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diff --git a/sipsimple/lookup.py b/sipsimple/lookup.py
index 015abd78..ec7752bc 100644
--- a/sipsimple/lookup.py
+++ b/sipsimple/lookup.py
@@ -1,560 +1,561 @@
"""
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
#TODO3: dnspython newer than 0.20 has a new API
if ('_set_polling_backend' in dir(dns.query)):
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.decode()):
return [(uri.host.decode(), 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.decode())
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.decode()], log_context=log_context)
if addresses[uri.host.decode()]:
return [(addr, service_port) for addr in addresses[uri.host.decode()]]
except dns.resolver.Timeout:
raise DNSLookupError('Timeout in lookup for %s servers for domain %s' % (service, uri.host.decode()))
else:
raise DNSLookupError('No %s servers found for domain %s' % (service, uri.host.decode()))
@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.decode()):
- transport = 'tls' if uri.secure else uri.transport.decode().lower()
+ 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.decode(), port=port, transport=transport)]
+ route = [Route(address=uri.host.decode(), port=port, transport=transport)]
+ return route
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.decode()], log_context=log_context)
if addresses[uri.host.decode()]:
return [Route(address=addr, port=uri.port, transport=transport) for addr in addresses[uri.host.decode()]]
# 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.decode())
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.decode()], log_context=log_context)
port = 5061 if transport=='tls' else 5060
if addresses[uri.host.decode()]:
return [Route(address=addr, port=port, transport=transport) for addr in addresses[uri.host.decode()]]
# 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.decode(), 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.decode())
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.decode()], log_context=log_context)
port = 5061 if transport=='tls' else 5060
if addresses[uri.host.decode()]:
return [Route(address=addr, port=port, transport=transport) for addr in addresses[uri.host.decode()]]
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.<uri.host> 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.decode()):
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.decode()
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.decode())
return results
except dns.resolver.Timeout:
raise DNSLookupError('Timeout in lookup for XCAP servers for domain %s' % uri.host.decode())
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

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