--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_limits/mod_limits.lua	Fri Jul 06 13:39:51 2012 +0100
@@ -0,0 +1,99 @@
+-- mod_limits: Rate-limiting for Prosody
+-- Version: Alpha
+-- Author: Matthew Wild <mwild1@gmail.com>
+
+-- Because we deal we pre-authed sessions and streams we can't be host-specific
+module:set_global();
+
+local filters = require "util.filters";
+local throttle = require "util.throttle";
+local timer = require "util.timer";
+
+local limits_cfg = module:get_option("limits", {});
+local limits_resolution = module:get_option_number("limits_resolution", 1);
+
+local default_bytes_per_second = 3000;
+local default_burst = 2;
+
+local rate_units = { b = 1, k = 3, m = 6, g = 9, t = 12 } -- Plan for the future.
+local function parse_rate(rate, sess_type)
+	local quantity, unit, exp;
+	if rate then
+		quantity, unit = rate:match("^(%d+) ?([^/]+)/s$");
+		exp = quantity and rate_units[unit:sub(1,1):lower()];
+	end
+	if not exp then
+		module:log("error", "Error parsing rate for %s: %q, using default rate (%d bytes/s)", sess_type, rate, default_bytes_per_second);
+		return default_bytes_per_second;
+	end
+	return quantity*(10^exp);
+end
+
+local function parse_burst(burst, sess_type)
+	if type(burst) == "string" then
+		burst = burst:match("^(%d+) ?s$");
+	end
+	local n_burst = tonumber(burst);
+	if not n_burst then
+		module:log("error", "Unable to parse burst for %s: %q, using default burst interval (%ds)", sess_type, tostring(burst), default_burst);
+	end
+	return n_burst or default_burst;
+end
+
+-- Process config option into limits table:
+-- limits = { c2s = { bytes_per_second = X, burst_seconds = Y } }
+local limits = {};
+
+for sess_type, sess_limits in pairs(limits_cfg) do
+	limits[sess_type] = {
+		bytes_per_second = parse_rate(sess_limits.rate, sess_type);
+		burst_seconds = parse_burst(sess_limits.burst, sess_type);
+	};
+end
+
+local default_filter_set = {};
+
+function default_filter_set.bytes_in(bytes, session)
+	local throttle = session.throttle;
+	if throttle then
+		local ok, balance, outstanding = throttle:poll(#bytes, true);
+		if not ok then
+			session.log("debug", "Session over rate limit (%d) with %d (by %d), pausing", throttle.max, #bytes, outstanding);
+			session.conn:pause(); -- Read no more data from the connection until there is no outstanding data
+			local outstanding_data = bytes:sub(-outstanding);
+			bytes = bytes:sub(1, #bytes-outstanding);
+			timer.add_task(limits_resolution, function ()
+				if not session.conn then return; end
+				if throttle:peek(#outstanding_data) then
+					session.log("debug", "Resuming paused session"); session.conn:resume();
+				end
+				-- Handle what we can of the outstanding data
+				session.data(outstanding_data);
+			end);
+		end
+	end
+	return bytes;
+end
+
+local type_filters = {
+	c2s = default_filter_set;
+	s2sin = default_filter_set;
+	s2sout = default_filter_set;
+};
+
+local function filter_hook(session)
+	local session_type = session.type:match("^[^_]+");
+	local filter_set, opts = type_filters[session_type], limits[session_type];
+	if opts then
+		session.throttle = throttle.create(opts.bytes_per_second * opts.burst_seconds, opts.burst_seconds);
+		filters.add_filter(session, "bytes/in", filter_set.bytes_in, 1000);
+	end
+end
+
+function module.load()
+	filters.add_filter_hook(filter_hook);
+end
+
+function module.unload()
+	filters.remove_filter_hook(filter_hook);
+end