Fix TTL handling for published service, align default TTL with RFC6762 (python-zeroconf#113)

Honor TTL passed in service registration
Set default TTL to 120 s as recommended by RFC6762

Author: emontnemery

test_zeroconf.py

@@ -538,6 +538,94 @@ def test_incoming_ipv6(self):
         pass
 
 
+class TestRegistrar(unittest.TestCase):
+
+    def test_ttl(self):
+
+        # instantiate a zeroconf instance
+        zc = Zeroconf(interfaces=['127.0.0.1'])
+
+        # service definition
+        type_ = "_test-srvc-type._tcp.local."
+        name = "xxxyyy"
+        registration_name = "%s.%s" % (name, type_)
+
+        desc = {'path': '/~paulsm/'}
+        info = ServiceInfo(
+            type_, registration_name,
+            socket.inet_aton("10.0.1.2"), 80, 0, 0,
+            desc, "ash-2.local.")
+
+        # we are going to monkey patch the zeroconf send to check packet sizes
+        old_send = zc.send
+
+        # needs to be a list so that we can modify it in our phony send
+        nbr_answers = [0, None]
+        nbr_additionals = [0, None]
+        nbr_authorities = [0, None]
+
+        def send(out, addr=r._MDNS_ADDR, port=r._MDNS_PORT):
+            """Sends an outgoing packet."""
+            for answer, time_ in out.answers:
+                nbr_answers[0] += 1
+                assert answer.ttl == expected_ttl
+            for answer in out.additionals:
+                nbr_additionals[0] += 1
+                assert answer.ttl == expected_ttl
+            for answer in out.authorities:
+                nbr_authorities[0] += 1
+                assert answer.ttl == expected_ttl
+            old_send(out, addr=addr, port=port)
+
+        # monkey patch the zeroconf send
+        zc.send = send
+
+        # register service with default TTL
+        expected_ttl = r._DNS_TTL
+        zc.register_service(info)
+        assert nbr_answers[0] == 12 and nbr_additionals[0] == 0 and nbr_authorities[0] == 3
+        nbr_answers[0] = nbr_additionals[0] = nbr_authorities[0] = 0
+
+        # query
+        query = r.DNSOutgoing(r._FLAGS_QR_QUERY | r._FLAGS_AA)
+        query.add_question(r.DNSQuestion(info.type, r._TYPE_PTR, r._CLASS_IN))
+        query.add_question(r.DNSQuestion(info.name, r._TYPE_SRV, r._CLASS_IN))
+        query.add_question(r.DNSQuestion(info.name, r._TYPE_TXT, r._CLASS_IN))
+        query.add_question(r.DNSQuestion(info.server, r._TYPE_A, r._CLASS_IN))
+        zc.handle_query(query, r._MDNS_ADDR, r._MDNS_PORT)
+        assert nbr_answers[0] == 4 and nbr_additionals[0] == 1 and nbr_authorities[0] == 0
+        nbr_answers[0] = nbr_additionals[0] = nbr_authorities[0] = 0
+
+        # unregister
+        expected_ttl = 0
+        zc.unregister_service(info)
+        assert nbr_answers[0] == 12 and nbr_additionals[0] == 0 and nbr_authorities[0] == 0
+        nbr_answers[0] = nbr_additionals[0] = nbr_authorities[0] = 0
+
+        # register service with custom TTL
+        expected_ttl = r._DNS_TTL * 2
+        assert expected_ttl != r._DNS_TTL
+        zc.register_service(info, ttl=expected_ttl)
+        assert nbr_answers[0] == 12 and nbr_additionals[0] == 0 and nbr_authorities[0] == 3
+        nbr_answers[0] = nbr_additionals[0] = nbr_authorities[0] = 0
+
+        # query
+        query = r.DNSOutgoing(r._FLAGS_QR_QUERY | r._FLAGS_AA)
+        query.add_question(r.DNSQuestion(info.type, r._TYPE_PTR, r._CLASS_IN))
+        query.add_question(r.DNSQuestion(info.name, r._TYPE_SRV, r._CLASS_IN))
+        query.add_question(r.DNSQuestion(info.name, r._TYPE_TXT, r._CLASS_IN))
+        query.add_question(r.DNSQuestion(info.server, r._TYPE_A, r._CLASS_IN))
+        zc.handle_query(query, r._MDNS_ADDR, r._MDNS_PORT)
+        assert nbr_answers[0] == 4 and nbr_additionals[0] == 1 and nbr_authorities[0] == 0
+        nbr_answers[0] = nbr_additionals[0] = nbr_authorities[0] = 0
+
+        # unregister
+        expected_ttl = 0
+        zc.unregister_service(info)
+        assert nbr_answers[0] == 12 and nbr_additionals[0] == 0 and nbr_authorities[0] == 0
+        nbr_answers[0] = nbr_additionals[0] = nbr_authorities[0] = 0
+
+        
 class TestDNSCache(unittest.TestCase):
 
     def test_order(self):

zeroconf.py

@@ -71,7 +71,7 @@
 _MDNS_ADDR = '224.0.0.251'
 _MDNS_PORT = 5353
 _DNS_PORT = 53
-_DNS_TTL = 60 * 60  # one hour default TTL
+_DNS_TTL = 120  # two minutes default TTL as recommended by RFC6762
 
 _MAX_MSG_TYPICAL = 1460  # unused
 _MAX_MSG_ABSOLUTE = 8966
@@ -1782,6 +1782,7 @@ def register_service(self, info, ttl=_DNS_TTL, allow_name_change=False):
         of 60 seconds.  Zeroconf will then respond to requests for
         information for that service.  The name of the service may be
         changed if needed to make it unique on the network."""
+        info.ttl = ttl
         self.check_service(info, allow_name_change)
         self.services[info.name.lower()] = info
         if info.type in self.servicetypes:
@@ -1917,7 +1918,7 @@ def check_service(self, info, allow_name_change):
             self.debug = out
             out.add_question(DNSQuestion(info.type, _TYPE_PTR, _CLASS_IN))
             out.add_authorative_answer(DNSPointer(
-                info.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, info.name))
+                info.type, _TYPE_PTR, _CLASS_IN, info.ttl, info.name))
             self.send(out)
             i += 1
             next_time += _CHECK_TIME
@@ -1995,7 +1996,7 @@ def handle_query(self, msg, addr, port):
                             out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
                         out.add_answer(msg, DNSPointer(
                             service.type, _TYPE_PTR,
-                            _CLASS_IN, _DNS_TTL, service.name))
+                            _CLASS_IN, service.ttl, service.name))
             else:
                 try:
                     if out is None:
@@ -2008,7 +2009,7 @@ def handle_query(self, msg, addr, port):
                                 out.add_answer(msg, DNSAddress(
                                     question.name, _TYPE_A,
                                     _CLASS_IN | _CLASS_UNIQUE,
-                                    _DNS_TTL, service.address))
+                                    service.ttl, service.address))
 
                     service = self.services.get(question.name.lower(), None)
                     if not service:
@@ -2017,16 +2018,16 @@ def handle_query(self, msg, addr, port):
                     if question.type in (_TYPE_SRV, _TYPE_ANY):
                         out.add_answer(msg, DNSService(
                             question.name, _TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE,
-                            _DNS_TTL, service.priority, service.weight,
+                            service.ttl, service.priority, service.weight,
                             service.port, service.server))
                     if question.type in (_TYPE_TXT, _TYPE_ANY):
                         out.add_answer(msg, DNSText(
                             question.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE,
-                            _DNS_TTL, service.text))
+                            service.ttl, service.text))
                     if question.type == _TYPE_SRV:
                         out.add_additional_answer(DNSAddress(
                             service.server, _TYPE_A, _CLASS_IN | _CLASS_UNIQUE,
-                            _DNS_TTL, service.address))
+                            service.ttl, service.address))
                 except Exception:  # TODO stop catching all Exceptions
                     self.log_exception_warning()