[Users] default behaviour

As an educational tool, I'm trying to write a pure proxy using openser. This proxy doesn't have users or domains or gateways, it just shuffles messages that happen to land on it. I'm starting with REGISTER where I have simply this: t_on_reply("10"); t_on_failure("10"); t_relay(); The onreply and onfailure callbacks just log stuff. The openser cookbook says: The implicit action after execution of the main route block is to drop the SIP request. To send a reply or forward the request, explicit actions must be called inside the route block. To find what happens in other route blocks (onreply, etc.), I searched the cookbook for "implicit" and learned: implicit action for branch_route is to forward the request. implicit action for onreply_route is to send the reply upstream according to Via header And that's all there is. Is there more written somewhere else? What I noticed is that informational responses (1xx) are not relayed by openser, but Final (200) or Client Error (401) are relayed. Is this conclusion correct? This implicit behaviour seems a little odd to me; I would think that if I've got a t_on_reply out there then I'm saying "Hey, I'll handle it" but in fact I cannot handle it (t_relay is not allowed in an onreply block). So, I must be missing something in my understanding... I'ld appreciate it if someone could clarify for me. Thanks, -mark