Summary
=======
The idea of this is that clients will not have to ping each server for
server infos which takes long, leaks the client's IP address even to
servers the user does not join and is a DoS vector of the game servers
for attackers.
For the Internet, DDNet and KoG tab, the server list is entirely fetched
from the master server, filtering out servers that don't belong into the
list.
The favorites tab is also supposed to work that way, except for servers
that are marked as "also ping this server if it's not in the master
server list".
The LAN tab continues to broadcast the server info packet to find
servers in the LAN.
How does it work?
=================
The client ships with a list of master server list URLs. On first start,
the client checks which of these work and selects the fastest one.
Querying the server list is a HTTP GET request on that URL. The
response is a JSON document that contains server infos, server addresses
as URLs and an approximate location.
It can also contain a legacy server list which is a list of bare IP
addresses similar to the functionality the old master servers provided
via UDP. This allows us to backtrack on the larger update if it won't
work out.
Lost functionality
==================
(also known as user-visible changes)
Since the client doesn't ping each server in the list anymore, it has no
way of knowing its latency to the servers.
This is alleviated a bit by providing an approximate location for each
server (continent) so the client only has to know its own location for
approximating pings.
Purely automatic change. In case of conflict with this change, apply the
other change and rerun the formatting to restore it:
$ python scripts/fix_style.py
- As requested by qshar and KoG players
- Similar to DDNet tab
- Info fetched from servers-kog entry from https://info.ddnet.tw/info
- Also supports countries and types
- Doesn't inform whether map has been finished
- Generalized the code a bit but it's still ugly
- Depends on #1533, also shows KoG servers as official/verified
This means that we have a reliable and fast way to query for extended info,
while also not wasting network bandwidth.
The protocol is designed to be extensible, there's four bytes space for
encoding more request types (currently zeroed), and there's one string in each
response packet and one string for each player available (currently the empty
string).
The protocol itself has no problems with more than 64 players, although the
current client implementation will drop the player info after the 64th player,
because it uses a static array for storage.
Also fixes#130, the player list is just sorted each time new player info
arrives.
