Xen devel - Jan 2011 - [PATCH]: xl: catch invalid numeric domain ID

Hi,

if you run any domain specific xl command with an invalid (aka 
non-existing) numeric domain ID, the command does not abort, but 
proceeds with some bogus number:
# xl destroy 42
libxl: error: libxl.c:692:libxl_domain_destroy xc_domain_pause failed for 42
libxl: error: libxl_dm.c:705:libxl__destroy_device_model Couldn''t find 
device model''s pid: No such file or directory
libxl: error: libxl.c:696:libxl_domain_destroy 
libxl__destroy_device_model failed for 42
libxl: error: libxl_device.c:325:libxl__devices_destroy 
/local/domain/42/device is empty
libxl: error: libxl_dom.c:536:userdata_path unable to find domain info 
for domain 42: Success
libxl: error: libxl.c:713:libxl_domain_destroy xc_domain_destroy failed 
for 42

The attached patch catches a non-existing domain and returns early (as 
an invalid domain _name_ would do).
Please apply to Xen 4.1.0-rc.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>

-- 
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany


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Andre Przywara writes ("[PATCH]: xl: catch invalid numeric domain
ID"):
> if you run any domain specific xl command with an invalid (aka 
> non-existing) numeric domain ID, the command does not abort, but 
> proceeds with some bogus number:
Thanks, but I''m not 100% convinced that it is impossible to ever get
into a situation where a domain exists but has no name.  In that case,
this patch of yours would leave an undestroyable domain.

I think the right answer is to use libxl_domain_info to check whether
the domain exists.  It returns ERROR_INVAL, without logging anything,
if the domain does not exist.  On other failures xl destroy should
probably carry on and attempt to destroy the domain.

Ian.

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On 01/21/2011 08:03 PM, Ian Jackson wrote:
> Andre Przywara writes ("[PATCH]: xl: catch invalid numeric domain
ID"):
>> if you run any domain specific xl command with an invalid (aka
>> non-existing) numeric domain ID, the command does not abort, but
>> proceeds with some bogus number:
>
> Thanks, but I''m not 100% convinced that it is impossible to ever
get
> into a situation where a domain exists but has no name.  In that case,
> this patch of yours would leave an undestroyable domain.
>
> I think the right answer is to use libxl_domain_info to check whether
> the domain exists.  It returns ERROR_INVAL, without logging anything,
> if the domain does not exist.  On other failures xl destroy should
> probably carry on and attempt to destroy the domain.
OK, I looked around the bit, libxl_domain_info really seems to be the 
easiest solution. So please consider the attached patch. I am not 100% 
happy with it, actually I think find_domain should return an error 
value. In this case we could abort the commands gracefully (like xl list 
does) and avoid the rather impolite exit(2).
On the other hand I am not sure if fixing the 30 or so callers of 
find_domain() is appropriate in this state of development.
Please tell me if you prefer this more elaborated version and I will 
send a patch.

Regards,
Andre.

-- 
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany



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