311 adapter lifecycle foundations (#293)

* mqtt5 connection reset support
* Rework adapter callback and ref counting 


Co-authored-by: Bret Ambrose <bambrose@amazon.com>

include/aws/mqtt/mqtt.h

@@ -78,6 +78,7 @@ enum aws_mqtt_error {
     AWS_ERROR_MQTT5_INVALID_INBOUND_TOPIC_ALIAS,
     AWS_ERROR_MQTT5_INVALID_OUTBOUND_TOPIC_ALIAS,
     AWS_ERROR_MQTT5_INVALID_UTF8_STRING,
+    AWS_ERROR_MQTT_CONNECTION_RESET_FOR_ADAPTER_CONNECT,
 
     AWS_ERROR_END_MQTT_RANGE = AWS_ERROR_ENUM_END_RANGE(AWS_C_MQTT_PACKAGE_ID),
 };

include/aws/mqtt/private/v5/mqtt5_client_impl.h

@@ -489,6 +489,29 @@ struct aws_mqtt5_client {
      * with clean start set to false.
      */
     bool has_connected_successfully;
+
+    /*
+     * A flag that allows in-thread observers (currently the mqtt3_to_5 adapter) to signal that the connection
+     * should be torn down and re-established.  Only relevant to the CONNECTING state which is not interruptible:
+     *
+     * If the mqtt5 client is in the CONNECTING state (ie waiting for bootstrap to complete) and the 3-adapter
+     * is asked to connect, then we *MUST* discard the in-progress connection attempt in order to guarantee the
+     * connection we establish uses all of the configuration parameters that are passed during the mqtt3 API's connect
+     * call (host, port, tls options, socket options, etc...).  Since we can't interrupt the CONNECTING state, we
+     * instead set a flag that tells the mqtt5 client to tear down the connection as soon as the initial bootstrap
+     * completes.  The reconnect will establish the requested connection using the parameters passed to
+     * the mqtt3 API.
+     *
+     * Rather than try and catch every escape path from CONNECTING, we lazily reset this flag to false when we
+     * enter the CONNECTING state.  On a similar note, we only check this flag as we transition to MQTT_CONNECT.
+     *
+     * This flag is ultimately only needed when the 3 adapter and 5 client are used out-of-sync.  If you use the
+     * 3 adapter exclusively after 5 client creation, it never comes into play.
+     *
+     * Even the adapter shouldn't manipulate this directly.  Instead, use the aws_mqtt5_client_reset_connection private
+     * API to tear down an in-progress or established connection in response to a connect() request on the adapter.
+     */
+    bool should_reset_connection;
 };
 
 AWS_EXTERN_C_BEGIN
@@ -638,10 +661,17 @@ AWS_MQTT_API void aws_mqtt5_client_statistics_change_operation_statistic_state(
  */
 AWS_MQTT_API const char *aws_mqtt5_client_state_to_c_string(enum aws_mqtt5_client_state state);
 
-/*
- * Temporary, private API to turn on total incoming packet logging at the byte level.
+/**
+ * An internal API used by the MQTT3 adapter to force any existing-or-in-progress connection to
+ * be torn down and re-established.  Necessary because the MQTT3 interface allows overrides on a large number
+ * of configuration parameters through the connect() call.  We must honor those parameters and the safest thing
+ * to do is to just throw away the current connection (if it exists) and make a new one.  In the case that an MQTT5
+ * client is being driven entirely by the MQTT3 adapter, this case never actually happens.
+ *
+ * @param client client to reset an existing or in-progress connection for
+ * @return true if a connection reset was triggered, false if there was nothing to do
  */
-AWS_MQTT_API void aws_mqtt5_client_enable_full_packet_logging(struct aws_mqtt5_client *client);
+AWS_MQTT_API bool aws_mqtt5_client_reset_connection(struct aws_mqtt5_client *client);
 
 AWS_EXTERN_C_END
 

source/mqtt.c

@@ -214,6 +214,12 @@ bool aws_mqtt_is_valid_topic_filter(const struct aws_byte_cursor *topic_filter)
             AWS_DEFINE_ERROR_INFO_MQTT(
                 AWS_ERROR_MQTT5_INVALID_OUTBOUND_TOPIC_ALIAS,
                 "Outgoing publish contained an invalid (too large or unknown) topic alias"),
+            AWS_DEFINE_ERROR_INFO_MQTT(
+                AWS_ERROR_MQTT5_INVALID_UTF8_STRING,
+                "Outbound packet contains invalid utf-8 data in a field that must be utf-8"),
+            AWS_DEFINE_ERROR_INFO_MQTT(
+                AWS_ERROR_MQTT_CONNECTION_RESET_FOR_ADAPTER_CONNECT,
+                "Mqtt5 connection was reset by the Mqtt3 adapter in order to guarantee correct connection configuration"),
         };
 /* clang-format on */
 #undef AWS_DEFINE_ERROR_INFO_MQTT