Re: [sr-dev] [kamailio/kamailio] lost: dynamic HELD url resolving (#2574)

NAPTR support is a good idea and basically also applicable to the LoST service (which I have on my ToDo list anyway). I will have a look at it - just one question:

I assume item (1) below refers to the device IP address (i.e. UE) for reverse DNS (as in https://tools.ietf.org/html/rfc7216#section-4), which may not work in any case. How about expanding the discovery procedure with a NAPTR request sent to the provider's domain (as found in From and/or P-A-I) in case (1) fails?

(1) Kamailio send reverse .in-addr.arpa. or .ip6.arpa. DNS request and caller host DNS name; (2) Kamailio send LIS:HELD NAPTR request for a resolved caller hostname and LIS server. (3) Kamailio send HELD request for resolved LIS address.