Hello, I'm currently struggling to find a way to force Freeswitch to only allow ZRTP based calls without a trusted MiTM. I've tried to use "is_zrtp_secure" from the features.xml to hang the call up with the Dialplan but it isn't getting me anywhere. I've also looked at using LUA scripts to detect when the call has been answered and then check on the variables set in switch_channel.c but this also doesn't work. I can see from switch_channel.c that it prints "ZRTP not negotiated on both sides; disabling ZRTP passthru mode." and sets zrtp_passthru_active to false when this happens. Can someone point me in the right direction for looking up the value of this var once the call has been answered to determine whether ZRTP support is available or if there is a better way to approach this? Cheers, Ollie