[PATCH] samba-tool dbcheck: handle missing objectClass
botner at univention.de
Tue Mar 11 09:18:43 MDT 2014
> Felix: Any news on testing this with a genuinely corrupted network?
Unfortunately not, but I think your analysis is correct with regard to the USN
ordering related attribute skip. We had a case in our internal testing
environments which looked like a replication issue related to USN ordering,
for details see https://forge.univention.org/bugzilla/show_bug.cgi?id=33904 .
> Are all the failing installations all pure Samba?
> Does this only happen on domains with additional objectclasses, or also
> on domains with stock schema? Is the corruption across ALL DCs, or just
This happened in a domain without schema extensions. The corruption may vary
between DCs, but I'm not 100% sure about this. Cannot confirm this currently.
> Looking at the bug:
> and the code, I think I've found a possible cause.
> get_nc_changes_build_object() has this code in it:
> /* if the attribute has not changed, and it is not the
> instanceType then don't include it */
> if (md.ctr.ctr1.array[i].local_usn < highest_usn &&
> extended_op != DRSUAPI_EXOP_REPL_SECRET &&
> md.ctr.ctr1.array[i].attid !=
> DRSUAPI_ATTID_instanceType) continue;
> The purpose of this chunk is to avoid re-sending changes that the client
> already has. This would be particularly important for jpegPhoto, for
> However, if the highest USN the client thought it had seen was actually
> higher than the one for which it had seen all objects, then a 'new'
> object could be downloaded without all it's attributes.
> I think that is how this corruption happens. While disturbing, this
> also suggests that the fix is to force re-replication, not to delete the
> object, as on at least one DC, the whole correct object exists.
Yes, this would pretty much explain the behavior we have seen.
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