[SR-Users] [REGISTRAR] Registered. How to match $sut to usrloc received ?

Hey Kamailio Users, So the scenario is we get the registers. Load them, slightly oddly as we also fill in the received section, not something I usually do. Then when they send an invite, the To and From headers are real phone numbers and for some reason the contact header isn't their username. So to compensate for that I'm trying to match their connection ($sut) using registered, but after a couple of hours I haven't been able to get it to match up. Not sure what I'm missing. ul.dump gets me Received: sip:sipclientpublicip:2353;transport=udp so we know that part is loading $sut correctly into the user location data. modparam("usrloc", "matching_mode", 2) modparam("registrar", "xavp_rcd", "ulrcd") modparam("registrar", "received_avp", "$avp(i:42)") $xavp(regcfg=>match_received) = $sut; if (registered("location","$sut", 2, 1)) { After that block of code $sut is sip: sipclientpublicip:2353;transport=udp which is what's in usrloc for received, but it's not match. There's probably a much smarter way of doing this that I've completely missed, if so then that'd be excellent. But if I'm on the right path somewhat then it would be great to get this working.