[Linphone-users] OpenVPN: INVITE RTP IP != Contact IP

[Anatoli]

Hi Devs!

First of all, thanks for this great opensource app & lib!

I found a VPN connectivity issue on iPhone. If I establish an OpenVPN 
connection to an Asterisk server in the OpenVPN intercept-all-traffic 
mode (i.e. redirect-gateway directive), then everything works well. Now, 
if the OpenVPN connection only adds a route to the Asterisk server 
without intercepting the rest of the traffic, Linphone connects well to 
the server (sends a correct IP in the Via and Contact headers), but 
then, when trying to call, it sends in the INVITE SIP - RTP block its 
WiFi IP, not the IP of the VPN connection.

Suppose the phone's WiFi IP is 192.168.0.10, the VPN IP in both modes is 
10.0.0.11 and the Asterisk server IP is 10.0.10.1. In both cases 
Linphone connects to the Asterisk without any problem, but in the 
intercept-all-traffic mode it sends in the INVITE RTP packet its correct 
(VPN) IP, i.e. 10.0.0.11, but when in the single-route mode, it sends 
the WiFi IP for RTP, i.e. 192.168.0.10:

INVITE sip:address@hidden SIP/2.0
Via: SIP/2.0/TCP 10.0.0.11:54337;branch=z9hG4bK.Jv2auTGwr;rport
...
Contact: 
<sip:address@hidden:54337;transport=tcp>;+sip.instance="<urn:uuid:1e603d84-0b11-42a7-83cb-7c34f71e0089>"
User-Agent: Linphone_iPhone.4S_iOS7.1.2/3.13.9 (belle-sip/1.4.2)

...
o=777 2097 2332 IN IP4 192.168.0.10
...
c=IN IP4 192.168.0.10


What could be the problem? In both cases the IPs of the phone are the 
same (e.g. when inspecting with System Status Lite/Pro), i.e. there's an 
IP for a 3g/4g connection, an IP for a WiFi connection and an IP for the 
VPN connection. The OpenVPN app also reports the same IP (for ifconfig 
command) in both cases, but Linphone somehow uses different IPs 
depending on whether it's in the intercept-all-traffic mode (it choses 
the VPN IP) or in the single-route mode (it choses the WiFi IP).

Is there any way to indicate what IP to use? If not, is it possible to 
fix the app in order to send the correct IP (i.e. the same as in the 
Contact/Via headers)?

Thanks,
Anatoli