With the IPv6 support, hosts now often list around 20 addresses.
However, most of these are local only and thus rarely result in a
successful connection. With the introduction of address sorting in
7d5596220 ("Sort addresses used for initial host connection",
2017-02-26), the connection succeeds with the first few addresses most
of the time.
This commit changes the initial connection process to start with only
the first four addresses. After 100 ms, it proceeds with the next four
addresses and so on. This should reduce the packet volume significantly
as the connection should be established after only one or two steps.
We may want to tweak the parameters if this turns out to make joining
slower in practise. In a "normal" setup, the first four addresses should
be the IPv6 privacy and stable addresses, and the next four addresses
should include the IPv4 addresses from masterserver and netpuncher.
100 ms are long enough to get an answer from the host and short enough
to not bother the player too much.
8ca3801741