freeswitch呼叫流程分析

今天翻文档时发现之前整理的关于freeswitch呼叫相关的内容，写成博文分享出来也方便我以后查阅。

整体结构图

FreeswitchCore

模块加载过程

freeswitch主程序初始化时会从modules.conf.xml文件中读取配置，如果配置中如下内容生效：

<load module="mod_sofia"/>

则执行加载sofia模块操作。

具体过程如下：

main

switch_core_init_and_modload

switch_loadable_module_init

switch_loadable_module_load_module_ex ： 读取xml文件并加载模块

状态机相关

状态机初始化

switch.c  : main

switch_core_init_and_modload

    => switch_core_init

        => switch_core_session_init

            => switch_core_session_thread_pool_manager

                => check_queue

                    => switch_core_session_thread_pool_worker

                        => switch_core_session_thread

                            => switch_core_session_run

改变状态

通过调用switch_channel_set_state来实现状态机的状态改变。

处理状态变化

当状态发生变化后，通过switch_channel_set_running_state函数来改变running_state，
并执行相关的回调来通知其状态已经发生改变了：
endpoint_interface->io_routines->state_run

主叫状态变化

CS_NEW

switch_core_session_run初始状态为CS_NEW

CS_INIT

sofia_handle_sip_i_state
case nua_callstate_received (收到invite请求) 修改状态机的状态：CS_NEW ==> CS_INIT switch_channel_set_state(channel, CS_INIT);

switch_core_session_run
状态机处理状态变化 STATE_MACRO(init, "INIT"); on_init 即： sofia_on_init
switch_core_standard_on_init
CS_ROUTING

sofia_on_init
```
修改状态机的状态 ： CS_INIT == > CS_ROUTING

switch_channel_set_state(channel, CS_ROUTING);
```
switch_core_session_run
状态机处理状态变化 STATE_MACRO(routing, "ROUTING"); on_routing 即： sofia_on_routing
switch_core_standard_on_routing
CS_EXECUTE

switch_core_standard_on_routing 修改状态机的状态： CS_ROUTING == > CS_EXECUTE switch_channel_set_state(session->channel, CS_EXECUTE);

switch_core_session_run
状态机处理状态变化 STATE_MACRO(execute, "EXECUTE"); on_execute 即： sofia_on_execute
switch_core_standard_on_execute
CS_HANGUP

sofia_handle_sip_i_bye switch_channel_hangup ：即 switch_channel_perform_hangup 修改状态机的状态 channel->state = CS_HANGUP;
```
    状态机处理状态变化

    switch_core_session_hangup_state

        STATE_MACRO(hangup, "HANGUP");
```

被叫状态变化

CS_NEW

switch_core_session_run初始状态为CS_NEW

CS_INIT

sofia_outgoing_channel 修改状态机的状态：CS_NEW ==> CS_INIT switch_channel_set_state(nchannel, CS_INIT);

状态机处理逻辑参考主叫。

CS_ROUTING

sofia_on_init
修改状态机的状态： CS_INIT == > CS_ROUTING switch_channel_set_state(channel, CS_ROUTING);

状态机处理逻辑参考主叫。

CS_CONSUME_MEDIA

originate_on_routing 修改状态机的状态：CS_ROUTING -> CS_CONSUME_MEDIA switch_channel_set_state(channel, CS_CONSUME_MEDIA);

switch_core_session_run
状态机处理状态变化 STATE_MACRO(consume_media, "CONSUME_MEDIA"); on_ consume_media 即： NULL switch_core_standard_on_consume_media
CS_EXCHANGE_MEDIA

switch_core_session_run
状态机处理状态变化 STATE_MACRO(exchange_media, "EXCHANGE_MEDIA"); on_exchange_media 即： sofia_on_exchange_media
switch_core_standard_on_exchange_media
CS_HANGUP

audio_bridge_on_exchange_media
switch_channel_hangup ：即 switch_channel_perform_hangup 修改状态机的状态 channel->state = CS_HANGUP;
```
    状态机处理状态变化

    switch_core_session_hangup_state

        STATE_MACRO(hangup, "HANGUP");
```

Sofia应用层

模块加载过程

启动事件处理线程池：

SWITCH_MODULE_LOAD_FUNCTION(mod_sofia_load)

    => sofia_msg_thread_start();

        => sofia_msg_thread_run

            => sofia_process_dispatch_event

                => our_sofia_event_callback : 处理消息

启动服务器监听：

SWITCH_MODULE_LOAD_FUNCTION(mod_sofia_load)

    => config_sofia(, NULL)

        => launch_sofia_profile_thread

            => sofia_profile_thread_run

                => nua_create

                    => su_home_new

                    => nua_stack_init

                        => nta_agent_create

                            => nta_agent_add_tport

                                => tport_tbind

                                    => tport_bind_server

                                        => tport_listen ： 监听客户端发来的数据

数据表

数据库默认路径：/usr/local/freeswitch/db

freeswitch core 相关：

aliases
calls
channels
complete
interfaces
nat
recovery
registrations
tasks

sofia相关：

sip_authentication
sip_dialogs
sip_presence
sip_registrations
sip_shared_appearance_dialogs
sip_shared_appearance_subscriptions
sip_subscriptions

limit相关：

db_data
group_data
limit_data

fifo相关：

fifo_bridge
fifo_callers
fifo_outbound

语音信箱相关：

voicemail_msgs
voicemail_prefs

呼叫流程涉及内容

1、收到A的nua_i_invite，返回407，具体如下:

sofia_handle_sip_i_invite => sofia_reg_handle_register => sofia_reg_auth_challenge => 407

2、收到A的nua_i_invite，返回180，具体如下：

sofia_handle_sip_i_invite => sofia_reg_handle_register => sofia_reg_parse_auth

处理nua_i_state消息
sofia.c : sofia_handle_sip_i_state
...
mod_dialplan_xml.c : dialplan_hunt (ring_ready)
解析拨号方案，执行lua脚本，设置通道变量。
…
发送180事件

涉及数据表：
sip_registrations、ip_dialogs

3、发送invite给B分机，具体如下：
处理nua_r_invite消息
sofia_handle_sip_r_invite => originate_on_routing
涉及数据表：
sip_dialogs

4、 B应答，双方通话，具体如下：

sofia_receive_message : SWITCH_MESSAGE_INDICATE_ANSWER

    => sofia_answer_channel

        => sofia_glue_tech_choose_port

        => sofia_glue_set_local_sdp

        => sofia_glue_activate_rtp

编码协商过程

这里描述下后协商流程

先匹配freeswitch默认的codec，从加载的模块中查找支持类型的具体码率信息

sofia_handle_sip_i_invite
=> sofia_glue_tech_prepare_codecs
=> switch_loadable_module_get_codecs_sorted

协商发给被叫的sdp

sofia_glue_do_invite
=> sofia_glue_tech_prepare_codecs
=> switch_loadable_module_get_codecs_sorted

    ocodec + codec_string

产生M头，并发送包含sdp的invite

sofia_glue_do_invite
=> sofia_glue_set_local_sdp
=> generate_m
=> nua_invite

协商200 OK的sdp

sofia_answer_channel
=> sofia_glue_tech_prepare_codecs
=> switch_loadable_module_get_codecs_sorted

媒体交互

RTP数据交互

audio_bridge_on_exchange_media
=> audio_bridge_thread

收发音频数据
=> switch_core_session_read_frame
=> session->endpoint_interface->io_routines->read_frame 即： sofia_read_frame

=> switch_core_session_write_frame
=> perform_write
=> session->endpoint_interface->io_routines->write_frame 即： sofia_write_frame

收发视频数据
1、启动线程
=> launch_video
=> video_bridge_thread

2、收发数据
=> switch_core_session_read_video_frame
=>session->endpoint_interface->io_routines->read_video_frame
即：sofia_read_video_frame

=> switch_core_session_write_video_frame
=> session->endpoint_interface->io_routines->write_video_frame
即：sofia_write_video_frame

终止RTP交互

audio_bridge_thread
=> switch_core_session_kill_channel(session_b, SWITCH_SIG_BREAK);
即：switch_core_session_perform_kill_channel
=> session->endpoint_interface->io_routines->kill_channel
即 : sofia_kill_channel
=> switch_rtp_break

Sofia协议栈

协议栈结构图

NUA : 基本的SIP用户代理的功能，其功能包括呼叫管理，消息和事件检索。
NTA : sofia SIP事务API（NTA）提供了简单的接口的SIP事务，传输和信息处理。
Tport : 该模块包含一个由SIP，RTSP 和HTTP协议使用的通用传输接口，这是一个协议栈和传输协议实现之间的抽象层。

SIP信令具体流程

场景描述： A 呼叫 B ，B接通后通话一段时间后，挂断电话。

A 发送 INVITE 请求

tport.c : tport_recv_data
nta.c : agent_recv_request

FS回应100给A分机

nua_server.c : nua_stack_process_request
nua_server.c : SR_STATUS1(sr, SIP_100_TRYING)
nta.c : nta_incoming_treply
nta.c : incoming_reply
tport.c: tport_tsend

FS发送认证请求给A分机

nua_application_event

处理nua_i_invite 消息

sofia.c : sofia_process_dispatch_event
sofia.c : our_sofia_event_callback
sofia.c : sofia_handle_sip_i_invite
sofia.c : sofia_reg_handle_register
sofia_reg.c : sofia_reg_auth_challenge

nua.c : nua_respond
nua_stack.c : nua_signal
nua_stack.c : nua_stack_signal
nua_server.c : nua_stack_respond
nua_server.c : nua_server_respond

发送407给A分机

nua_invite_server_respond
nua_base_server_respond
nta_incoming_mreply
incoming_reply
tport_tsend
tport_resolve
tport_by_addrinfo
tport_prepare_and_send
tport_send_msg
tport_vsend
sent 407 Proxy Authentication Required for INVITE (1)

call state(A) : init -> received
call state(A) : received -> terminated

A分机发送ACK
nta.c : agent_recv_message
nta.c : agent_recv_request
A分机重新发送 INVITE 请求，附加认证信息
tport.c : tport_recv_data
nta.c : agent_recv_request
FS回应100给A分机

nua_server.c : nua_stack_process_request
nua_server.c : SR_STATUS1(sr, SIP_100_TRYING)
nta.c : nta_incoming_treply
nta.c : incoming_reply
tport.c: tport_tsend

FS发送 INVITE 给 B分机

switch_ivr_originate.c : switch_ivr_originate

sofia_on_init
sofia_glue_do_invite
nua_invite : nua_r_invite 消息
nua_signal

sofia.c : sofia_process_dispatch_event
sofia.c : our_sofia_event_callback
sofia.c : sofia_handle_sip_r_invite
...
sofia_on_init
sofia_on_routing
switch_ivr_originate.c ：originate_on_routing
...
nua_stack_signal
nua_stack_invite
...
nta_leg_tcreate
...
执行发送invite请求
nta.c : outgoing_send
tport_tsend

call state(B) : init -> calling

B分机回应180给FS
tport_recv_event
agent_recv_response

处理 nua_r_invite 消息

sofia.c : sofia_process_dispatch_event
sofia.c : our_sofia_event_callback
sofia.c : sofia_handle_sip_r_invite

call state(B) : calling -> proceeding

FS发送180给A分机

nua_session.c : signal_call_state_change
nua_stack_tevent : nua_i_state
nua_application_event

处理nua_i_invite 消息

sofia.c : sofia_process_dispatch_event
sofia.c : our_sofia_event_callback
sofia.c : sofia_handle_sip_i_invite
sofia_reg.c : sofia_reg_handle_register
sofia_reg.c : sofia_reg_parse_auth

处理nua_i_state消息
sofia.c : sofia_handle_sip_i_state
...
mod_dialplan_xml.c : dialplan_hunt (ring_ready)
解析拨号方案，执行lua脚本，设置通道变量。
…

发送180
switch_channel_mark_ring_ready

nua_invite_server_respond
nua_base_server_respond
nta_incoming_mreply
incoming_reply
tport_tsend
tport_resolve
tport_by_addrinfo
tport_prepare_and_send
tport_send_msg
tport_vsend

call state(A) : init -> received

 B发送200 ok
tport_recv_event
agent_recv_response

处理 nua_r_invite 消息

sofia.c : sofia_process_dispatch_event
sofia.c : our_sofia_event_callback
sofia.c : sofia_handle_sip_r_invite

call state(B) : proceeding -> completing

FS发送ACK给B
nua_ack
nua_signal : nua_r_ack
outgoing_send
tport_tsend

call state(A) : received -> early
call state(B) : completing -> ready

FS发送200 OK给A
sofia_glue_tech_set_codec
switch_rtp_create
sofia_glue_negotiate_sdp
sofia_glue_activate_rtp
...
switch_channel_perform_answer : SWITCH_MESSAGE_INDICATE_ANSWER
switch_channel_perform_mark_answered
...
auto_record.lua ：执行录音操作B
...
auto_record.lua ：执行录音操作A
...
sofia_receive_message (SWITCH_MESSAGE_INDICATE_ANSWER)
...
发送200 OK
nua_respond : 200
nua_signal : nua_r_respond
nua_stack_signal
nua_stack_respond
nua_server_respond
nta_incoming_treply
nta_incoming_mreply
incoming_reply
tport_tsend

call state(A) : early -> completed

A回应ACK
nta.c : agent_recv_message
nta.c : agent_recv_request

call state(A) : completed -> ready

通话一段时间后，A主动发送BYE
tport_recv_event
agent_recv_message
agent_recv_request
...
sofia_on_hangup
FS发送BYE给B
nua_bye : nua_r_bye
nua_stack_signal
outgoing_send
tport_tsend
FS发送200 OK给A
nta ： sent 200 OK for BYE
tport_tsend

call state(A) : ready -> terminating
call state(A) : terminated

B发送200 OK给FS，回应挂断请求
nta: received 200 OK for BYE

状态变化：
call state(B) : ready -> terminating
call state(B) : terminating -> terminated

本文github地址：

https://github.com/mike-zhang/mikeBlogEssays/blob/master/2016/20160907_freeswitch呼叫流程分析.md

欢迎补充