Provisioning Link Establishment

[smart_life]

Hey everyone, 

1) can you explain me please what is going on by the Link Establishment Process by the Provisioning: do we set up a connection like by the TCP and after the Link is Opened we will get an acknowledgement  for every provisioning message ?  (why do wee need the link establishment process in this point ?)

2) where can i find code for he private key derivation from the exchanged public keys on both sides  ?

[Bjørn Kvaale]

Regarding Q2 in your original question, see the mesh_provisionee.c file of the light switch server in mesh sdk v2.2.0:

        case NRF_MESH_PROV_EVT_STATIC_REQUEST:
            APP_ERROR_CHECK(nrf_mesh_prov_auth_data_provide(&m_prov_ctx,
                                                                 m_params.p_static_data,
                                                                 NRF_MESH_KEY_SIZE));

In the provisioner example, you can take a look at prov_provisioner.c:

        case NRF_MESH_PROV_OOB_METHOD_STATIC:
            /* Request static provisioning data from the application. */
            event.type = NRF_MESH_PROV_EVT_STATIC_REQUEST;
            event.params.static_request.p_context =  p_ctx;
            p_ctx->state = NRF_MESH_PROV_STATE_WAIT_OOB_STATIC;
            p_ctx->event_handler(&event);

& also provisioner_helper.c:

   case NRF_MESH_PROV_EVT_STATIC_REQUEST:
        {
            const uint8_t static_data[NRF_MESH_KEY_SIZE] = STATIC_AUTH_DATA;
            ERROR_CHECK(nrf_mesh_prov_auth_data_provide(p_evt->params.static_request.p_context, static_data, NRF_MESH_KEY_SIZE));
            __LOG(LOG_SRC_APP, LOG_LEVEL_INFO, "Static authentication data provided\n");
            break;

[smart_life]

Thank you for the answer,  it is not satisfactory but i think i got it now.  I thought the link establishment message is an indicator for the Provisionee that after that link open message and till the link is closed ,each message has to be acknowledged on some provisioning protocol layer. In other words i thought link establishment == connection  , like the TCP connection. TCP provides reliable, ordered, and error-checked delivery of a stream of octets.  But it seams that we need the link establishment just to distinguish between sessions and we need it to say how long the session will be. We still have an unreliable delivery without of packet order and error checked delivery. But in case of PB-GATT we have a real connection right ? 

 In Mesh Specification in 5.3.2 we have the definition of the  link establishment procedure:

The Link Establishment procedure is used to establish a session for a bearer that does not have inherent
session management. A session is identified by using a Link ID that is static for the duration of the
session and shall be randomly generated to prevent collisions between sessions.

The Link Open message contains the Device UUID of the device. On PB-ADV, the PB-ADV PDU format includes a Link ID field.

[Bjørn Kvaale]

smart_life said:

But in case of PB-GATT we have a real connection right ? 

 In PB-GATT you have a standard BLE connection. See the documentation: "After provisioning, the proxy server application starts advertising a connectable proxy beacon, which can be connected to by a Proxy Client to interact with the mesh. The Proxy Client acts like any other mesh device, but sends all its mesh communication over a BLE connection to a Proxy Server, which relays it into the mesh."

If that is what you mean by "real connection", then yes, you are correct.