i would like to add and when hostpart of r-uri is ipv4 address, wireshark tells me that kamailio does NOT try to resolve it from dns, but when hostpart is [ipv6 address] then (as i have shown earlier), kamailio tries to resolve it.
if it would be possible to make treatment of ipv6 hostpart the same as ipv4 hostpart, no addition checks would be needed.
-- juha