Diff: iothubtransport_amqp_device.c

Revision:

30:20a85b733111

Child:

34:51d158b409d2

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/iothubtransport_amqp_device.c	Fri Mar 10 11:46:55 2017 -0800
@@ -0,0 +1,1351 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+#include <stdlib.h>
+#include "iothubtransport_amqp_messenger.h"
+#include "azure_c_shared_utility/optimize_size.h"
+#include "azure_c_shared_utility/gballoc.h"
+#include "azure_c_shared_utility/agenttime.h" 
+#include "azure_c_shared_utility/xlogging.h"
+#include "azure_c_shared_utility/strings.h"
+#include "iothubtransport_amqp_cbs_auth.h"
+#include "iothubtransport_amqp_device.h"
+
+#define RESULT_OK                                  0
+#define INDEFINITE_TIME                            ((time_t)-1)
+#define DEFAULT_AUTH_STATE_CHANGED_TIMEOUT_SECS    60
+#define DEFAULT_MSGR_STATE_CHANGED_TIMEOUT_SECS    60
+
+static const char* DEVICE_OPTION_SAVED_AUTH_OPTIONS = "saved_device_auth_options";
+static const char* DEVICE_OPTION_SAVED_MESSENGER_OPTIONS = "saved_device_messenger_options";
+
+typedef struct DEVICE_INSTANCE_TAG
+{
+	DEVICE_CONFIG* config;
+	DEVICE_STATE state;
+
+	SESSION_HANDLE session_handle;
+	CBS_HANDLE cbs_handle;
+
+	AUTHENTICATION_HANDLE authentication_handle;
+	AUTHENTICATION_STATE auth_state;
+	AUTHENTICATION_ERROR_CODE auth_error_code;
+	time_t auth_state_last_changed_time;
+	size_t auth_state_change_timeout_secs;
+
+	MESSENGER_HANDLE messenger_handle;
+	MESSENGER_STATE msgr_state;
+	time_t msgr_state_last_changed_time;
+	size_t msgr_state_change_timeout_secs;
+
+	ON_DEVICE_C2D_MESSAGE_RECEIVED on_message_received_callback;
+	void* on_message_received_context;
+} DEVICE_INSTANCE;
+
+typedef struct DEVICE_SEND_EVENT_TASK_TAG
+{
+	ON_DEVICE_D2C_EVENT_SEND_COMPLETE on_event_send_complete_callback;
+	void* on_event_send_complete_context;
+} DEVICE_SEND_EVENT_TASK;
+
+
+// Internal state control
+
+static void update_state(DEVICE_INSTANCE* instance, DEVICE_STATE new_state)
+{
+	if (new_state != instance->state)
+	{
+		DEVICE_STATE previous_state = instance->state;
+		instance->state = new_state;
+
+		if (instance->config->on_state_changed_callback != NULL)
+		{
+			instance->config->on_state_changed_callback(instance->config->on_state_changed_context, previous_state, new_state);
+		}
+	}
+}
+
+static int is_timeout_reached(time_t start_time, size_t timeout_in_secs, int *is_timed_out)
+{
+	int result;
+
+	if (start_time == INDEFINITE_TIME)
+	{
+		LogError("Failed to verify timeout (start_time is INDEFINITE)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		time_t current_time;
+
+		if ((current_time = get_time(NULL)) == INDEFINITE_TIME)
+		{
+			LogError("Failed to verify timeout (get_time failed)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			if (get_difftime(current_time, start_time) >= timeout_in_secs)
+			{
+				*is_timed_out = 1;
+			}
+			else
+			{
+				*is_timed_out = 0;
+			}
+
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+
+// Callback Handlers
+
+static D2C_EVENT_SEND_RESULT get_d2c_event_send_result_from(MESSENGER_EVENT_SEND_COMPLETE_RESULT result)
+{
+	D2C_EVENT_SEND_RESULT d2c_esr;
+
+	switch (result)
+	{
+		case MESSENGER_EVENT_SEND_COMPLETE_RESULT_OK:
+			d2c_esr = D2C_EVENT_SEND_COMPLETE_RESULT_OK;
+			break;
+		case MESSENGER_EVENT_SEND_COMPLETE_RESULT_ERROR_CANNOT_PARSE:
+			d2c_esr = D2C_EVENT_SEND_COMPLETE_RESULT_ERROR_CANNOT_PARSE;
+			break;
+		case MESSENGER_EVENT_SEND_COMPLETE_RESULT_ERROR_FAIL_SENDING:
+			d2c_esr = D2C_EVENT_SEND_COMPLETE_RESULT_ERROR_FAIL_SENDING;
+			break;
+		case MESSENGER_EVENT_SEND_COMPLETE_RESULT_ERROR_TIMEOUT:
+			d2c_esr = D2C_EVENT_SEND_COMPLETE_RESULT_ERROR_TIMEOUT;
+			break;
+		case MESSENGER_EVENT_SEND_COMPLETE_RESULT_MESSENGER_DESTROYED:
+			d2c_esr = D2C_EVENT_SEND_COMPLETE_RESULT_DEVICE_DESTROYED;
+			break;
+		default:
+			// This is not expected. All states should be mapped.
+			d2c_esr = D2C_EVENT_SEND_COMPLETE_RESULT_ERROR_UNKNOWN;
+			break;
+	};
+
+	return d2c_esr;
+}
+
+static void on_event_send_complete_messenger_callback(IOTHUB_MESSAGE_LIST* iothub_message, MESSENGER_EVENT_SEND_COMPLETE_RESULT ev_send_comp_result, void* context)
+{
+	if (iothub_message == NULL || context == NULL)
+	{
+		LogError("on_event_send_complete_messenger_callback was invoked, but either iothub_message (%p) or context (%p) are NULL", iothub_message, context);
+	}
+	else
+	{
+		DEVICE_SEND_EVENT_TASK* send_task = (DEVICE_SEND_EVENT_TASK*)context;
+
+		// Codes_SRS_DEVICE_09_059: [If `ev_send_comp_result` is MESSENGER_EVENT_SEND_COMPLETE_RESULT_OK, D2C_EVENT_SEND_COMPLETE_RESULT_OK shall be reported as `event_send_complete`]
+		// Codes_SRS_DEVICE_09_060: [If `ev_send_comp_result` is MESSENGER_EVENT_SEND_COMPLETE_RESULT_ERROR_CANNOT_PARSE, D2C_EVENT_SEND_COMPLETE_RESULT_ERROR_CANNOT_PARSE shall be reported as `event_send_complete`]
+		// Codes_SRS_DEVICE_09_061: [If `ev_send_comp_result` is MESSENGER_EVENT_SEND_COMPLETE_RESULT_ERROR_FAIL_SENDING, D2C_EVENT_SEND_COMPLETE_RESULT_ERROR_FAIL_SENDING shall be reported as `event_send_complete`]
+		// Codes_SRS_DEVICE_09_062: [If `ev_send_comp_result` is MESSENGER_EVENT_SEND_COMPLETE_RESULT_ERROR_TIMEOUT, D2C_EVENT_SEND_COMPLETE_RESULT_ERROR_TIMEOUT shall be reported as `event_send_complete`]
+		// Codes_SRS_DEVICE_09_063: [If `ev_send_comp_result` is MESSENGER_EVENT_SEND_COMPLETE_RESULT_MESSENGER_DESTROYED, D2C_EVENT_SEND_COMPLETE_RESULT_DEVICE_DESTROYED shall be reported as `event_send_complete`]
+		D2C_EVENT_SEND_RESULT device_send_result = get_d2c_event_send_result_from(ev_send_comp_result);
+
+		// Codes_SRS_DEVICE_09_064: [If provided, the user callback and context saved in `send_task` shall be invoked passing the device `event_send_complete`]
+		if (send_task->on_event_send_complete_callback != NULL)
+		{
+			send_task->on_event_send_complete_callback(iothub_message, device_send_result, send_task->on_event_send_complete_context);
+		}
+
+		// Codes_SRS_DEVICE_09_065: [The memory allocated for `send_task` shall be released]
+		free(send_task);
+	}
+}
+
+static void on_authentication_error_callback(void* context, AUTHENTICATION_ERROR_CODE error_code)
+{
+	if (context == NULL)
+	{
+		LogError("on_authentication_error_callback was invoked with error %d, but context is NULL", error_code);
+	}
+	else
+	{ 
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)context;
+		instance->auth_error_code = error_code;
+	}
+}
+
+static void on_authentication_state_changed_callback(void* context, AUTHENTICATION_STATE previous_state, AUTHENTICATION_STATE new_state)
+{
+	if (context == NULL)
+	{
+		LogError("on_authentication_state_changed_callback was invoked with new_state %d, but context is NULL", new_state);
+	}
+	else if (new_state != previous_state)
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)context;
+		instance->auth_state = new_state;
+
+		if ((instance->auth_state_last_changed_time = get_time(NULL)) == INDEFINITE_TIME)
+		{
+			LogError("Device '%s' failed to set time of last authentication state change (get_time failed)", instance->config->device_id);
+		}
+	}
+}
+
+static void on_messenger_state_changed_callback(void* context, MESSENGER_STATE previous_state, MESSENGER_STATE new_state)
+{
+	if (context == NULL)
+	{
+		LogError("on_messenger_state_changed_callback was invoked with new_state %d, but context is NULL", new_state);
+	}
+	else if (new_state != previous_state)
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)context;
+		instance->msgr_state = new_state;
+
+		if ((instance->msgr_state_last_changed_time = get_time(NULL)) == INDEFINITE_TIME)
+		{
+			LogError("Device '%s' failed to set time of last messenger state change (get_time failed)", instance->config->device_id);
+		}
+	}
+}
+
+static DEVICE_MESSAGE_DISPOSITION_INFO* create_device_message_disposition_info_from(MESSENGER_MESSAGE_DISPOSITION_INFO* messenger_disposition_info)
+{
+	DEVICE_MESSAGE_DISPOSITION_INFO* device_disposition_info;
+
+	if ((device_disposition_info = (DEVICE_MESSAGE_DISPOSITION_INFO*)malloc(sizeof(DEVICE_MESSAGE_DISPOSITION_INFO))) == NULL)
+	{
+		LogError("Failed creating DEVICE_MESSAGE_DISPOSITION_INFO (malloc failed)");
+	}
+	else if (mallocAndStrcpy_s(&device_disposition_info->source, messenger_disposition_info->source) != RESULT_OK)
+	{
+		LogError("Failed creating DEVICE_MESSAGE_DISPOSITION_INFO (mallocAndStrcpy_s failed)");
+		free(device_disposition_info);
+		device_disposition_info = NULL;
+	}
+	else
+	{
+		device_disposition_info->message_id = messenger_disposition_info->message_id;
+	}
+
+	return device_disposition_info;
+}
+
+static void destroy_device_disposition_info(DEVICE_MESSAGE_DISPOSITION_INFO* disposition_info)
+{
+	free(disposition_info->source);
+	free(disposition_info);
+}
+
+static MESSENGER_MESSAGE_DISPOSITION_INFO* create_messenger_disposition_info(DEVICE_MESSAGE_DISPOSITION_INFO* device_disposition_info)
+{
+	MESSENGER_MESSAGE_DISPOSITION_INFO* messenger_disposition_info;
+
+	if ((messenger_disposition_info = (MESSENGER_MESSAGE_DISPOSITION_INFO*)malloc(sizeof(MESSENGER_MESSAGE_DISPOSITION_INFO))) == NULL)
+	{
+		LogError("Failed creating MESSENGER_MESSAGE_DISPOSITION_INFO (malloc failed)");
+	}
+	else if (mallocAndStrcpy_s(&messenger_disposition_info->source, device_disposition_info->source) != RESULT_OK)
+	{
+		LogError("Failed creating MESSENGER_MESSAGE_DISPOSITION_INFO (mallocAndStrcpy_s failed)");
+		free(messenger_disposition_info);
+		messenger_disposition_info = NULL;
+	}
+	else
+	{
+		messenger_disposition_info->message_id = device_disposition_info->message_id;
+	}
+
+	return messenger_disposition_info;
+}
+
+static void destroy_messenger_disposition_info(MESSENGER_MESSAGE_DISPOSITION_INFO* messenger_disposition_info)
+{
+	free(messenger_disposition_info->source);
+	free(messenger_disposition_info);
+}
+
+static MESSENGER_DISPOSITION_RESULT get_messenger_message_disposition_result_from(DEVICE_MESSAGE_DISPOSITION_RESULT device_disposition_result)
+{
+	MESSENGER_DISPOSITION_RESULT messenger_disposition_result;
+
+	switch (device_disposition_result)
+	{
+		case DEVICE_MESSAGE_DISPOSITION_RESULT_NONE:
+			messenger_disposition_result = MESSENGER_DISPOSITION_RESULT_NONE;
+			break;
+		case DEVICE_MESSAGE_DISPOSITION_RESULT_ACCEPTED:
+			messenger_disposition_result = MESSENGER_DISPOSITION_RESULT_ACCEPTED;
+			break;
+		case DEVICE_MESSAGE_DISPOSITION_RESULT_REJECTED:
+			messenger_disposition_result = MESSENGER_DISPOSITION_RESULT_REJECTED;
+			break;
+		case DEVICE_MESSAGE_DISPOSITION_RESULT_RELEASED:
+			messenger_disposition_result = MESSENGER_DISPOSITION_RESULT_RELEASED;
+			break;
+		default:
+			LogError("Failed to get the corresponding MESSENGER_DISPOSITION_RESULT (%d is not supported)", device_disposition_result);
+			messenger_disposition_result = MESSENGER_DISPOSITION_RESULT_RELEASED;
+			break;
+	}
+
+	return messenger_disposition_result;
+}
+
+static MESSENGER_DISPOSITION_RESULT on_messenger_message_received_callback(IOTHUB_MESSAGE_HANDLE iothub_message_handle, MESSENGER_MESSAGE_DISPOSITION_INFO* disposition_info, void* context)
+{
+	MESSENGER_DISPOSITION_RESULT msgr_disposition_result;
+
+	// Codes_SRS_DEVICE_09_070: [If `iothub_message_handle` or `context` is NULL, on_messenger_message_received_callback shall return MESSENGER_DISPOSITION_RESULT_RELEASED]
+	if (iothub_message_handle == NULL || context == NULL)
+	{
+		LogError("Failed receiving incoming C2D message (message handle (%p) or context (%p) is NULL)", iothub_message_handle, context);
+		msgr_disposition_result = MESSENGER_DISPOSITION_RESULT_RELEASED;
+	}
+	else
+	{
+		DEVICE_INSTANCE* device_instance = (DEVICE_INSTANCE*)context;
+
+		if (device_instance->on_message_received_callback == NULL)
+		{
+			LogError("Device '%s' failed receiving incoming C2D message (callback is NULL)", device_instance->config->device_id);
+			msgr_disposition_result = MESSENGER_DISPOSITION_RESULT_RELEASED;
+		}
+		else
+		{
+			DEVICE_MESSAGE_DISPOSITION_INFO* device_message_disposition_info;
+
+			// Codes_SRS_DEVICE_09_119: [A DEVICE_MESSAGE_DISPOSITION_INFO instance shall be created containing a copy of `disposition_info->source` and `disposition_info->message_id`]
+			if ((device_message_disposition_info = create_device_message_disposition_info_from(disposition_info)) == NULL)
+			{
+				// Codes_SRS_DEVICE_09_120: [If the DEVICE_MESSAGE_DISPOSITION_INFO instance fails to be created, on_messenger_message_received_callback shall return MESSENGER_DISPOSITION_RESULT_RELEASED]
+				LogError("Device '%s' failed receiving incoming C2D message (failed creating DEVICE_MESSAGE_DISPOSITION_INFO)", device_instance->config->device_id);
+				msgr_disposition_result = MESSENGER_DISPOSITION_RESULT_RELEASED;
+			}
+			else
+			{
+				// Codes_SRS_DEVICE_09_071: [The user callback shall be invoked, passing the context it provided]
+				DEVICE_MESSAGE_DISPOSITION_RESULT device_disposition_result = device_instance->on_message_received_callback(iothub_message_handle, device_message_disposition_info, device_instance->on_message_received_context);
+
+				// Codes_SRS_DEVICE_09_072: [If the user callback returns DEVICE_MESSAGE_DISPOSITION_RESULT_ACCEPTED, on_messenger_message_received_callback shall return MESSENGER_DISPOSITION_RESULT_ACCEPTED]
+				// Codes_SRS_DEVICE_09_073: [If the user callback returns DEVICE_MESSAGE_DISPOSITION_RESULT_REJECTED, on_messenger_message_received_callback shall return MESSENGER_DISPOSITION_RESULT_REJECTED]
+				// Codes_SRS_DEVICE_09_074: [If the user callback returns DEVICE_MESSAGE_DISPOSITION_RESULT_RELEASED, on_messenger_message_received_callback shall return MESSENGER_DISPOSITION_RESULT_RELEASED]
+				msgr_disposition_result = get_messenger_message_disposition_result_from(device_disposition_result);
+
+				// Codes_SRS_DEVICE_09_121: [on_messenger_message_received_callback shall release the memory allocated for DEVICE_MESSAGE_DISPOSITION_INFO]
+				destroy_device_disposition_info(device_message_disposition_info);
+			}
+		}
+	}
+
+	return msgr_disposition_result;
+}
+
+
+// Configuration Helpers
+
+static void destroy_device_config(DEVICE_CONFIG* config)
+{
+	if (config != NULL)
+	{
+		free(config->device_id);
+		free(config->iothub_host_fqdn);
+		free(config->device_primary_key);
+		free(config->device_secondary_key);
+		free(config->device_sas_token);
+		free(config);
+	}
+}
+
+static DEVICE_CONFIG* clone_device_config(DEVICE_CONFIG *config)
+{
+	DEVICE_CONFIG* new_config;
+
+	if ((new_config = (DEVICE_CONFIG*)malloc(sizeof(DEVICE_CONFIG))) == NULL)
+	{
+		LogError("Failed copying the DEVICE_CONFIG (malloc failed)");
+	}
+	else
+	{
+		int result;
+
+		memset(new_config, 0, sizeof(DEVICE_CONFIG));
+
+		if (mallocAndStrcpy_s(&new_config->device_id, config->device_id) != RESULT_OK)
+		{
+			LogError("Failed copying the DEVICE_CONFIG (failed copying device_id)");
+			result = __FAILURE__;
+		}
+		else if (mallocAndStrcpy_s(&new_config->iothub_host_fqdn, config->iothub_host_fqdn) != RESULT_OK)
+		{
+			LogError("Failed copying the DEVICE_CONFIG (failed copying iothub_host_fqdn)");
+			result = __FAILURE__;
+		}
+		else if (config->device_sas_token != NULL &&
+			mallocAndStrcpy_s(&new_config->device_sas_token, config->device_sas_token) != RESULT_OK)
+		{
+			LogError("Failed copying the DEVICE_CONFIG (failed copying device_sas_token)");
+			result = __FAILURE__;
+		}
+		else if (config->device_primary_key != NULL &&
+			mallocAndStrcpy_s(&new_config->device_primary_key, config->device_primary_key) != RESULT_OK)
+		{
+			LogError("Failed copying the DEVICE_CONFIG (failed copying device_primary_key)");
+			result = __FAILURE__;
+		}
+		else if (config->device_secondary_key != NULL &&
+			mallocAndStrcpy_s(&new_config->device_secondary_key, config->device_secondary_key) != RESULT_OK)
+		{
+			LogError("Failed copying the DEVICE_CONFIG (failed copying device_secondary_key)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			new_config->authentication_mode = config->authentication_mode;
+			new_config->on_state_changed_callback = config->on_state_changed_callback;
+			new_config->on_state_changed_context = config->on_state_changed_context;
+
+			result = RESULT_OK;
+		}
+
+		if (result != RESULT_OK)
+		{
+			destroy_device_config(new_config);
+			new_config = NULL;
+		}
+	}
+
+	return new_config;
+}
+
+static void set_authentication_config(DEVICE_INSTANCE* device_instance, AUTHENTICATION_CONFIG* auth_config)
+{
+	DEVICE_CONFIG *device_config = device_instance->config;
+
+	auth_config->device_id = device_config->device_id;
+	auth_config->iothub_host_fqdn = device_config->iothub_host_fqdn;
+	auth_config->on_error_callback = on_authentication_error_callback;
+	auth_config->on_error_callback_context = device_instance;
+	auth_config->on_state_changed_callback = on_authentication_state_changed_callback;
+	auth_config->on_state_changed_callback_context = device_instance;
+	auth_config->device_primary_key = device_config->device_primary_key;
+	auth_config->device_secondary_key = device_config->device_secondary_key;
+	auth_config->device_sas_token = device_config->device_sas_token;
+}
+
+
+// Create and Destroy Helpers
+
+static void internal_destroy_device(DEVICE_INSTANCE* instance)
+{
+	if (instance != NULL)
+	{
+		if (instance->messenger_handle != NULL)
+		{
+			messenger_destroy(instance->messenger_handle);
+		}
+
+		if (instance->authentication_handle != NULL)
+		{
+			authentication_destroy(instance->authentication_handle);
+		}
+
+		destroy_device_config(instance->config);
+		free(instance);
+	}
+}
+
+static int create_authentication_instance(DEVICE_INSTANCE *instance)
+{
+	int result;
+	AUTHENTICATION_CONFIG auth_config;
+
+	set_authentication_config(instance, &auth_config);
+
+	if ((instance->authentication_handle = authentication_create(&auth_config)) == NULL)
+	{
+		LogError("Failed creating the AUTHENTICATION_HANDLE (authentication_create failed)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		result = RESULT_OK;
+	}
+
+	return result;
+}
+
+static int create_messenger_instance(DEVICE_INSTANCE* instance)
+{
+	int result;
+
+	MESSENGER_CONFIG messenger_config;
+	messenger_config.device_id = instance->config->device_id;
+	messenger_config.iothub_host_fqdn = instance->config->iothub_host_fqdn;
+	messenger_config.on_state_changed_callback = on_messenger_state_changed_callback;
+	messenger_config.on_state_changed_context = instance;
+
+	if ((instance->messenger_handle = messenger_create(&messenger_config)) == NULL)
+	{
+		LogError("Failed creating the MESSENGER_HANDLE (messenger_create failed)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		result = RESULT_OK;
+	}
+
+	return result;
+}
+
+// ---------- Set/Retrieve Options Helpers ----------//
+
+static void* device_clone_option(const char* name, const void* value)
+{
+	void* result;
+
+	if (name == NULL || value == NULL)
+	{
+		LogError("Failed to clone device option (either name (%p) or value (%p) is NULL)", name, value);
+		result = NULL;
+	}
+	else
+	{
+		if (strcmp(DEVICE_OPTION_SAVED_AUTH_OPTIONS, name) == 0 ||
+			strcmp(DEVICE_OPTION_SAVED_MESSENGER_OPTIONS, name) == 0)
+		{
+			if ((result = (void*)OptionHandler_Clone((OPTIONHANDLER_HANDLE)value)) == NULL)
+			{
+				LogError("Failed to clone device option (OptionHandler_Clone failed for option %s)", name);
+			}
+		}
+		else
+		{
+			LogError("Failed to clone device option (option with name '%s' is not suppported)", name);
+			result = NULL;
+		}
+	}
+
+	return result;
+}
+
+static void device_destroy_option(const char* name, const void* value)
+{
+	if (name == NULL || value == NULL)
+	{
+		LogError("Failed to destroy device option (either name (%p) or value (%p) is NULL)", name, value);
+	}
+	else
+	{
+		if (strcmp(name, DEVICE_OPTION_SAVED_AUTH_OPTIONS) == 0 ||
+			strcmp(name, DEVICE_OPTION_SAVED_MESSENGER_OPTIONS) == 0)
+		{
+			OptionHandler_Destroy((OPTIONHANDLER_HANDLE)value);
+		}
+		else
+		{
+			LogError("Failed to clone device option (option with name '%s' is not suppported)", name);
+		}
+	}
+}
+
+
+// Public APIs:
+
+DEVICE_HANDLE device_create(DEVICE_CONFIG *config)
+{
+	DEVICE_INSTANCE *instance;
+
+	// Codes_SRS_DEVICE_09_001: [If `config` or device_id or iothub_host_fqdn or on_state_changed_callback are NULL then device_create shall fail and return NULL]
+	if (config == NULL)
+	{
+		LogError("Failed creating the device instance (config is NULL)");
+		instance = NULL;
+	}
+	else if (config->device_id == NULL)
+	{
+		LogError("Failed creating the device instance (config->device_id is NULL)");
+		instance = NULL;
+	}
+	else if (config->iothub_host_fqdn == NULL)
+	{
+		LogError("Failed creating the device instance (config->iothub_host_fqdn is NULL)");
+		instance = NULL;
+	}
+	else if (config->on_state_changed_callback == NULL)
+	{
+		LogError("Failed creating the device instance (config->on_state_changed_callback is NULL)");
+		instance = NULL;
+	}
+	// Codes_SRS_DEVICE_09_002: [device_create shall allocate memory for the device instance structure]
+	else if ((instance = (DEVICE_INSTANCE*)malloc(sizeof(DEVICE_INSTANCE))) == NULL)
+	{
+		// Codes_SRS_DEVICE_09_003: [If malloc fails, device_create shall fail and return NULL]
+		LogError("Failed creating the device instance (malloc failed)");
+	}
+	else
+	{
+		int result;
+
+		memset(instance, 0, sizeof(DEVICE_INSTANCE));
+
+		// Codes_SRS_DEVICE_09_004: [All `config` parameters shall be saved into `instance`]
+		if ((instance->config = clone_device_config(config)) == NULL)
+		{
+			// Codes_SRS_DEVICE_09_005: [If any `config` parameters fail to be saved into `instance`, device_create shall fail and return NULL]
+			LogError("Failed creating the device instance for device '%s' (failed copying the configuration)", config->device_id);
+			result = __FAILURE__;
+		}
+		// Codes_SRS_DEVICE_09_006: [If `instance->authentication_mode` is DEVICE_AUTH_MODE_CBS, `instance->authentication_handle` shall be set using authentication_create()]
+		else if (instance->config->authentication_mode == DEVICE_AUTH_MODE_CBS &&
+			     create_authentication_instance(instance) != RESULT_OK)
+		{
+			// Codes_SRS_DEVICE_09_007: [If the AUTHENTICATION_HANDLE fails to be created, device_create shall fail and return NULL]
+			LogError("Failed creating the device instance for device '%s' (failed creating the authentication instance)", instance->config->device_id);
+			result = __FAILURE__;
+		}
+		// Codes_SRS_DEVICE_09_008: [`instance->messenger_handle` shall be set using messenger_create()]
+		else if (create_messenger_instance(instance) != RESULT_OK)
+		{
+			// Codes_SRS_DEVICE_09_009: [If the MESSENGER_HANDLE fails to be created, device_create shall fail and return NULL]
+			LogError("Failed creating the device instance for device '%s' (failed creating the messenger instance)", instance->config->device_id);
+			result = __FAILURE__;
+		}
+		else
+		{
+			instance->auth_state = AUTHENTICATION_STATE_STOPPED;
+			instance->msgr_state = MESSENGER_STATE_STOPPED;
+			instance->state = DEVICE_STATE_STOPPED;
+			instance->auth_state_last_changed_time = INDEFINITE_TIME;
+			instance->auth_state_change_timeout_secs = DEFAULT_AUTH_STATE_CHANGED_TIMEOUT_SECS;
+			instance->msgr_state_last_changed_time = INDEFINITE_TIME;
+			instance->msgr_state_change_timeout_secs = DEFAULT_MSGR_STATE_CHANGED_TIMEOUT_SECS;
+
+			result = RESULT_OK;
+		}
+
+		if (result != RESULT_OK)
+		{
+			// Codes_SRS_DEVICE_09_010: [If device_create fails it shall release all memory it has allocated]
+			internal_destroy_device(instance);
+			instance = NULL;
+		}
+	}
+
+	// Codes_SRS_DEVICE_09_011: [If device_create succeeds it shall return a handle to its `instance` structure]
+	return (DEVICE_HANDLE)instance;
+}
+
+int device_start_async(DEVICE_HANDLE handle, SESSION_HANDLE session_handle, CBS_HANDLE cbs_handle)
+{
+	int result;
+
+	// Codes_SRS_DEVICE_09_017: [If `handle` is NULL, device_start_async shall return a non-zero result]
+	if (handle == NULL)
+	{
+		LogError("Failed starting device (handle is NULL)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+		// Codes_SRS_DEVICE_09_018: [If the device state is not DEVICE_STATE_STOPPED, device_start_async shall return a non-zero result]
+		if (instance->state != DEVICE_STATE_STOPPED)
+		{
+			LogError("Failed starting device (device is not stopped)");
+			result = __FAILURE__;
+		}
+		// Codes_SRS_DEVICE_09_019: [If `session_handle` is NULL, device_start_async shall return a non-zero result]
+		else if (session_handle == NULL)
+		{
+			LogError("Failed starting device (session_handle is NULL)");
+			result = __FAILURE__;
+		}
+		// Codes_SRS_DEVICE_09_020: [If using CBS authentication and `cbs_handle` is NULL, device_start_async shall return a non-zero result]
+		else if (instance->config->authentication_mode == DEVICE_AUTH_MODE_CBS && cbs_handle == NULL)
+		{
+			LogError("Failed starting device (device using CBS authentication, but cbs_handle is NULL)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			// Codes_SRS_DEVICE_09_021: [`session_handle` and `cbs_handle` shall be saved into the `instance`]
+			instance->session_handle = session_handle;
+			instance->cbs_handle = cbs_handle;
+
+			// Codes_SRS_DEVICE_09_022: [The device state shall be updated to DEVICE_STATE_STARTING, and state changed callback invoked]
+			update_state(instance, DEVICE_STATE_STARTING);
+
+			// Codes_SRS_DEVICE_09_023: [If no failures occur, device_start_async shall return 0]
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+// @brief
+//     stops a device instance (stops messenger and authentication) synchronously.
+// @returns
+//     0 if the function succeeds, non-zero otherwise.
+int device_stop(DEVICE_HANDLE handle)
+{
+	int result;
+
+	// Codes_SRS_DEVICE_09_024: [If `handle` is NULL, device_stop shall return a non-zero result]
+	if (handle == NULL)
+	{
+		LogError("Failed stopping device (handle is NULL)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+		// Codes_SRS_DEVICE_09_025: [If the device state is already DEVICE_STATE_STOPPED or DEVICE_STATE_STOPPING, device_stop shall return a non-zero result]
+		if (instance->state == DEVICE_STATE_STOPPED || instance->state == DEVICE_STATE_STOPPING)
+		{
+			LogError("Failed stopping device '%s' (device is already stopped or stopping)", instance->config->device_id);
+			result = __FAILURE__;
+		}
+		else
+		{
+			// Codes_SRS_DEVICE_09_026: [The device state shall be updated to DEVICE_STATE_STOPPING, and state changed callback invoked]
+			update_state(instance, DEVICE_STATE_STOPPING);
+
+			// Codes_SRS_DEVICE_09_027: [If `instance->messenger_handle` state is not MESSENGER_STATE_STOPPED, messenger_stop shall be invoked]
+			if (instance->msgr_state != MESSENGER_STATE_STOPPED && 
+				instance->msgr_state != MESSENGER_STATE_STOPPING &&
+				messenger_stop(instance->messenger_handle) != RESULT_OK)
+			{
+				// Codes_SRS_DEVICE_09_028: [If messenger_stop fails, the `instance` state shall be updated to DEVICE_STATE_ERROR_MSG and the function shall return non-zero result]
+				LogError("Failed stopping device '%s' (messenger_stop failed)", instance->config->device_id);
+				result = __FAILURE__;
+				update_state(instance, DEVICE_STATE_ERROR_MSG);
+			}
+			// Codes_SRS_DEVICE_09_029: [If CBS authentication is used, if `instance->authentication_handle` state is not AUTHENTICATION_STATE_STOPPED, authentication_stop shall be invoked]
+			else if (instance->config->authentication_mode == DEVICE_AUTH_MODE_CBS &&
+				instance->auth_state != AUTHENTICATION_STATE_STOPPED &&
+				authentication_stop(instance->authentication_handle) != RESULT_OK)
+			{
+				// Codes_SRS_DEVICE_09_030: [If authentication_stop fails, the `instance` state shall be updated to DEVICE_STATE_ERROR_AUTH and the function shall return non-zero result]
+				LogError("Failed stopping device '%s' (authentication_stop failed)", instance->config->device_id);
+				result = __FAILURE__;
+				update_state(instance, DEVICE_STATE_ERROR_AUTH);
+			}
+			else
+			{
+				// Codes_SRS_DEVICE_09_031: [The device state shall be updated to DEVICE_STATE_STOPPED, and state changed callback invoked]
+				update_state(instance, DEVICE_STATE_STOPPED);
+
+				// Codes_SRS_DEVICE_09_032: [If no failures occur, device_stop shall return 0]
+				result = RESULT_OK;
+			}
+		}
+	}
+
+	return result;
+}
+
+void device_do_work(DEVICE_HANDLE handle)
+{
+	// Codes_SRS_DEVICE_09_033: [If `handle` is NULL, device_do_work shall return]
+	if (handle == NULL)
+	{
+		LogError("Failed to perform device_do_work (handle is NULL)");
+	}
+	else
+	{
+		// Cranking the state monster:
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+		if (instance->state == DEVICE_STATE_STARTING)
+		{
+			// Codes_SRS_DEVICE_09_034: [If CBS authentication is used and authentication state is AUTHENTICATION_STATE_STOPPED, authentication_start shall be invoked]
+			if (instance->config->authentication_mode == DEVICE_AUTH_MODE_CBS)
+			{
+				if (instance->auth_state == AUTHENTICATION_STATE_STOPPED)
+				{
+					if (authentication_start(instance->authentication_handle, instance->cbs_handle) != RESULT_OK)
+					{
+						// Codes_SRS_DEVICE_09_035: [If authentication_start fails, the device state shall be updated to DEVICE_STATE_ERROR_AUTH]
+						LogError("Device '%s' failed to be authenticated (authentication_start failed)", instance->config->device_id);
+
+						update_state(instance, DEVICE_STATE_ERROR_AUTH);
+					}
+				}
+				// Codes_SRS_DEVICE_09_036: [If authentication state is AUTHENTICATION_STATE_STARTING, the device shall track the time since last event change and timeout if needed]
+				else if (instance->auth_state == AUTHENTICATION_STATE_STARTING)
+				{
+					int is_timed_out;
+					if (is_timeout_reached(instance->auth_state_last_changed_time, instance->auth_state_change_timeout_secs, &is_timed_out) != RESULT_OK)
+					{
+						LogError("Device '%s' failed verifying the timeout for authentication start (is_timeout_reached failed)", instance->config->device_id);
+						update_state(instance, DEVICE_STATE_ERROR_AUTH);
+					}
+					// Codes_SRS_DEVICE_09_037: [If authentication_start times out, the device state shall be updated to DEVICE_STATE_ERROR_AUTH_TIMEOUT]
+					else if (is_timed_out == 1)
+					{
+						LogError("Device '%s' authentication did not complete starting within expected timeout (%d)", instance->config->device_id, instance->auth_state_change_timeout_secs);
+
+						update_state(instance, DEVICE_STATE_ERROR_AUTH_TIMEOUT);
+					}
+				}
+				else if (instance->auth_state == AUTHENTICATION_STATE_ERROR)
+				{
+					// Codes_SRS_DEVICE_09_038: [If authentication state is AUTHENTICATION_STATE_ERROR and error code is AUTH_FAILED, the device state shall be updated to DEVICE_STATE_ERROR_AUTH]
+					if (instance->auth_error_code == AUTHENTICATION_ERROR_AUTH_FAILED)
+					{
+						update_state(instance, DEVICE_STATE_ERROR_AUTH);
+					}
+					// Codes_SRS_DEVICE_09_039: [If authentication state is AUTHENTICATION_STATE_ERROR and error code is TIMEOUT, the device state shall be updated to DEVICE_STATE_ERROR_AUTH_TIMEOUT]
+					else // DEVICE_STATE_ERROR_TIMEOUT
+					{
+						update_state(instance, DEVICE_STATE_ERROR_AUTH_TIMEOUT);
+					}
+				}
+				// There is no AUTHENTICATION_STATE_STOPPING
+			}
+
+			// Codes_SRS_DEVICE_09_040: [Messenger shall not be started if using CBS authentication and authentication start has not completed yet]
+			if (instance->config->authentication_mode == DEVICE_AUTH_MODE_X509 || instance->auth_state == AUTHENTICATION_STATE_STARTED)
+			{
+				// Codes_SRS_DEVICE_09_041: [If messenger state is MESSENGER_STATE_STOPPED, messenger_start shall be invoked]
+				if (instance->msgr_state == MESSENGER_STATE_STOPPED)
+				{
+					// Codes_SRS_DEVICE_09_042: [If messenger_start fails, the device state shall be updated to DEVICE_STATE_ERROR_MSG]
+					if (messenger_start(instance->messenger_handle, instance->session_handle) != RESULT_OK)
+					{
+						LogError("Device '%s' messenger failed to be started (messenger_start failed)", instance->config->device_id);
+
+						update_state(instance, DEVICE_STATE_ERROR_MSG);
+					}
+				}
+				// Codes_SRS_DEVICE_09_043: [If messenger state is MESSENGER_STATE_STARTING, the device shall track the time since last event change and timeout if needed]
+				else if (instance->msgr_state == MESSENGER_STATE_STARTING)
+				{
+					int is_timed_out;
+					if (is_timeout_reached(instance->msgr_state_last_changed_time, instance->msgr_state_change_timeout_secs, &is_timed_out) != RESULT_OK)
+					{
+						LogError("Device '%s' failed verifying the timeout for messenger start (is_timeout_reached failed)", instance->config->device_id);
+
+						update_state(instance, DEVICE_STATE_ERROR_MSG);
+					}
+					// Codes_SRS_DEVICE_09_044: [If messenger_start times out, the device state shall be updated to DEVICE_STATE_ERROR_MSG]
+					else if (is_timed_out == 1)
+					{
+						LogError("Device '%s' messenger did not complete starting within expected timeout (%d)", instance->config->device_id, instance->msgr_state_change_timeout_secs);
+
+						update_state(instance, DEVICE_STATE_ERROR_MSG);
+					}
+				}
+				// Codes_SRS_DEVICE_09_045: [If messenger state is MESSENGER_STATE_ERROR, the device state shall be updated to DEVICE_STATE_ERROR_MSG]
+				else if (instance->msgr_state == MESSENGER_STATE_ERROR)
+				{
+					LogError("Device '%s' messenger failed to be started (messenger got into error state)", instance->config->device_id);
+					
+					update_state(instance, DEVICE_STATE_ERROR_MSG);
+				}
+				// Codes_SRS_DEVICE_09_046: [If messenger state is MESSENGER_STATE_STARTED, the device state shall be updated to DEVICE_STATE_STARTED]
+				else if (instance->msgr_state == MESSENGER_STATE_STARTED)
+				{
+					update_state(instance, DEVICE_STATE_STARTED);
+				}
+			}
+		}
+		else if (instance->state == DEVICE_STATE_STARTED)
+		{
+			// Codes_SRS_DEVICE_09_047: [If CBS authentication is used and authentication state is not AUTHENTICATION_STATE_STARTED, the device state shall be updated to DEVICE_STATE_ERROR_AUTH]
+			if (instance->config->authentication_mode == DEVICE_AUTH_MODE_CBS &&
+				instance->auth_state != AUTHENTICATION_STATE_STARTED)
+			{
+				LogError("Device '%s' is started but authentication reported unexpected state %d", instance->config->device_id, instance->auth_state);
+
+				if (instance->auth_state != AUTHENTICATION_STATE_ERROR)
+				{
+					if (instance->auth_error_code == AUTHENTICATION_ERROR_AUTH_FAILED)
+					{
+						update_state(instance, DEVICE_STATE_ERROR_AUTH);
+					}
+					else // AUTHENTICATION_ERROR_AUTH_TIMEOUT
+					{
+						update_state(instance, DEVICE_STATE_ERROR_AUTH_TIMEOUT);
+					}
+				}
+				else
+				{
+					update_state(instance, DEVICE_STATE_ERROR_AUTH);
+				}
+			}
+			else
+			{
+				// Codes_SRS_DEVICE_09_048: [If messenger state is not MESSENGER_STATE_STARTED, the device state shall be updated to DEVICE_STATE_ERROR_MSG]
+				if (instance->msgr_state != MESSENGER_STATE_STARTED)
+				{
+					LogError("Device '%s' is started but messenger reported unexpected state %d", instance->config->device_id, instance->msgr_state);
+					update_state(instance, DEVICE_STATE_ERROR_MSG);
+				}
+			}
+		}
+
+		// Invoking the do_works():
+		if (instance->config->authentication_mode == DEVICE_AUTH_MODE_CBS)
+		{
+			if (instance->auth_state != AUTHENTICATION_STATE_STOPPED && instance->auth_state != AUTHENTICATION_STATE_ERROR)
+			{
+				// Codes_SRS_DEVICE_09_049: [If CBS is used for authentication and `instance->authentication_handle` state is not STOPPED or ERROR, authentication_do_work shall be invoked]
+				authentication_do_work(instance->authentication_handle);
+			}
+		}
+
+		if (instance->msgr_state != MESSENGER_STATE_STOPPED && instance->msgr_state != MESSENGER_STATE_ERROR)
+		{
+			// Codes_SRS_DEVICE_09_050: [If `instance->messenger_handle` state is not STOPPED or ERROR, authentication_do_work shall be invoked]
+			messenger_do_work(instance->messenger_handle);
+		}
+	}
+}
+
+void device_destroy(DEVICE_HANDLE handle)
+{
+	// Codes_SRS_DEVICE_09_012: [If `handle` is NULL, device_destroy shall return]
+	if (handle == NULL)
+	{
+		LogError("Failed destroying device handle (handle is NULL)");
+	}
+	else
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+		// Codes_SRS_DEVICE_09_013: [If the device is in state DEVICE_STATE_STARTED or DEVICE_STATE_STARTING, device_stop() shall be invoked]
+		if (instance->state == DEVICE_STATE_STARTED || instance->state == DEVICE_STATE_STARTING)
+		{
+			(void)device_stop((DEVICE_HANDLE)instance);
+		}
+
+		// Codes_SRS_DEVICE_09_014: [`instance->messenger_handle shall be destroyed using messenger_destroy()`]
+		// Codes_SRS_DEVICE_09_015: [If created, `instance->authentication_handle` shall be destroyed using authentication_destroy()`]
+		// Codes_SRS_DEVICE_09_016: [The contents of `instance->config` shall be detroyed and then it shall be freed]
+		internal_destroy_device((DEVICE_INSTANCE*)handle);
+	}
+}
+
+int device_send_event_async(DEVICE_HANDLE handle, IOTHUB_MESSAGE_LIST* message, ON_DEVICE_D2C_EVENT_SEND_COMPLETE on_device_d2c_event_send_complete_callback, void* context)
+{
+	int result;
+
+	// Codes_SRS_DEVICE_09_051: [If `handle` are `message` are NULL, device_send_event_async shall return a non-zero result]
+	if (handle == NULL || message == NULL)
+	{
+		LogError("Failed sending event (either handle (%p) or message (%p) are NULL)", handle, message);
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_SEND_EVENT_TASK* send_task;
+
+		// Codes_SRS_DEVICE_09_052: [A structure (`send_task`) shall be created to track the send state of the message]
+		if ((send_task = (DEVICE_SEND_EVENT_TASK*)malloc(sizeof(DEVICE_SEND_EVENT_TASK))) == NULL)
+		{
+			// Codes_SRS_DEVICE_09_053: [If `send_task` fails to be created, device_send_event_async shall return a non-zero value]
+			LogError("Failed sending event (failed creating task to send event)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+			// Codes_SRS_DEVICE_09_054: [`send_task` shall contain the user callback and the context provided]
+			memset(send_task, 0, sizeof(DEVICE_SEND_EVENT_TASK));
+			send_task->on_event_send_complete_callback = on_device_d2c_event_send_complete_callback;
+			send_task->on_event_send_complete_context = context;
+			
+			// Codes_SRS_DEVICE_09_055: [The message shall be sent using messenger_send_async, passing `on_event_send_complete_messenger_callback` and `send_task`]
+			if (messenger_send_async(instance->messenger_handle, message, on_event_send_complete_messenger_callback, (void*)send_task) != RESULT_OK)
+			{
+				// Codes_SRS_DEVICE_09_056: [If messenger_send_async fails, device_send_event_async shall return a non-zero value]
+				LogError("Failed sending event (messenger_send_async failed)");
+				// Codes_SRS_DEVICE_09_057: [If any failures occur, device_send_event_async shall release all memory it has allocated]
+				free(send_task);
+				result = __FAILURE__;
+			}
+			else
+			{	
+				// Codes_SRS_DEVICE_09_058: [If no failures occur, device_send_event_async shall return 0]
+				result = RESULT_OK;
+			}
+		}
+	}
+
+	return result;
+}
+
+int device_get_send_status(DEVICE_HANDLE handle, DEVICE_SEND_STATUS *send_status)
+{
+	int result;
+
+
+	// Codes_SRS_DEVICE_09_105: [If `handle` or `send_status` is NULL, device_get_send_status shall return a non-zero result]
+	if (handle == NULL || send_status == NULL)
+	{
+		LogError("Failed getting the device messenger send status (NULL parameter received; handle=%p, send_status=%p)", handle, send_status);
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+		MESSENGER_SEND_STATUS messenger_send_status;
+		
+		// Codes_SRS_DEVICE_09_106: [The status of `instance->messenger_handle` shall be obtained using messenger_get_send_status]
+		if (messenger_get_send_status(instance->messenger_handle, &messenger_send_status) != RESULT_OK)
+		{
+			// Codes_SRS_DEVICE_09_107: [If messenger_get_send_status fails, device_get_send_status shall return a non-zero result]
+			LogError("Failed getting the device messenger send status (messenger_get_send_status failed)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			// Codes_SRS_DEVICE_09_108: [If messenger_get_send_status returns MESSENGER_SEND_STATUS_IDLE, device_get_send_status return status DEVICE_SEND_STATUS_IDLE]
+			if (messenger_send_status == MESSENGER_SEND_STATUS_IDLE)
+			{
+				*send_status = DEVICE_SEND_STATUS_IDLE;
+			}
+			// Codes_SRS_DEVICE_09_109: [If messenger_get_send_status returns MESSENGER_SEND_STATUS_BUSY, device_get_send_status return status DEVICE_SEND_STATUS_BUSY]
+			else // i.e., messenger_send_status == MESSENGER_SEND_STATUS_BUSY
+			{
+				*send_status = DEVICE_SEND_STATUS_BUSY;
+			}
+
+			// Codes_SRS_DEVICE_09_110: [If device_get_send_status succeeds, it shall return zero as result]
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+int device_subscribe_message(DEVICE_HANDLE handle, ON_DEVICE_C2D_MESSAGE_RECEIVED on_message_received_callback, void* context)
+{
+	int result;
+
+	// Codes_SRS_DEVICE_09_066: [If `handle` or `on_message_received_callback` or `context` is NULL, device_subscribe_message shall return a non-zero result]
+	if (handle == NULL || on_message_received_callback == NULL || context == NULL)
+	{
+		LogError("Failed subscribing to C2D messages (either handle (%p), on_message_received_callback (%p) or context (%p) is NULL)",
+			handle, on_message_received_callback, context);
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+		// Codes_SRS_DEVICE_09_067: [messenger_subscribe_for_messages shall be invoked passing `on_messenger_message_received_callback` and the user callback and context]
+		if (messenger_subscribe_for_messages(instance->messenger_handle, on_messenger_message_received_callback, handle) != RESULT_OK)
+		{
+			// Codes_SRS_DEVICE_09_068: [If messenger_subscribe_for_messages fails, device_subscribe_message shall return a non-zero result]
+			LogError("Failed subscribing to C2D messages (messenger_subscribe_for_messages failed)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			instance->on_message_received_callback = on_message_received_callback;
+			instance->on_message_received_context = context;
+
+			// Codes_SRS_DEVICE_09_069: [If no failures occur, device_subscribe_message shall return 0]
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+int device_unsubscribe_message(DEVICE_HANDLE handle)
+{
+	int result;
+
+	// Codes_SRS_DEVICE_09_076: [If `handle` is NULL, device_unsubscribe_message shall return a non-zero result]
+	if (handle == NULL)
+	{
+		LogError("Failed unsubscribing to C2D messages (handle is NULL)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+		// Codes_SRS_DEVICE_09_077: [messenger_unsubscribe_for_messages shall be invoked passing `instance->messenger_handle`]
+		if (messenger_unsubscribe_for_messages(instance->messenger_handle) != RESULT_OK)
+		{
+			// Codes_SRS_DEVICE_09_078: [If messenger_unsubscribe_for_messages fails, device_unsubscribe_message shall return a non-zero result]
+			LogError("Failed unsubscribing to C2D messages (messenger_unsubscribe_for_messages failed)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			// Codes_SRS_DEVICE_09_079: [If no failures occur, device_unsubscribe_message shall return 0]
+			result = RESULT_OK;
+		}
+	}
+
+	return result;
+}
+
+int device_send_message_disposition(DEVICE_HANDLE device_handle, DEVICE_MESSAGE_DISPOSITION_INFO* disposition_info, DEVICE_MESSAGE_DISPOSITION_RESULT disposition_result)
+{
+	int result;
+
+	// Codes_SRS_DEVICE_09_111: [If `device_handle` or `disposition_info` are NULL, device_send_message_disposition() shall fail and return __FAILURE__]
+	if (device_handle == NULL || disposition_info == NULL)
+	{
+		LogError("Failed sending message disposition (either device_handle (%p) or disposition_info (%p) are NULL)", device_handle, disposition_info);
+		result = __FAILURE__;
+	}
+	// Codes_SRS_DEVICE_09_112: [If `disposition_info->source` is NULL, device_send_message_disposition() shall fail and return __FAILURE__]  
+	else if (disposition_info->source == NULL)
+	{
+		LogError("Failed sending message disposition (disposition_info->source is NULL)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_INSTANCE* device = (DEVICE_INSTANCE*)device_handle;
+		MESSENGER_MESSAGE_DISPOSITION_INFO* messenger_disposition_info;
+
+		// Codes_SRS_DEVICE_09_113: [A MESSENGER_MESSAGE_DISPOSITION_INFO instance shall be created with a copy of the `source` and `message_id` contained in `disposition_info`]  
+		if ((messenger_disposition_info = create_messenger_disposition_info(disposition_info)) == NULL)
+		{
+			// Codes_SRS_DEVICE_09_114: [If the MESSENGER_MESSAGE_DISPOSITION_INFO fails to be created, device_send_message_disposition() shall fail and return __FAILURE__]  
+			LogError("Failed sending message disposition (failed to create MESSENGER_MESSAGE_DISPOSITION_INFO)");
+			result = __FAILURE__;
+		}
+		else
+		{
+			MESSENGER_DISPOSITION_RESULT messenger_disposition_result = get_messenger_message_disposition_result_from(disposition_result);
+
+			// Codes_SRS_DEVICE_09_115: [`messenger_send_message_disposition()` shall be invoked passing the MESSENGER_MESSAGE_DISPOSITION_INFO instance and the corresponding MESSENGER_DISPOSITION_RESULT]  
+			if (messenger_send_message_disposition(device->messenger_handle, messenger_disposition_info, messenger_disposition_result) != RESULT_OK)
+			{
+				// Codes_SRS_DEVICE_09_116: [If `messenger_send_message_disposition()` fails, device_send_message_disposition() shall fail and return __FAILURE__]  
+				LogError("Failed sending message disposition (messenger_send_message_disposition failed)");
+				result = __FAILURE__;
+			}
+			else
+			{
+				// Codes_SRS_DEVICE_09_118: [If no failures occurr, device_send_message_disposition() shall return 0]  
+				result = RESULT_OK;
+			}
+
+			// Codes_SRS_DEVICE_09_117: [device_send_message_disposition() shall destroy the MESSENGER_MESSAGE_DISPOSITION_INFO instance]  
+			destroy_messenger_disposition_info(messenger_disposition_info);
+		}
+	}
+
+	return result;
+}
+
+int device_set_retry_policy(DEVICE_HANDLE handle, IOTHUB_CLIENT_RETRY_POLICY policy, size_t retry_timeout_limit_in_seconds)
+{
+	(void)retry_timeout_limit_in_seconds;
+	(void)policy;
+	int result;
+
+	// Codes_SRS_DEVICE_09_080: [If `handle` is NULL, device_set_retry_policy shall return a non-zero result]
+	if (handle == NULL)
+	{
+		LogError("Failed setting retry policy (handle is NULL)");
+		result = __FAILURE__;
+	}
+	else
+	{
+		// Codes_SRS_DEVICE_09_081: [device_set_retry_policy shall return a non-zero result]
+		LogError("Failed setting retry policy (functionality not supported)");
+		result = __FAILURE__;
+	}
+
+	return result;
+}
+
+int device_set_option(DEVICE_HANDLE handle, const char* name, void* value)
+{
+	int result;
+
+	// Codes_SRS_DEVICE_09_082: [If `handle` or `name` or `value` are NULL, device_set_option shall return a non-zero result]
+	if (handle == NULL || name == NULL || value == NULL)
+	{
+		LogError("failed setting device option (one of the followin are NULL: _handle=%p, name=%p, value=%p)",
+			handle, name, value);
+		result = __FAILURE__;
+	}
+	else
+	{
+		DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+		if (strcmp(DEVICE_OPTION_CBS_REQUEST_TIMEOUT_SECS, name) == 0 ||
+			strcmp(DEVICE_OPTION_SAS_TOKEN_REFRESH_TIME_SECS, name) == 0 ||
+			strcmp(DEVICE_OPTION_SAS_TOKEN_LIFETIME_SECS, name) == 0)
+		{
+			// Codes_SRS_DEVICE_09_083: [If `name` refers to authentication but CBS authentication is not used, device_set_option shall return a non-zero result]
+			if (instance->authentication_handle == NULL)
+			{
+				LogError("failed setting option for device '%s' (cannot set authentication option '%s'; not using CBS authentication)", instance->config->device_id, name);
+				result = __FAILURE__;
+			}
+			// Codes_SRS_DEVICE_09_084: [If `name` refers to authentication, it shall be passed along with `value` to authentication_set_option]
+			else if(authentication_set_option(instance->authentication_handle, name, value) != RESULT_OK)
+			{
+				// Codes_SRS_DEVICE_09_085: [If authentication_set_option fails, device_set_option shall return a non-zero result]
+				LogError("failed setting option for device '%s' (failed setting authentication option '%s')", instance->config->device_id, name);
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+		}
+		else if (strcmp(DEVICE_OPTION_EVENT_SEND_TIMEOUT_SECS, name) == 0)
+		{
+			// Codes_SRS_DEVICE_09_086: [If `name` refers to messenger module, it shall be passed along with `value` to messenger_set_option]
+			if (messenger_set_option(instance->messenger_handle, name, value) != RESULT_OK)
+			{
+				// Codes_SRS_DEVICE_09_087: [If messenger_set_option fails, device_set_option shall return a non-zero result]
+				LogError("failed setting option for device '%s' (failed setting messenger option '%s')", instance->config->device_id, name);
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+		}
+		else if (strcmp(DEVICE_OPTION_SAVED_AUTH_OPTIONS, name) == 0)
+		{
+			// Codes_SRS_DEVICE_09_088: [If `name` is DEVICE_OPTION_SAVED_AUTH_OPTIONS but CBS authentication is not being used, device_set_option shall return a non-zero result]
+			if (instance->authentication_handle == NULL)
+			{
+				LogError("failed setting option for device '%s' (cannot set authentication option '%s'; not using CBS authentication)", instance->config->device_id, name);
+				result = __FAILURE__;
+			}
+			else if (OptionHandler_FeedOptions((OPTIONHANDLER_HANDLE)value, instance->authentication_handle) != OPTIONHANDLER_OK)
+			{
+				// Codes_SRS_DEVICE_09_091: [If any call to OptionHandler_FeedOptions fails, device_set_option shall return a non-zero result]
+				LogError("failed setting option for device '%s' (OptionHandler_FeedOptions failed for authentication instance)", instance->config->device_id);
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+		}
+		else if (strcmp(DEVICE_OPTION_SAVED_MESSENGER_OPTIONS, name) == 0)
+		{
+			// Codes_SRS_DEVICE_09_089: [If `name` is DEVICE_OPTION_SAVED_MESSENGER_OPTIONS, `value` shall be fed to `instance->messenger_handle` using OptionHandler_FeedOptions]
+			if (OptionHandler_FeedOptions((OPTIONHANDLER_HANDLE)value, instance->messenger_handle) != OPTIONHANDLER_OK)
+			{
+				// Codes_SRS_DEVICE_09_091: [If any call to OptionHandler_FeedOptions fails, device_set_option shall return a non-zero result]
+				LogError("failed setting option for device '%s' (OptionHandler_FeedOptions failed for messenger instance)", instance->config->device_id);
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+		}
+		else if (strcmp(DEVICE_OPTION_SAVED_OPTIONS, name) == 0)
+		{
+			// Codes_SRS_DEVICE_09_090: [If `name` is DEVICE_OPTION_SAVED_OPTIONS, `value` shall be fed to `instance` using OptionHandler_FeedOptions]
+			if (OptionHandler_FeedOptions((OPTIONHANDLER_HANDLE)value, handle) != OPTIONHANDLER_OK)
+			{
+				// Codes_SRS_DEVICE_09_091: [If any call to OptionHandler_FeedOptions fails, device_set_option shall return a non-zero result]
+				LogError("failed setting option for device '%s' (OptionHandler_FeedOptions failed)", instance->config->device_id);
+				result = __FAILURE__;
+			}
+			else
+			{
+				result = RESULT_OK;
+			}
+		}
+		else
+		{
+			// Codes_SRS_DEVICE_09_092: [If no failures occur, device_set_option shall return 0]
+			LogError("failed setting option for device '%s' (option with name '%s' is not suppported)", instance->config->device_id, name);
+			result = __FAILURE__;
+		}
+	}
+
+	return result;
+}
+
+OPTIONHANDLER_HANDLE device_retrieve_options(DEVICE_HANDLE handle)
+{
+	OPTIONHANDLER_HANDLE result;
+
+	// Codes_SRS_DEVICE_09_093: [If `handle` is NULL, device_retrieve_options shall return NULL]
+	if (handle == NULL)
+	{
+		LogError("Failed to retrieve options from device instance (handle is NULL)");
+		result = NULL;
+	}
+	else
+	{
+		// Codes_SRS_DEVICE_09_094: [A OPTIONHANDLER_HANDLE instance, aka `options` shall be created using OptionHandler_Create]
+		OPTIONHANDLER_HANDLE options = OptionHandler_Create(device_clone_option, device_destroy_option, (pfSetOption)device_set_option);
+
+		if (options == NULL)
+		{
+			// Codes_SRS_DEVICE_09_095: [If OptionHandler_Create fails, device_retrieve_options shall return NULL]
+			LogError("Failed to retrieve options from device instance (OptionHandler_Create failed)");
+			result = NULL;
+		}
+		else
+		{
+			DEVICE_INSTANCE* instance = (DEVICE_INSTANCE*)handle;
+
+			OPTIONHANDLER_HANDLE dependency_options = NULL;
+
+			// Codes_SRS_DEVICE_09_096: [If CBS authentication is used, `instance->authentication_handle` options shall be retrieved using authentication_retrieve_options]
+			if (instance->authentication_handle != NULL &&
+				(dependency_options = authentication_retrieve_options(instance->authentication_handle)) == NULL)
+			{
+				// Codes_SRS_DEVICE_09_097: [If authentication_retrieve_options fails, device_retrieve_options shall return NULL]
+				LogError("Failed to retrieve options from device '%s' (failed to retrieve options from authentication instance)", instance->config->device_id);
+				result = NULL;
+			}
+			// Codes_SRS_DEVICE_09_098: [The authentication options shall be added to `options` using OptionHandler_AddOption as DEVICE_OPTION_SAVED_AUTH_OPTIONS]
+			else if (instance->authentication_handle != NULL &&
+				OptionHandler_AddOption(options, DEVICE_OPTION_SAVED_AUTH_OPTIONS, (const void*)dependency_options) != OPTIONHANDLER_OK)
+			{
+				// Codes_SRS_DEVICE_09_102: [If any call to OptionHandler_AddOption fails, device_retrieve_options shall return NULL]
+				LogError("Failed to retrieve options from device '%s' (OptionHandler_AddOption failed for option '%s')", instance->config->device_id, DEVICE_OPTION_SAVED_AUTH_OPTIONS);
+				result = NULL;
+			}
+			// Codes_SRS_DEVICE_09_099: [`instance->messenger_handle` options shall be retrieved using messenger_retrieve_options]
+			else if ((dependency_options = messenger_retrieve_options(instance->messenger_handle)) == NULL)
+			{
+				// Codes_SRS_DEVICE_09_100: [If messenger_retrieve_options fails, device_retrieve_options shall return NULL]
+				LogError("Failed to retrieve options from device '%s' (failed to retrieve options from messenger instance)", instance->config->device_id);
+				result = NULL;
+			}
+			// Codes_SRS_DEVICE_09_101: [The messenger options shall be added to `options` using OptionHandler_AddOption as DEVICE_OPTION_SAVED_MESSENGER_OPTIONS]
+			else if (OptionHandler_AddOption(options, DEVICE_OPTION_SAVED_MESSENGER_OPTIONS, (const void*)dependency_options) != OPTIONHANDLER_OK)
+			{
+				// Codes_SRS_DEVICE_09_102: [If any call to OptionHandler_AddOption fails, device_retrieve_options shall return NULL]
+				LogError("Failed to retrieve options from device '%s' (OptionHandler_AddOption failed for option '%s')", instance->config->device_id, DEVICE_OPTION_SAVED_MESSENGER_OPTIONS);
+				result = NULL;
+			}
+			else
+			{
+				// Codes_SRS_DEVICE_09_104: [If no failures occur, a handle to `options` shall be return]
+				result = options;
+			}
+
+			if (result == NULL)
+			{
+				// Codes_SRS_DEVICE_09_103: [If any failure occurs, any memory allocated by device_retrieve_options shall be destroyed]
+				OptionHandler_Destroy(options);
+			}
+		}
+	}
+
+	return result;
+}