[Feature request] 6rd IPv4 address choice

[tamer]

(I'm not sure whether this is the correct place to post this, so please move it to the right board if it is not.)

I was wondering if you could add the possibility of choosing/setting the IPv4 of the interface that 6rd uses.

I ask because my external static IP is not the same as the IP that is assigned to my WAN interface. The one assigned to the WAN is a local IPv4 (eg 10.x.x.x) address, which cannot be used for 6rd. Through NAT I am able to set all of my outgoing traffic to use the correct public IPv4. My ISP does this as a way to protect their PBX server from external attacks as it remains internal to their network that can be access using the main WAS address but all other traffic should use the public address. A simple diagram of the situation:

+-----------+
|           | ----- 10.x.x.x (SIP traffic) -----------> ISP internal network
|    WAN    |
|           | ----- public_ip (everything else) ------> Internet
+-----------+

To be able to use my ISP 6rd deployment I need to generate a prefix corresponding to my external IP address rather than one corresponding to my internal one.

The easiest way I can see for this to be implemented is that an extra field could be added to the 5rd settings to set this IP address.

I have gave a quick look at the php file dealing with this but I wasn't able to pin it down to what exactly need to be changed. I someone could provide some pointers as to how this is best done, I can try to create a pull request for it.