Re-add banlist features

This effectively reverts commit b366290118.

config-example.py

@@ -13,6 +13,14 @@ PORT = 5000
 # only announce once every 5 minutes, so this should be more than 300.
 PURGE_TIME = 350
 
+# List of banned IP addresses for announce
+# e.g. ['2620:101::44']
+BANNED_IPS = []
+
+# List of banned servers as IP/port pairs
+# e.g. ['1.2.3.4/30000']
+BANNED_SERVERS = []
+
 # Creates server entries if a server sends an 'update' and there is no entry yet.
 # This should only be used to populate the server list after list.json was deleted.
 # This WILL cause problems such as mapgen, mods and privilege information missing from the list

server.py

@@ -39,6 +39,9 @@ def announce():
 	if ip.startswith("::ffff:"):
 		ip = ip[7:]
 
+	if ip in app.config["BANNED_IPS"]:
+		return "Banned (IP).", 403
+
 	data = request.values["json"]
 
 	if len(data) > 5000:
@@ -72,6 +75,9 @@ def announce():
 		server["port"] = int(server["port"])
 	#### End compatability code ####
 
+	if "%s/%d" % (server["ip"], server["port"]) in app.config["BANNED_SERVERS"]:
+		return "Banned (Server).", 403
+
 	old = serverList.get(ip, server["port"])
 
 	if action == "delete":