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replmd: Try to add forward-link for unknown cross-partition links

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Previously Samba would just drop cross-partition links where the link
target object is unknown. Instead, what we want to do is try to add the
forward link for the GUID specified. We can't add the backlink because
we don't know the target, however, dbcheck should be able to fix any
missing backlinks.

The new behaviour should now mean dbcheck will detect the problem and be
able to fix it. It's still not ideal, but it's better than dropping the
link completely.

I've updated the log so that it has higher severity and tells the user
what they need to do to fix it.

These changes now mean that the selftests now detect an error - instead
of completely dropping the serverReference, we now have a missing
backlink. I've updated the selftests to fix up any missing
serverReference backlinks before running dbcheck.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Garming Sam <garming@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
BUG: https://bugzilla.samba.org/show_bug.cgi?id=12972
This commit is contained in:
Tim Beale 2017-07-24 16:20:58 +12:00 committed by Andrew Bartlett
parent 89cf5c3f76
commit fae5df891c
2 changed files with 15 additions and 7 deletions
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14
source4/dsdb/samdb/ldb_modules/repl_meta_data.c
View File

@ -374,8 +374,9 @@ static int replmd_process_backlink(struct ldb_module *module, struct la_backlink
ret = dsdb_module_dn_by_guid(module, frame, &bl->target_guid, &target_dn, parent);
if (ret != LDB_SUCCESS) {
struct GUID_txt_buf guid_str;
DEBUG(2,(__location__ ": WARNING: Failed to find target DN for linked attribute with GUID %s\n",
GUID_buf_string(&bl->target_guid, &guid_str)));
DBG_WARNING("Failed to find target DN for linked attribute with GUID %s\n",
GUID_buf_string(&bl->target_guid, &guid_str));
DBG_WARNING("Please run 'samba-tool dbcheck' to resolve any missing backlinks.\n");
talloc_free(frame);
return LDB_SUCCESS;
}
@ -6816,15 +6817,14 @@ static int replmd_check_target_exists(struct ldb_module *module,
} else {
/*
* TODO:
* We don't handle cross-partition links well here (we
* could potentially lose them), but don't fail the
* replication.
* The target of the cross-partition link is missing.
* Continue and try to at least add the forward-link.
* This isn't great, but if we can add a partial link
* then it's better than nothing.
*/
DEBUG(2,("Failed to resolve cross-partition link between %s and %s\n",
ldb_dn_get_linearized(source_dn),
ldb_dn_get_linearized(dsdb_dn->dn)));
*ignore_link = true;
}
} else if (target_res->count != 1) {
ldb_asprintf_errstring(ldb, "More than one object found matching objectGUID %s\n",

8
testprogs/blackbox/dbcheck.sh
View File

@ -27,6 +27,13 @@ dbcheck_fix_stale_links() {
$BINDIR/samba-tool dbcheck --quiet --fix --yes remove_plausible_deleted_DN_links --attrs="member msDS-NC-Replica-Locations msDS-NC-RO-Replica-Locations" --cross-ncs $ARGS
}
# This list of attributes can be freely extended
dbcheck_fix_crosspartition_backlinks() {
# we may not know the target yet when we receive a cross-partition link,
# which can result in a missing backlink
$BINDIR/samba-tool dbcheck --quiet --fix --yes fix_all_missing_backlinks --attrs="serverReference" --cross-ncs $ARGS
}
# This test shows that this does not do anything to a current
# provision (that would be a bug)
dbcheck_reset_well_known_acls() {
@ -47,6 +54,7 @@ force_modules() {
dbcheck_fix_one_way_links
dbcheck_fix_stale_links
dbcheck_fix_crosspartition_backlinks
testit "dbcheck" dbcheck
testit "reindex" reindex
testit "fixed_attrs" fixed_attrs