[Serusers] Handling CANCELS when a UAC doesn't answer and t_relay has maintained state

Hello All, Looking for some input if anyone else has run into this situation and/or figured a way around it. - Call comes in from PSTN gateway to a local user - SER finds the user in the location table and t_relay pushes the request off to them - The user is behind an ACL and is not sending keep-alives (yes I know the client is broken) so the INVITE never makes it to them and hence no 180/183 Ringing message comes back - PSTN user gives up and hangs up the phone after 3 seconds of no ringing - PSTN gateway forwards the CANCEL message in and SER cancels the branch - However since t_relay is stateful and re-tries transmissions the INVITE is sent another time or two - Finally the connection times out and the failure_route set for the t_relay kicks in and the INVITE gets pushed off to the voicemail server. - Voicemail server OK's the INVITE and starts retransmitting the OK over and over and over since the PSTN GW doesn't ACK the OK since it knows that call-id as being cancelled. So, should I handle cancel's a little more explicitly by doing something similar to: if ((method=="CANCEL") && (t_lookup_request())) { t_release(); }; What side effects, if any, would this cause? Is there a better way to handle it? Thanks, -Evan