net/adns.lua
author Matthew Wild <mwild1@gmail.com>
Fri, 18 Sep 2009 02:46:11 +0100
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net.adns: Utilise new net.dns API to handle DNS network errors
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-- Prosody IM
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-- Copyright (C) 2008-2009 Matthew Wild
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-- Copyright (C) 2008-2009 Waqas Hussain
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-- 
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-- This project is MIT/X11 licensed. Please see the
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-- COPYING file in the source package for more information.
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--
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local server = require "net.server";
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local dns = require "net.dns";
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local log = require "util.logger".init("adns");
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local t_insert, t_remove = table.insert, table.remove;
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local coroutine, tostring, pcall = coroutine, tostring, pcall;
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module "adns"
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function lookup(handler, qname, qtype, qclass)
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	return coroutine.wrap(function (peek)
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				if peek then
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					log("debug", "Records for %s already cached, using those...", qname);
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					handler(peek);
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					return;
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				end
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				log("debug", "Records for %s not in cache, sending query (%s)...", qname, tostring(coroutine.running()));
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				dns.query(qname, qtype, qclass);
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				coroutine.yield({ qclass or "IN", qtype or "A", qname, coroutine.running()}); -- Wait for reply
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				log("debug", "Reply for %s (%s)", qname, tostring(coroutine.running()));
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				local ok, err = pcall(handler, dns.peek(qname, qtype, qclass));
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				if not ok then
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					log("debug", "Error in DNS response handler: %s", tostring(err));
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				end
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			end)(dns.peek(qname, qtype, qclass));
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end
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function cancel(handle, call_handler)
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	log("warn", "Cancelling DNS lookup for %s", tostring(handle[3]));
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	dns.cancel(handle);
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	if call_handler then
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		coroutine.resume(handle[4]);
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	end
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end
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function new_async_socket(sock, resolver)
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	local newconn, peername = {}, "<unknown>";
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	local listener = {};
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	function listener.incoming(conn, data)
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		dns.feed(sock, data);
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	end
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	function listener.disconnect(conn, err)
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		log("warn", "DNS socket for %s disconnected: %s", peername, err);
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		local servers = resolver.server;
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		if resolver.socketset[newconn.handler] == resolver.best_server and resolver.best_server == #servers then
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			log("error", "Exhausted all %d configured DNS servers, next lookup will try %s again", #servers, servers[1]);
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		end
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		resolver:servfail(conn); -- Let the magic commence
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	end
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	newconn.handler, newconn._socket = server.wrapclient(sock, "dns", 53, listener);
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	if not newconn.handler then
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		log("warn", "handler is nil");
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	end
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	if not newconn._socket then
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		log("warn", "socket is nil");
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	end
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	newconn.handler.settimeout = function () end
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	newconn.handler.setsockname = function (_, ...) return sock:setsockname(...); end
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	newconn.handler.setpeername = function (_, ...) peername = (...); local ret = sock:setpeername(...); _.setsend(sock.send); return ret; end
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	newconn.handler.connect = function (_, ...) return sock:connect(...) end	
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	newconn.handler.send = function (_, data) _.write(data); return _.sendbuffer(); end	
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	return newconn.handler;
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end
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dns:socket_wrapper_set(new_async_socket);
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return _M;