gajim-plural/src/common/resolver.py

##	common/resolver.py
##
## Copyright (C) 2006 Dimitur Kirov <dkirov@gmail.com>
##
## This file is part of Gajim.
##
## Gajim is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published
## by the Free Software Foundation; version 3 only.
##
## Gajim is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Gajim.  If not, see <http://www.gnu.org/licenses/>.
##

import sys
import os
import re
import logging
log = logging.getLogger('gajim.c.resolver')

from common import helpers
from xmpp.idlequeue import IdleCommand

# it is good to check validity of arguments, when calling system commands
ns_type_pattern = re.compile('^[a-z]+$')

# match srv host_name
host_pattern = re.compile('^[a-z0-9\-._]*[a-z0-9]\.[a-z]{2,}$')

try:
	#raise ImportError("Manually disabled libasync")
	import libasyncns 
	USE_LIBASYNCNS = True
	log.info("libasyncns-python loaded")
except ImportError:
	USE_LIBASYNCNS = False
	log.debug("Import of libasyncns-python failed, getaddrinfo will block", exc_info=True)

	# FIXME: Remove these prints before release, replace with a warning dialog.
	print >> sys.stderr, "=" * 79
	print >> sys.stderr, "libasyncns-python not installed which means:"
	print >> sys.stderr, " - nslookup will be used for SRV and TXT requests"
	print >> sys.stderr, " - getaddrinfo will block"
	print >> sys.stderr, "libasyncns-python can be found at https://launchpad.net/libasyncns-python"
	print >> sys.stderr, "=" * 79


def get_resolver(idlequeue):
	if USE_LIBASYNCNS:
		return LibAsyncNSResolver()
	else:
		return NSLookupResolver(idlequeue)

class CommonResolver():
	def __init__(self):
		# dict {"host+type" : list of records}
		self.resolved_hosts = {}
		# dict {"host+type" : list of callbacks}
		self.handlers = {}

	def resolve(self, host, on_ready, type='srv'):
		assert(type in ['srv', 'txt'])
		if not host:
			# empty host, return empty list of srv records
			on_ready([])
			return
		if self.resolved_hosts.has_key(host+type):
			# host is already resolved, return cached values
			on_ready(host, self.resolved_hosts[host+type])
			return
		if self.handlers.has_key(host+type):
			# host is about to be resolved by another connection,
			# attach our callback 
			self.handlers[host+type].append(on_ready)
		else:
			# host has never been resolved, start now
			self.handlers[host+type] = [on_ready]
			self.start_resolve(host, type)

	def _on_ready(self, host, type, result_list):
		# practically it is impossible to be the opposite, but who knows :)
		if not self.resolved_hosts.has_key(host+type):
			self.resolved_hosts[host+type] = result_list
		if self.handlers.has_key(host+type):
			for callback in self.handlers[host+type]:
				callback(host, result_list)
			del(self.handlers[host+type])

	def start_resolve(self, host, type):
		pass

# FIXME: API usage is not consistent! This one requires that process is called
class LibAsyncNSResolver(CommonResolver):
	'''
	Asynchronous resolver using libasyncns-python. process() method has to be 
	called in order to proceed the pending requests.
	Based on patch submitted by Damien Thebault. 
	'''	
	def __init__(self):
		self.asyncns = libasyncns.Asyncns()
		CommonResolver.__init__(self)

	def start_resolve(self, host, type):
		type = libasyncns.ns_t_srv
		if type == 'txt': type = libasyncns.ns_t_txt
		resq = self.asyncns.res_query(host, libasyncns.ns_c_in, type)
		resq.userdata = {'host':host, 'type':type}

	# getaddrinfo to be done
	#def resolve_name(self, dname, callback):
		#resq = self.asyncns.getaddrinfo(dname)
		#resq.userdata = {'callback':callback, 'dname':dname}

	def _on_ready(self, host, type, result_list):
		if type == libasyncns.ns_t_srv: type = 'srv'
		elif type == libasyncns.ns_t_txt: type = 'txt'

		CommonResolver._on_ready(self, host, type, result_list)

	def process(self):
		try:
			self.asyncns.wait(False)
			resq = self.asyncns.get_next()
		except:
			return True
		if type(resq) == libasyncns.ResQuery:
			# TXT or SRV result
			while resq is not None:
				try:
					rl = resq.get_done()
				except:
					rl = []
				if rl:
					for r in rl:
						r['prio'] = r['pref']
				self._on_ready(
					host = resq.userdata['host'],
					type = resq.userdata['type'],
					result_list = rl)
				try:
					resq = self.asyncns.get_next()
				except:
					resq = None
		elif type(resq) == libasyncns.AddrInfoQuery:
			# getaddrinfo result (A or AAAA)
			rl = resq.get_done()
			resq.userdata['callback'](resq.userdata['dname'], rl)
		return True


class NSLookupResolver(CommonResolver):
	'''
	Asynchronous DNS resolver calling nslookup. Processing of pending requests
	is invoked from idlequeue which is watching file descriptor of pipe of stdout
	of nslookup process.
	'''
	def __init__(self, idlequeue):
		self.idlequeue = idlequeue
		self.process = False
		CommonResolver.__init__(self)
	
	def parse_srv_result(self, fqdn, result):
		''' parse the output of nslookup command and return list of 
		properties: 'host', 'port','weight', 'priority'	corresponding to the found
		srv hosts '''
		if os.name == 'nt':
			return self._parse_srv_result_nt(fqdn, result)
		elif os.name == 'posix':
			return self._parse_srv_result_posix(fqdn, result)
	
	def _parse_srv_result_nt(self, fqdn, result):
		# output from win32 nslookup command
		if not result:
			return []
		hosts = []
		lines = result.replace('\r','').split('\n')
		current_host = None
		for line in lines:
			line = line.lstrip()
			if line == '':
				continue
			if line.startswith(fqdn):
				rest = line[len(fqdn):]
				if rest.find('service') > -1:
					current_host = {}
			elif isinstance(current_host, dict):
				res = line.strip().split('=')
				if len(res) != 2:
					if len(current_host) == 4:
						hosts.append(current_host)
					current_host = None
					continue
				prop_type = res[0].strip() 
				prop_value = res[1].strip()
				if prop_type.find('prio') > -1:
					try:
						current_host['prio'] = int(prop_value)
					except ValueError:
						continue
				elif prop_type.find('weight') > -1:
					try:
						current_host['weight'] = int(prop_value)
					except ValueError:
						continue
				elif prop_type.find('port') > -1:
					try:
						current_host['port'] = int(prop_value)
					except ValueError:
						continue
				elif prop_type.find('host') > -1:
					# strip '.' at the end of hostname
					if prop_value[-1] == '.':
						prop_value = prop_value[:-1]
					current_host['host'] = prop_value
				if len(current_host) == 4:
					hosts.append(current_host)
					current_host = None
		return hosts
	
	def _parse_srv_result_posix(self, fqdn, result):
		# typical output of bind-tools nslookup command:
		# _xmpp-client._tcp.jabber.org    service = 30 30 5222 jabber.org.
		if not result:
			return []
		ufqdn = helpers.ascii_to_idn(fqdn) # Unicode domain name
		hosts = []
		lines = result.split('\n')
		for line in lines:
			if line == '':
				continue
			domain = None
			if line.startswith(fqdn):
				domain = fqdn # For nslookup 9.5
			elif helpers.decode_string(line).startswith(ufqdn):
				line = helpers.decode_string(line)
				domain = ufqdn # For nslookup 9.6
			if domain:
				rest = line[len(domain):].split('=')
				if len(rest) != 2:
					continue
				answer_type, props_str = rest
				if answer_type.strip() != 'service':
					continue
				props = props_str.strip().split(' ')
				if len(props) < 4:
					continue
				prio, weight, port, host  = props[-4:]
				if host[-1] == '.':
					host = host[:-1]
				try:
					prio = int(prio)
					weight = int(weight)
					port = int(port)
				except ValueError:
					continue
				hosts.append({'host': host, 'port': port, 'weight': weight,
					'prio': prio})
		return hosts
	
	def _on_ready(self, host, type, result):
		# nslookup finished, parse the result and call the handlers
		result_list = self.parse_srv_result(host, result)
		CommonResolver._on_ready(self, host, type, result_list)
		
	def start_resolve(self, host, type):
		''' spawn new nslookup process and start waiting for results '''
		ns = NsLookup(self._on_ready, host, type)
		ns.set_idlequeue(self.idlequeue)
		ns.commandtimeout = 10
		ns.start()


class NsLookup(IdleCommand):
	def __init__(self, on_result, host='_xmpp-client', type='srv'):
		IdleCommand.__init__(self, on_result)
		self.commandtimeout = 10 
		self.host = host.lower()
		self.type = type.lower()
		if not host_pattern.match(self.host):
			# invalid host name
			log.error('Invalid host: %s' % self.host)
			self.canexecute = False
			return
		if not ns_type_pattern.match(self.type):
			log.error('Invalid querytype: %s' % self.type)
			self.canexecute = False
			return
	
	def _compose_command_args(self):
		return ['nslookup', '-type=' + self.type , self.host]
	
	def _return_result(self):
		if self.result_handler:
			self.result_handler(self.host, self.type, self.result)
		self.result_handler = None
	
# below lines is on how to use API and assist in testing
if __name__ == '__main__':
	import gobject
	import gtk
	from xmpp import idlequeue
	
	idlequeue = idlequeue.get_idlequeue()
	resolver = get_resolver(idlequeue)
	
	def clicked(widget):
		global resolver
		host = text_view.get_text()
		def on_result(host, result_array):
			print 'Result:\n' + repr(result_array)
		resolver.resolve(host, on_result)
	win = gtk.Window()
	win.set_border_width(6)
	text_view = gtk.Entry()
	text_view.set_text('_xmpp-client._tcp.jabber.org')
	hbox = gtk.HBox()
	hbox.set_spacing(3)
	but = gtk.Button(' Lookup SRV ')
	hbox.pack_start(text_view, 5)
	hbox.pack_start(but, 0)
	but.connect('clicked', clicked)
	win.add(hbox)
	win.show_all()
	gobject.timeout_add(200, idlequeue.process)
	gtk.main()

# vim: se ts=3: