the attached version on OpenBSD and Linux, pty name is
>  >  > printed correctly.
>  >
>  >
>  > Passing a non-NULL value to openpty()'s name parameter is not safe
>  >
>  >  [quote openpty(1)]
>  >  BUGS
>  >        Nobody knows how much space should be reserved for name.  So, call-
>  >        ing openpty() or forkpty() with non-NULL name may not be secure.
>  >  [/quote]
>
>
> Maybe in theory, but in practice the name will be
>  /dev/pty[0-9a-z][a-z] or /dev/pts/[0-9]* or something similar. Even if
>  they are not, PATH_MAX should be enough.
>
>
>  >  If BSD has no other way to determine the PTY name, then at least it
>  >  should be conditionalized so that systems with ptsname() use it, only
>  >  falling back to using the 'name' arg to openpty() for OS lacking ptsname
>
>
> I'm not convinced (yet?) this will be worth it.

Glibc uses an internal PATH_MAX buffer. If the name does not fit, the
buffer will be doubled in size:
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/login/openpty.c?rev=1.8&content-type=text/x-cvsweb-markup&cvsroot=glibc

But in practice the pty will be allocated using getpt(), which uses
hard coded ptmx name:
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/sysdeps/unix/sysv/linux/getpt.c?rev=1.10&content-type=text/x-cvsweb-markup&cvsroot=glibc

And ptsname() is used to get the pty name, which uses either hard
coded buffer length of _PATH_DEVPTS or _PATH_TTY:
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/sysdeps/unix/sysv/linux/ptsname.c?rev=1.15&content-type=text/x-cvsweb-markup&cvsroot=glibc

OpenBSD forces the name to be in format "/dev/ptyXX":
http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libutil/pty.c?rev=1.15&content-type=text/x-cvsweb-markup

NetBSD is similar, except also /dev/ttyXX is possible:
http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libutil/pty.c?rev=1.29&content-type=text/x-cvsweb-markup

I still maintain that in reality, PATH_MAX should be enough.

Re: [Qemu-devel] pty/tty functions for BSD too

[Daniel P. Berrange]

On Mon, Aug 18, 2008 at 09:08:50PM +0300, Blue Swirl wrote:
> On 8/18/08, Blue Swirl <blauwirbel@gmail.com> wrote:
> > On 8/18/08, Daniel P. Berrange <berrange@redhat.com> wrote:
> >  >
> >  >  [quote openpty(1)]
> >  >  BUGS
> >  >        Nobody knows how much space should be reserved for name.  So, call-
> >  >        ing openpty() or forkpty() with non-NULL name may not be secure.
> >  >  [/quote]
> >
> >
> > Maybe in theory, but in practice the name will be
> >  /dev/pty[0-9a-z][a-z] or /dev/pts/[0-9]* or something similar. Even if
> >  they are not, PATH_MAX should be enough.
> >
> >
> >  >  If BSD has no other way to determine the PTY name, then at least it
> >  >  should be conditionalized so that systems with ptsname() use it, only
> >  >  falling back to using the 'name' arg to openpty() for OS lacking ptsname
> >
> >
> > I'm not convinced (yet?) this will be worth it.
> 
> Glibc uses an internal PATH_MAX buffer. If the name does not fit, the
> buffer will be doubled in size:
> http://sourceware.org/cgi-bin/cvsweb.cgi/libc/login/openpty.c?rev=1.8&content-type=text/x-cvsweb-markup&cvsroot=glibc
> 
> But in practice the pty will be allocated using getpt(), which uses
> hard coded ptmx name:
> http://sourceware.org/cgi-bin/cvsweb.cgi/libc/sysdeps/unix/sysv/linux/getpt.c?rev=1.10&content-type=text/x-cvsweb-markup&cvsroot=glibc
> 
> And ptsname() is used to get the pty name, which uses either hard
> coded buffer length of _PATH_DEVPTS or _PATH_TTY:
> http://sourceware.org/cgi-bin/cvsweb.cgi/libc/sysdeps/unix/sysv/linux/ptsname.c?rev=1.15&content-type=text/x-cvsweb-markup&cvsroot=glibc
> 
> OpenBSD forces the name to be in format "/dev/ptyXX":
> http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libutil/pty.c?rev=1.15&content-type=text/x-cvsweb-markup
> 
> NetBSD is similar, except also /dev/ttyXX is possible:
> http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libutil/pty.c?rev=1.29&content-type=text/x-cvsweb-markup
> 
> I still maintain that in reality, PATH_MAX should be enough.

Ok, I guess its safe enough in practice then.

Regards,
Daniel
-- 
|: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
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Re: [Qemu-devel] pty/tty functions for BSD too

[Jamie Lokier]

Blue Swirl wrote:
> And ptsname() is used to get the pty name, which uses either hard
> coded buffer length of _PATH_DEVPTS or _PATH_TTY:
> http://sourceware.org/cgi-bin/cvsweb.cgi/libc/sysdeps/unix/sysv/linux/ptsname.c?rev=1.15&content-type=text/x-cvsweb-markup&cvsroot=glibc
> 
> OpenBSD forces the name to be in format "/dev/ptyXX":
> http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libutil/pty.c?rev=1.15&content-type=text/x-cvsweb-markup
> 
> NetBSD is similar, except also /dev/ttyXX is possible:
> http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libutil/pty.c?rev=1.29&content-type=text/x-cvsweb-markup

Other platforms use slightly longer names, but I've never heard of one
that wouldn't fit into PATH_MAX - assuming PATH_MAX is sane.

I'd still use ptsname()/ptsname_r() when available though.

-- Jamie

Re: [Qemu-devel] pty/tty functions for BSD too

[Bernhard Reutner-Fischer]

On Mon, Aug 18, 2008 at 09:08:50PM +0300, Blue Swirl wrote:

>Glibc uses an internal PATH_MAX buffer. If the name does not fit, the
>buffer will be doubled in size:
>http://sourceware.org/cgi-bin/cvsweb.cgi/libc/login/openpty.c?rev=1.8&content-type=text/x-cvsweb-markup&cvsroot=glibc
>
>But in practice the pty will be allocated using getpt(), which uses

They, too, should switch to posix_openpt(), fwiw.

Re: [Qemu-devel] pty/tty functions for BSD too

[François Revol]

> On Mon, Aug 18, 2008 at 09:08:50PM +0300, Blue Swirl wrote:
>
> >Glibc uses an internal PATH_MAX buffer. If the name does not fit,
> > the
> >buffer will be doubled in size:
> >http://sourceware.org/cgi-bin/cvsweb.cgi/libc/login/openpty.c?rev=1.8&content-type=text/x-cvsweb-markup&cvsroot=glibc
> > > >
> >But in practice the pty will be allocated using getpt(), which uses
>
> They, too, should switch to posix_openpt(), fwiw.

Please don't start dictating what an OS should have or not, or this
will turn into ffmpeg-like porting flames.
It's not about porting all OSes to QEMU, but porting QEMU to OSes :P

François.

Re: [Qemu-devel] pty/tty functions for BSD too

[Bernhard Reutner-Fischer]

On Tue, Aug 19, 2008 at 01:21:27PM +0200, François Revol wrote:
>> On Mon, Aug 18, 2008 at 09:08:50PM +0300, Blue Swirl wrote:
>>
>> >Glibc uses an internal PATH_MAX buffer. If the name does not fit,
>> > the
>> >buffer will be doubled in size:
>> >http://sourceware.org/cgi-bin/cvsweb.cgi/libc/login/openpty.c?rev=1.8&content-type=text/x-cvsweb-markup&cvsroot=glibc
>> > > >
>> >But in practice the pty will be allocated using getpt(), which uses
>>
>> They, too, should switch to posix_openpt(), fwiw.
>
>Please don't start dictating what an OS should have or not, or this

I'm not talking about an OS but a libc that should try to use standard
conforming functions where possible. Whether or not they provide the
non-standard getpt() for legacy applications is not the question.

A libc that is POSIX.1-2001 compliant has to provide posix_openpt()
anyway, thus it doesn't make too much sense to use the non-standard
getpt() but i guess nobody cared enough to adjust glibc yet.

>will turn into ffmpeg-like porting flames.
>It's not about porting all OSes to QEMU, but porting QEMU to OSes :P

Well, i talked about glibc interna, not QEMU interna, so my comment was
a bit OT, admittedly ;)

Re: [Qemu-devel] pty/tty functions for BSD too

[Samuel Thibault]

Bernhard Reutner-Fischer, le Tue 19 Aug 2008 13:40:29 +0200, a écrit :
> A libc that is POSIX.1-2001 compliant has to provide posix_openpt()
> anyway, thus it doesn't make too much sense to use the non-standard
> getpt() but i guess nobody cared enough to adjust glibc yet.

Err, glibc does have posix_openpt, in getpt.c

Samuel

Re: [Qemu-devel] pty/tty functions for BSD too

[Klaus Heinz]

Samuel Thibault wrote:

> Err, glibc does have posix_openpt, in getpt.c

As have FreeBSD and NetBSD in their currently supported releases (6/7
for FreeBSD, 3/4 for NetBSD).

ciao
     Klaus

Re: [Qemu-devel] pty/tty functions for BSD too

[Blue Swirl]

[-- Attachment #1: Type: text/plain, Size: 340 bytes --]

On 8/19/08, Klaus Heinz <k.heinz@augacht.kh-22.de> wrote:
> Samuel Thibault wrote:
>
>  > Err, glibc does have posix_openpt, in getpt.c
>
>
> As have FreeBSD and NetBSD in their currently supported releases (6/7
>  for FreeBSD, 3/4 for NetBSD).

Here's an updated patch that avoids ptsname only on OpenBSD and
enables pty also for FreeBSD.

[-- Attachment #2: obsd_enable_pty_code.diff --]
[-- Type: plain/text, Size: 1772 bytes --]

Re: [Qemu-devel] pty/tty functions for BSD too

[Todd T. Fries]

>From the OpenBSD man page...

DESCRIPTION
     The openpty(), login_tty(), and forkpty() functions perform manipulations
     on ttys and pseudo-ttys.

     The openpty() function finds an available pseudo-tty and returns file de-
     scriptors for the master and slave in amaster and aslave.  If name is
     non-null, the filename of the slave is returned in name (a string of at
     least 16 characters).  If termp is non-null, the terminal parameters of
     the slave will be set to the values in termp.  If winp is non-null, the
     window size of the slave will be set to the values in winp.

     The openpty() function works in the following way: first it attempts to
     allocate the pseudo-tty through the /dev/ptm device (see pty(4) for de-
     tails) and if that fails it searches for a free pseudo-tty by iterating
     through all existing pseudo-tty devices in /dev.  When a free pseudo-tty
     is found, its ownership is changed to the UID of the caller, permissions
     are set to correct values, and all earlier uses of that device are re-
     voked (see revoke(2) for details).  The first method can work for any us-
     er, the second method requires super-user privileges in most cases.

In OpenBSD, it's a pretty safe bet that 16chars is overkill.  The tty and/or
pty name will never be longer than /dev/?ty??.

Thanks,
-- 
Todd Fries .. todd@fries.net

 _____________________________________________
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Penned by Daniel P. Berrange on 20080818 17:26.18, we have:
| On Mon, Aug 18, 2008 at 07:16:36PM +0300, Blue Swirl wrote:
| > On 8/18/08, Samuel Thibault <samuel.thibault@ens-lyon.org> wrote:
| > > Anthony Liguori, le Mon 18 Aug 2008 09:06:41 -0500, a ?crit :
| > >
| > > > Samuel Thibault wrote:
| > >  > >In Xen, pty/tty functions are enabled for BSD too, shouldn't we enable
| > >  > >them in upstream qemu too, as patched below?
| > >  > >
| > >  >
| > >  > And you're sure that these functions compile/work on NetBSD/OpenBSD?
| > >
| > >
| > > The defines are explicit in Xen, so I guess somebody tested it.  I
| > >  haven't myself.  I wonder why there is no FreeBSD however.
| > 
| > The patch does not work on OpenBSD, because while openpty() is
| > available, ptsname() isn't.
| > 
| > I tested the attached version on OpenBSD and Linux, pty name is
| > printed correctly.
| 
| Passing a non-NULL value to openpty()'s name parameter is not safe
| 
| [quote openpty(1)]
| BUGS
|        Nobody knows how much space should be reserved for name.  So, call-
|        ing openpty() or forkpty() with non-NULL name may not be secure.
| [/quote]
| 
| If BSD has no other way to determine the PTY name, then at least it
| should be conditionalized so that systems with ptsname() use it, only
| falling back to using the 'name' arg to openpty() for OS lacking ptsname
| 
| Regards,
| Daniel
| -- 
| |: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
| |: http://libvirt.org  -o-  http://virt-manager.org  -o-  http://ovirt.org :|
| |: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
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|