net: lwm2m: Fixed LwM2M message wrong error response

LwM2M was not reported properly case when message "Accept"
coap option was not not supported. In that case LwM2M transport
specification define 4.06 "Not Accepted"

Signed-off-by: Juha Heiskanen <[email protected]>

Author: Juha Heiskanen

subsys/net/lib/lwm2m/lwm2m_message_handling.c

@@ -618,7 +618,7 @@ static int select_writer(struct lwm2m_output_context *out, uint16_t accept)
 
 	default:
 		LOG_WRN("Unknown content type %u", accept);
-		return -ENOMSG;
+		return -ECANCELED;
 	}
 
 	return 0;
@@ -2100,6 +2100,8 @@ int handle_request(struct coap_packet *request, struct lwm2m_message *msg)
 		msg->code = COAP_RESPONSE_CODE_UNSUPPORTED_CONTENT_FORMAT;
 	} else if (r == -EACCES) {
 		msg->code = COAP_RESPONSE_CODE_UNAUTHORIZED;
+	} else if (r == -ECANCELED) {
+		msg->code = COAP_RESPONSE_CODE_NOT_ACCEPTABLE;
 	} else {
 		/* Failed to handle the request */
 		msg->code = COAP_RESPONSE_CODE_INTERNAL_ERROR;