Re: [Linphone-users] How to tell linphone which IP address to use

[Gelonida N]

On 03/03/2012 09:04 PM, Brian J. Murrell wrote:
> On 12-02-21 05:52 PM, Koos Pol wrote:
>>
>> You don't get to choose an IP address. That is a function of the network
>> stack.
> 
> But within the Session Initiation protocol by way of the Session
> Description Protocol each end informs the other end of which IP address
> and port that it should be trying to establish the RTP session with.  So
> it's the actual SIP implementation that is choosing an IP address to
> include in that SDP message.
> 
> So to be clear we are not talking about the selection of IP addresses on
> the packets that leave the machine headed out for the remote machine.
> Yes, you are correct.  Those are selected by the network stack.
> 
> The address that's written into the SDP is not chosen by the network
> stack and that is the address that is typically wrong on a configuration
> where a machine is on a public network (i.e. the Internet) and has a VPN
> connection on top of that public network, effectively giving the host
> two interfaces and two addresses.
> 
> What linphone needs to be doing is effectively:
> 
> $ ip route get 10.75.22.8
> 
> and then extracting what the source ip address for that route will be
> out of the answer.  For example:
> 
> 10.75.22.8 via 10.8.0.13 dev tun0 src 10.8.0.14
>                                       ^^^^^^^^^
> The address that should go into the SDP is therefore 10.8.0.15, not the
> address that will be on typically eth0 or wlan0, etc., which seems to be
> the address linphone most frequently uses.
> 
Thanks a lot Brian for your very clear explanation.

Yes exactly this is my problem.
Ideally linphone should do something like you explained above.

Does anybody know what would be the related code in the linphone sources
which is currently 'deciding' what address will be put into the SDP message?