Adds max occupant module.

resources/prosody-plugins/mod_muc_max_occupants.lua

@@ -0,0 +1,65 @@
+-- MUC Max Occupants
+-- Configuring muc_max_occupants will set a limit of the maximum number
+-- of participants that will be able to join in a room.
+-- Participants in muc_access_whitelist will not be counted for the
+-- max occupants value (values are jids like recorder@jitsi.meeet.example.com).
+-- This module is configured under the muc component that is used for jitsi-meet
+local split_jid = require "util.jid".split;
+local st = require "util.stanza";
+local it = require "util.iterators";
+
+local whitelist = module:get_option_set("muc_access_whitelist");
+local MAX_OCCUPANTS = module:get_option_number("muc_max_occupants", -1);
+
+local function count_keys(t)
+  return it.count(it.keys(t));
+end
+
+local function check_for_max_occupants(event)
+  local room, origin, stanza = event.room, event.origin, event.stanza;
+
+	local actor = stanza.attr.from;
+  local user, domain, res = split_jid(stanza.attr.from);
+
+  --no user object means no way to check for max occupants
+  if user == nil then
+    return
+  end
+  -- If we're a whitelisted user joining the room, don't bother checking the max
+  -- occupants.
+  if whitelist and whitelist:contains(domain) or whitelist:contains(user..'@'..domain) then
+    return;
+  end
+
+	if room and not room._jid_nick[stanza.attr.from] then
+		local count = count_keys(room._occupants);
+		local slots = MAX_OCCUPANTS;
+
+		-- If there is no whitelist, just check the count.
+		if not whitelist and count >= MAX_OCCUPANTS then
+			module:log("info", "Attempt to enter a maxed out MUC");
+			origin.send(st.error_reply(stanza, "cancel", "service-unavailable"));
+			return true;
+		end
+
+		-- TODO: Are Prosody hooks atomic, or is this a race condition?
+		-- For each person in the room that's not on the whitelist, subtract one
+		-- from the count.
+		for _, occupant in room:each_occupant() do
+			if not whitelist:contains(domain) and not whitelist:contains(user..'@'..domain) then
+				slots = slots - 1
+			end
+		end
+
+		-- If the room is full (<0 slots left), error out.
+		if slots <= 0 then
+			module:log("info", "Attempt to enter a maxed out MUC");
+			origin.send(st.error_reply(stanza, "cancel", "service-unavailable"));
+			return true;
+		end
+	end
+end
+
+if MAX_OCCUPANTS > 0 then
+	module:hook("muc-occupant-pre-join", check_for_max_occupants, 10);
+end