Detected message duplications stop mbed-client

[ghseb]

Description

• Type: Bug
• Priority: Major

I enabled duplication detection by setting SN_COAP_DUPLICATION_MAX_MSGS_COUNT to 4. If a duplication is detected in the function sn_coap_protocol_parse of sn_coap_protocol.c. sn_coap_protocol_linked_list_duplication_info_search returns a coap_duplication_info_s* response where response->packet_ptr is NULL and response->packet_len is zero. response->coap->sn_coap_tx_callback is called then with those values as parameter and finaly M2MConnectionHandlerPimpl::send_data returns false because of the NULL/zero values. The result is that M2MInterfaceImpl::coap_message_ready emits a M2MInterface::NetworkError (is this the expected behaviour?). This is no problem so far but it seems that if those errors are emitted often the lwm2m stack somehow just stops. I could not yet investigate why. If the code is altered not to propagate those NULL-responses to sn_coap_tx_callback everything seems to work fine.

Related code sections:

sn_coap_protocol_parse of file sn_coap_protocol.c:

#if SN_COAP_DUPLICATION_MAX_MSGS_COUNT/* If Message duplication is used, this part of code will not be compiled */

    /* * * * Manage received CoAP message duplicate detection  * * * */

    /* If no message duplication detected */
    if ((returned_dst_coap_msg_ptr->msg_type == COAP_MSG_TYPE_CONFIRMABLE ||
            returned_dst_coap_msg_ptr->msg_type == COAP_MSG_TYPE_NON_CONFIRMABLE) &&
            handle->sn_coap_duplication_buffer_size != 0) {
        if (sn_coap_protocol_linked_list_duplication_info_search(handle, src_addr_ptr, returned_dst_coap_msg_ptr->msg_id) == NULL) {
            /* * * No Message duplication: Store received message for detecting later duplication * * */

            /* Get count of stored duplication messages */
            uint16_t stored_duplication_msgs_count = handle->count_duplication_msgs;

            /* Check if there is no room to store message for duplication detection purposes */
            if (stored_duplication_msgs_count >= handle->sn_coap_duplication_buffer_size) {
                /* Get oldest stored duplication message */
                coap_duplication_info_s *stored_duplication_info_ptr = ns_list_get_first(&handle->linked_list_duplication_msgs);

                /* Remove oldest stored duplication message for getting room for new duplication message */
                sn_coap_protocol_linked_list_duplication_info_remove(handle,
                                                                     stored_duplication_info_ptr->address->addr_ptr,
                                                                     stored_duplication_info_ptr->address->port,
                                                                     stored_duplication_info_ptr->msg_id);
            }

            /* Store Duplication info to Linked list */
            sn_coap_protocol_linked_list_duplication_info_store(handle, src_addr_ptr, returned_dst_coap_msg_ptr->msg_id, param);
        } else { /* * * Message duplication detected * * */
            /* Set returned status to User */
            returned_dst_coap_msg_ptr->coap_status = COAP_STATUS_PARSER_DUPLICATED_MSG;
            coap_duplication_info_s* response = sn_coap_protocol_linked_list_duplication_info_search(handle,
                                                                                                     src_addr_ptr,
                                                                                                     returned_dst_coap_msg_ptr->msg_id);
            /* Send ACK response */
            if (response) {
                response->coap->sn_coap_tx_callback(response->packet_ptr,
                        response->packet_len, response->address, response->param);

            }

            return returned_dst_coap_msg_ptr;
        }
    }
#endif

M2MConnectionHandlerPimpl::send_data of file m2mconnectionhandlerimpl.cpp:

bool M2MConnectionHandlerPimpl::send_data(uint8_t *data,
                                          uint16_t data_len,
                                          sn_nsdl_addr_s *address)
{
    arm_event_s event;

    tr_debug("send_data()");
    if (address == NULL || data == NULL || !data_len || !_running) {
        tr_warn("send_data() too early");
        return false;
    }
//...

M2MInterfaceImpl::coap_message_ready of file m2minterfaceimpl.cpp:

void M2MInterfaceImpl::coap_message_ready(uint8_t *data_ptr,
                                          uint16_t data_len,
                                          sn_nsdl_addr_s *address_ptr)
{
    tr_debug("M2MInterfaceImpl::coap_message_ready");
    if (_current_state != STATE_IDLE) {
        internal_event(STATE_SENDING_COAP_DATA);
        if(!_connection_handler.send_data(data_ptr,data_len,address_ptr)) {
            internal_event( STATE_IDLE);
            tr_error("M2MInterfaceImpl::coap_message_ready() - M2MInterface::NetworkError");
            if (!_reconnecting) {
                _observer.error(M2MInterface::NetworkError);
            }
        }
    }
}

Version Info:
Project (None)
|- mbed-client (31e5ce2)
| |- mbed-client-c (ecfa619e42b2)
| |- mbed-client-classic (4e66929607c3)
| - mbed-client-mbed-tls (7e1b6d815038) |- mbed-os (8828635da469) - pal (60ce64d5ec35)

[ciarmcom]

ARM Internal Ref: IOTCLT-1883