repl_meta_data: linked attributes use DRS sort order

Links come over the wire as if sorted by memcmp() on the binary blobs,
not as sorted by GUID_compare(). Until a few patches ago, a newly
joined DC would have its linked attributes in the memcmp order. This
restores that behaviour.

This comparison could be made more efficient by storing the GUID in
the original state, but it does not seem to be a bottleneck.

Signed-off-by:    Andrew Bartlett <abartlet@samba.org>
Pair-programmed-with: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>

1 files changed, 26 insertions, 2 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
index 47f05bda9fe..d818faebdf3 100644
--- a/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
+++ b/source4/dsdb/samdb/ldb_modules/repl_meta_data.c
@@ -1824,9 +1824,33 @@ static int really_parse_trusted_dn(TALLOC_CTX *mem_ctx, struct ldb_context *ldb,
 	return LDB_SUCCESS;
 }
 
+/*
+ * We choose, as the sort order, the same order as is used in DRS replication,
+ * which is the memcmp() order of the NDR GUID, not that obtained from
+ * GUID_compare().
+ *
+ * This means that sorted links will be in the same order as a new DC would
+ * see them.
+ */
+static int ndr_guid_compare(struct GUID *guid1, struct GUID *guid2)
+{
+	uint8_t v1_data[16];
+	struct ldb_val v1 = data_blob_const(v1_data, sizeof(v1_data));
+	uint8_t v2_data[16];
+	struct ldb_val v2 = data_blob_const(v2_data, sizeof(v2_data));
+
+	/* This can't fail */
+	ndr_push_struct_into_fixed_blob(&v1, guid1,
+					(ndr_push_flags_fn_t)ndr_push_GUID);
+	/* This can't fail */
+	ndr_push_struct_into_fixed_blob(&v2, guid2,
+					(ndr_push_flags_fn_t)ndr_push_GUID);
+	return data_blob_cmp(&v1, &v2);
+}
+
 static int parsed_dn_compare(struct parsed_dn *pdn1, struct parsed_dn *pdn2)
 {
-	return GUID_compare(&pdn1->guid, &pdn2->guid);
+	return ndr_guid_compare(&pdn1->guid, &pdn2->guid);
 }
 
 static int la_guid_compare_with_trusted_dn(struct compare_ctx *ctx,
@@ -1863,7 +1887,7 @@ static int la_guid_compare_with_trusted_dn(struct compare_ctx *ctx,
 		}
 	}
 
-	return GUID_compare(ctx->guid, &p->guid);
+	return ndr_guid_compare(ctx->guid, &p->guid);
 }