freeswitch呼叫流程分析

 

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(0);
        => 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(0, 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

回复407

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