[SR-Users] nating private uas to public ip addr

I have a multi-homed kam with a uas behind one private interface and a public interface for the uac+sip provider. When the uac initiates a call, kam sends the invite to the private uas which sets up a b-leg call back to kam with a Contact header that has the uas' private ip address. I want to change that private ip address to be Kamailio's advertised/public ip address before it gets forwarded to the sip provider. I am rewriting Contact in a route from request_route like this: This seems to work fine for the INVITE going to the provider. There's also the 200 OK that the uas sends for the uac (a-leg) with a private ip address in Contact -- I want to rewrite that before sending it to the UAC, too. Using the same method as above (but inside onreply_route), what happens is the UAC receives the modified OK and sends back an ACK with the modified Contact (kam's public ip addr) in the ACK r-uri, and kam gets in a loop of sending an ACK from its private ip address to its public ip address and replying to itself. call flows: https://imgur.com/a/Yj2DJpn Is there a right way to do this?