Xen devel - Jun 2006 - bug: Cannot create vbd / cannot create vif

Last week, I mentioned an error to xen-users an error I was receiving, 
relevant description provided below.  I''ve seen several mailing list 
posts  describing a similar problem as far back as December, 2005.  This 
seems to be a problem plaguing all Xen 3 releases (to
date).
>
> The error I receive is (approximately) ''(vif) could not be 
> connected''.  If I comment the ''vif='' line in the
domain''s
> configuration, I then receive ''(vbd) could not be
connected''.  Both
> messages were also followed by "Hotplug scripts not working."  (I
am
> using udev)
Upon review, I''m pretty certain the problem is happening when a new 
domain is created that is specifying a MAC address identical to that 
assigned to an existing guest domain.  When a new domain comes online 
with the conflicting MAC address, Xen will rightfully refuse to create 
the vif, and exits -- but it does NOT properly clean up.  After that 
point, Xen will refuse to create ANY new guest domains, even  if 
properly-configured.  The only way I am aware of to then create a new 
domain is to reboot the iron.  I haven''t yet found a workaround.

Once the system has encountered this problem, I see several variables 
within xenstore-ls associated with each of the domains which failed to 
''create''.  I manually removed the associated variable trees
with
xenstore-rm, but I still wasn''t able to create a new domain, again with
the message "(vdb) could not be connected".   Killing xenstored and 
restarting xend did not help, nor did nuking xenstored''s tdb file.

While we know it is already dangerous to allow incoming live migrations 
from untrusted networks, imagine if someone was to cause the 
above-described bug via a live migration?

Please let me know if you need further information to reproduce the 
error.  My host system is a PentiumD 830 /w 4gb memory -- that is a 
dual-core x86_64 processor.

Below is an excerpt from xenstore-ls showing information about a domain 
(rjackson) which was never created.. (I attempted to start it a few 
times, as you can see)

Thank you.

-- 
Eric Windisch


local = ""
 domain = ""
  0 = ""
   cpu = ""
    0 = ""
     availability = "online"
    1 = ""
     availability = "online"
   memory = ""
    target = "1896448"
   name = "Domain-0"
   console = ""
    limit = "1048576"
   vm = "/vm/00000000-0000-0000-0000-000000000000"
   domid = "0"
   backend = ""
    vbd = ""
     23 = ""
      2049 = ""
       domain = "rjackson"
       frontend = "/local/domain/23/device/vbd/2049"
       dev = "sda1"
       state = "5"
       params = "mapper/XenDomains-rjackson"
       mode = "w"
       frontend-id = "23"
       type = "phy"
      2050 = ""
       domain = "rjackson"
       frontend = "/local/domain/23/device/vbd/2050"
       dev = "sda2"
       state = "1"
       params = "mapper/Swap-rjackson"
       mode = "w"
       frontend-id = "23"
       type = "phy"
     24 = ""
      2049 = ""
       domain = "rjackson"
       frontend = "/local/domain/24/device/vbd/2049"
       dev = "sda1"
       state = "5"
       params = "mapper/XenDomains-rjackson"
       mode = "w"
       frontend-id = "24"
       type = "phy"
      2050 = ""
       domain = "rjackson"
       frontend = "/local/domain/24/device/vbd/2050"
       dev = "sda2"
       state = "1"
       params = "mapper/Swap-rjackson"
       mode = "w"
       frontend-id = "24"
       type = "phy"
     25 = ""
      2049 = ""
       domain = "rjackson"
       frontend = "/local/domain/25/device/vbd/2049"
       dev = "sda1"
       state = "5"
       params = "mapper/XenDomains-rjackson"
       mode = "w"
       frontend-id = "25"
       type = "phy"
      2050 = ""
       domain = "rjackson"
       frontend = "/local/domain/25/device/vbd/2050"
       dev = "sda2"
       state = "1"
       params = "mapper/Swap-rjackson"
       mode = "w"
       frontend-id = "25"
       type = "phy"

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On Fri, Jun 09, 2006 at 11:06:12AM -0400, Eric Windisch wrote:
> Last week, I mentioned an error to xen-users an error I was receiving, 
> relevant description provided below.  I''ve seen several mailing
list
> posts  describing a similar problem as far back as December, 2005.  This 
> seems to be a problem plaguing all Xen 3 releases (to date).
> >
> >The error I receive is (approximately) ''(vif) could not be 
> >connected''.  If I comment the ''vif='' line in
the domain''s
> >configuration, I then receive ''(vbd) could not be
connected''.  Both
> >messages were also followed by "Hotplug scripts not working."
(I am
> >using udev)
> 
> Upon review, I''m pretty certain the problem is happening when a
new
> domain is created that is specifying a MAC address identical to that 
> assigned to an existing guest domain.  When a new domain comes online 
> with the conflicting MAC address, Xen will rightfully refuse to create 
> the vif, and exits -- but it does NOT properly clean up.  After that 
> point, Xen will refuse to create ANY new guest domains, even  if 
> properly-configured.  The only way I am aware of to then create a new 
> domain is to reboot the iron.  I haven''t yet found a workaround.
> 
> Once the system has encountered this problem, I see several variables 
> within xenstore-ls associated with each of the domains which failed to 
> ''create''.  I manually removed the associated variable
trees with
> xenstore-rm, but I still wasn''t able to create a new domain, again
with
> the message "(vdb) could not be connected".   Killing xenstored
and
> restarting xend did not help, nor did nuking xenstored''s tdb file.
Please use xen-bugtool to collect your system''s logs, and submit those
-- I''ll
take a look.

Thanks,

Ewan.

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