NAMESTORE — Storage of local GNS zones — GNUnet documentation

# NAMESTORE — Storage of local GNS zones

The NAMESTORE subsystem provides persistent storage for local GNS zone information. All local GNS zone information are managed by NAMESTORE. It provides both the functionality to administer local GNS information (e.g. delete and add records) as well as to retrieve GNS information (e.g to list name information in a client). NAMESTORE does only manage the persistent storage of zone information belonging to the user running the service: GNS information from other users obtained from the DHT are stored by the NAMECACHE subsystem.

NAMESTORE uses a plugin-based database backend to store GNS information with good performance. Here sqlite, MySQL and PostgreSQL are supported database backends. NAMESTORE clients interact with the IDENTITY subsystem to obtain cryptographic information about zones based on egos as described with the IDENTITY subsystem, but internally NAMESTORE refers to zones using the ECDSA private key. In addition, it collaborates with the NAMECACHE subsystem and stores zone information when local information are modified in the GNS cache to increase look-up performance for local information.

NAMESTORE provides functionality to look-up and store records, to iterate over a specific or all zones and to monitor zones for changes. NAMESTORE functionality can be accessed using the NAMESTORE api or the NAMESTORE command line tool.

## libgnunetnamestore

To interact with NAMESTORE clients first connect to the NAMESTORE service using the `GNUNET_NAMESTORE_connect` passing a configuration handle. As a result they obtain a NAMESTORE handle, they can use for operations, or NULL is returned if the connection failed.

To disconnect from NAMESTORE, clients use `GNUNET_NAMESTORE_disconnect` and specify the handle to disconnect.

NAMESTORE internally uses the ECDSA private key to refer to zones. These private keys can be obtained from the IDENTITY subsystem. Here egos can be used to refer to zones or the default ego assigned to the GNS subsystem can be used to obtained the master zone's private key.

### Editing Zone Information

NAMESTORE provides functions to lookup records stored under a label in a zone and to store records under a label in a zone.

To store (and delete) records, the client uses the `GNUNET_NAMESTORE_records_store` function and has to provide namestore handle to use, the private key of the zone, the label to store the records under, the records and number of records plus an callback function. After the operation is performed NAMESTORE will call the provided callback function with the result GNUNET_SYSERR on failure (including timeout/queue drop/failure to validate), GNUNET_NO if content was already there or not found GNUNET_YES (or other positive value) on success plus an additional error message.

Records are deleted by using the store command with 0 records to store. It is important to note, that records are not merged when records exist with the label. So a client has first to retrieve records, merge with existing records and then store the result.

To perform a lookup operation, the client uses the `GNUNET_NAMESTORE_records_store` function. Here it has to pass the namestore handle, the private key of the zone and the label. It also has to provide a callback function which will be called with the result of the lookup operation: the zone for the records, the label, and the records including the number of records included.

A special operation is used to set the preferred nickname for a zone. This nickname is stored with the zone and is automatically merged with all labels and records stored in a zone. Here the client uses the `GNUNET_NAMESTORE_set_nick` function and passes the private key of the zone, the nickname as string plus a the callback with the result of the operation.

### Iterating Zone Information

A client can iterate over all information in a zone or all zones managed by NAMESTORE. Here a client uses the `GNUNET_NAMESTORE_zone_iteration_start` function and passes the namestore handle, the zone to iterate over and a callback function to call with the result. To iterate over all the zones, it is possible to pass NULL for the zone. A `GNUNET_NAMESTORE_ZoneIterator` handle is returned to be used to continue iteration.

NAMESTORE calls the callback for every result and expects the client to call `GNUNET_NAMESTORE_zone_iterator_next` to continue to iterate or `GNUNET_NAMESTORE_zone_iterator_stop` to interrupt the iteration. When NAMESTORE reached the last item it will call the callback with a NULL value to indicate.

### Monitoring Zone Information

Clients can also monitor zones to be notified about changes. Here the clients uses the `GNUNET_NAMESTORE_zone_monitor_start` function and passes the private key of the zone and and a callback function to call with updates for a zone. The client can specify to obtain zone information first by iterating over the zone and specify a synchronization callback to be called when the client and the namestore are synced.

On an update, NAMESTORE will call the callback with the private key of the zone, the label and the records and their number.

To stop monitoring, the client calls `GNUNET_NAMESTORE_zone_monitor_stop` and passes the handle obtained from the function to start the monitoring.