FreeSWITCH 處理Refer盲轉時，UUI傳遞不對(沒有將SIP 訊息頭Refer-To中的User-to-User傳遞給B-Leg)
阿新 • • 發佈：2020-09-22
執行環境：
CentOS 7.6
FreeSWICH 1.6.18
一、問題場景：
FreeSWITCH收到REFER命令後，重新發起的INVITE訊息中的 "User-to-User" 訊息頭資訊不對，跟REFER命令的 "Refer-To" 訊息頭中的User-to-User引數值不同。
具體報文情況如下(省略了部分SIP資訊)：
REFER sip:[email protected]:5080 SIP/2.0 Via: SIP/2.0/UDP 10.2.32.116:5080;rport;branch=z9hG4bKryvUZZerH16DN From: <sip:[email protected]:5080>;tag=XH27mSc4ZyjaF To: "Extension 296898" <sip:[email protected]>;tag=6g430SNK5Be3m Call-ID: 46eda73c-76b2-1239-e1b5-487b6b8ad630 Contact: <sip:[email protected]:5080;transport=udp> Refer-To: <sip:[email protected]?User-to-User=00C82b264F7267416E693D3131313337303035303030303139393433333634264F7267446E69733D333030393637%3Bencoding%3Dhex> Referred-By: <sip:10.2.32.116:5080> User-to-User: 00C8426613D31%3Bencoding%3Dhex INVITE sip:[email protected]:50078;rinstance=b4e528536c8c5a3d SIP/2.0 Via: SIP/2.0/UDP 10.2.32.90;rport;branch=z9hG4bKtK4yS4SH849vD Route: <sip:[email protected]:50078>;rinstance=b4e528536c8c5a3d From: "Extension 296898" <sip:[email protected]>;tag=ymDeQZt2ZcK1B To: <sip:[email protected]:50078;rinstance=b4e528536c8c5a3d> Call-ID: 4992bbb6-76b2-1239-e1b5-487b6b8ad630 Contact: <sip:[email protected]:5060> Referred-By: <sip:10.2.32.116:5080> User-to-User: 00C8426613D31%3Bencoding%3Dhex Remote-Party-ID: "Extension 296898" <sip:[email protected]>;party=calling;screen=yes;privacy=off
二、問題原因： FreeSWICH預設情況下，處理REFER命令進行盲轉時，新發起的INVITE訊息中的 "User-to-User" 是從REFER的 "User-to-User" 頭中獲取的，而非"Refer-to"裡的引數 FS處理Refer命令的邏輯：
- 信令互動邏輯
- 信令處理邏輯
- REFER的SIP訊息頭"Refer-To"中的資訊，只提取盲轉的被叫號碼，忽略其他引數(如User-to-User)，然後發起新的INVITE
- 新的INVITE訊息中的“User-to-User”頭，是根據REFER命令中的“User-to-User”頭獲取，非“Refer-To”裡的引數值
三、解決方案 FreeSWITCH 收到 REFER 後，取出sip_refer_to頭中的值，執行export nolocal 命令，將值設定到未來bridge的B-leg通道上即可。 增加下面撥號方案即可：
<extension name="refer request" continue="true">
<condition field="${sip_refer_to}" expression=".+User-to-User=(.+)%3B">
<action application="log" data="INFO yuxiu:change User-to-User by sip_refer_to : sip_refer-to [$1]"/>
<action application="export" data="nolocal:sip_h_User-to-User=$1;encoding=hex"/>
</condition>
</extension>REFER sip:[email protected]:5080 SIP/2.0 From: <sip:[email protected]:5080>;tag=XH27mSc4ZyjaF To: "Extension 296898" <sip:[email protected]>;tag=6g430SNK5Be3m Refer-To: <sip:[email protected]?User-to-User=00C82b264F7267416E693D3131313337303035303030303139393433333634264F7267446E69733D333030393637%3Bencoding%3Dhex> User-to-User: 00C8426613D31%3Bencoding%3Dhex INVITE sip:[email protected]:50078;rinstance=b4e528536c8c5a3d SIP/2.0 From: "Extension 296898" <sip:[email protected]>;tag=ymDeQZt2ZcK1B To: <sip:[email protected]:50078;rinstance=b4e528536c8c5a3d> User-to-User: 00C82b264F7267416E693D3131313337303035303030303139393433333634264F7267446E69733D333030393637%3Bencoding%3Dhex Remote-Party-ID: "Extension 296898" <sip:[email protected]>;party=calling;screen=yes;privacy=off
四、模擬的呼叫場景：
4.1、PBX-FS機器：充當分機註冊伺服器 在PBX-FS (10.2.32.90:5060)上註冊兩個分機：296896 和 296898 然後讓296989 呼叫 449998 進行測試
- 撥號方案詳情：default.xml
<!-- 處理refer訊息頭 -->
<extension name="refer request" continue="true">
<condition field="${sip_refer_to}" expression=".+User-to-User=(.+)%3B">
<action application="log" data="WARNING yuxiu:change User-to-User by sip_refer_to : sip_refer-to [$1]"/>
<action application="export" data="nolocal:sip_h_User-to-User=$1;encoding=hex"/>
</condition>
</extension>
<!-- 模擬呼叫IVR -->
<extension name="outbound-ivr">
<condition field="destination_number" expression="^(449998)$">
<action application="bridge" data="sofia/external/[email protected]:5080"/>
<action application="hangup" data="Esl Server ERROR"/>
</condition>
</extension>
<!-- 模擬呼叫PBX分機 -->
<extension name="outbound-pbx">
<condition field="destination_number" expression="^(296\d{3})$">
<action application="bridge" data="user/${1}"/>
<action application="hangup" data="Esl Server ERROR"/>
</condition>
</extension>
4.2、IVR-FS機器：充當IVR導航伺服器
收到來電後，自動應答，然後播放一段提示音後，refer 盲轉到296896
<extension name="outbound-test2">
<condition field="destination_number" expression="^449998$">
<action application="log" data="INFO uui=${sip_h_User-to-User}"/>
<action application="answer"/>
<action application="playback" data="/usr/local/freeswitch/sounds/welcom_to_call_yuxiu_ivr.wav"/>
<action application="deflect" data="sip:[email protected]?User-to-User=00C82b264F7267416E693D3131313337303035303030303139393433333634264F7267446E69733D333030393637%3Bencoding%3Dhex"/>
<action application="log" data="WARNING refer finished"/>
<action application="hangup" data="refer finished"/>
</condition>
</extension>
4.3、FS測試日誌
EXECUTE sofia/internal/[email protected] bridge(sofia/external_90/[email protected]:5080) [DEBUG] sofia.c:8544 Process REFER to [[email protected]] [INFO] mod_dialplan_xml.c:637 Processing 296898 <296898>->296896 in context default EXECUTE sofia/internal/[email protected] bridge(user/296896)