Improper handling of fast-resumed domains by O/Cxenstored

[Andrii Sultanov <andriy.sultanov@xxxxxxxxxx>]

Both Oxenstored and Cxenstored don't properly handle a shutdown domain
(even if shutdown_code == SHUTDOWN_suspend) coming back because of
xc_domain_resume(fast=1).

Cxenstored correctly sends @introduceDomain watch events on the
initial INTRODUCE call:

     IN 0x1f78610 20260619 15:45:37 INTRODUCE (1 1044476 2 )
     CREATE connection 0x1f75870
     OUT 0x1f76f00 20260619 15:45:37 WATCH_EVENT (@introduceDomain domlist )
     OUT 0x1f76ce0 20260619 15:45:37 WATCH_EVENT (@introduceDomain 
squeezed )
     OUT 0x1f77c40 20260619 15:45:37 WATCH_EVENT (@introduceDomain  )
     OUT 0x1f78610 20260619 15:45:37 WATCH_EVENT (@introduceDomain  )
     OUT 0x1f78610 20260619 15:45:37 INTRODUCE (OK )

And it sends @releaseDomain when it notices dominfo.shutdown (without
checking for shutdown_code):

     OUT 0x1f76f00 20260619 15:46:56 WATCH_EVENT (@releaseDomain domlist )
     OUT 0x1f76ce0 20260619 15:46:56 WATCH_EVENT (@releaseDomain squeezed )
     OUT 0x1f77c40 20260619 15:46:56 WATCH_EVENT (@releaseDomain )
     OUT 0x1f78610 20260619 15:46:56 WATCH_EVENT (@releaseDomain )

But after fast resume, even though INTRODUCE returns successfully,
@introduceDomain watch events are not re-sent:

     IN 0x1f78610 20260619 15:47:06 INTRODUCE (1 1044476 2 )
     <----- no watch events
     OUT 0x1f78610 20260619 15:47:06 INTRODUCE (OK )

Oxenstored likewise avoids sending @introduceDomain for "re-connecting"
domains (which is what it thinks a domain coming back like this looks like).

RESUME does not re-send @introduceDomain either, it just marks the domain as
live internally in Cxenstored and is a no-op for Oxenstored.

This missing notification leads to all kinds of issues since the toolstacks
don't notice the resumed domain is back (at least on the XAPI side).

Is this a real issue or is the toolstack holding xenstored wrong here?

If it is, I see two possible options for handling this:

1) Don't consider SHUTDOWN_suspend domains as dead, only drop them when they
    are definitively gone. This avoids the @releaseDomain notification
    and hence doesn't require another @introduceDomain

2) Do actually send out @introduceDomain for thought-to-be-shutdown domains
    on INTRODUCE

Thoughts?



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