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net.server_epoll: Call :shutdown() on TLS sockets when supported Comment from Matthew: This fixes a potential issue where the Prosody process gets blocked on sockets waiting for them to close. Unlike non-TLS sockets, closing a TLS socket sends layer 7 data, and this can cause problems for sockets which are in the process of being cleaned up. This depends on LuaSec changes which are not yet upstream. From Martijn's original email: So first my analysis of luasec. in ssl.c the socket is put into blocking mode right before calling SSL_shutdown() inside meth_destroy(). My best guess to why this is is because meth_destroy is linked to the __close and __gc methods, which can't exactly be called multiple times and luasec does want to make sure that a tls session is shutdown as clean as possible. I can't say I disagree with this reasoning and don't want to change this behaviour. My solution to this without changing the current behaviour is to introduce a shutdown() method. I am aware that this overlaps in a conflicting way with tcp's shutdown method, but it stays close to the OpenSSL name. This method calls SSL_shutdown() in the current (non)blocking mode of the underlying socket and returns a boolean whether or not the shutdown is completed (matching SSL_shutdown()'s 0 or 1 return values), and returns the familiar ssl_ioerror() strings on error with a false for completion. This error can then be used to determine if we have wantread/wantwrite to finalize things. Once meth_shutdown() has been called once a shutdown flag will be set, which indicates to meth_destroy() that the SSL_shutdown() has been handled by the application and it shouldn't be needed to set the socket to blocking mode. I've left the SSL_shutdown() call in the LSEC_STATE_CONNECTED to prevent TOCTOU if the application reaches a timeout for the shutdown code, which might allow SSL_shutdown() to clean up anyway at the last possible moment. Another thing I've changed to luasec is the call to socket_setblocking() right before calling close(2) in socket_destroy() in usocket.c. According to the latest POSIX[0]: Note that the requirement for close() on a socket to block for up to the current linger interval is not conditional on the O_NONBLOCK setting. Which I read to mean that removing O_NONBLOCK on the socket before close doesn't impact the behaviour and only causes noise in system call tracers. I didn't touch the windows bits of this, since I don't do windows. For the prosody side of things I've made the TLS shutdown bits resemble interface:onwritable(), and put it under a combined guard of self._tls and self.conn.shutdown. The self._tls bit is there to prevent getting stuck on this condition, and self.conn.shutdown is there to prevent the code being called by instances where the patched luasec isn't deployed. The destroy() method can be called from various places and is read by me as the "we give up" error path. To accommodate for these unexpected entrypoints I've added a single call to self.conn:shutdown() to prevent the socket being put into blocking mode. I have no expectations that there is any other use here. Same as previous, the self.conn.shutdown check is there to make sure it's not called on unpatched luasec deployments and self._tls is there to make sure we don't call shutdown() on tcp sockets. I wouldn't recommend logging of the conn:shutdown() error inside close(), since a lot of clients simply close the connection before SSL_shutdown() is done.

module:set_global();

local have_unix, unix = pcall(require, "socket.unix");

if have_unix and type(unix) == "function" then
	-- COMPAT #1717
	-- Before the introduction of datagram support, only the stream socket
	-- constructor was exported instead of a module table. Due to the lack of a
	-- proper release of LuaSocket, distros have settled on shipping either the
	-- last RC tag or some commit since then.
	-- Here we accommodate both variants.
	unix = { stream = unix };
end
if not have_unix or type(unix) ~= "table" then
	module:log_status("error", "LuaSocket unix socket support not available or incompatible, ensure it is up to date");
	return;
end

local server = require "prosody.net.server";

local adminstream = require "prosody.util.adminstream";
local st = require "prosody.util.stanza";

local socket_path = module:get_option_path("admin_socket", "prosody.sock", "data");

local sessions = module:shared("sessions");

local function fire_admin_event(session, stanza)
	local event_data = {
		origin = session, stanza = stanza;
	};
	local event_name;
	if stanza.attr.xmlns then
		event_name = "admin/"..stanza.attr.xmlns..":"..stanza.name;
	else
		event_name = "admin/"..stanza.name;
	end
	module:log("debug", "Firing %s", event_name);
	local ret = module:fire_event(event_name, event_data);
	if ret == nil then
		session.send(st.stanza("repl-result", { type = "error" }):text("No module handled this query. Is mod_admin_shell enabled?"));
	end
	return ret;
end

module:hook("server-stopping", function ()
	for _, session in pairs(sessions) do
		session:close("system-shutdown");
	end
	os.remove(socket_path);
end);

--- Unix domain socket management

local conn, sock;

local admin_server = adminstream.server(sessions, fire_admin_event);
local listeners = admin_server.listeners;

module:hook_object_event(admin_server.events, "disconnected", function (event)
	return module:fire_event("admin-disconnected", event);
end);

local function accept_connection()
	module:log("debug", "accepting...");
	local client = sock:accept();
	if not client then return; end
	server.wrapclient(client, "unix", 0, listeners, "*a");
end

function module.load()
	sock = unix.stream();
	sock:settimeout(0);
	os.remove(socket_path);
	local ok, err = sock:bind(socket_path);
	if not ok then
		module:log_status("error", "Unable to bind admin socket %s: %s", socket_path, err);
		return;
	end
	local ok, err = sock:listen();
	if not ok then
		module:log_status("error", "Unable to listen on admin socket %s: %s", socket_path, err);
		return;
	end
	if server.wrapserver then
		conn = server.wrapserver(sock, socket_path, 0, listeners);
	else
		conn = server.watchfd(sock:getfd(), accept_connection);
	end
end

function module.unload()
	if conn then
		conn:close();
	end
	if sock then
		sock:close();
	end
	os.remove(socket_path);
end