s4-repl: don't do double replication

When we replicate from a remote DC, we need to note the new uSN that
the local changes have resulted in, and modify the uSN that the notify
task uses to determine if it should send a ReplicaSync message back to
the remote DC. Otherwise we end up always triggering a ReplicaSync
every time we replicate from another DC

2 files changed, 36 insertions, 2 deletions

diff --git a/source4/dsdb/repl/drepl_out_helpers.c b/source4/dsdb/repl/drepl_out_helpers.c
index 168aacdde9..5c63c111f3 100644
--- a/source4/dsdb/repl/drepl_out_helpers.c
+++ b/source4/dsdb/repl/drepl_out_helpers.c
@@ -414,7 +414,8 @@ static void dreplsrv_op_pull_source_apply_changes_send(struct dreplsrv_op_pull_s
 							 &rf1,
 							 uptodateness_vector,
 							 &drsuapi->gensec_skey,
-							 st, NULL);
+							 st, NULL, 
+							 &st->op->source_dsa->notify_uSN);
 	if (!W_ERROR_IS_OK(status)) {
 		DEBUG(0,("Failed to commit objects: %s\n", win_errstr(status)));
 		composite_error(c, werror_to_ntstatus(status));
diff --git a/source4/dsdb/repl/replicated_objects.c b/source4/dsdb/repl/replicated_objects.c
index 2f4efc0fee..5ae622eeaa 100644
--- a/source4/dsdb/repl/replicated_objects.c
+++ b/source4/dsdb/repl/replicated_objects.c
@@ -212,7 +212,8 @@ WERROR dsdb_extended_replicated_objects_commit(struct ldb_context *ldb,
 					       const struct drsuapi_DsReplicaCursor2CtrEx *uptodateness_vector,
 					       const DATA_BLOB *gensec_skey,
 					       TALLOC_CTX *mem_ctx,
-					       struct dsdb_extended_replicated_objects **_out)
+					       struct dsdb_extended_replicated_objects **_out,
+					       uint64_t *notify_uSN)
 {
 	WERROR status;
 	const struct dsdb_schema *schema;
@@ -221,6 +222,7 @@ WERROR dsdb_extended_replicated_objects_commit(struct ldb_context *ldb,
 	const struct drsuapi_DsReplicaObjectListItemEx *cur;
 	uint32_t i;
 	int ret;
+	uint64_t seq_num1, seq_num2;
 
 	schema = dsdb_get_schema(ldb);
 	if (!schema) {
@@ -280,6 +282,14 @@ WERROR dsdb_extended_replicated_objects_commit(struct ldb_context *ldb,
 		return WERR_FOOBAR;
 	}
 
+	ret = dsdb_load_partition_usn(ldb, out->partition_dn, &seq_num1);
+	if (ret != LDB_SUCCESS) {
+		DEBUG(0,(__location__ " Failed to load partition uSN\n"));
+		talloc_free(out);
+		ldb_transaction_cancel(ldb);
+		return WERR_FOOBAR;		
+	}
+
 	ret = ldb_extended(ldb, DSDB_EXTENDED_REPLICATED_OBJECTS_OID, out, &ext_res);
 	if (ret != LDB_SUCCESS) {
 		DEBUG(0,("Failed to apply records: %s: %s\n",
@@ -290,6 +300,28 @@ WERROR dsdb_extended_replicated_objects_commit(struct ldb_context *ldb,
 	}
 	talloc_free(ext_res);
 
+	ret = ldb_transaction_prepare_commit(ldb);
+	if (ret != LDB_SUCCESS) {
+		DEBUG(0,(__location__ " Failed to prepare commit of transaction\n"));
+		talloc_free(out);
+		return WERR_FOOBAR;
+	}
+
+	ret = dsdb_load_partition_usn(ldb, out->partition_dn, &seq_num2);
+	if (ret != LDB_SUCCESS) {
+		DEBUG(0,(__location__ " Failed to load partition uSN\n"));
+		talloc_free(out);
+		ldb_transaction_cancel(ldb);
+		return WERR_FOOBAR;		
+	}
+
+	/* if this replication partner didn't need to be notified
+	   before this transaction then it still doesn't need to be
+	   notified, as the changes came from this server */	
+	if (seq_num2 > seq_num1 && seq_num1 <= *notify_uSN) {
+		*notify_uSN = seq_num2;
+	}
+
 	ret = ldb_transaction_commit(ldb);
 	if (ret != LDB_SUCCESS) {
 		DEBUG(0,(__location__ " Failed to commit transaction\n"));
@@ -297,6 +329,7 @@ WERROR dsdb_extended_replicated_objects_commit(struct ldb_context *ldb,
 		return WERR_FOOBAR;
 	}
 
+
 	DEBUG(2,("Replicated %u objects (%u linked attributes) for %s\n",
 		 out->num_objects, out->linked_attributes_count,
 		 ldb_dn_get_linearized(out->partition_dn)));