[Serusers] Routing Logic Question

[Java Rockx]

Hi All.

I'm a confused when handling CANCEL messages when the call is between
my SER proxy and a PSTN gateway.

I've had a few discussions with Jan regarding when lookup("location")
needs to be called and as I understand it CANCEL is sort of an odd
message that is not really mid-dialog, and therefore not
record-routed. So lookup("location") needs to be called before
t_relay()ing a CANCEL.

This is fine for calls between two UAs on the same SER proxy since
both UAs have a contact record and lookup("location") will return
TRUE.

But when calling SIP->PSTN, and you hang up from the SIP side, the
CANCEL is sent from the SIP UA to SER. Then SER tries to find the
contact record in the location table, but since this is a PSTN
destination, lookup(location) returns false, thus a 404 and the CANCEL
is not relayed to the PSTN gateway.

So what is the best way to process CANCEL messages? Just ignore
lookup("location") when it returns false for CANCEL messages?

My basic ser.cfg is like this:

route {
    # sanity checks
    if (method!="REGISTER") record_route();
    if (loose_route()) {
        t_relay();
        break;
    };

    if (uri!=myself) {
        t_relay();
        break;
    };

    if (uri==myself) {
         if (method=="REGISTER") {
             save("location");
             break;
         };
         if (!lookup("location")) {
             sl_send_reply("404", "Not Found");
             break;
         };
     };
     t_relay();
}

Regards,
Paul