基于C语言的SIP服务器开源项目kamailio设计源码

1. The Kamailio RPC Control Interface __________________________________________________________________ 1.1. Overview of Operation 1.2. Module API 1.2.1. RPC Functions 1.2.2. Data Types 1.2.3. Getting Parameters 1.2.3.1. scan 1.2.3.2. struct_scan 1.2.3.3. Retrieving Parameters Example 1.2.4. Building Reply 1.2.4.1. fault 1.2.4.2. send 1.2.4.3. add 1.2.4.4. rpl_printf 1.2.4.5. struct_add 1.2.5. Real World Example 1.3. Client Examples 1.4. Implementing New Transports 1.5. Examples using xmlrpc 1.1. Overview of Operation The RPC (Remote Procedure Call) interface is an interface for communicating with external applications. Using it an external application can call a function or procedure that will be executed inside Kamailio. Function parameters are supported as well as returning multiple values as results. By itself RPC consists of two APIs, one for defining RPC functions in a transport independent way (called the rpc module api) and one for implementing RPC transports. The RPC transports are implemented by writing a RPC transport module. The most used transport modules are ctl , xmlrpc and jsonrpc-s . ctl implements a proprietary fast and space efficient RPC encoding over different protocols (unix sockets, UDP, TCP, fifo). xmlrpc uses the de-facto XML-RPC standard encoding (over HTTP TCP or TLS). jsonrpc-s uses the de-facto JSON-RPC standard encoding (over HTTP TCP or TLS). For more information about the existing transport modules, please refer to their documentation. When writing a RPC procedure or function, one needs only use the RPC API and it will work automatically with all the transports and encodings. One needs only to load the desired RPC transport module (e.g. xmlrpc). The RPC interface (or API) was created in such a way that would allow supporting XML-RPC (because XML-RPC is a de-facto standard), while in the same time being very easy to use. 1.2. Module API Each module can export RPC functions just like it can export parameters and functions to be called from the script. Whenever Kamailio receives an RPC request, it will search through the list of exported RPC functions and the function with matching name will be executed. A couple of essential RPC functions are also embedded into the SIP server core. This section gives a detailed overview of the whole RPC API. Section 1.2.1, "RPC Functions" describes the prototype and conventions used in RPC functions. Section 1.2.2, "Data Types" gives a detailed overview of available data types that can be used in function parameters and return value. Section 1.2.3, "Getting Parameters" describes functions of the RPC API that can be used to retrieve parameters of the function, and finally Section 1.2.4, "Building Reply" describes functions of the API that can be used to build the result value that will be sent in the reply to the caller. The whole RPC API is described in header file kamailio/rpc.h. This file defines the set of functions that must be implemented by RPC transport modules, as described in Section 1.4, "Implementing New Transports", prototypes of RPC functions and structures used for the communication between RPC transport modules and ordinary modules exporting RPC functions. 1.2.1. RPC Functions RPC functions are standard C functions with the following prototype: typedef void (*rpc_function_t)(rpc_t* rpc, void* ctx); RPC functions take two parameters, first parameter is a pointer to rpc_t structure and the context. The rpc_t structure contains references to all API functions available to the RPC function as well as all data necessary to create the response. RPC functions do not return any value, instead the return value is created using functions from the context. The motivation for this decision is the fact that RPC functions should always return a response and even the API functions called from RPC functions should have the possibility to indicate an error (and should not rely on RPC functions doing so). If no reply is sent explicitely, the RPC transport module will automatically send a "success" reply (e.g. 200 OK for XML-RPC) when the RPC function finishes. If no values are added to the response, the reponse will be an empty "success" reply (e.g. a 200 OK with empty body for XML-RPC). RPC API functions will automatically send an error reply upon a failure. Each RPC function has associated an array of documentation strings. The purpose of the documentation strings is to give a short overview of the function, accepted parameters, and format of the reply. By convention the name of the documentation string array is same as the name of the function with "_doc" suffix. Each module containing RPC functions has to export all the RPC functions to the Kamailio core in order to make them visible to the RPC transport modules. The export process involves a rpc_export_t structure (either by itself or in an array): typedef struct rpc_export { const char* name; /* Name of the RPC function (null terminated) */ rpc_function_t function; /* Pointer to the function */ const char** doc_str; /* Documentation strings, method signature and desc ription */ unsigned int flags; /* Various flags, reserved for future use */ } rpc_export_t; The flags attribute of the rpc_export structure is reserved for future use and is currently unused. There are several ways of exporting the RPC functions to the Kamailio core: * register a null terminated array of rpc_export_t structures using the rpc_register_array() function (defined in rpc_lookup.h), from the module init function (mod_init()). This is the recommended method for all the new modules. Example 1. usrloc RPC Exports Declaration The rpc_export_t array for the modules_s/usrloc module looks like: rpc_export_t ul_rpc[] = { {"usrloc.statistics", rpc_stats, rpc_stats_doc, 0}, {"usrloc.delete_aor", rpc_delete_aor, rpc_delete_aor_doc, 0}, {"usrloc.delete_contact", rpc_delete_contact, rpc_delete_contact_doc, 0}, {"usrloc.dump", rpc_dump, rpc_dump_doc, 0}, {"usrloc.flush", rpc_flush, rpc_flush_doc, 0}, {"usrloc.add_contact", rpc_add_contact, rpc_add_contact_doc, 0}, {"usrloc.show_contacts", rpc_show_contacts, rpc_show_contacts_doc, 0}, {0, 0, 0, 0} }; To register it from the module init function one would use something similar to: if (rpc_register_array(ul_rpc) != 0) { ERR("failed to register RPC commands\n"); return -1; } * register RPCs one by one using the rpc_register_function() (defined in rpc_lookup.h), from the module init function. * register a null terminated array of rpc_export_t structures using the Kamailio module interface SER_MOD_INTERFACE For this purpose, the module_exports structure of the Kamailio module API contains a new attribute called rpc_methods: struct module_exports { char* name; /* null terminated module name */ cmd_export_t* cmds; /* null terminated array of the exported command s */ rpc_export_t* rpc_methods; /* null terminated array of exported rpc methods */ param_export_t* params; /* null terminated array of the exported module parameters */ init_function init_f; /* Initialization function */ response_function response_f; /* function used for responses */ destroy_function destroy_f; /* function called upon shutdown */ onbreak_function onbr