le_messaging.h

    1 /**
    2  * @page c_messaging Low-level Messaging API
    3  *
    4  * @subpage le_messaging.h "API Reference"
    5  *
    6  * <HR>
    7  *
    8  * Message-based interfaces in Legato are implemented in layers.
    9  * This low-level messaging API is at the bottom layer.
   10  * It's designed to support higher layers of the messaging system.  But it's also
   11  * intended to be easy to hand-code low-level messaging in C, when necessary.
   12  *
   13  * Two messaging types are supported, Local and Socket.  "Local" allows logically distinct apps to
   14  * be combined in one executable, and essentially mediates the direct function calls between them.
   15  * "Socket" uses UNIX domain sockets to communicate between distinct processes.
   16  *
   17  * This low-level messaging API supports:
   18  *  - (Socket only) remote party identification (addressing)
   19  *  - (Socket only) very late (runtime) discovery and binding of parties
   20  *  - (Socket only) in-process and inter-process message delivery
   21  *  - location transparency
   22  *  - sessions
   23  *  - (Socket only) access control
   24  *  - request/reply transactions
   25  *  - message buffer memory management
   26  *  - support for single-threaded and multi-threaded programs
   27  *  - some level of protection from protocol mismatches between parties in a session.
   28  *
   29  * This API is integrated with the Legato Event Loop API so components can interact with each
   30  * other using messaging without having to create threads or file descriptor
   31  * sets that block other software from handling other events.  Support for
   32  * integration with legacy POSIX-based programs is also provided.
   33  *
   34  * @section c_messagingInteractionModel Interaction Model
   35  *
   36  * The Legato low-level messaging system follows a service-oriented pattern:
   37  *  - Service providers advertise their service.
   38  *  - Clients open sessions with those services
   39  *  - Both sides can send and receive messages through the session.
   40  *
   41  * Clients and servers can both send one-way messages within a session.
   42  * Clients can start a request-response transaction by sending a request to the server,
   43  * and the server can send a response. Request-response transactions can be blocking or
   44  * non-blocking (with a completion callback). If the server dies or terminates the session
   45  * before sending the response, Legato will automatically terminate the transaction.
   46  *
   47  * Servers are prevented from sending blocking requests to clients as a safety measure.
   48  * If a server were to block waiting for one of its clients, it would open up the server
   49  * to being blocked indefinitely by one of its clients, which would allow one client to cause
   50  * a server to deny service to other clients.  Also, if a client started a blocking request-response
   51  * transaction at the same time that the server started a blocking request-response transaction
   52  * in the other direction, a deadlock would occur.
   53  *
   54  * @section c_messagingAddressing Addressing
   55  *
   56  * Servers and clients have interfaces that can been connected to each other via bindings.  Both
   57  * client-side and server-side interfaces are identified by name, but the names don't have to match
   58  * for them to be bound to each other.  The binding determines which server-side interface will
   59  * be connected to when a client opens a session.
   60  *
   61  * Server-side interfaces are also known as "services".
   62  *
   63  * When a session is opened by a client, a session reference is provided to both the client
   64  * and the server.  Messages are then sent within the session using the session reference.
   65  * This session reference becomes invalid when the session is closed.
   66  *
   67  * @section c_messagingProtocols Protocols
   68  *
   69  * Communication between client and server is done using a message-based protocol. This protocol
   70  * is defined at a higher layer than this API, so this API doesn't know the structure of the
   71  * message payloads or the correct message sequences. That means this API can't check
   72  * for errors in the traffic it carries. However, it does provide a basic mechanism for detecting
   73  * protocol mismatches by forcing both client and server to provide the protocol identifier
   74  * of the protocol to be used.  The client and server must also provide
   75  * the maximum message size, as an extra sanity check.
   76  *
   77  * To make this possible, the client and server must independently call
   78  * @c le_msg_GetProtocolRef(), to get a reference to a "Protocol" object that encapsulates these
   79  * protocol details:
   80  *
   81  * @code
   82  * protocolRef = le_msg_GetProtocolRef(MY_PROTOCOL_ID, sizeof(myproto_Msg_t));
   83  * @endcode
   84  *
   85  * @note In this example, the protocol identifier (which is a string uniquely identifying a
   86  *       specific version of a specific protocol) and the message structure
   87  *       would be defined elsewhere, in a header file shared between the client and the
   88  *       server.  The structure @c myproto_Msg_t contains a
   89  *       @c union of all of the different messages included in the protocol, thereby
   90  *       making @c myproto_Msg_t as big as the biggest message in the protocol.
   91  *
   92  * When a server creates a service (by calling le_msg_CreateService()) and when a client creates
   93  * a session (by calling le_msg_CreateSession()), they are required to provide a reference to a
   94  * Protocol object that they obtained from le_msg_GetProtocolRef().
   95  *
   96  * @section c_messagingClientUsage Client Usage Model
   97  *
   98  * @ref c_messagingClientSending <br>
   99  * @ref c_messagingClientReceiving <br>
  100  * @ref c_messagingClientClosing <br>
  101  * @ref c_messagingClientMultithreading <br>
  102  * @ref c_messagingClientExample
  103  *
  104  * Clients that want to use a service do the following:
  105  *  -# Get a reference to the protocol they want to use by calling @c le_msg_GetProtocolRef().
  106  *  -# Create a session using @c le_msg_CreateSession(), passing in the protocol reference and
  107  *     the client's interface name.
  108  *  -# Optionally register a message receive callback using @c le_msg_SetSessionRecvHandler().
  109  *  -# Open the session using le_msg_OpenSession(), le_msg_OpenSessionSync(), or
  110  *     le_msg_TryOpenSessionSync().
  111  *
  112  * @code
  113  *     protocolRef = le_msg_GetProtocolRef(PROTOCOL_ID, sizeof(myproto_Msg_t));
  114  *     sessionRef = le_msg_CreateSession(protocolRef, MY_INTERFACE_NAME);
  115  *     le_msg_SetSessionRecvHandler(sessionRef, NotifyMsgHandlerFunc, NULL);
  116  *     le_msg_OpenSession(sessionRef, SessionOpenHandlerFunc, NULL);
  117  * @endcode
  118  *
  119  * The Legato framework takes care of setting up any IPC connections, as needed (or not, if the
  120  * client and server happen to be in the same process).
  121  *
  122  * When the session opens, the Event Loop will call the "session open handler" call-back function
  123  * that was passed into le_msg_OpenSession().
  124  *
  125  * le_msg_OpenSessionSync() is a synchronous alternative to le_msg_OpenSession(). The difference
  126  * is that le_msg_OpenSessionSync() will not return until the session has opened or failed to
  127  * open (most likely due to permissions settings).
  128  *
  129  * le_msg_TryOpenSessionSync() is like le_msg_OpenSessionSync() except that it will not wait
  130  * for a server session to become available if it's not already available at the time of the
  131  * call.  That is, if the client's interface is not bound to any service, or if the service that
  132  * it's bound to is not currently advertised by the server, then le_msg_TryOpenSessionSync()
  133  * will return an error code.
  134  *
  135  * @subsection c_messagingClientSending Sending a Message
  136  *
  137  * Before sending a message, the client must first allocate the message from the session's message
  138  * pool using le_msg_CreateMsg(). It can then get a pointer to the payload part of the
  139  * message using le_msg_GetPayloadPtr(). Once the message payload is populated, the client sends
  140  * the message.
  141  *
  142  * @code
  143  *     msgRef = le_msg_CreateMsg(sessionRef);
  144  *     msgPayloadPtr = le_msg_GetPayloadPtr(msgRef);
  145  *     msgPayloadPtr->... = ...; // <-- Populate message payload...
  146  * @endcode
  147  *
  148  * If no response is required from the server, the client sends the message using le_msg_Send().
  149  * At this point, the client has handed off the message to the messaging system, and the messaging
  150  * system will delete the message automatically once it has finished sending it.
  151  *
  152  * @code
  153  *     le_msg_Send(msgRef);
  154  * @endcode
  155  *
  156  * If the client expects a response from the server, the client can use
  157  * le_msg_RequestResponse() to send their message and specify a callback function to be called
  158  * when the response arrives.  This callback will be called by the event loop of the thread that
  159  * created the session (i.e., the thread that called le_msg_CreateSession()).
  160  *
  161  * @code
  162  *     le_msg_RequestResponse(msgRef, ResponseHandlerFunc, NULL);
  163  * @endcode
  164  *
  165  * If the client expects an immediate response from the server, and the client wants to block until
  166  * that response is received, it can use le_msg_RequestSyncResponse() instead of
  167  * le_msg_RequestResponse().  However, keep in mind that blocking the client thread will
  168  * block all event handlers that share that thread.  That's why le_msg_RequestSyncResponse() should
  169  * only be used when the server is expected to respond immediately, or when the client thread
  170  * is not shared by other event handlers.
  171  *
  172  * @code
  173  *     responseMsgRef = le_msg_RequestSyncResponse(msgRef);
  174  * @endcode
  175  *
  176  * @warning If the client and server are running in the same thread, and the
  177  * client calls le_msg_RequestSyncResponse(), it will return an error immediately, instead of
  178  * blocking the thread.  If the thread were blocked in this scenario, the server would also be
  179  * blocked and would therefore be unable to receive the request and respond to it, resulting in
  180  * a deadlock.
  181  *
  182  * When the client is finished with it, the <b> client must release its reference
  183  * to the response message </b> by calling le_msg_ReleaseMsg().
  184  *
  185  * @code
  186  *     le_msg_ReleaseMsg(responseMsgRef);
  187  * @endcode
  188  *
  189  * @subsection c_messagingClientReceiving Receiving a Non-Response Message
  190  *
  191  * When a server sends a message to the client that is not a response to a request from the client,
  192  * that non-response message will be passed to the receive handler that the client
  193  * registered using le_msg_SetSessionRecvHandler().  In fact, this is the only kind of message
  194  * that will result in that receive handler being called.
  195  *
  196  * @note Some protocols don't include any messages that are not responses to client requests,
  197  * which is why it's optional to register a receive handler on the client side.
  198  *
  199  * The payload of a received message can be accessed using le_msg_GetPayloadPtr(), and the client
  200  * can check what session the message arrived through by calling le_msg_GetSession().
  201  *
  202  * When the client is finished with the message, the <b> client must release its reference
  203  * to the message </b> by calling le_msg_ReleaseMsg().
  204  *
  205  * @code
  206  * // Function will be called whenever the server sends us a notification message.
  207  * static void NotifyHandlerFunc
  208  * (
  209  *     le_msg_MessageRef_t  msgRef,    // Reference to the received message.
  210  *     void*                contextPtr // contextPtr passed into le_msg_SetSessionRecvHandler().
  211  * )
  212  * {
  213  *     // Process notification message from the server.
  214  *     myproto_Msg_t* msgPayloadPtr = le_msg_GetPayloadPtr(msgRef);
  215  *     ...
  216  *
  217  *     // Release the message, now that we are finished with it.
  218  *     le_msg_ReleaseMsg(msgRef);
  219  * }
  220  *
  221  * COMPONENT_INIT
  222  * {
  223  *     le_msg_ProtocolRef_t protocolRef;
  224  *     le_msg_SessionRef_t sessionRef;
  225  *
  226  *     protocolRef = le_msg_GetProtocolRef(PROTOCOL_ID, sizeof(myproto_Msg_t));
  227  *     sessionRef = le_msg_CreateSession(protocolRef, MY_INTERFACE_NAME);
  228  *     le_msg_SetSessionRecvHandler(sessionRef, NotifyHandlerFunc, NULL);
  229  *     le_msg_OpenSession(sessionRef, SessionOpenHandlerFunc, NULL);
  230  * }
  231  * @endcode
  232  *
  233  * @subsection c_messagingClientClosing Closing Sessions
  234  *
  235  * When the client is done using a service, it can close the session using le_msg_CloseSession().
  236  * This will leave the session object in existence, though, so that it can be opened again
  237  * using le_msg_OpenSession().
  238  *
  239  * @code
  240  *     le_msg_CloseSession(sessionRef);
  241  * @endcode
  242  *
  243  * To delete a session object, call le_msg_DeleteSession().  This will automatically close the
  244  * session, if it's still open (but won't automatically delete any messages).
  245  *
  246  * @code
  247  *     le_msg_DeleteSession(sessionRef);
  248  * @endcode
  249  *
  250  * @note If a client process dies while it has a session open, that session will be
  251  * automatically closed and deleted by the Legato framework, so there's no need to register process
  252  * clean-up handlers or anything like that for this purpose.
  253  *
  254  * Additionally, clients can choose to call le_msg_SetSessionCloseHandler() to register to be
  255  * notified when a session gets closed by the server.  Servers often keep state on behalf of their
  256  * clients, and if the server closes the session (or if the system closes the session because the
  257  * server died), the client most likely will still be operating under the assumption (now false)
  258  * that the server is maintaining state on its behalf.  If a client is designed to recover from
  259  * the server losing its state, the client can register a close handler and handle the close.
  260  *
  261  * @code
  262  *     le_msg_SetSessionCloseHandler(sessionRef, SessionCloseHandler, NULL);
  263  * @endcode
  264  *
  265  * However, most clients are not designed to recover from their session being closed by someone
  266  * else, so if a close handler is not registered by a client and the session closes for some
  267  * reason other than the client calling le_msg_CloseSession(), then the client process
  268  * will be terminated.
  269  *
  270  * @note If the client closes the session, the client-side session close handler will not be called,
  271  * even if one is registered.
  272  *
  273  * @subsection c_messagingClientMultithreading Multithreading
  274  *
  275  * The Low-Level Messaging API is thread safe, but not async safe.
  276  *
  277  * When a client creates a session, that session gets "attached" to the thread that created it
  278  * (i.e., the thread that called le_msg_CreateSession()).  That thread will then call any callbacks
  279  * registered for that session.
  280  *
  281  * Note that this implies that if the client thread that creates the session does not
  282  * run the Legato event loop then no callbacks will ever be called for that session.
  283  * To work around this, move the session creation to another thread that that uses the Legato event
  284  * loop.
  285  *
  286  * Furthermore, to prevent race conditions, only the thread that is attached to a given session
  287  * is allowed to call le_msg_RequestSyncResponse() for that session.
  288  *
  289  * @subsection c_messagingClientExample Sample Code
  290  *
  291  * @code
  292  * // Function will be called whenever the server sends us a notification message.
  293  * static void NotifyHandlerFunc
  294  * (
  295  *     le_msg_MessageRef_t  msgRef,    // Reference to the received message.
  296  *     void*                contextPtr // contextPtr passed into le_msg_SetSessionRecvHandler().
  297  * )
  298  * {
  299  *     // Process notification message from the server.
  300  *     myproto_Msg_t* msgPayloadPtr = le_msg_GetPayloadPtr(msgRef);
  301  *     ...
  302  *
  303  *     // Release the message, now that we are finished with it.
  304  *     le_msg_ReleaseMsg(msgRef);
  305  * }
  306  *
  307  * // Function will be called whenever the server sends us a response message or our
  308  * // request-response transaction fails.
  309  * static void ResponseHandlerFunc
  310  * (
  311  *     le_msg_MessageRef_t  msgRef,    // Reference to response message (NULL if transaction failed).
  312  *     void*                contextPtr // contextPtr passed into le_msg_RequestResponse().
  313  * )
  314  * {
  315  *     // Check if we got a response.
  316  *     if (msgRef == NULL)
  317  *     {
  318  *         // Transaction failed.  No response received.
  319  *         // This might happen if the server deleted the request without sending a response,
  320  *         // or if we had registered a "Session End Handler" and the session terminated before
  321  *         // the response was sent.
  322  *         LE_ERROR("Transaction failed!");
  323  *     }
  324  *     else
  325  *     {
  326  *         // Process response message from the server.
  327  *         myproto_Msg_t* msgPayloadPtr = le_msg_GetPayloadPtr(msgRef);
  328  *         ...
  329  *
  330  *         // Release the response message, now that we are finished with it.
  331  *         le_msg_ReleaseMsg(msgRef);
  332  *     }
  333  * }
  334  *
  335  * // Function will be called when the client-server session opens.
  336  * static void SessionOpenHandlerFunc
  337  * (
  338  *     le_msg_SessionRef_t  sessionRef, // Reference tp the session that opened.
  339  *     void*                contextPtr  // contextPtr passed into le_msg_OpenSession().
  340  * )
  341  * {
  342  *     le_msg_MessageRef_t msgRef;
  343  *     myproto_Msg_t* msgPayloadPtr;
  344  *
  345  *     // Send a request to the server.
  346  *     msgRef = le_msg_CreateMsg(sessionRef);
  347  *     msgPayloadPtr = le_msg_GetPayloadPtr(msgRef);
  348  *     msgPayloadPtr->... = ...; // <-- Populate message payload...
  349  *     le_msg_RequestResponse(msgRef, ResponseHandlerFunc, NULL);
  350  * }
  351  *
  352  * COMPONENT_INIT
  353  * {
  354  *     le_msg_ProtocolRef_t protocolRef;
  355  *     le_msg_SessionRef_t sessionRef;
  356  *
  357  *     // Open a session.
  358  *     protocolRef = le_msg_GetProtocolRef(PROTOCOL_ID, sizeof(myproto_Msg_t));
  359  *     sessionRef = le_msg_CreateSession(protocolRef, MY_INTERFACE_NAME);
  360  *     le_msg_SetSessionRecvHandler(sessionRef, NotifyHandlerFunc, NULL);
  361  *     le_msg_OpenSession(sessionRef, SessionOpenHandlerFunc, NULL);
  362  * }
  363  * @endcode
  364  *
  365  * @section c_messagingServerUsage Server Usage Model
  366  *
  367  * @ref c_messagingServerProcessingMessages <br>
  368  * @ref c_messagingServerSendingNonResponse <br>
  369  * @ref c_messagingServerCleanUp <br>
  370  * @ref c_messagingRemovingService <br>
  371  * @ref c_messagingServerMultithreading <br>
  372  * @ref c_messagingServerExample
  373  *
  374  * Servers that wish to offer a service do the following:
  375  *  -# Get a reference to the protocol they want to use by calling le_msg_GetProtocolRef().
  376  *  -# Create a Service object using le_msg_CreateService(), passing in the protocol reference and
  377  *     the service name.
  378  *  -# Call le_msg_SetServiceRecvHandler() to register a function to handle messages received from
  379  *     clients.
  380  *  -# Advertise the service using le_msg_AdvertiseService().
  381  *
  382  * @code
  383  *     protocolRef = le_msg_GetProtocolRef(PROTOCOL_ID, sizeof(myproto_Msg_t));
  384  *     serviceRef = le_msg_CreateService(protocolRef, SERVER_INTERFACE_NAME);
  385  *     le_msg_SetServiceRecvHandler(serviceRef, RequestMsgHandlerFunc, NULL);
  386  *     le_msg_AdvertiseService(serviceRef);
  387  * @endcode
  388  *
  389  * Once the service is advertised, clients can open it and start sending it messages.  The server
  390  * will receive messages via callbacks to the function it registered using
  391  * le_msg_SetServiceRecvHandler().
  392  *
  393  * Servers also have the option of being notified when sessions are opened by clients.  They
  394  * get this notification by registering a handler function using le_msg_AddServiceOpenHandler().
  395  *
  396  * @code
  397  * // Function will be called whenever a client opens a session with our service.
  398  * static void SessionOpenHandlerFunc
  399  * (
  400  *     le_msg_SessionRef_t  sessionRef, ///< [in] Reference to the session object.
  401  *     void*                contextPtr  ///< [in] contextPtr passed to le_msg_SetSessionOpenHandler().
  402  * )
  403  * {
  404  *     // Handle new session opening...
  405  *     ...
  406  * }
  407  *
  408  * COMPONENT_INIT
  409  * {
  410  *     le_msg_ProtocolRef_t protocolRef;
  411  *     le_msg_ServiceRef_t serviceRef;
  412  *
  413  *     // Create my service and advertise it.
  414  *     protocolRef = le_msg_GetProtocolRef(PROTOCOL_ID, sizeof(myproto_Msg_t));
  415  *     serviceRef = le_msg_CreateService(protocolRef, SERVER_INTERFACE_NAME);
  416  *     le_msg_AddServiceOpenHandler(serviceRef, SessionOpenHandlerFunc, NULL);
  417  *     le_msg_AdvertiseService(serviceRef);
  418  * }
  419  * @endcode
  420  *
  421  * Both the "Open Handler" and the "Receive Handler" will be called by the Legato event loop in
  422  * the thread that registered those handlers (which must also be the same thread that created the
  423  * service).
  424  *
  425  * @subsection c_messagingServerProcessingMessages Processing Messages from Clients
  426  *
  427  * The payload of any received message can be accessed using le_msg_GetPayloadPtr().
  428  *
  429  * If a received message does not require a response (i.e., if the client sent it using
  430  * le_msg_Send()), then when the server is finished with the message, the server must release
  431  * the message by calling le_msg_ReleaseMsg().
  432  *
  433  * @code
  434  * void RequestMsgHandlerFunc
  435  * (
  436  *     le_msg_MessageRef_t msgRef  // Reference to the received message.
  437  * )
  438  * {
  439  *     myproto_Msg_t* msgPtr = le_msg_GetPayloadPtr(msgRef);
  440  *     LE_INFO("Received request '%s'", msgPtr->request.string);
  441  *
  442  *     // No response required and I'm done with this message, so release it.
  443  *     le_msg_ReleaseMsg(msgRef);
  444  * }
  445  * @endcode
  446  *
  447  * If a received message requires a response (i.e., if the client sent it using
  448  * le_msg_RequestResponse() or le_msg_RequestSyncResponse()), the server must eventually respond
  449  * to that message by calling le_msg_Respond() on that message.  le_msg_Respond() sends the message
  450  * back to the client that sent the request.  The response payload is stored inside the same
  451  * payload buffer that contained the request payload.
  452  *
  453  * To do this, the request payload pointer can be cast to a pointer to the response
  454  * payload structure, and then the response payload can be written into it.
  455  *
  456  * @code
  457  * void RequestMsgHandlerFunc
  458  * (
  459  *     le_msg_MessageRef_t msgRef  // Reference to the received message.
  460  * )
  461  * {
  462  *     myproto_RequestMsg_t* requestPtr = le_msg_GetPayloadPtr(msgRef);
  463  *     myproto_ResponseMsg_t* responsePtr;
  464  *
  465  *     LE_INFO("Received request '%s'", requestPtr->string);
  466  *
  467  *     responsePtr = (myproto_ResponseMsg_t*)requestPtr;
  468  *     responsePtr->value = Value;
  469  *     le_msg_Respond(msgRef);
  470  * }
  471  * @endcode
  472  *
  473  * Alternatively, the request payload structure and the response payload structure could be placed
  474  * into a union together.
  475  *
  476  * @code
  477  * typedef union
  478  * {
  479  *     myproto_Request_t request;
  480  *     myproto_Response_t response;
  481  * }
  482  * myproto_Msg_t;
  483  *
  484  *  ...
  485  *
  486  * void RequestMsgHandlerFunc
  487  * (
  488  *     le_msg_MessageRef_t msgRef  // Reference to the received message.
  489  * )
  490  * {
  491  *     myproto_Msg_t* msgPtr = le_msg_GetPayloadPtr(msgRef);
  492  *     LE_INFO("Received request '%s'", msgPtr->request.string);
  493  *     msgPtr->response.value = Value;
  494  *     le_msg_Respond(msgRef);
  495  * }
  496  * @endcode
  497  *
  498  * @warning Of course, once you've started writing the response payload into the buffer, the request payload
  499  * is no longer available, so if you still need it, copy it somewhere else first.
  500  *
  501  * @note The server doesn't have to send the response back to the client right away.  It could
  502  *       hold onto the request for an indefinite amount of time, for whatever reason.
  503  *
  504  * Whenever any message is received from a client, the message is associated with the session
  505  * through which the client sent it.  A reference to the session can be retrieved from the message,
  506  * if needed, by calling le_msg_GetSession().  This can be handy for tagging things in the
  507  * server's internal data structures that need to be cleaned up when the client closes the session
  508  * (see @ref c_messagingServerCleanUp for more on this).
  509  *
  510  * The function le_msg_NeedsResponse() can be used to check if a received message requires a
  511  * response or not.
  512  *
  513  * @subsection c_messagingServerSendingNonResponse Sending Non-Response Messages to Clients
  514  *
  515  * If a server wants to send a non-response message to a client, it first needs a reference
  516  * to the session that client opened.  It could have got the session reference from a previous
  517  * message received from the client (by calling le_msg_GetSession() on that message).
  518  * Or, it could have got the session reference from a Session Open Handler callback (see
  519  * le_msg_AddServiceOpenHandler()).  Either way, once it has the session reference, it can call
  520  * le_msg_CreateMsg() to create a message from that session's server-side message pool.  The
  521  * message can then be populated and sent in the same way that a client would send a message
  522  * to the server using le_msg_GetPayloadPtr() and le_msg_Send().
  523  *
  524  * @todo Explain how to configure the sizes of the server-side message pools.
  525  *
  526  * @code
  527  * // Function will be called whenever a client opens a session with our service.
  528  * static void SessionOpenHandlerFunc
  529  * (
  530  *     le_msg_SessionRef_t  sessionRef, ///< [in] Reference to the session object.
  531  *     void*                contextPtr  ///< [in] contextPtr passed to le_msg_SetSessionOpenHandler().
  532  * )
  533  * {
  534  *     le_msg_MessageRef_t msgRef;
  535  *     myproto_Msg_t* msgPayloadPtr;
  536  *
  537  *     // Send a "Welcome" message to the client.
  538  *     msgRef = le_msg_CreateMsg(sessionRef);
  539  *     msgPayloadPtr = le_msg_GetPayloadPtr(msgRef);
  540  *     msgPayloadPtr->... = ...; // <-- Populate message payload...
  541  *     le_msg_Send(msgRef);
  542  * }
  543  *
  544  * COMPONENT_INIT
  545  * {
  546  *     le_msg_ProtocolRef_t protocolRef;
  547  *     le_msg_ServiceRef_t serviceRef;
  548  *
  549  *     // Create my service and advertise it.
  550  *     protocolRef = le_msg_GetProtocolRef(PROTOCOL_ID, sizeof(myproto_Msg_t));
  551  *     serviceRef = le_msg_CreateService(protocolRef, SERVER_INTERFACE_NAME);
  552  *     le_msg_AddServiceOpenHandler(serviceRef, SessionOpenHandlerFunc, NULL);
  553  *     le_msg_AdvertiseService(serviceRef);
  554  * }
  555  * @endcode
  556  *
  557  * @subsection c_messagingServerCleanUp Cleaning up when Sessions Close
  558  *
  559  * If a server keeps state on behalf of its clients, it can call le_msg_AddServiceCloseHandler()
  560  * to ask to be notified when clients close sessions with a given service.  This allows the server
  561  * to clean up any state associated with a given session when the client closes that session
  562  * (or when the system closes the session because the client died).  The close handler is passed a
  563  * session reference, so the server can check its internal data structures and clean up anything
  564  * that it has previously tagged with that same session reference.
  565  *
  566  * @note    Servers don't delete sessions.  On the server side, sessions are automatically deleted
  567  *          when they close.
  568  *
  569  * @subsection c_messagingRemovingService Removing Service
  570  *
  571  * If a server wants to stop offering a service, it can hide the service by calling
  572  * le_msg_HideService().  This will not terminate any sessions that are already open, but it
  573  * will prevent clients from opening new sessions until it's advertised again.
  574  *
  575  * @warning Watch out for race conditions here. It's possible that a client is in the process
  576  * of opening a session when you decide to hide your service.  In this case, a new session may
  577  * open after you hid the service.  Be prepared to handle that gracefully.
  578  *
  579  * The server also has the option to delete the service. This hides the service and closes
  580  * all open sessions.
  581  *
  582  * If a server process dies, the Legato framework will automatically delete all of its services.
  583  *
  584  * @subsection c_messagingServerMultithreading Multithreading
  585  *
  586  * The Low-Level Messaging API is thread safe, but not async safe.
  587  *
  588  * When a server creates a service, that service gets attached to the thread that created it
  589  * (i.e., the thread that called le_msg_CreateService()).  That thread will call any handler
  590  * functions registered for that service.
  591  *
  592  * This implies that if the thread that creates the service doesn't
  593  * run the Legato event loop, then no callbacks will ever be called for that service.
  594  * To work around this, you could move the service to another thread that that runs the Legato event
  595  * loop.
  596  *
  597  * @subsection c_messagingServerExample Sample Code
  598  *
  599  * @code
  600  * void RequestMsgHandlerFunc
  601  * (
  602  *     le_msg_MessageRef_t msgRef,     // Reference to the received message.
  603  *     void*               contextPtr  ///< [in] contextPtr passed to le_msg_SetServiceRecvHandler().
  604  * )
  605  * {
  606  *     // Check the message type to decide what to do.
  607  *     myproto_Msg_t* msgPtr = le_msg_GetPayloadPtr(msgRef);
  608  *     switch (msgPtr->type)
  609  *     {
  610  *         case MYPROTO_MSG_TYPE_SET_VALUE:
  611  *              // Message doesn't require a response.
  612  *              Value = msgPtr->...;
  613  *              le_msg_ReleaseMsg(msgRef);
  614  *              break;
  615  *
  616  *         case MYPROTO_MSG_TYPE_GET_VALUE:
  617  *              // Message is a request that requires a response.
  618  *              // Notice that we just reuse the request message buffer for the response.
  619  *              msgPtr->... = Value;
  620  *              le_msg_Respond(msgRef);
  621  *              break;
  622  *
  623  *         default:
  624  *              // Unexpected message type!
  625  *              LE_ERROR("Received unexpected message type %d from session %s.",
  626  *                       msgPtr->type,
  627  *                       le_msg_GetInterfaceName(le_msg_GetSessionInterface(le_msg_GetSession(msgRef))));
  628  *              le_msg_ReleaseMsg(msgRef);
  629  *     }
  630  * }
  631  *
  632  * COMPONENT_INIT
  633  * {
  634  *     le_msg_ProtocolRef_t protocolRef;
  635  *     le_msg_ServiceRef_t serviceRef;
  636  *
  637  *     // Create my service and advertise it.
  638  *     protocolRef = le_msg_GetProtocolRef(PROTOCOL_ID, sizeof(myproto_Msg_t));
  639  *     serviceRef = le_msg_CreateService(protocolRef, SERVER_INTERFACE_NAME);
  640  *     le_msg_SetServiceRecvHandler(serviceRef, RequestMsgHandlerFunc, NULL);
  641  *     le_msg_AdvertiseService(serviceRef);
  642  * }
  643  * @endcode
  644  *
  645  * @section c_messagingStartUp Start Up Sequencing
  646  *
  647  * Worthy of special mention is the fact that the low-level messaging system can be used to
  648  * solve the age-old problem of coordinating the start-up sequence of processes that interact with
  649  * each other. Far too often, the start-up sequence of multiple interacting processes is addressed
  650  * using hacks like polling or sleeping for arbitrary lengths of time. These solutions can
  651  * waste a lot of CPU cycles and battery power, slow down start-up, and (in the case of arbitrary
  652  * sleeps) introduce race conditions that can cause failures in the field.
  653  *
  654  * In Legato, a messaging client can attempt to open a session before the server process has even
  655  * started.  The client will be notified asynchronously (via callback) when the server advertises
  656  * its service.
  657  *
  658  * In this way, clients are guaranteed to wait for the servers they use, without the inefficiency
  659  * of polling, and without having to add code elsewhere to coordinate the start-up sequence.
  660  * If there's work that needs to be done by the client at start-up before it opens
  661  * a session with the server, the client is allowed to do that work in parallel with the start-up
  662  * of the server, so the CPU can be more fully utilized to shorten the overall duration of the
  663  * start-up sequence.
  664  *
  665  * @section c_messagingMemoryManagement Memory Management
  666  *
  667  * Message buffer memory is allocated and controlled behind the scenes, inside the Messaging API.
  668  * This allows the Messaging API to
  669  *  - take some steps to remove programmer pitfalls,
  670  *  - provide some built-in remote troubleshooting features
  671  *  - encapsulate the IPC implementation, allowing for future optimization and porting.
  672  *
  673  * Each message object is allocated from a session. The sessions' message pool sizes can
  674  * be tuned through component and application configuration files and device configuration
  675  * settings.
  676  *
  677  * @todo    Explain how to configure message pools.
  678  *
  679  * Generally speaking, message payload sizes are determined by the protocol that is being used.
  680  * Application protocols and the packing of messages into message buffers are the domain of
  681  * higher-layers of the software stack. But, at this low layer, servers and clients just declare
  682  * the name and version of the protocol, and the size of the largest message in the protocol.
  683  * From this, they obtain a protocol reference that they provide to sessions when they create
  684  * them.
  685  *
  686  * @section c_messagingSecurity Security
  687  *
  688  * Security is provided in the form of authentication and access control.
  689  *
  690  * Clients cannot open sessions with servers until their client-side interface is "bound" to a
  691  * server-side interface (service).  The binding thereby provides configuration of both routing and
  692  * access control.
  693  *
  694  * Neither the client-side nor the server-side IPC sockets are named.  Therefore, no process other
  695  * than the Service Directory has access to these sockets.  The Service Directory passes client
  696  * connections to the appropriate server based on the binding configuration of the client's interface.
  697  *
  698  * The binding configuration is kept in the "system" configuration tree, so clients that do not
  699  * have write access to the "system" configuration tree have no control over their own binding
  700  * configuration.  By default, sandboxed apps do not have any access (read or write) to the
  701  * "system" configuration tree.
  702  *
  703  * @section c_messagingGetClientInfo Get Client Info
  704  *
  705  * In rare cases, a server may wish to check the user ID of the remote client.  Generally,
  706  * this is not necessary because the IPC system enforces user-based access control restrictions
  707  * automatically before allowing an IPC connection to be established.  However, sometimes it
  708  * may be useful when the service wishes to change the way it behaves, based on what user is
  709  * connected to it.
  710  *
  711  * le_msg_GetClientUserId() can be used to fetch the user ID of the client at the far end of a
  712  * given IPC session.
  713  *
  714  * @code
  715  * uid_t clientUserId;
  716  * if (le_msg_GetClientUserId(sessionRef, &clientUserId) != LE_OK)
  717  * {
  718  *     // The session must have closed.
  719  *     ...
  720  * }
  721  * else
  722  * {
  723  *     LE_INFO("My client has user ID %ud.", clientUserId);
  724  * }
  725  * @endcode
  726  *
  727  * le_msg_GetClientProcessId() can be used to fetch the process ID from the client.
  728  *
  729  * @code
  730  * pid_t clientProcessId;
  731  * if (le_msg_GetClientProcessId (sessionRef, &clientProcessId) != LE_OK)
  732  * {
  733  * {
  734  *     // The session must have closed.
  735  *     ...
  736  * }
  737  * else
  738  * {
  739  *    LE_INFO("My client has process ID %ud.", clientProcessId);
  740  * }
  741  * @endcode
  742  *
  743  * le_msg_GetClientUserCreds() can be used to fetch the user credentials from the client.
  744  *
  745  * @code
  746  *    le_msg_SessionRef_t sessionRef,
  747  *    uid_t*              userIdPtr,
  748  *    pid_t*              processIdPtr
  749  * @endcode
  750  *
  751  * @section c_messagingSendingFileDescriptors Sending File Descriptors
  752  *
  753  * It's possible to send an open file descriptor through an IPC session by adding an fd to a
  754  * message before sending it.  On the sender's side, le_msg_SetFd() is used to set the
  755  * file descriptor to be sent.  On the receiver's side, le_msg_GetFd() is used to get the fd
  756  * from the message.
  757  *
  758  * The IPC API will close the original fd in the sender's address space once it has
  759  * been sent, so if the sender still needs the fd open on its side, it should duplicate the fd
  760  * (e.g., using dup() ) before sending it.
  761  *
  762  * On the receiving side, if the fd is not extracted from the message, it will be closed when
  763  * the message is released.  The fd can only be extracted from the message once.  Subsequent
  764  * calls to le_msg_GetFd() will return -1.
  765  *
  766  * @warning DO NOT SEND DIRECTORY FILE DESCRIPTORS.  They can be exploited and used to break out of
  767  * chroot() jails.
  768  *
  769  * @section c_messagingFutureEnhancements Future Enhancements
  770  *
  771  * As an optimization to reduce the number of copies in cases where the sender of a message
  772  * already has the message payload of their message assembled somewhere (perhaps as static data
  773  * or in another message buffer received earlier from somewhere), a pointer to the payload could
  774  * be passed to the message, instead of having to copy the payload into the message.
  775  *
  776  * @code
  777  *     msgRef = le_msg_CreateMsg(sessionRef);
  778  *     le_msg_SetPayloadBuff(msgRef, &msgPayload, sizeof(msgPayload));
  779  *     msgRef = le_msg_RequestResponse(msgRef, ResponseHandlerFunc, contextPtr);
  780  * @endcode
  781  *
  782  * Perhaps an "iovec" version could be added to do scatter-gather too?
  783  *
  784  * @section c_messagingDesignNotes Design Notes
  785  *
  786  * We explored the option of having asynchronous messages automatically released when their
  787  * handler function returns, unless the handler calls an "AddRef" function before returning.
  788  * That would reduce the amount of code required in the common case.  However, we chose to require
  789  * that the client release the message explicitly in all cases, because the consequences of using
  790  * an invalid reference can be catastrophic and much more difficult to debug than forgetting to
  791  * release a message (which will generate pool growth warning messages in the log).
  792  *
  793  * @section c_messagingTroubleshooting Troubleshooting
  794  *
  795  * If you're running as the super-user (root), you can trace messaging traffic using @b TBD.
  796  * You can also inspect message queues and view lists of outstanding message objects within
  797  * processes using the Process Inspector tool.
  798  *
  799  * If you're leaking messages by forgetting to release them when you're finished with them,
  800  * you'll see warning messages in the log indicating your message pool is growing.
  801  * You should be able to tell the related messaging service by the name of the expanding pool.
  802  *
  803  * @todo Finish this section later, when the diagnostic tools become available.
  804  *
  805  * <HR>
  806  *
  807  * Copyright (C) Sierra Wireless Inc.
  808  */
  809 
  810 
  811 /** @file le_messaging.h
  812  *
  813  * Legato @ref c_messaging include file.
  814  *
  815  * Copyright (C) Sierra Wireless Inc.
  816  */
  817 
  818 #ifndef LE_MESSAGING_H_INCLUDE_GUARD
  819 #define LE_MESSAGING_H_INCLUDE_GUARD
  820 
  821 #include "le_semaphore.h"
  822 
  823 // =======================================
  824 //  DATA TYPES
  825 // =======================================
  826 
  827 //--------------------------------------------------------------------------------------------------
  828 /**
  829  * Reference to a protocol.
  830  */
  831 //--------------------------------------------------------------------------------------------------
  832 typedef struct le_msg_Protocol* le_msg_ProtocolRef_t;
  833 
  834 //--------------------------------------------------------------------------------------------------
  835 /**
  836  * Reference to an interface's service instance.
  837  */
  838 //--------------------------------------------------------------------------------------------------
  839 typedef struct le_msg_Interface* le_msg_InterfaceRef_t;
  840 
  841 //--------------------------------------------------------------------------------------------------
  842 /**
  843  * Reference to a server's service instance.
  844  */
  845 //--------------------------------------------------------------------------------------------------
  846 typedef struct le_msg_Service* le_msg_ServiceRef_t;
  847 
  848 //--------------------------------------------------------------------------------------------------
  849 /**
  850  * Reference to a client's service instance.
  851  */
  852 //--------------------------------------------------------------------------------------------------
  853 typedef struct le_msg_ClientInterface* le_msg_ClientInterfaceRef_t;
  854 
  855 //--------------------------------------------------------------------------------------------------
  856 /**
  857  * Reference to a client-server session.
  858  */
  859 //--------------------------------------------------------------------------------------------------
  860 typedef struct le_msg_Session* le_msg_SessionRef_t;
  861 
  862 //--------------------------------------------------------------------------------------------------
  863 /**
  864  * Reference to a message.
  865  */
  866 //--------------------------------------------------------------------------------------------------
  867 typedef struct le_msg_Message* le_msg_MessageRef_t;
  868 
  869 //--------------------------------------------------------------------------------------------------
  870 /**
  871  * Reference to a handler (call-back) function for events that can occur on a service (such as
  872  * opening and closing of sessions and receipt of messages).
  873  */
  874 //--------------------------------------------------------------------------------------------------
  875 typedef struct le_msg_SessionEventHandler* le_msg_SessionEventHandlerRef_t;
  876 
  877 //--------------------------------------------------------------------------------------------------
  878 /**
  879  * Handler function prototype for handlers that take session references as their arguments.
  880  *
  881  * See le_msg_SetSessionCloseHandler(), le_msg_AddServiceOpenHandler(), and
  882  * le_msg_AddServiceCloseHandler().
  883  *
  884  * @param sessionRef [in] Reference to the session that experienced the event.
  885  *
  886  * @param contextPtr [in] Opaque contextPtr value provided when the handler was registered.
  887  */
  888 //--------------------------------------------------------------------------------------------------
  889 typedef void (* le_msg_SessionEventHandler_t)
  890 (
  891     le_msg_SessionRef_t sessionRef,
  892     void*               contextPtr
  893 );
  894 
  895 
  896 //--------------------------------------------------------------------------------------------------
  897 /**
  898  * Receive handler function prototype.
  899  *
  900  * See le_msg_SetSessionRecvHandler() and le_msg_SetServiceRecvHandler().
  901  *
  902  * @param msgRef       [in] Reference to the received message.  Don't forget to release this using
  903  *                          le_msg_ReleaseMsg() when you're finished with it.
  904  *
  905  * @param contextPtr   [in] Opaque contextPtr value provided when the handler was registered.
  906  */
  907 //--------------------------------------------------------------------------------------------------
  908 typedef void (* le_msg_ReceiveHandler_t)
  909 (
  910     le_msg_MessageRef_t msgRef,
  911     void*               contextPtr
  912 );
  913 
  914 
  915 //--------------------------------------------------------------------------------------------------
  916 /**
  917  * Asynchronous response callback function prototype.
  918  *
  919  * See le_msg_RequestResponse().
  920  *
  921  * @param msgRef       [in] Reference to the received response message, or NULL if the transaction
  922  *                          failed and no response was received.  If not NULL, don't forget to
  923  *                          release it by calling le_msg_ReleaseMsg() when you're finished with it.
  924  *
  925  * @param contextPtr   [in] Opaque contextPtr value passed to le_msg_RequestResponse().
  926  */
  927 //--------------------------------------------------------------------------------------------------
  928 typedef void (* le_msg_ResponseCallback_t)
  929 (
  930     le_msg_MessageRef_t msgRef,
  931     void*               contextPtr
  932 );
  933 
  934 
  935 
  936 
  937 //--------------------------------------------------------------------------------------------------
  938 /**
  939  * Generic service object.  Used internally as part of low-level messaging implementation.
  940  */
  941 //--------------------------------------------------------------------------------------------------
  942 struct le_msg_Service
  943 {
  944     enum
  945     {
  946         LE_MSG_SERVICE_UNIX_SOCKET,
  947         LE_MSG_SERVICE_LOCAL
  948     } type;
  949 };
  950 
  951 
  952 //--------------------------------------------------------------------------------------------------
  953 /**
  954  * Generic message object.  Holds a pointer to the session the message is associated with.
  955  */
  956 //--------------------------------------------------------------------------------------------------
  957 struct le_msg_Message
  958 {
  959     le_msg_SessionRef_t sessionRef;   ///< Session for this message
  960 };
  961 
  962 
  963 //--------------------------------------------------------------------------------------------------
  964 /**
  965  * Message handler receiver for local messages
  966  */
  967 //--------------------------------------------------------------------------------------------------
  968 typedef struct
  969 {
  970     le_thread_Ref_t thread;           ///< Thread on which receive should be processes.
  971     le_msg_ReceiveHandler_t handler;  ///< Handler function which should be called on thread
  972     void* contextPtr;                 ///< Context pointer to pass to the handler
  973 } le_msg_LocalReceiver_t;
  974 
  975 
  976 //--------------------------------------------------------------------------------------------------
  977 /**
  978  * Local service object.
  979  *
  980  * Create an instance of this object for each local service used by your program.
  981  *
  982  * @note  This structure should never be accessed directly; instead access through le_msg_...()
  983  *        functions.
  984  */
  985 //--------------------------------------------------------------------------------------------------
  986 typedef struct
  987 {
  988     struct le_msg_Service service;          ///< Service
  989 #if LE_CONFIG_CUSTOM_OS && defined(LE_MSG_SERVICE_READY_FLAG)
  990     LE_MSG_SERVICE_READY_FLAG;       ///< Indicate if service is ready in an OS-specific manner
  991 #else
  992     bool serviceReady;               ///< Indicate if service is ready
  993 #endif
  994     le_msg_LocalReceiver_t receiver; ///< Server destination
  995     le_mem_PoolRef_t messagePool;    ///< Pool for messages on this service
  996 } le_msg_LocalService_t;
  997 
  998 
  999 //--------------------------------------------------------------------------------------------------
 1000 /**
 1001  * Message that's sent over a queue transport.
 1002  */
 1003 //--------------------------------------------------------------------------------------------------
 1004 typedef struct le_msg_LocalMessage
 1005 {
 1006     struct le_msg_Message message;          ///< Pointer to base message
 1007     int fd;                                 ///< File descriptor sent with message (via Get/SetFd)
 1008     le_sem_Ref_t responseReady;             ///< Semaphore which will be set when response is ready
 1009     bool needsResponse;                     ///< True if message needs a response
 1010     le_msg_ResponseCallback_t completionCallback; ///< Function to be called when transaction done.
 1011     void* contextPtr;                       ///< Opaque value to be passed to handler function.
 1012     uint8_t data[] __attribute__((aligned));   ///< Start of message data.
 1013                                                ///< Align so any type of data can be stored inside.
 1014 } le_msg_LocalMessage_t;
 1015 
 1016 
 1017 //--------------------------------------------------------------------------------------------------
 1018 /**
 1019  * Size of local message header (needs to be added to size of message in local message pools).
 1020  */
 1021 //--------------------------------------------------------------------------------------------------
 1022 #define LE_MSG_LOCAL_HEADER_SIZE      sizeof(le_msg_LocalMessage_t)
 1023 
 1024 
 1025 // =======================================
 1026 //  PROTOCOL FUNCTIONS
 1027 // =======================================
 1028 
 1029 //--------------------------------------------------------------------------------------------------
 1030 /**
 1031  * Gets a reference to refer to a particular version of a particular protocol.
 1032  *
 1033  * @return  Protocol reference.
 1034  */
 1035 //--------------------------------------------------------------------------------------------------
 1036 LE_FULL_API le_msg_ProtocolRef_t le_msg_GetProtocolRef
 1037 (
 1038     const char* protocolId,     ///< [in] String uniquely identifying the the protocol and version.
 1039     size_t largestMsgSize       ///< [in] Size (in bytes) of the largest message in the protocol.
 1040 );
 1041 
 1042 
 1043 //--------------------------------------------------------------------------------------------------
 1044 /**
 1045  * Gets the unique identifier string of the protocol.
 1046  *
 1047  * @return  Pointer to the protocol identifier (null-terminated, UTF-8 string).
 1048  */
 1049 //--------------------------------------------------------------------------------------------------
 1050 LE_FULL_API const char* le_msg_GetProtocolIdStr
 1051 (
 1052     le_msg_ProtocolRef_t protocolRef    ///< [in] Reference to the protocol.
 1053 );
 1054 
 1055 
 1056 //--------------------------------------------------------------------------------------------------
 1057 /**
 1058  * Gets the protocol's maximum message size.
 1059  *
 1060  * @return  The size, in bytes.
 1061  */
 1062 //--------------------------------------------------------------------------------------------------
 1063 LE_FULL_API size_t le_msg_GetProtocolMaxMsgSize
 1064 (
 1065     le_msg_ProtocolRef_t protocolRef    ///< [in] Reference to the protocol.
 1066 );
 1067 
 1068 
 1069 // =======================================
 1070 //  SESSION FUNCTIONS
 1071 // =======================================
 1072 
 1073 //--------------------------------------------------------------------------------------------------
 1074 /**
 1075  * Creates a session that will make use of a protocol to talk to a service on a given client
 1076  * interface.
 1077  *
 1078  * @note    This doesn't actually attempt to open the session.  It just creates the session
 1079  *          object, allowing the client the opportunity to register handlers for the session
 1080  *          before attempting to open it using le_msg_OpenSession().
 1081  *
 1082  * @return  Session reference.
 1083  */
 1084 //--------------------------------------------------------------------------------------------------
 1085 LE_FULL_API le_msg_SessionRef_t le_msg_CreateSession
 1086 (
 1087     le_msg_ProtocolRef_t    protocolRef,    ///< [in] Reference to the protocol to be used.
 1088     const char*             interfaceName   ///< [in] Name of the client-side interface.
 1089 );
 1090 
 1091 
 1092 //--------------------------------------------------------------------------------------------------
 1093 /**
 1094  * Create a session that will always use message boxes to talk to a service in the same process
 1095  * space.
 1096  *
 1097  * @return   Session reference.
 1098  */
 1099 //--------------------------------------------------------------------------------------------------
 1100 le_msg_SessionRef_t le_msg_CreateLocalSession
 1101 (
 1102     le_msg_LocalService_t*             servicePtr  ///< [in] Reference to the service.
 1103 );
 1104 
 1105 
 1106 //--------------------------------------------------------------------------------------------------
 1107 /**
 1108  * Sets an opaque context value (void pointer) that can be retrieved from that session later using
 1109  * le_msg_GetSessionContextPtr().
 1110  */
 1111 //--------------------------------------------------------------------------------------------------
 1112 LE_FULL_API void le_msg_SetSessionContextPtr
 1113 (
 1114     le_msg_SessionRef_t sessionRef, ///< [in] Reference to the session.
 1115 
 1116     void*               contextPtr  ///< [in] Opaque value to be returned by
 1117                                     ///         le_msg_GetSessionContextPtr().
 1118 );
 1119 
 1120 //--------------------------------------------------------------------------------------------------
 1121 /**
 1122  * Fetches the opaque context value (void pointer) that was set earlier using
 1123  * le_msg_SetSessionContextPtr().
 1124  *
 1125  * @return  Context Ptr value passed into le_msg_SetSessionContextPtr(), or NULL if
 1126  *          le_msg_SetSessionContextPtr() has not been called for this session yet.
 1127  */
 1128 //--------------------------------------------------------------------------------------------------
 1129 LE_FULL_API void* le_msg_GetSessionContextPtr
 1130 (
 1131     le_msg_SessionRef_t sessionRef  ///< [in] Reference to the session.
 1132 );
 1133 
 1134 
 1135 //--------------------------------------------------------------------------------------------------
 1136 /**
 1137  * Deletes a session.  This will end the session and free up any resources associated
 1138  * with it.  Any pending request-response transactions in this session will be terminated.
 1139  * If the far end has registered a session close handler callback, it will be called.
 1140  *
 1141  * @note    Function is only used by clients.  On the server side, sessions are automatically
 1142  *          deleted when they close.
 1143  */
 1144 //--------------------------------------------------------------------------------------------------
 1145 void le_msg_DeleteSession
 1146 (
 1147     le_msg_SessionRef_t sessionRef  ///< [in] Reference to the session.
 1148 );
 1149 
 1150 
 1151 //--------------------------------------------------------------------------------------------------
 1152 /**
 1153  * Sets the receive handler callback function to be called when a non-response message arrives
 1154  * on this session.
 1155  *
 1156  * The handler function will be called by the Legato event loop of the thread that created
 1157  * the session.
 1158  *
 1159  * @note    This is a client-only function.  Servers are expected to use
 1160  *          le_msg_SetServiceRecvHandler() instead.
 1161  */
 1162 //--------------------------------------------------------------------------------------------------
 1163 void le_msg_SetSessionRecvHandler
 1164 (
 1165     le_msg_SessionRef_t     sessionRef, ///< [in] Reference to the session.
 1166     le_msg_ReceiveHandler_t handlerFunc,///< [in] Handler function.
 1167     void*                   contextPtr  ///< [in] Opaque pointer value to pass to the handler.
 1168 );
 1169 
 1170 
 1171 //--------------------------------------------------------------------------------------------------
 1172 /**
 1173  * Sets the handler callback function to be called when the session is closed from the other
 1174  * end.  A local termination of the session will not trigger this callback.
 1175  *
 1176  * The handler function will be called by the Legato event loop of the thread that created
 1177  * the session.
 1178  *
 1179  * @note
 1180  * - If this isn't set on the client side, the framework assumes the client is not designed
 1181  *   to recover from the server terminating the session, and the client process will terminate
 1182  *   if the session is terminated by the server.
 1183  * - This is a client-only function.  Servers are expected to use le_msg_AddServiceCloseHandler()
 1184  *   instead.
 1185  */
 1186 //--------------------------------------------------------------------------------------------------
 1187 LE_FULL_API void le_msg_SetSessionCloseHandler
 1188 (
 1189     le_msg_SessionRef_t             sessionRef, ///< [in] Reference to the session.
 1190     le_msg_SessionEventHandler_t    handlerFunc,///< [in] Handler function.
 1191     void*                           contextPtr  ///< [in] Opaque pointer value to pass to handler.
 1192 );
 1193 
 1194 
 1195 //--------------------------------------------------------------------------------------------------
 1196 /**
 1197  * Gets the handler callback function to be called when the session is closed from the other
 1198  * end.
 1199  */
 1200 //--------------------------------------------------------------------------------------------------
 1201 void le_msg_GetSessionCloseHandler
 1202 (
 1203     le_msg_SessionRef_t             sessionRef, ///< [in] Reference to the session.
 1204     le_msg_SessionEventHandler_t*   handlerFunc,///< [out] Handler function.
 1205     void**                          contextPtr  ///< [out] Opaque pointer value to pass to
 1206                                                 ///<       the handler.
 1207 );
 1208 
 1209 
 1210 //--------------------------------------------------------------------------------------------------
 1211 /**
 1212  * Opens a session with a service, providing a function to be called-back when the session is
 1213  * open.
 1214  *
 1215  * Asynchronous sessions are not supported by mailbox sessions.
 1216  *
 1217  * @note    Only clients open sessions.  Servers must patiently wait for clients to open sessions
 1218  *          with them.
 1219  *
 1220  * @warning If the client and server don't agree on the maximum message size for the protocol,
 1221  *          a fatal error will be logged and the client process will be killed.
 1222  */
 1223 //--------------------------------------------------------------------------------------------------
 1224 void le_msg_OpenSession
 1225 (
 1226     le_msg_SessionRef_t             sessionRef,     ///< [in] Reference to the session.
 1227     le_msg_SessionEventHandler_t    callbackFunc,   ///< [in] Function to be called when open.
 1228                                                     ///       NULL if no notification is needed.
 1229     void*                           contextPtr      ///< [in] Opaque value to pass to the callback.
 1230 );
 1231 
 1232 
 1233 //--------------------------------------------------------------------------------------------------
 1234 /**
 1235  * Synchronously open a session with a service.  Blocks until the session is open.
 1236  *
 1237  * This function logs a fatal error and terminates the calling process if unsuccessful.
 1238  *
 1239  * @note    Only clients open sessions.  Servers must patiently wait for clients to open sessions
 1240  *          with them.
 1241  *
 1242  * @warning If the client and server do not agree on the maximum message size for the protocol,
 1243  *          a fatal error will be logged and the client process will be killed.
 1244  */
 1245 //--------------------------------------------------------------------------------------------------
 1246 void le_msg_OpenSessionSync
 1247 (
 1248     le_msg_SessionRef_t             sessionRef      ///< [in] Reference to the session.
 1249 );
 1250 
 1251 
 1252 //--------------------------------------------------------------------------------------------------
 1253 /**
 1254  * Synchronously open a session with a service.  Does not wait for the session to become available
 1255  * if not available..
 1256  *
 1257  * le_msg_TryOpenSessionSync() differs from le_msg_OpenSessionSync() in that
 1258  * le_msg_TryOpenSessionSync() will not wait for a server session to become available if it's
 1259  * not already available at the time of the call.  That is, if the client's interface is not
 1260  * bound to any service, or if the service that it's bound to is not currently advertised
 1261  * by the server, then le_msg_TryOpenSessionSync() will return an error code, while
 1262  * le_msg_OpenSessionSync() will wait until the binding is created or the server advertises
 1263  * the service (or both).
 1264  *
 1265  * @return
 1266  *  - LE_OK if the session was successfully opened.
 1267  *  - LE_NOT_FOUND if the server is not currently offering the service to which the client is bound.
 1268  *  - LE_NOT_PERMITTED if the client interface is not bound to any service (doesn't have a binding).
 1269  *  - LE_COMM_ERROR if the Service Directory cannot be reached.
 1270  *
 1271  * @note    Only clients open sessions.  Servers' must patiently wait for clients to open sessions
 1272  *          with them.
 1273  *
 1274  * @warning If the client and server do not agree on the maximum message size for the protocol,
 1275  *          a fatal error will be logged and the client process will be killed.
 1276  */
 1277 //--------------------------------------------------------------------------------------------------
 1278 le_result_t le_msg_TryOpenSessionSync
 1279 (
 1280     le_msg_SessionRef_t             sessionRef      ///< [in] Reference to the session.
 1281 );
 1282 
 1283 
 1284 //--------------------------------------------------------------------------------------------------
 1285 /**
 1286  * Terminates a session.
 1287  */
 1288 //--------------------------------------------------------------------------------------------------
 1289 void le_msg_CloseSession
 1290 (
 1291     le_msg_SessionRef_t sessionRef  ///< [in] Reference to the session.
 1292 );
 1293 
 1294 
 1295 //--------------------------------------------------------------------------------------------------
 1296 /**
 1297  * Terminates a session, already having acquired the Mutex lock.
 1298  */
 1299 //--------------------------------------------------------------------------------------------------
 1300 void le_msg_CloseSessionLocked
 1301 (
 1302     le_msg_SessionRef_t sessionRef  ///< [in] Reference to the session.
 1303 );
 1304 
 1305 
 1306 //--------------------------------------------------------------------------------------------------
 1307 /**
 1308  * Fetches a reference to the protocol that is being used for a given session.
 1309  *
 1310  * @return Reference to the protocol.
 1311  */
 1312 //--------------------------------------------------------------------------------------------------
 1313 LE_FULL_API le_msg_ProtocolRef_t le_msg_GetSessionProtocol
 1314 (
 1315     le_msg_SessionRef_t sessionRef  ///< [in] Reference to the session.
 1316 );
 1317 
 1318 
 1319 //--------------------------------------------------------------------------------------------------
 1320 /**
 1321  * Fetches a reference to the interface that is associated with a given session.
 1322  *
 1323  * @return Reference to the interface.
 1324  */
 1325 //--------------------------------------------------------------------------------------------------
 1326 LE_FULL_API le_msg_InterfaceRef_t le_msg_GetSessionInterface
 1327 (
 1328     le_msg_SessionRef_t sessionRef  ///< [in] Reference to the session.
 1329 );
 1330 
 1331 //--------------------------------------------------------------------------------------------------
 1332 /**
 1333  * Fetches the user ID of the client at the far end of a given IPC session.
 1334  *
 1335  * @warning This function can only be called for the server-side of a session.
 1336  *
 1337  * @return LE_OK if successful.
 1338  *         LE_CLOSED if the session has closed.
 1339  **/
 1340 //--------------------------------------------------------------------------------------------------
 1341 le_result_t le_msg_GetClientUserId
 1342 (
 1343     le_msg_SessionRef_t sessionRef, ///< [in] Reference to the session.
 1344     uid_t*              userIdPtr   ///< [out] Ptr to where the result is to be stored on success.
 1345 );
 1346 
 1347 //--------------------------------------------------------------------------------------------------
 1348 /**
 1349  * Fetches the user PID of the client at the far end of a given IPC session.
 1350  *
 1351  * @warning This function can only be called for the server-side of a session.
 1352  *
 1353  * @return LE_OK if successful.
 1354  *         LE_CLOSED if the session has closed.
 1355  **/
 1356 //--------------------------------------------------------------------------------------------------
 1357 le_result_t le_msg_GetClientProcessId
 1358 (
 1359     le_msg_SessionRef_t sessionRef,   ///< [in] Reference to the session.
 1360     pid_t*              processIdPtr  ///< [out] Ptr to where the result is to be stored on success.
 1361 );
 1362 
 1363 //--------------------------------------------------------------------------------------------------
 1364 /**
 1365  * Fetches the user credentials of the client at the far end of a given IPC session.
 1366  *
 1367  * @warning This function can only be called for the server-side of a session.
 1368  *
 1369  * @return LE_OK if successful.
 1370  *         LE_CLOSED if the session has closed.
 1371  **/
 1372 //--------------------------------------------------------------------------------------------------
 1373 le_result_t le_msg_GetClientUserCreds
 1374 (
 1375     le_msg_SessionRef_t sessionRef,   ///< [in] Reference to the session.
 1376     uid_t*              userIdPtr,    ///< [out] Ptr to where the uid is to be stored on success.
 1377     pid_t*              processIdPtr  ///< [out] Ptr to where the pid is to be stored on success.
 1378 );
 1379 
 1380 
 1381 
 1382 // =======================================
 1383 //  MESSAGE FUNCTIONS
 1384 // =======================================
 1385 
 1386 //--------------------------------------------------------------------------------------------------
 1387 /**
 1388  * Creates a message to be sent over a given session.
 1389  *
 1390  * @return  Message reference.
 1391  *
 1392  * @note
 1393  * - Function never returns on failure, there's no need to check the return code.
 1394  * - If you see warnings on message pools expanding, then you may be forgetting to
 1395  *   release the messages you have received.
 1396  * - In full API this can be called by either client or server, otherwise it can only
 1397  *   be called by the client.
 1398  */
 1399 //--------------------------------------------------------------------------------------------------
 1400 le_msg_MessageRef_t le_msg_CreateMsg
 1401 (
 1402     le_msg_SessionRef_t sessionRef  ///< [in] Reference to the session.
 1403 );
 1404 
 1405 
 1406 //--------------------------------------------------------------------------------------------------
 1407 /**
 1408  * Adds to the reference count on a message object.
 1409  */
 1410 //--------------------------------------------------------------------------------------------------
 1411 void le_msg_AddRef
 1412 (
 1413     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1414 );
 1415 
 1416 
 1417 //--------------------------------------------------------------------------------------------------
 1418 /**
 1419  * Releases a message object, decrementing its reference count.  If the reference count has reached
 1420  * zero, the message object is deleted.
 1421  */
 1422 //--------------------------------------------------------------------------------------------------
 1423 void le_msg_ReleaseMsg
 1424 (
 1425     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1426 );
 1427 
 1428 
 1429 //--------------------------------------------------------------------------------------------------
 1430 /**
 1431  * Checks whether a message requires a response or not.
 1432  *
 1433  * @note    This is intended for use on the server side only.
 1434  *
 1435  * @return
 1436  *  - TRUE if the message needs to be responded to using le_msg_Respond().
 1437  *  - FALSE if the message doesn't need to be responded to, and should be disposed of using
 1438  *    le_msg_ReleaseMsg() when it's no longer needed.
 1439  */
 1440 //--------------------------------------------------------------------------------------------------
 1441 bool le_msg_NeedsResponse
 1442 (
 1443     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1444 );
 1445 
 1446 
 1447 //--------------------------------------------------------------------------------------------------
 1448 /**
 1449  * Gets a pointer to the message payload memory buffer.
 1450  *
 1451  * @return Pointer to the payload buffer.
 1452  *
 1453  * @warning Be careful not to overflow this buffer.
 1454  */
 1455 //--------------------------------------------------------------------------------------------------
 1456 void* le_msg_GetPayloadPtr
 1457 (
 1458     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1459 );
 1460 
 1461 
 1462 //--------------------------------------------------------------------------------------------------
 1463 /**
 1464  * Gets the size, in bytes, of the message payload memory buffer.
 1465  *
 1466  * @return The size, in bytes.
 1467  */
 1468 //--------------------------------------------------------------------------------------------------
 1469 size_t le_msg_GetMaxPayloadSize
 1470 (
 1471     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1472 );
 1473 
 1474 
 1475 //--------------------------------------------------------------------------------------------------
 1476 /**
 1477  * Sets the file descriptor to be sent with this message.
 1478  *
 1479  * This file descriptor will be closed when the message is sent (or when it's deleted without
 1480  * being sent).
 1481  *
 1482  * At most one file descriptor is allowed to be sent per message.
 1483  **/
 1484 //--------------------------------------------------------------------------------------------------
 1485 void le_msg_SetFd
 1486 (
 1487     le_msg_MessageRef_t msgRef,     ///< [in] Reference to the message.
 1488     int                 fd          ///< [in] File descriptor.
 1489 );
 1490 
 1491 
 1492 //--------------------------------------------------------------------------------------------------
 1493 /**
 1494  * Fetches a received file descriptor from the message.
 1495  *
 1496  * @return The file descriptor, or -1 if no file descriptor was sent with this message or if the
 1497  *         fd was already fetched from the message.
 1498  **/
 1499 //--------------------------------------------------------------------------------------------------
 1500 int le_msg_GetFd
 1501 (
 1502     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1503 );
 1504 
 1505 
 1506 //--------------------------------------------------------------------------------------------------
 1507 /**
 1508  * Sends a message.  No response expected.
 1509  */
 1510 //--------------------------------------------------------------------------------------------------
 1511 void le_msg_Send
 1512 (
 1513     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1514 );
 1515 
 1516 //--------------------------------------------------------------------------------------------------
 1517 /**
 1518  * Gets a reference to the session to which a given message belongs.
 1519  *
 1520  * @return Session reference.
 1521  */
 1522 //--------------------------------------------------------------------------------------------------
 1523 le_msg_SessionRef_t le_msg_GetSession
 1524 (
 1525     le_msg_MessageRef_t msgRef      ///< [in] Reference to the message.
 1526 );
 1527 
 1528 
 1529 //--------------------------------------------------------------------------------------------------
 1530 /**
 1531  * Requests a response from a server by sending it a request.  Doesn't block.  Instead,
 1532  * provides a callback function to be called when the response arrives or the transaction
 1533  * terminates without a response (due to the session terminating or the server deleting the
 1534  * request without responding).
 1535  *
 1536  * Async response not supported with mailbox API
 1537  *
 1538  * @note
 1539  *     - The thread attached to the session (i.e., thread created by the session)
 1540  *       will trigger the callback from its main event loop.  This means if
 1541  *       that thread doesn't run its main event loop, it won't trigger the callback.
 1542  *     - Function can only be used on the client side of a session.
 1543  */
 1544 //--------------------------------------------------------------------------------------------------
 1545 void le_msg_RequestResponse
 1546 (
 1547     le_msg_MessageRef_t         msgRef,     ///< [in] Reference to the request message.
 1548     le_msg_ResponseCallback_t   handlerFunc,///< [in] Function to be called when transaction done.
 1549     void*                       contextPtr  ///< [in] Opaque value to be passed to handler function.
 1550 );
 1551 
 1552 
 1553 //--------------------------------------------------------------------------------------------------
 1554 /**
 1555  * Requests a response from a server by sending it a request.  Blocks until the response arrives
 1556  * or until the transaction terminates without a response (i.e., if the session terminates or
 1557  * the server deletes the request without responding).
 1558  *
 1559  * @return  Reference to the response message, or NULL if the transaction terminated without a
 1560  *          response.
 1561  *
 1562  * @note
 1563  *        - To prevent deadlocks, this function can only be used on the client side of a session.
 1564  *          Servers can't use this function.
 1565  *        - To prevent race conditions, only the client thread attached to the session
 1566  *          (the thread that created the session) is allowed to perform a synchronous
 1567  *          request-response transaction.
 1568  *
 1569  * @warning
 1570  *        - The calling (client) thread will be blocked until the server responds, so no other
 1571  *          event handling will happen in that client thread until the response is received (or the
 1572  *          server dies).  This function should only be used when the server is certain
 1573  *          to respond quickly enough to ensure that it will not cause any event response time
 1574  *          deadlines to be missed by the client.  Consider using le_msg_RequestResponse()
 1575  *          instead.
 1576  *        - If this function is used when the client and server are in the same thread, then the
 1577  *          message will be discarded and NULL will be returned.  This is a deadlock prevention
 1578  *          measure.
 1579  */
 1580 //--------------------------------------------------------------------------------------------------
 1581 le_msg_MessageRef_t le_msg_RequestSyncResponse
 1582 (
 1583     le_msg_MessageRef_t msgRef      ///< [in] Reference to the request message.
 1584 );
 1585 
 1586 
 1587 //--------------------------------------------------------------------------------------------------
 1588 /**
 1589  * Sends a response back to the client that send the request message.
 1590  *
 1591  * Takes a reference to the request message.  Copy the response payload (if any) into the
 1592  * same payload buffer that held the request payload, then call le_msg_Respond().
 1593  *
 1594  * The messaging system will delete the message automatically when it's finished sending
 1595  * the response.
 1596  *
 1597  * @note    Function can only be used on the server side of a session.
 1598  */
 1599 //--------------------------------------------------------------------------------------------------
 1600 void le_msg_Respond
 1601 (
 1602     le_msg_MessageRef_t msgRef      ///< [in] Reference to the request message.
 1603 );
 1604 
 1605 
 1606 // =======================================
 1607 //  INTERFACE FUNCTIONS
 1608 // =======================================
 1609 
 1610 //--------------------------------------------------------------------------------------------------
 1611 /**
 1612  * Creates a service that is accessible using a protocol.
 1613  *
 1614  * Mailbox services should be created statically.
 1615  *
 1616  * @return  Service reference.
 1617  */
 1618 //--------------------------------------------------------------------------------------------------
 1619 LE_FULL_API le_msg_ServiceRef_t le_msg_CreateService
 1620 (
 1621     le_msg_ProtocolRef_t    protocolRef,    ///< [in] Reference to the protocol to be used.
 1622     const char*             interfaceName   ///< [in] Server-side interface name.
 1623 );
 1624 
 1625 
 1626 //--------------------------------------------------------------------------------------------------
 1627 /**
 1628  * Initialize a mailbox service.
 1629  *
 1630  * This must be called before any client can connect to the service, for example in COMPONENT_INIT
 1631  * before any other threads are created.
 1632  */
 1633 //--------------------------------------------------------------------------------------------------
 1634 le_msg_ServiceRef_t le_msg_InitLocalService
 1635 (
 1636     le_msg_LocalService_t* servicePtr,
 1637     const char* serviceNameStr,
 1638     le_mem_PoolRef_t messagingPoolRef
 1639 );
 1640 
 1641 
 1642 //--------------------------------------------------------------------------------------------------
 1643 /**
 1644  * Deletes a service. Any open sessions will be terminated.
 1645  *
 1646  * @note    Server-only function.
 1647  */
 1648 //--------------------------------------------------------------------------------------------------
 1649 LE_FULL_API void le_msg_DeleteService
 1650 (
 1651     le_msg_ServiceRef_t             serviceRef  ///< [in] Reference to the service.
 1652 );
 1653 
 1654 //--------------------------------------------------------------------------------------------------
 1655 /**
 1656  * Registers a function to be called when clients open sessions with this service.
 1657  *
 1658  * @note    Server-only function.
 1659  */
 1660 //--------------------------------------------------------------------------------------------------
 1661 LE_FULL_API le_msg_SessionEventHandlerRef_t le_msg_AddServiceOpenHandler
 1662 (
 1663     le_msg_ServiceRef_t             serviceRef, ///< [in] Reference to the service.
 1664     le_msg_SessionEventHandler_t    handlerFunc,///< [in] Handler function.
 1665     void*                           contextPtr  ///< [in] Opaque pointer value to pass to handler.
 1666 );
 1667 
 1668 //--------------------------------------------------------------------------------------------------
 1669 /**
 1670  * Registers a function to be called whenever one of this service's sessions is closed by
 1671  * the client.
 1672  *
 1673  * @note    Server-only function.
 1674  */
 1675 //--------------------------------------------------------------------------------------------------
 1676 le_msg_SessionEventHandlerRef_t le_msg_AddServiceCloseHandler
 1677 (
 1678     le_msg_ServiceRef_t             serviceRef, ///< [in] Reference to the service.
 1679     le_msg_SessionEventHandler_t    handlerFunc,///< [in] Handler function.
 1680     void*                           contextPtr  ///< [in] Opaque pointer value to pass to handler.
 1681 );
 1682 
 1683 //--------------------------------------------------------------------------------------------------
 1684 /**
 1685  * Remove a function previously registered by le_msg_AddServiceOpenHandler or
 1686  * le_msg_AddServiceCloseHandler.
 1687  *
 1688  * @note    This is a server-only function.
 1689  */
 1690 //--------------------------------------------------------------------------------------------------
 1691 LE_FULL_API void le_msg_RemoveServiceHandler
 1692 (
 1693     le_msg_SessionEventHandlerRef_t handlerRef   ///< [in] Reference to a previously call of
 1694                                                  ///       le_msg_AddServiceCloseHandler()
 1695 );
 1696 
 1697 //--------------------------------------------------------------------------------------------------
 1698 /**
 1699  * Registers a function to be called when messages are received from clients via sessions
 1700  * that they have open with this service.
 1701  *
 1702  * @note    Server-only function.
 1703  */
 1704 //--------------------------------------------------------------------------------------------------
 1705 void le_msg_SetServiceRecvHandler
 1706 (
 1707     le_msg_ServiceRef_t     serviceRef, ///< [in] Reference to the service.
 1708     le_msg_ReceiveHandler_t handlerFunc,///< [in] Handler function.
 1709     void*                   contextPtr  ///< [in] Opaque pointer value to pass to the handler.
 1710 );
 1711 
 1712 
 1713 //--------------------------------------------------------------------------------------------------
 1714 /**
 1715  * Associates an opaque context value (void pointer) with a given service that can be retrieved
 1716  * later using le_msg_GetServiceContextPtr().
 1717  *
 1718  * @note    Server-only function.
 1719  */
 1720 //--------------------------------------------------------------------------------------------------
 1721 LE_FULL_API void le_msg_SetServiceContextPtr
 1722 (
 1723     le_msg_ServiceRef_t serviceRef, ///< [in] Reference to the service.
 1724 
 1725     void*               contextPtr  ///< [in] Opaque value to be returned by
 1726                                     ///         le_msg_GetServiceContextPtr().
 1727 );
 1728 
 1729 
 1730 //--------------------------------------------------------------------------------------------------
 1731 /**
 1732  * Fetches the opaque context value (void pointer) associated with a specified service using
 1733  * le_msg_SetServiceContextPtr().
 1734  *
 1735  * @return  Context pointer value, or NULL if le_msg_SetServiceContextPtr() was never called
 1736  *          for this service.
 1737  *
 1738  * @note    Server-only function.
 1739  */
 1740 //--------------------------------------------------------------------------------------------------
 1741 LE_FULL_API void* le_msg_GetServiceContextPtr
 1742 (
 1743     le_msg_ServiceRef_t serviceRef  ///< [in] Reference to the service.
 1744 );
 1745 
 1746 
 1747 //--------------------------------------------------------------------------------------------------
 1748 /**
 1749  * Makes a given service available for clients to find.
 1750  *
 1751  * @note    Server-only function.
 1752  */
 1753 //--------------------------------------------------------------------------------------------------
 1754 void le_msg_AdvertiseService
 1755 (
 1756     le_msg_ServiceRef_t serviceRef  ///< [in] Reference to the service.
 1757 );
 1758 
 1759 
 1760 //--------------------------------------------------------------------------------------------------
 1761 /**
 1762  * Makes a specified service unavailable for clients to find without terminating any ongoing
 1763  * sessions.
 1764  *
 1765  * @note    Server-only function.
 1766  */
 1767 //--------------------------------------------------------------------------------------------------
 1768 LE_FULL_API void le_msg_HideService
 1769 (
 1770     le_msg_ServiceRef_t serviceRef  ///< [in] Reference to the service.
 1771 );
 1772 
 1773 
 1774 //--------------------------------------------------------------------------------------------------
 1775 /**
 1776  * Fetches a pointer to the name of an interface.
 1777  *
 1778  * @return Pointer to a null-terminated string.
 1779  *
 1780  * @warning Pointer returned will remain valid only until the interface is deleted.
 1781  */
 1782 //--------------------------------------------------------------------------------------------------
 1783 LE_FULL_API const char* le_msg_GetInterfaceName
 1784 (
 1785     le_msg_InterfaceRef_t interfaceRef  ///< [in] Reference to the interface.
 1786 );
 1787 
 1788 
 1789 //--------------------------------------------------------------------------------------------------
 1790 /**
 1791  * Fetches a reference to the protocol supported by a specified interface.
 1792  *
 1793  * @return  Protocol reference.
 1794  */
 1795 //--------------------------------------------------------------------------------------------------
 1796 LE_FULL_API le_msg_ProtocolRef_t le_msg_GetInterfaceProtocol
 1797 (
 1798     le_msg_InterfaceRef_t interfaceRef  ///< [in] Reference to the interface.
 1799 );
 1800 
 1801 
 1802 //--------------------------------------------------------------------------------------------------
 1803 /**
 1804  * Check if the calling thread is currently running a Service's message receive handler;
 1805  *  if so, return a reference to the message object being handled.
 1806  *
 1807  * @return  Reference to the message being handled, or NULL if no Service message receive handler
 1808  *          is currently running.
 1809  **/
 1810 //--------------------------------------------------------------------------------------------------
 1811 le_msg_MessageRef_t le_msg_GetServiceRxMsg
 1812 (
 1813     void
 1814 );
 1815 
 1816 
 1817 //--------------------------------------------------------------------------------------------------
 1818 /**
 1819  * Logs an error message (at EMERGENCY level) and:
 1820  *  - if the caller is running a server-side IPC function, kills the connection to the client
 1821  *    and returns.
 1822  *  - if the caller is not running a server-side IPC function, kills the caller (doesn't return).
 1823  **/
 1824 //--------------------------------------------------------------------------------------------------
 1825 #define LE_KILL_CLIENT(formatString, ...)  \
 1826 { \
 1827     le_msg_MessageRef_t msgRef = le_msg_GetServiceRxMsg(); \
 1828     LE_FATAL_IF(msgRef == NULL, formatString, ##__VA_ARGS__); \
 1829     LE_EMERG(formatString, ##__VA_ARGS__); \
 1830     le_msg_CloseSession(le_msg_GetSession(msgRef)); \
 1831 }
 1832 
 1833 #endif // LEGATO_MESSAGING_INCLUDE_GUARD
le_msg_GetServiceRxMsg
le_msg_MessageRef_t le_msg_GetServiceRxMsg(void)
le_msg_AddRef
void le_msg_AddRef(le_msg_MessageRef_t msgRef)
le_msg_NeedsResponse
bool le_msg_NeedsResponse(le_msg_MessageRef_t msgRef)
le_msg_GetSessionInterface
LE_FULL_API le_msg_InterfaceRef_t le_msg_GetSessionInterface(le_msg_SessionRef_t sessionRef)
le_msg_LocalMessage_t::contextPtr
void * contextPtr
Opaque value to be passed to handler function. 
Definition: le_messaging.h:1011
le_msg_ReleaseMsg
void le_msg_ReleaseMsg(le_msg_MessageRef_t msgRef)
le_msg_GetClientUserCreds
le_result_t le_msg_GetClientUserCreds(le_msg_SessionRef_t sessionRef, uid_t *userIdPtr, pid_t *processIdPtr)
le_result_t
le_result_t
Definition: le_basics.h:45
le_sem_Ref_t
struct le_sem_t * le_sem_Ref_t
Definition: le_semaphore.h:68
le_msg_DeleteService
LE_FULL_API void le_msg_DeleteService(le_msg_ServiceRef_t serviceRef)
le_msg_LocalReceiver_t
Definition: le_messaging.h:968
le_msg_SetServiceRecvHandler
void le_msg_SetServiceRecvHandler(le_msg_ServiceRef_t serviceRef, le_msg_ReceiveHandler_t handlerFunc, void *contextPtr)
le_msg_CreateLocalSession
le_msg_SessionRef_t le_msg_CreateLocalSession(le_msg_LocalService_t *servicePtr)
le_msg_SessionEventHandler_t
void(* le_msg_SessionEventHandler_t)(le_msg_SessionRef_t sessionRef, void *contextPtr)
Definition: le_messaging.h:890
le_msg_TryOpenSessionSync
le_result_t le_msg_TryOpenSessionSync(le_msg_SessionRef_t sessionRef)
le_msg_AdvertiseService
void le_msg_AdvertiseService(le_msg_ServiceRef_t serviceRef)
le_msg_Service
Definition: le_messaging.h:942
le_msg_DeleteSession
void le_msg_DeleteSession(le_msg_SessionRef_t sessionRef)
le_msg_SetSessionRecvHandler
void le_msg_SetSessionRecvHandler(le_msg_SessionRef_t sessionRef, le_msg_ReceiveHandler_t handlerFunc, void *contextPtr)
le_msg_GetPayloadPtr
void * le_msg_GetPayloadPtr(le_msg_MessageRef_t msgRef)
le_msg_GetSessionCloseHandler
void le_msg_GetSessionCloseHandler(le_msg_SessionRef_t sessionRef, le_msg_SessionEventHandler_t *handlerFunc, void **contextPtr)
le_msg_InitLocalService
le_msg_ServiceRef_t le_msg_InitLocalService(le_msg_LocalService_t *servicePtr, const char *serviceNameStr, le_mem_PoolRef_t messagingPoolRef)
le_msg_SetServiceContextPtr
LE_FULL_API void le_msg_SetServiceContextPtr(le_msg_ServiceRef_t serviceRef, void *contextPtr)
le_msg_AddServiceOpenHandler
LE_FULL_API le_msg_SessionEventHandlerRef_t le_msg_AddServiceOpenHandler(le_msg_ServiceRef_t serviceRef, le_msg_SessionEventHandler_t handlerFunc, void *contextPtr)
le_msg_ClientInterfaceRef_t
struct le_msg_ClientInterface * le_msg_ClientInterfaceRef_t
Definition: le_messaging.h:853
le_msg_LocalMessage_t
Definition: le_messaging.h:1004
le_msg_GetMaxPayloadSize
size_t le_msg_GetMaxPayloadSize(le_msg_MessageRef_t msgRef)
le_msg_GetSession
le_msg_SessionRef_t le_msg_GetSession(le_msg_MessageRef_t msgRef)
le_msg_GetSessionProtocol
LE_FULL_API le_msg_ProtocolRef_t le_msg_GetSessionProtocol(le_msg_SessionRef_t sessionRef)
le_msg_SetFd
void le_msg_SetFd(le_msg_MessageRef_t msgRef, int fd)
le_msg_ReceiveHandler_t
void(* le_msg_ReceiveHandler_t)(le_msg_MessageRef_t msgRef, void *contextPtr)
Definition: le_messaging.h:909
le_msg_GetSessionContextPtr
LE_FULL_API void * le_msg_GetSessionContextPtr(le_msg_SessionRef_t sessionRef)
le_msg_Send
void le_msg_Send(le_msg_MessageRef_t msgRef)
le_msg_SessionEventHandlerRef_t
struct le_msg_SessionEventHandler * le_msg_SessionEventHandlerRef_t
Definition: le_messaging.h:875
le_msg_SetSessionContextPtr
LE_FULL_API void le_msg_SetSessionContextPtr(le_msg_SessionRef_t sessionRef, void *contextPtr)
le_msg_LocalReceiver_t::thread
le_thread_Ref_t thread
Thread on which receive should be processes. 
Definition: le_messaging.h:970
le_msg_CloseSession
void le_msg_CloseSession(le_msg_SessionRef_t sessionRef)
le_mem_PoolRef_t
struct le_mem_Pool * le_mem_PoolRef_t
Definition: le_mem.h:542
le_msg_LocalService_t::serviceReady
bool serviceReady
Indicate if service is ready. 
Definition: le_messaging.h:992
le_msg_LocalService_t::messagePool
le_mem_PoolRef_t messagePool
Pool for messages on this service. 
Definition: le_messaging.h:995
le_msg_LocalReceiver_t::handler
le_msg_ReceiveHandler_t handler
Handler function which should be called on thread. 
Definition: le_messaging.h:971
le_msg_LocalMessage_t::fd
int fd
File descriptor sent with message (via Get/SetFd) 
Definition: le_messaging.h:1007
le_msg_CreateSession
LE_FULL_API le_msg_SessionRef_t le_msg_CreateSession(le_msg_ProtocolRef_t protocolRef, const char *interfaceName)
le_msg_GetInterfaceName
LE_FULL_API const char * le_msg_GetInterfaceName(le_msg_InterfaceRef_t interfaceRef)
le_msg_CreateMsg
le_msg_MessageRef_t le_msg_CreateMsg(le_msg_SessionRef_t sessionRef)
le_msg_CloseSessionLocked
void le_msg_CloseSessionLocked(le_msg_SessionRef_t sessionRef)
le_msg_GetFd
int le_msg_GetFd(le_msg_MessageRef_t msgRef)
le_msg_SessionRef_t
struct le_msg_Session * le_msg_SessionRef_t
Definition: le_messaging.h:860
LE_FULL_API
#define LE_FULL_API
Definition: le_apiFeatures.h:40
le_msg_RequestResponse
void le_msg_RequestResponse(le_msg_MessageRef_t msgRef, le_msg_ResponseCallback_t handlerFunc, void *contextPtr)
le_msg_LocalService_t
Definition: le_messaging.h:986
le_msg_GetClientProcessId
le_result_t le_msg_GetClientProcessId(le_msg_SessionRef_t sessionRef, pid_t *processIdPtr)
le_msg_OpenSession
void le_msg_OpenSession(le_msg_SessionRef_t sessionRef, le_msg_SessionEventHandler_t callbackFunc, void *contextPtr)
le_msg_LocalService_t::receiver
le_msg_LocalReceiver_t receiver
Server destination. 
Definition: le_messaging.h:994
le_msg_GetServiceContextPtr
LE_FULL_API void * le_msg_GetServiceContextPtr(le_msg_ServiceRef_t serviceRef)
le_msg_LocalMessage_t::completionCallback
le_msg_ResponseCallback_t completionCallback
Function to be called when transaction done. 
Definition: le_messaging.h:1010
le_msg_LocalReceiver_t::contextPtr
void * contextPtr
Context pointer to pass to the handler. 
Definition: le_messaging.h:972
le_msg_Respond
void le_msg_Respond(le_msg_MessageRef_t msgRef)
le_semaphore.h
le_msg_HideService
LE_FULL_API void le_msg_HideService(le_msg_ServiceRef_t serviceRef)
le_msg_GetProtocolRef
LE_FULL_API le_msg_ProtocolRef_t le_msg_GetProtocolRef(const char *protocolId, size_t largestMsgSize)
le_msg_SetSessionCloseHandler
LE_FULL_API void le_msg_SetSessionCloseHandler(le_msg_SessionRef_t sessionRef, le_msg_SessionEventHandler_t handlerFunc, void *contextPtr)
le_msg_ProtocolRef_t
struct le_msg_Protocol * le_msg_ProtocolRef_t
Definition: le_messaging.h:832
le_msg_ResponseCallback_t
void(* le_msg_ResponseCallback_t)(le_msg_MessageRef_t msgRef, void *contextPtr)
Definition: le_messaging.h:929
le_msg_GetClientUserId
le_result_t le_msg_GetClientUserId(le_msg_SessionRef_t sessionRef, uid_t *userIdPtr)
le_msg_GetInterfaceProtocol
LE_FULL_API le_msg_ProtocolRef_t le_msg_GetInterfaceProtocol(le_msg_InterfaceRef_t interfaceRef)
le_msg_RequestSyncResponse
le_msg_MessageRef_t le_msg_RequestSyncResponse(le_msg_MessageRef_t msgRef)
le_msg_RemoveServiceHandler
LE_FULL_API void le_msg_RemoveServiceHandler(le_msg_SessionEventHandlerRef_t handlerRef)
le_msg_LocalMessage_t::responseReady
le_sem_Ref_t responseReady
Semaphore which will be set when response is ready. 
Definition: le_messaging.h:1008
le_msg_InterfaceRef_t
struct le_msg_Interface * le_msg_InterfaceRef_t
Definition: le_messaging.h:839
le_msg_OpenSessionSync
void le_msg_OpenSessionSync(le_msg_SessionRef_t sessionRef)
le_msg_CreateService
LE_FULL_API le_msg_ServiceRef_t le_msg_CreateService(le_msg_ProtocolRef_t protocolRef, const char *interfaceName)
le_msg_GetProtocolIdStr
LE_FULL_API const char * le_msg_GetProtocolIdStr(le_msg_ProtocolRef_t protocolRef)
le_msg_Message::sessionRef
le_msg_SessionRef_t sessionRef
Session for this message. 
Definition: le_messaging.h:959
le_msg_GetProtocolMaxMsgSize
LE_FULL_API size_t le_msg_GetProtocolMaxMsgSize(le_msg_ProtocolRef_t protocolRef)
le_msg_Message
Definition: le_messaging.h:957
le_msg_AddServiceCloseHandler
le_msg_SessionEventHandlerRef_t le_msg_AddServiceCloseHandler(le_msg_ServiceRef_t serviceRef, le_msg_SessionEventHandler_t handlerFunc, void *contextPtr)
le_msg_LocalMessage_t::needsResponse
bool needsResponse
True if message needs a response. 
Definition: le_messaging.h:1009