i'm returning to this old thread where peter wrote:

The way to get this working is: 1) Use Git master so that unregister() with ruid is supported 2) Modify save() so that upon successful creation of new contact it copies the ruid created by usrloc into the sip_msg.ruid variable for the current SIP message. This means that on return from save() the $ruid PV will work. ...

and

Actually save() can store the ruid in an xavp, one has to set the module parameter:

http://kamailio.org/docs/modules/stable/modules/registrar.html#idp1752184

my understanding is that a single register request may contain more than one contact and if so, several ruids would be generated, one per contact. if so, what would $ruid contain after save()?

regarding xavp_rcd, after reading registrar module code, it seems that it is only set upon lookup(), not upon save().

-- juha