This is a little overlapping since the utp code can be closed more-or-less immediately, but the udp manager needs to stay open in order to process the udp tracker connection requests before sending out event=stopped. Moreover DNS resolver can be shut down after the UDP tracker is shutdown.
This handles converting the data in a sockaddr_storage to a tr_address + port, and removes redundant code from fdlimit.c and tr-udp.c that previously did this work.
There's no need to test for DHT/uTP being enabled in tr-udp. The DHT
will silently discard any packets directed at the wrong session (see the
beginning of dhtCallback). As to uTP, we need to grok uTP packets
to close any remaining connections after we disabled uTP, so it's better
to participate in uTP, just reject any incoming connections.
This adds code to participate in the UTP protocol, but without doing anything
useful yet -- we just shut down immediately any incoming connexion request.
Jordan Lee