[Serusers] Dest IP

Hello, I need the destination IP of the user of the first INVITE message (user -> ser)... but dst_ip == xxx.xxx.xxx.xxx gives me the IP of ser. The problem is that I only want to force the rtp_proxy if the users are behind a Port restricted cone NAT (the scr-ips of them are known) Here is my code: # Force rtpproxy for users that are behind a Port Restricted Cone NAT if ((src_ip == xxx.xxx.xxx.xxx | dst_ip == xxx.xxx.xxx.xxx) && !(uri=~"sip:[0-9]{9,30}@.*")) { fix_nated_contact(); # Rewrite contact with source IP of signalling force_rport(); # Add rport parameter to topmost Via setflag(6); } Has anyone an idea how I can get the IP of the user? For example in the location database? Thanks! Sebastian