[Serusers] Rewriting SDP Infos for NAT Traversal

Hi, When an INVITE request is incoming, I need to rewrite VIA Header Field, Contact Header Field, (c=) field in SDP message core and (o=) field in SDP message core too with IP public adress of UAC. Those are needed by my SIP Server before SER Proxy forward the request to him. I got some success with rewriting Contact Header File by using fix_nated_contact() function and (c=) field with fix_nated_sdp("1") function. But I don't succeed at all in rewriting (o=) field and partially for VIA Header Field. To do so, I tried to use the following function : fix_nated_sdp("8"); No Result :( forcerport(); It seems to add real IP public adress and port in VIA header field but it's not rewriting IP private adress So, finally is it the good way to do this thing or is there something wrong with my behaviour ? Thanks,