diff --git a/sipsimple/lookup.py b/sipsimple/lookup.py index aa56a3da..77a1f5b5 100644 --- a/sipsimple/lookup.py +++ b/sipsimple/lookup.py @@ -1,557 +1,557 @@ """ Implements DNS lookups in the context of SIP, STUN and MSRP relay based on RFC3263 and related standards. This can be used to determine the next hop(s) and failover for routing of SIP messages and reservation of network resources prior the starting of a SIP session. """ import re from itertools import chain from time import time from urllib.parse import urlparse # patch dns.entropy module which is not thread-safe import dns import sys from functools import partial from random import randint, randrange dns.entropy = dns.__class__('dns.entropy') dns.entropy.__file__ = dns.__file__.replace('__init__.py', 'entropy.py') dns.entropy.__builtins__ = dns.__builtins__ dns.entropy.random_16 = partial(randrange, 2**16) dns.entropy.between = randint sys.modules['dns.entropy'] = dns.entropy del partial, randint, randrange, sys # replace standard select and socket modules with versions from eventlib from eventlib import coros, proc from eventlib.green import select from eventlib.green import socket import dns.name import dns.resolver import dns.query dns.resolver.socket = socket dns.query.socket = socket dns.query.select = select -dns.query._set_polling_backend(dns.query._select_for) +#dns.query._set_polling_backend(dns.query._select_for) from application.notification import IObserver, NotificationCenter, NotificationData from application.python import Null, limit from application.python.decorator import decorator, preserve_signature from application.python.types import Singleton from dns import exception, rdatatype from twisted.internet import reactor from zope.interface import implementer from sipsimple.core import Route from sipsimple.threading import run_in_twisted_thread from sipsimple.threading.green import Command, InterruptCommand, run_in_waitable_green_thread def domain_iterator(domain): """ A generator which returns the domain and its parent domains. """ while domain not in ('.', ''): yield domain domain = (domain.split('.', 1)+[''])[1] @decorator def post_dns_lookup_notifications(func): @preserve_signature(func) def wrapper(obj, *args, **kwargs): notification_center = NotificationCenter() try: result = func(obj, *args, **kwargs) except DNSLookupError as e: notification_center.post_notification('DNSLookupDidFail', sender=obj, data=NotificationData(error=str(e))) raise else: notification_center.post_notification('DNSLookupDidSucceed', sender=obj, data=NotificationData(result=result)) return result return wrapper class DNSLookupError(Exception): """ The error raised by DNSLookup when a lookup cannot be performed. """ class DNSCache(object): """ A simple DNS cache which uses twisted's timers to invalidate its expired data. """ def __init__(self): self.data = {} def get(self, key): return self.data.get(key, None) def put(self, key, value): expiration = value.expiration-time() if expiration > 0: self.data[key] = value reactor.callLater(limit(expiration, max=3600), self.data.pop, key, None) def flush(self, key=None): if key is not None: self.data.pop(key, None) else: self.data = {} class InternalResolver(dns.resolver.Resolver): def __init__(self, *args, **kw): super(InternalResolver, self).__init__(*args, **kw) if self.domain.to_text().endswith('local.'): self.domain = dns.name.root self.search = [item for item in self.search if not item.to_text().endswith('local.')] class DNSResolver(dns.resolver.Resolver): """ The resolver used by DNSLookup. The lifetime setting on it applies to all the queries made on this resolver. Each time a query is performed, its duration is subtracted from the lifetime value. """ def __init__(self): dns.resolver.Resolver.__init__(self, configure=False) dns_manager = DNSManager() self.search = dns_manager.search self.domain = dns_manager.domain self.nameservers = dns_manager.nameservers def query(self, *args, **kw): start_time = time() try: return dns.resolver.Resolver.query(self, *args, **kw) finally: self.lifetime -= min(self.lifetime, time()-start_time) class SRVResult(object): """ Internal object used to save the result of SRV queries. """ def __init__(self, priority, weight, port, address): self.priority = priority self.weight = weight self.port = port self.address = address class NAPTRResult(object): """ Internal object used to save the result of NAPTR queries. """ def __init__(self, service, order, preference, priority, weight, port, address): self.service = service self.order = order self.preference = preference self.priority = priority self.weight = weight self.port = port self.address = address class DNSLookup(object): cache = DNSCache() @run_in_waitable_green_thread @post_dns_lookup_notifications def lookup_service(self, uri, service, timeout=3.0, lifetime=15.0): """ Performs an SRV query to determine the servers used for the specified service from the domain in uri.host. If this fails and falling back is supported, also performs an A query on uri.host, returning the default port of the service along with the IP addresses in the answer. The services supported are `stun' and 'msrprelay'. The DNSLookupDidSucceed notification contains a result attribute which is a list of (address, port) tuples. The DNSLookupDidFail notification contains an error attribute describing the error encountered. """ service_srv_record_map = {"stun": ("_stun._udp", 3478, False), "msrprelay": ("_msrps._tcp", 2855, True)} log_context = dict(context='lookup_service', service=service, uri=uri) try: service_prefix, service_port, service_fallback = service_srv_record_map[service] except KeyError: raise DNSLookupError("Unknown service: %s" % service) try: # If the host part of the URI is an IP address, we will not do any lookup if re.match("^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$", uri.host): return [(uri.host, uri.port or service_port)] resolver = DNSResolver() resolver.cache = self.cache resolver.timeout = timeout resolver.lifetime = lifetime record_name = '%s.%s' % (service_prefix, uri.host) services = self._lookup_srv_records(resolver, [record_name], log_context=log_context) if services[record_name]: return [(result.address, result.port) for result in services[record_name]] elif service_fallback: addresses = self._lookup_a_records(resolver, [uri.host], log_context=log_context) if addresses[uri.host]: return [(addr, service_port) for addr in addresses[uri.host]] except dns.resolver.Timeout: raise DNSLookupError('Timeout in lookup for %s servers for domain %s' % (service, uri.host)) else: raise DNSLookupError('No %s servers found for domain %s' % (service, uri.host)) @run_in_waitable_green_thread @post_dns_lookup_notifications def lookup_sip_proxy(self, uri, supported_transports, timeout=3.0, lifetime=15.0): """ Performs an RFC 3263 compliant lookup of transport/ip/port combinations for a particular SIP URI. As arguments it takes a SIPURI object and a list of supported transports, in order of preference of the application. It returns a list of Route objects that can be used in order of preference. The DNSLookupDidSucceed notification contains a result attribute which is a list of Route objects. The DNSLookupDidFail notification contains an error attribute describing the error encountered. """ naptr_service_transport_map = {"sips+d2t": "tls", "sip+d2t": "tcp", "sip+d2u": "udp"} transport_service_map = {"udp": "_sip._udp", "tcp": "_sip._tcp", "tls": "_sips._tcp"} log_context = dict(context='lookup_sip_proxy', uri=uri) if not supported_transports: raise DNSLookupError("No transports are supported") supported_transports = [transport.lower() for transport in supported_transports] unknown_transports = set(supported_transports).difference(transport_service_map) if unknown_transports: raise DNSLookupError("Unknown transports: %s" % ', '.join(unknown_transports)) try: # If the host part of the URI is an IP address, we will not do any lookup if re.match("^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$", uri.host): transport = 'tls' if uri.secure else uri.transport.lower() if transport not in supported_transports: raise DNSLookupError("Transport %s dictated by URI is not supported" % transport) port = uri.port or (5061 if transport=='tls' else 5060) return [Route(address=uri.host, port=port, transport=transport)] resolver = DNSResolver() resolver.cache = self.cache resolver.timeout = timeout resolver.lifetime = lifetime # If the port is specified in the URI, we will only do an A lookup if uri.port: transport = 'tls' if uri.secure else uri.transport.lower() if transport not in supported_transports: raise DNSLookupError("Transport %s dictated by URI is not supported" % transport) addresses = self._lookup_a_records(resolver, [uri.host], log_context=log_context) if addresses[uri.host]: return [Route(address=addr, port=uri.port, transport=transport) for addr in addresses[uri.host]] # If the transport was already set as a parameter on the SIP URI, only do SRV lookups elif 'transport' in uri.parameters: transport = uri.parameters['transport'].lower() if transport not in supported_transports: raise DNSLookupError("Requested lookup for URI with %s transport, but it is not supported" % transport) if uri.secure and transport != 'tls': raise DNSLookupError("Requested lookup for SIPS URI, but with %s transport parameter" % transport) record_name = '%s.%s' % (transport_service_map[transport], uri.host) services = self._lookup_srv_records(resolver, [record_name], log_context=log_context) if services[record_name]: return [Route(address=result.address, port=result.port, transport=transport) for result in services[record_name]] else: # If SRV lookup fails, try A lookup addresses = self._lookup_a_records(resolver, [uri.host], log_context=log_context) port = 5061 if transport=='tls' else 5060 if addresses[uri.host]: return [Route(address=addr, port=port, transport=transport) for addr in addresses[uri.host]] # Otherwise, it means we don't have a numeric IP address, a port isn't specified and neither is a transport. So we have to do a full NAPTR lookup else: # If the URI is a SIPS URI, we only support the TLS transport. if uri.secure: if 'tls' not in supported_transports: raise DNSLookupError("Requested lookup for SIPS URI, but TLS transport is not supported") supported_transports = ['tls'] # First try NAPTR lookup naptr_services = [service for service, transport in list(naptr_service_transport_map.items()) if transport in supported_transports] try: pointers = self._lookup_naptr_record(resolver, uri.host, naptr_services, log_context=log_context) except dns.resolver.Timeout: pointers = [] if pointers: return [Route(address=result.address, port=result.port, transport=naptr_service_transport_map[result.service]) for result in pointers] else: # If that fails, try SRV lookup routes = [] for transport in supported_transports: record_name = '%s.%s' % (transport_service_map[transport], uri.host) try: services = self._lookup_srv_records(resolver, [record_name], log_context=log_context) except dns.resolver.Timeout: continue if services[record_name]: routes.extend(Route(address=result.address, port=result.port, transport=transport) for result in services[record_name]) if routes: return routes else: # If SRV lookup fails, try A lookup transport = 'tls' if uri.secure else 'udp' if transport in supported_transports: addresses = self._lookup_a_records(resolver, [uri.host], log_context=log_context) port = 5061 if transport=='tls' else 5060 if addresses[uri.host]: return [Route(address=addr, port=port, transport=transport) for addr in addresses[uri.host]] except dns.resolver.Timeout: raise DNSLookupError("Timeout in lookup for routes for SIP URI %s" % uri) else: raise DNSLookupError("No routes found for SIP URI %s" % uri) @run_in_waitable_green_thread @post_dns_lookup_notifications def lookup_xcap_server(self, uri, timeout=3.0, lifetime=15.0): """ Performs a TXT query against xcap. and returns all results that look like HTTP URIs. """ log_context = dict(context='lookup_xcap_server', uri=uri) notification_center = NotificationCenter() try: # If the host part of the URI is an IP address, we cannot not do any lookup if re.match("^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$", uri.host): raise DNSLookupError("Cannot perform DNS query because the host is an IP address") resolver = DNSResolver() resolver.cache = self.cache resolver.timeout = timeout resolver.lifetime = lifetime record_name = 'xcap.%s' % uri.host results = [] try: answer = resolver.query(record_name, rdatatype.TXT) except dns.resolver.Timeout as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='TXT', query_name=str(record_name), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) raise except exception.DNSException as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='TXT', query_name=str(record_name), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) else: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='TXT', query_name=str(record_name), nameservers=resolver.nameservers, answer=answer, error=None, **log_context)) for result_uri in list(chain(*(r.strings for r in answer.rrset))): parsed_uri = urlparse(result_uri) if parsed_uri.scheme in ('http', 'https') and parsed_uri.netloc: results.append(result_uri) if not results: raise DNSLookupError('No XCAP servers found for domain %s' % uri.host) return results except dns.resolver.Timeout: raise DNSLookupError('Timeout in lookup for XCAP servers for domain %s' % uri.host) def _lookup_a_records(self, resolver, hostnames, additional_records=[], log_context={}): notification_center = NotificationCenter() additional_addresses = dict((rset.name.to_text(), rset) for rset in additional_records if rset.rdtype == rdatatype.A) addresses = {} for hostname in hostnames: if hostname in additional_addresses: addresses[hostname] = [r.address for r in additional_addresses[hostname]] else: try: answer = resolver.query(hostname, rdatatype.A) except dns.resolver.Timeout as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='A', query_name=str(hostname), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) raise except exception.DNSException as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='A', query_name=str(hostname), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) addresses[hostname] = [] else: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='A', query_name=str(hostname), nameservers=resolver.nameservers, answer=answer, error=None, **log_context)) addresses[hostname] = [r.address for r in answer.rrset] return addresses def _lookup_srv_records(self, resolver, srv_names, additional_records=[], log_context={}): notification_center = NotificationCenter() additional_services = dict((rset.name.to_text(), rset) for rset in additional_records if rset.rdtype == rdatatype.SRV) services = {} for srv_name in srv_names: services[srv_name] = [] if srv_name in additional_services: addresses = self._lookup_a_records(resolver, [r.target.to_text() for r in additional_services[srv_name]], additional_records) for record in additional_services[srv_name]: services[srv_name].extend(SRVResult(record.priority, record.weight, record.port, addr) for addr in addresses.get(record.target.to_text(), ())) else: try: answer = resolver.query(srv_name, rdatatype.SRV) except dns.resolver.Timeout as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='SRV', query_name=str(srv_name), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) raise except exception.DNSException as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='SRV', query_name=str(srv_name), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) else: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='SRV', query_name=str(srv_name), nameservers=resolver.nameservers, answer=answer, error=None, **log_context)) addresses = self._lookup_a_records(resolver, [r.target.to_text() for r in answer.rrset], answer.response.additional, log_context) for record in answer.rrset: services[srv_name].extend(SRVResult(record.priority, record.weight, record.port, addr) for addr in addresses.get(record.target.to_text(), ())) services[srv_name].sort(key=lambda result: (result.priority, -result.weight)) return services def _lookup_naptr_record(self, resolver, domain, services, log_context={}): notification_center = NotificationCenter() pointers = [] try: answer = resolver.query(domain, rdatatype.NAPTR) except dns.resolver.Timeout as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='NAPTR', query_name=str(domain), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) raise except exception.DNSException as e: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='NAPTR', query_name=str(domain), nameservers=resolver.nameservers, answer=None, error=e, **log_context)) else: notification_center.post_notification('DNSLookupTrace', sender=self, data=NotificationData(query_type='NAPTR', query_name=str(domain), nameservers=resolver.nameservers, answer=answer, error=None, **log_context)) records = [r for r in answer.rrset if r.service.lower() in services] services = self._lookup_srv_records(resolver, [r.replacement.to_text() for r in records], answer.response.additional, log_context) for record in records: pointers.extend(NAPTRResult(record.service.lower(), record.order, record.preference, r.priority, r.weight, r.port, r.address) for r in services.get(record.replacement.to_text(), ())) pointers.sort(key=lambda result: (result.order, result.preference)) return pointers @implementer(IObserver) class DNSManager(object, metaclass=Singleton): def __init__(self): default_resolver = InternalResolver() self.search = default_resolver.search self.domain = default_resolver.domain self.nameservers = default_resolver.nameservers self.google_nameservers = ['8.8.8.8', '8.8.4.4'] self.probed_domain = 'sip2sip.info.' self._channel = coros.queue() self._proc = None self._timer = None self._wakeup_timer = None notification_center = NotificationCenter() notification_center.add_observer(self, name='SystemIPAddressDidChange') notification_center.add_observer(self, name='SystemDidWakeUpFromSleep') @property def nameservers(self): return self.__dict__['nameservers'] @nameservers.setter def nameservers(self, value): old_value = self.__dict__.get('nameservers', Null) self.__dict__['nameservers'] = value if old_value is Null: NotificationCenter().post_notification('DNSResolverDidInitialize', sender=self, data=NotificationData(nameservers=value)) elif value != old_value: NotificationCenter().post_notification('DNSNameserversDidChange', sender=self, data=NotificationData(nameservers=value)) def start(self): self._proc = proc.spawn(self._run) self._channel.send(Command('probe_dns')) def stop(self): if self._proc is not None: self._proc.kill() self._proc = None if self._timer is not None and self._timer.active(): self._timer.cancel() self._timer = None if self._wakeup_timer is not None and self._wakeup_timer.active(): self._wakeup_timer.cancel() self._wakeup_timer = None def _run(self): while True: try: command = self._channel.wait() handler = getattr(self, '_CH_%s' % command.name) handler(command) except InterruptCommand: pass def _CH_probe_dns(self, command): if self._timer is not None and self._timer.active(): self._timer.cancel() self._timer = None resolver = InternalResolver() self.domain = resolver.domain self.search = resolver.search local_nameservers = resolver.nameservers # probe local resolver resolver.timeout = 1 resolver.lifetime = 3 try: answer = resolver.query(self.probed_domain, rdatatype.NAPTR) if not any(record.rdtype == rdatatype.NAPTR for record in answer.rrset): raise exception.DNSException("No NAPTR records found") answer = resolver.query("_sip._udp.%s" % self.probed_domain, rdatatype.SRV) if not any(record.rdtype == rdatatype.SRV for record in answer.rrset): raise exception.DNSException("No SRV records found") except (dns.resolver.Timeout, exception.DNSException): pass else: self.nameservers = resolver.nameservers return # local resolver failed. probe google resolver resolver.nameservers = self.google_nameservers resolver.timeout = 2 resolver.lifetime = 4 try: answer = resolver.query(self.probed_domain, rdatatype.NAPTR) if not any(record.rdtype == rdatatype.NAPTR for record in answer.rrset): raise exception.DNSException("No NAPTR records found") except (dns.resolver.Timeout, exception.DNSException): pass else: self.nameservers = resolver.nameservers return # google resolver failed. fallback to local resolver and schedule another probe for later self.nameservers = local_nameservers self._timer = reactor.callLater(15, self._channel.send, Command('probe_dns')) @run_in_twisted_thread def handle_notification(self, notification): handler = getattr(self, '_NH_%s' % notification.name, Null) handler(notification) def _NH_SystemIPAddressDidChange(self, notification): self._proc.kill(InterruptCommand) self._channel.send(Command('probe_dns')) def _NH_SystemDidWakeUpFromSleep(self, notification): if self._wakeup_timer is None: def wakeup_action(): self._proc.kill(InterruptCommand) self._channel.send(Command('probe_dns')) self._wakeup_timer = None self._wakeup_timer = reactor.callLater(5, wakeup_action) # wait for system to stabilize