[SR-Users] Suspend INVITE between ip4 and ip6 users

Hi, I try to modify the kamailio configuration to work between ipv4 and ipv6 clients. Clients are mobile sofphones, so they are mostly in background without registration. 1. When an INVITE arrives from IPV4 address, transaction is suspended and a push notification is sent to callee. 2. Callee gets push notification and registers to kamailio. 3. INVITE transaction continues. My kamailio config is based on this article: https://kb.asipto.com/kamailio:kamailio-mixed-ipv4-ipv6 using rtpengine. If clients are in foreground it works fine. But, when a client is in background, kamailio knows nothing about the callee’s IP address (ipv4 or ipv6). The problematic case is the call from IPV4 to IPV6. In this case the FLB_V4V6 flag is missing at continue, since in IPV4V6 route it cannot be set and the rtpengine tries the IPV4->IPV4 case. From the other side IPV6->IPV6. It is understandable, since FLB_V4V6 flag is missing in this case. My question is: where and when should I set this flag? Thanks. Peter