操作系统 ：CentOS 7.6_x64
FreeSWITCH版本 ：1.10.9
日常开发过程中会遇到需要扩展FreeSWITCH对接其它系统的情况，这里记录下编写FreeSWITCH自定义endpoint的过程。
一、模块定义函数
使用FreeSWITCH自带的框架来定义模块函数，函数指针及参数列表定义如下（src/include/switch_types.h）
#define SWITCH_MODULE_LOAD_ARGS (switch_loadable_module_interface_t **module_interface, switch_memory_pool_t *pool) #define SWITCH_MODULE_RUNTIME_ARGS (void) #define SWITCH_MODULE_SHUTDOWN_ARGS (void) typedef switch_status_t (*switch_module_load_t) SWITCH_MODULE_LOAD_ARGS; typedef switch_status_t (*switch_module_runtime_t) SWITCH_MODULE_RUNTIME_ARGS; typedef switch_status_t (*switch_module_shutdown_t) SWITCH_MODULE_SHUTDOWN_ARGS; #define SWITCH_MODULE_LOAD_FUNCTION(name) switch_status_t name SWITCH_MODULE_LOAD_ARGS #define SWITCH_MODULE_RUNTIME_FUNCTION(name) switch_status_t name SWITCH_MODULE_RUNTIME_ARGS #define SWITCH_MODULE_SHUTDOWN_FUNCTION(name) switch_status_t name SWITCH_MODULE_SHUTDOWN_ARGS
1、模块加载
SWITCH_MODULE_LOAD_FUNCTION
模块加载函数，负责系统启动时或运行时加载模块，可以进行配置读取及资源初始化。
2、模块卸载
SWITCH_MODULE_SHUTDOWN_FUNCTION
模块卸载函数，负载模块卸载及相关资源回收。
3、模块运行时
SWITCH_MODULE_RUNTIME_FUNCTION
模块运行时函数，可以启动线程处理请求，监听socket等。
4、模块定义
SWITCH_MODULE_DEFINITION
相关代码：
typedef struct switch_loadable_module_function_table { int switch_api_version; switch_module_load_t load; switch_module_shutdown_t shutdown; switch_module_runtime_t runtime; switch_module_flag_t flags; } switch_loadable_module_function_table_t; #define SWITCH_MODULE_DEFINITION_EX(name, load, shutdown, runtime, flags) \ static const char modname[] = #name ; \ SWITCH_MOD_DECLARE_DATA switch_loadable_module_function_table_t name##_module_interface = { \ SWITCH_API_VERSION, \ load, \ shutdown, \ runtime, \ flags \ } #define SWITCH_MODULE_DEFINITION(name, load, shutdown, runtime) \ SWITCH_MODULE_DEFINITION_EX(name, load, shutdown, runtime, SMODF_NONE)
二、模块加载流程
FreeSWITCH使用 switch_loadable_module_load_module 或 switch_loadable_module_load_module_ex 进行模块加载，具体实现逻辑可以在 switch_loadable_module.c 中查看，这里做下简单介绍。
1、模块加载函数
通过 switch_loadable_module_load_module 函数加载模块，函数调用链如下：
switch_loadable_module_load_module => switch_loadable_module_load_module_ex => switch_loadable_module_load_file => switch_loadable_module_process => switch_core_launch_thread => switch_loadable_module_exec
通过 switch_dso_data_sym 根据定义的 XXX_module_interface 从动态库里面获取回调函数指针，使用 switch_loadable_module_function_table_t 数据结构进行回调函数绑定。
switch_dso_data_sym 函数实现如下（src/switch_dso.c)：
void *switch_dso_data_sym(switch_dso_lib_t lib, const char *sym, char **err) { void *addr = dlsym(lib, sym); if (!addr) { char *err_str = NULL; dlerror(); if (!(addr = dlsym(lib, sym))) { err_str = (char *)dlerror(); } if (err_str) { *err = strdup(err_str); } } return addr; }
switch_loadable_module_exec函数：
static void *SWITCH_THREAD_FUNC switch_loadable_module_exec(switch_thread_t *thread, void *obj) { switch_status_t status = SWITCH_STATUS_SUCCESS; switch_core_thread_session_t *ts = obj; switch_loadable_module_t *module = ts->objs[0]; int restarts; switch_assert(thread != NULL); switch_assert(module != NULL); for (restarts = 0; status != SWITCH_STATUS_TERM && !module->shutting_down; restarts++) { status = module->switch_module_runtime(); } switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_NOTICE, "Thread ended for %s\n", module->module_interface->module_name); if (ts->pool) { switch_memory_pool_t *pool = ts->pool; switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_DEBUG, "Destroying Pool for %s\n", module->module_interface->module_name); switch_core_destroy_memory_pool(&pool); } switch_thread_exit(thread, 0); return NULL; }
switch_loadable_module_exec 函数为独立线程中运行，模块运行时通过 module->switch_module_runtime() 触发。
2、FreeSWITCH启动时加载模块
1)整体结构
函数调用链如下：
main => switch_core_init_and_modload => switch_core_init => switch_loadable_module_init => switch_loadable_module_load_module
main函数在switch.c中实现。
2)加载顺序
先加载系统核心模块：
switch_loadable_module_load_module_ex("", "CORE_SOFTTIMER_MODULE", SWITCH_FALSE, SWITCH_FALSE, &err, SWITCH_LOADABLE_MODULE_TYPE_COMMON, event_hash); switch_loadable_module_load_module_ex("", "CORE_PCM_MODULE", SWITCH_FALSE, SWITCH_FALSE, &err, SWITCH_LOADABLE_MODULE_TYPE_COMMON, event_hash); switch_loadable_module_load_module_ex("", "CORE_SPEEX_MODULE", SWITCH_FALSE, SWITCH_FALSE, &err, SWITCH_LOADABLE_MODULE_TYPE_COMMON, event_hash);
使用 switch_xml_open_cfg 函数（src/switch_xml.c中定义）先后加载以下文件中定义的模块：
pre_load_modules.conf
modules.conf
post_load_modules.conf
具体格式参考 conf/autoload_configs/modules.conf.xml
3）xml加载过程
函数调用链如下：
main => switch_core_init_and_modload => switch_core_init => switch_xml_init => switch_xml_open_root => XML_OPEN_ROOT_FUNCTION
其中 SWITCH_GLOBAL_filenames 变量定义如下（main => switch_core_set_globals）：
if (!SWITCH_GLOBAL_filenames.conf_name && (SWITCH_GLOBAL_filenames.conf_name = (char *) malloc(BUFSIZE))) { switch_snprintf(SWITCH_GLOBAL_filenames.conf_name, BUFSIZE, "%s", "freeswitch.xml"); }
XML_OPEN_ROOT_FUNCTION实现如下（src/switch_xml.c）：
static switch_xml_open_root_function_t XML_OPEN_ROOT_FUNCTION = (switch_xml_open_root_function_t)__switch_xml_open_root; SWITCH_DECLARE_NONSTD(switch_xml_t) __switch_xml_open_root(uint8_t reload, const char **err, void *user_data) { char path_buf[1024]; uint8_t errcnt = 0; switch_xml_t new_main, r = NULL; if (MAIN_XML_ROOT) { if (!reload) { r = switch_xml_root(); goto done; } } switch_snprintf(path_buf, sizeof(path_buf), "%s%s%s", SWITCH_GLOBAL_dirs.conf_dir, SWITCH_PATH_SEPARATOR, SWITCH_GLOBAL_filenames.conf_name); if ((new_main = switch_xml_parse_file(path_buf))) { *err = switch_xml_error(new_main); switch_copy_string(not_so_threadsafe_error_buffer, *err, sizeof(not_so_threadsafe_error_buffer)); *err = not_so_threadsafe_error_buffer; if (!zstr(*err)) { switch_xml_free(new_main); new_main = NULL; errcnt++; } else { *err = "Success"; switch_xml_set_root(new_main); } } else { *err = "Cannot Open log directory or XML Root!"; errcnt++; } if (errcnt == 0) { r = switch_xml_root(); } done: return r; }
freeswitch.xml 为xml文件的总入口，配置的有加载各个模块的数据：
<section name="configuration" description="Various Configuration"> <X-PRE-PROCESS cmd="include" data="autoload_configs/*.xml"/> </section>
3、控制台动态加载
在fs_cli中可以使用load及reload加载模块，具体流程如下：
fs_cli => load ... => SWITCH_STANDARD_API(load_function) => switch_loadable_module_load_module
fs_cli => reload ... => SWITCH_STANDARD_API(reload_function) => switch_loadable_module_unload_module
=> switch_loadable_module_load_module
三、关键数据结构
1、switch_loadable_module_t
作用：用于定义模块信息。
结构体定义：
struct switch_loadable_module { char *key; char *filename; int perm; switch_loadable_module_interface_t *module_interface; switch_dso_lib_t lib; switch_module_load_t switch_module_load; switch_module_runtime_t switch_module_runtime; switch_module_shutdown_t switch_module_shutdown; switch_memory_pool_t *pool; switch_status_t status; switch_thread_t *thread; switch_bool_t shutting_down; switch_loadable_module_type_t type; }; typedef struct switch_loadable_module switch_loadable_module_t;
字段解释：
key =》 模块文件名称
filename => 模块文件路径（动态库路径）
perm =》 定义模块是否允许被卸载
module_interface =》 模块接口（由switch_module_load函数赋值）
lib =》 动态库句柄（dlopen函数返回）
switch_module_load =》 模块加载函数
switch_module_runtime =》 模块运行时函数
switch_module_shutdown =》 模块关闭（卸载）函数
pool =》 模块内存池
status =》 switch_module_shutdown 函数的返回值
shutting_down => 模块是否关闭
2、switch_loadable_module_interface
作用： 模块接口（入口）
结构体定义：
struct switch_loadable_module_interface { /*! the name of the module */ const char *module_name; /*! the table of endpoints the module has implemented */ switch_endpoint_interface_t *endpoint_interface; /*! the table of timers the module has implemented */ switch_timer_interface_t *timer_interface; /*! the table of dialplans the module has implemented */ switch_dialplan_interface_t *dialplan_interface; /*! the table of codecs the module has implemented */ switch_codec_interface_t *codec_interface; /*! the table of applications the module has implemented */ switch_application_interface_t *application_interface; /*! the table of chat applications the module has implemented */ switch_chat_application_interface_t *chat_application_interface; /*! the table of api functions the module has implemented */ switch_api_interface_t *api_interface; /*! the table of json api functions the module has implemented */ switch_json_api_interface_t *json_api_interface; /*! the table of file formats the module has implemented */ switch_file_interface_t *file_interface; /*! the table of speech interfaces the module has implemented */ switch_speech_interface_t *speech_interface; /*! the table of directory interfaces the module has implemented */ switch_directory_interface_t *directory_interface; /*! the table of chat interfaces the module has implemented */ switch_chat_interface_t *chat_interface; /*! the table of say interfaces the module has implemented */ switch_say_interface_t *say_interface; /*! the table of asr interfaces the module has implemented */ switch_asr_interface_t *asr_interface; /*! the table of management interfaces the module has implemented */ switch_management_interface_t *management_interface; /*! the table of limit interfaces the module has implemented */ switch_limit_interface_t *limit_interface; /*! the table of database interfaces the module has implemented */ switch_database_interface_t *database_interface; switch_thread_rwlock_t *rwlock; int refs; switch_memory_pool_t *pool; }; typedef struct switch_loadable_module_interface switch_loadable_module_interface_t;
字段解释：
module_name => 模块的名称
endpoint_interface => 模块endpoint的具体实现
timer_interface => 模块timer的具体实现
dialplan_interface => 模块dialplan的具体实现
codec_interface => 模块编解码的具体实现
application_interface => 模块提供的app工具的具体实现
chat_application_interface => 模块提供的文本聊天app工具的具体实现
api_interface => 模块提供的api具体实现
json_api_interface => 模块提供的json格式api的具体实现
file_interface => 模块支持的文件格式的具体实现（比如mp4、mkv等文件格式）
speech_interface => 模块使用的speech接口实现
directory_interface => 模块使用的directory接口实现
chat_interface => 模块使用的chat接口实现
say_interface => 模块使用的say接口实现
asr_interface => 模块使用的asr接口实现
management_interface => 模块使用的管理接口实现
limit_interface => 模块使用的limit接口实现
database_interface => 模块使用的limit接口实现
rwlock => 模块使用的锁
refs => 模块锁的计数器
pool =》 模块内存池
使用 switch_loadable_module_create_module_interface 来创建 switch_loadable_module_interface_t 实例。
SWITCH_DECLARE(switch_loadable_module_interface_t *) switch_loadable_module_create_module_interface(switch_memory_pool_t *pool, const char *name) { switch_loadable_module_interface_t *mod; mod = switch_core_alloc(pool, sizeof(switch_loadable_module_interface_t)); switch_assert(mod != NULL); mod->pool = pool; mod->module_name = switch_core_strdup(mod->pool, name); switch_thread_rwlock_create(&mod->rwlock, mod->pool); return mod; }
使用 switch_loadable_module_create_interface 来创建模块里面的子接口，示例如下：
*module_interface = switch_loadable_module_create_module_interface(pool, modname); rtc_endpoint_interface = switch_loadable_module_create_interface(*module_interface, SWITCH_ENDPOINT_INTERFACE); rtc_endpoint_interface->interface_name = "rtc"; rtc_endpoint_interface->io_routines = &rtc_io_routines; rtc_endpoint_interface->state_handler = &rtc_event_handlers; rtc_endpoint_interface->recover_callback = rtc_recover_callback;
具体实现如下：
SWITCH_DECLARE(void *) switch_loadable_module_create_interface(switch_loadable_module_interface_t *mod, switch_module_interface_name_t iname) { switch (iname) { case SWITCH_ENDPOINT_INTERFACE: ALLOC_INTERFACE(endpoint) case SWITCH_TIMER_INTERFACE: ALLOC_INTERFACE(timer) case SWITCH_DIALPLAN_INTERFACE: ALLOC_INTERFACE(dialplan) case SWITCH_CODEC_INTERFACE: ALLOC_INTERFACE(codec) case SWITCH_APPLICATION_INTERFACE: ALLOC_INTERFACE(application) case SWITCH_CHAT_APPLICATION_INTERFACE: ALLOC_INTERFACE(chat_application) case SWITCH_API_INTERFACE: ALLOC_INTERFACE(api) case SWITCH_JSON_API_INTERFACE: ALLOC_INTERFACE(json_api) case SWITCH_FILE_INTERFACE: ALLOC_INTERFACE(file) case SWITCH_SPEECH_INTERFACE: ALLOC_INTERFACE(speech) case SWITCH_DIRECTORY_INTERFACE: ALLOC_INTERFACE(directory) case SWITCH_CHAT_INTERFACE: ALLOC_INTERFACE(chat) case SWITCH_SAY_INTERFACE: ALLOC_INTERFACE(say) case SWITCH_ASR_INTERFACE: ALLOC_INTERFACE(asr) case SWITCH_MANAGEMENT_INTERFACE: ALLOC_INTERFACE(management) case SWITCH_LIMIT_INTERFACE: ALLOC_INTERFACE(limit) case SWITCH_DATABASE_INTERFACE: ALLOC_INTERFACE(database) default: switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_WARNING, "Invalid Module Type!\n"); return NULL; } }
3、switch_endpoint_interface_t
作用：endpoint的入口
结构体定义：
struct switch_endpoint_interface { /*! the interface's name */ const char *interface_name; /*! channel abstraction methods */ switch_io_routines_t *io_routines; /*! state machine methods */ switch_state_handler_table_t *state_handler; /*! private information */ void *private_info; switch_thread_rwlock_t *rwlock; int refs; switch_mutex_t *reflock; /* parent */ switch_loadable_module_interface_t *parent; /* to facilitate linking */ struct switch_endpoint_interface *next; switch_core_recover_callback_t recover_callback; }; typedef struct switch_endpoint_interface switch_endpoint_interface_t;
字段解释：
interface_name => endpoint名称，比如："rtc"
io_routines => endpoint对应的io操作回调函数
state_handler => endpoint对应的事件处理回调函数
private_info => endpoint私有参数配置（比如编码格式、采样率等）
rwlock => endpoint锁
refs => endpoint锁的引用次数
reflock => endpoint引用锁
parent => endpoint所属模块
next => next指针
recover_callback => endpoint对应的recover回调函数
4、switch_io_routines
作用：存储io操作的回调函数
结构体定义：
struct switch_io_routines { /*! creates an outgoing session from given session, caller profile */ switch_io_outgoing_channel_t outgoing_channel; /*! read a frame from a session */ switch_io_read_frame_t read_frame; /*! write a frame to a session */ switch_io_write_frame_t write_frame; /*! send a kill signal to the session's channel */ switch_io_kill_channel_t kill_channel; /*! send a string of DTMF digits to a session's channel */ switch_io_send_dtmf_t send_dtmf; /*! receive a message from another session */ switch_io_receive_message_t receive_message; /*! queue a message for another session */ switch_io_receive_event_t receive_event; /*! change a sessions channel state */ switch_io_state_change_t state_change; /*! read a video frame from a session */ switch_io_read_video_frame_t read_video_frame; /*! write a video frame to a session */ switch_io_write_video_frame_t write_video_frame; /*! read a video frame from a session */ switch_io_read_text_frame_t read_text_frame; /*! write a video frame to a session */ switch_io_write_text_frame_t write_text_frame; /*! change a sessions channel run state */ switch_io_state_run_t state_run; /*! get sessions jitterbuffer */ switch_io_get_jb_t get_jb; void *padding[10]; }; typedef struct switch_io_routines switch_io_routines_t;
字段解释：
outgoing_channel => 创建外呼channel的回调函数
read_frame => 读session音频数据的回调函数
write_frame => 写session音频数据的回调函数
kill_channel => kill信号处理函数，用于处理channel接收的kill信号
send_dtmf => send dtmf操作的回调函数，用于处理channel接收的DTMF字符串
receive_message => 处理channel消息的回调函数，用于处理其它channel发来的消息
receive_event => 发送channel消息的回调函数，用于向目标session发送自定义事件（比如rtc session、rtmp session等）
state_change => channel状态修改的回调函数
read_video_frame => 读session视频数据的回调函数
write_video_frame => 写session视频数据的回调函数
read_text_frame => 读session文本数据的回调函数
write_text_frame => 写session文本数据的回调函数
state_run => 改变session的运行状态，目前没见到有endpoint使用过
get_jb => 获取session的jitter_buffer
5、switch_state_handler_table_t
作用：用于存储状态机的回调函数。
定义如下：
struct switch_state_handler_table { /*! executed when the state changes to init */ switch_state_handler_t on_init; /*! executed when the state changes to routing */ switch_state_handler_t on_routing; /*! executed when the state changes to execute */ switch_state_handler_t on_execute; /*! executed when the state changes to hangup */ switch_state_handler_t on_hangup; /*! executed when the state changes to exchange_media */ switch_state_handler_t on_exchange_media; /*! executed when the state changes to soft_execute */ switch_state_handler_t on_soft_execute; /*! executed when the state changes to consume_media */ switch_state_handler_t on_consume_media; /*! executed when the state changes to hibernate */ switch_state_handler_t on_hibernate; /*! executed when the state changes to reset */ switch_state_handler_t on_reset; /*! executed when the state changes to park */ switch_state_handler_t on_park; /*! executed when the state changes to reporting */ switch_state_handler_t on_reporting; /*! executed when the state changes to destroy */ switch_state_handler_t on_destroy; int flags; void *padding[10]; }; typedef struct switch_state_handler_table switch_state_handler_table_t;
参数解释：
on_init => channel进入 CS_INIT 状态的回调函数
on_routing => channel进入 CS_ROUTING 状态的回调函数
on_execute => channel进入 CS_EXECUTE 状态的回调函数，用于执行操作
on_hangup => channel进入 CS_HANGUP 状态的回调函数
on_exchange_media => channel进入 CS_EXCHANGE_MEDIA 状态的回调函数
on_soft_execute => channel进入 CS_SOFT_EXECUTE 状态的回调函数，用于从其它channel接收或发送数据
on_consume_media => channel进入 CS_CONSUME_MEDIA 状态的回调函数，
on_hibernate => channel进入 CS_HIBERNATE 状态的回调函数，sleep操作
on_reset => channel进入 CS_RESET 状态的回调函数
on_park => channel进入 CS_PARK 状态的回调函数
on_reporting => channel进入 CS_REPORTING 状态的回调函数
on_destroy => channel进入 CS_DESTROY 状态的回调函数
switch_core_state_machine.c中使用 STATE_MACRO 触发，部分触发代码如下：
case CS_ROUTING: /* Look for a dialplan and find something to do */ STATE_MACRO(routing, "ROUTING"); break; case CS_RESET: /* Reset */ STATE_MACRO(reset, "RESET"); break; /* These other states are intended for prolonged durations so we do not signal lock for them */ case CS_EXECUTE: /* Execute an Operation */ STATE_MACRO(execute, "EXECUTE"); break; case CS_EXCHANGE_MEDIA: /* loop all data back to source */ STATE_MACRO(exchange_media, "EXCHANGE_MEDIA"); break; case CS_SOFT_EXECUTE: /* send/recieve data to/from another channel */ STATE_MACRO(soft_execute, "SOFT_EXECUTE"); break; case CS_PARK: /* wait in limbo */ STATE_MACRO(park, "PARK"); break; case CS_CONSUME_MEDIA: /* wait in limbo */ STATE_MACRO(consume_media, "CONSUME_MEDIA"); break; case CS_HIBERNATE: /* sleep */ STATE_MACRO(hibernate, "HIBERNATE"); break;
四、模块编写示例
1、编写c风格的endpoint模块
仿照mod_rtc模块编写，核心文件只有两个：
mod_rtc.c
Makefile.am
1）复制mod_artc目录
cp mod_rtc mod_ctest -r
2）修改文件名
mv mod_rtc.c mod_ctest.c
3）修改文件内容，将rtc关键字替换成ctest
4）修改编译选项
文件： freeswitch-1.10.9.-release/configure.ac
仿照rtc模块，添加ctest模块内容：
src/mod/endpoints/mod_ctest/Makefile
5）开启模块编译
文件：freeswitch-1.10.9.-release/modules.conf
仿照rtc模块，添加ctest模块编译：
endpoints/mod_ctest
6）生成Makefile
./rebootstrap.sh && ./configure
7)安装模块
在 freeswitch-1.10.9.-release 根目录（或mod_ctest目录）执行如下指令：
make && make install
8）加载模块
文件：conf/autoload_configs/modules.conf.xml
添加如下内容：
9）模块测试
控制台加载测试：
reload mod_ctest
c风格endpoint模块编译及运行效果视频：
关注微信公众号（聊聊博文，文末可扫码）后回复 2023052801 获取。
2、编写c++风格的endpoint模块
仿照mod_h323模块编写，目录结构、编译等参考c风格endpoint模块编写部分。
加载效果如下：
c++风格endpoint模块编译及运行效果视频：
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五、资源下载
本文涉及源码和文件，可以从如下途径获取：
关注微信公众号（聊聊博文，文末可扫码）后回复 20230528 获取。
