[Serusers] add_rcv_param() for INVITEs

[Martin Koenig]

Hello,

is it possible to use add_rcv_param() also for Contact-HF of INVITEs, 
instead of fix_nated_contact()?

This would make sure that the NATed End Device gets fed exactly the 
contact as R-URI that it announced in the INVITE:

Example R-URI in Loose-Route Requests for fix_nated_contact():

Ser (1.2.3.4):
INVITE device at 4.5.6.7
Route: 1.2.3.4;lr=on

Device (10.0.0.1, NAT 4.5.6.7):
INVITE device at 123.123.123.123

With add_rcv_param():

Ser:
INVITE device at 10.0.0.1;rcv_param=4.5.6.7
Route: 1.2.3.4;lr=on

Device:
INVITE device at 10.0.0.1

The problem is that the End-Device, in the fix_nated_contact() callflow, 
has to accept a Request that is not really for this device (IP in 
Request-URI != IP of the Device). Imagine a Ser checkip uri == myself. 
This would fail without knowing the public IP of the NAT and 
hard-conding it into Ser.cfg.

Does Ser support the rcv_param in Request-URI also?

What do you think? Any experience on this?

Regards,
Martin