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[Linphone-developers] no audio in vpn call using kitkat android

From: Adrian Schwartz
Subject: [Linphone-developers] no audio in vpn call using kitkat android
Date: Sun, 14 Dec 2014 09:52:19 +0200

Hello linphone developers group

I created a testing lab, wifi router ( connected to asterisk server that is behind a vpn gateway , the wifi network is ( and vpn network for smartphone, for the sip server (vpn tunnel,<=>

I'm  seeing a strange behavior in the S5 phone ( ; vpn is enabled ( tested both manual and automatic mode), run the sip client application, and it registers, Established a sip call and saw that on S5 all the audio is going through the non vpn interface (un encrypted) while all other date is going over the vpn interface.

when using other phone (sip2.pcap file) it seems that all data (sip, rtp and h264) is going over the vpn tunnel, it is observed that while the S5 (kit kat) is indicating in the sip header its via address 192.168.111.x the other is doing right and goes through the vpn  tunnel 192.168.165.y
for example 
Sip5.pcap message 18 the via header in S5 indicating in the via header while , the other phone indicates normal or no via header for example message 68 in the same file.

1. When I disable the vpn, the s5 audio is working well,
2. When I enable h264 video and then disable it, audio starts working.(sip1.pcap)
3. I changed the forwarding routing rule for vpn and it didn't solved the it. 
4.When using the adb it shows many interfaces including wifi, rmnet and ipsec, the default route goes through non vpn interface, I also found this issue in android that may be relevant,

attached (  few pcap files:

Sip5.pcap: showing h264 and sip packets over 165 network + rtp audio packets going unencrypted directly over 11.0/24 network.
Sip2.pcap: showing the behavior of Other phone where all data (audio and sip) goes encrypted.
Sip1.pcap: similar to Sip5 just without the video packets (h264)
Another difference between the sip1.pcap and sip5.pcap is that when there is h264 packets going in sib5.pcap, audio is also working.

Can you help me in bypassing this issue, I don't mind patching the linphone and getting the right via header from file, can you please point me to the right area?


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