Re: [Ekiga-list] Bug prevents VPN use

[Mikael Abrahamsson <swmike swm pp se>]

On Wed, 2 Oct 2013, Damien Sandras wrote:

> If user B has two local interfaces (eth0: 192.x and tun: 10.x), when EkigaB 
> will send a SIP message to userA, it will send it twice (because it can not 
> determine how routing will work, that's the kernel responsibility) :
> - one SIP message to userA through tun0 with tun0 source IP address to userA 
> IP and port
> - one SIP message to userA through eth0 with eth0 source IP address to user 
> IP and port
>
> One of them should work.
>
> Your mail suggests that both messages are sent using the same interface but 
> with different source IP and ports. That's weird.

How does Ekiga assure that the packet is actually sent out eth0 with eth0 
source IP? By default routing and source address selection are completely 
decoupled and if default route is to tun0, then all packets regardless of 
source address will go out tun0. One has to put policy routing in place to 
avoid this and assure that eth0 IP packets actually go out eth0 (and then 
you have to have the concept of multiple default routes that might change 
over time that needs to influence the policy routing settings).

--
Mikael Abrahamsson    email: swmike swm pp se