Refactor and bugfix for resove_service (#4427)

2 files changed, 108 insertions, 14 deletions

diff --git a/tests/http/federation/__init__.py b/tests/http/federation/__init__.py
new file mode 100644
index 0000000000..1453d04571
--- /dev/null
+++ b/tests/http/federation/__init__.py
@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/tests/test_dns.py b/tests/http/federation/test_srv_resolver.py
index 90bd34be34..1271a495e1 100644
--- a/tests/test_dns.py
+++ b/tests/http/federation/test_srv_resolver.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2019 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -16,40 +17,63 @@
 from mock import Mock
 
 from twisted.internet import defer
+from twisted.internet.defer import Deferred
+from twisted.internet.error import ConnectError
 from twisted.names import dns, error
 
-from synapse.http.endpoint import resolve_service
+from synapse.http.federation.srv_resolver import resolve_service
+from synapse.util.logcontext import LoggingContext
 
+from tests import unittest
 from tests.utils import MockClock
 
-from . import unittest
 
-
-@unittest.DEBUG
-class DnsTestCase(unittest.TestCase):
-    @defer.inlineCallbacks
+class SrvResolverTestCase(unittest.TestCase):
     def test_resolve(self):
         dns_client_mock = Mock()
 
-        service_name = "test_service.example.com"
-        host_name = "example.com"
+        service_name = b"test_service.example.com"
+        host_name = b"example.com"
 
         answer_srv = dns.RRHeader(
             type=dns.SRV, payload=dns.Record_SRV(target=host_name)
         )
 
-        dns_client_mock.lookupService.return_value = defer.succeed(
-            ([answer_srv], None, None)
-        )
+        result_deferred = Deferred()
+        dns_client_mock.lookupService.return_value = result_deferred
 
         cache = {}
 
-        servers = yield resolve_service(
-            service_name, dns_client=dns_client_mock, cache=cache
-        )
+        @defer.inlineCallbacks
+        def do_lookup():
+            with LoggingContext("one") as ctx:
+                resolve_d = resolve_service(
+                    service_name, dns_client=dns_client_mock, cache=cache
+                )
+
+                self.assertNoResult(resolve_d)
+
+                # should have reset to the sentinel context
+                self.assertIs(LoggingContext.current_context(), LoggingContext.sentinel)
+
+                result = yield resolve_d
+
+                # should have restored our context
+                self.assertIs(LoggingContext.current_context(), ctx)
+
+                defer.returnValue(result)
+
+        test_d = do_lookup()
+        self.assertNoResult(test_d)
 
         dns_client_mock.lookupService.assert_called_once_with(service_name)
 
+        result_deferred.callback(
+            ([answer_srv], None, None)
+        )
+
+        servers = self.successResultOf(test_d)
+
         self.assertEquals(len(servers), 1)
         self.assertEquals(servers, cache[service_name])
         self.assertEquals(servers[0].host, host_name)
@@ -127,3 +151,59 @@ class DnsTestCase(unittest.TestCase):
 
         self.assertEquals(len(servers), 0)
         self.assertEquals(len(cache), 0)
+
+    def test_disabled_service(self):
+        """
+        test the behaviour when there is a single record which is ".".
+        """
+        service_name = b"test_service.example.com"
+
+        lookup_deferred = Deferred()
+        dns_client_mock = Mock()
+        dns_client_mock.lookupService.return_value = lookup_deferred
+        cache = {}
+
+        resolve_d = resolve_service(
+            service_name, dns_client=dns_client_mock, cache=cache
+        )
+        self.assertNoResult(resolve_d)
+
+        # returning a single "." should make the lookup fail with a ConenctError
+        lookup_deferred.callback((
+            [dns.RRHeader(type=dns.SRV, payload=dns.Record_SRV(target=b"."))],
+            None,
+            None,
+        ))
+
+        self.failureResultOf(resolve_d, ConnectError)
+
+    def test_non_srv_answer(self):
+        """
+        test the behaviour when the dns server gives us a spurious non-SRV response
+        """
+        service_name = b"test_service.example.com"
+
+        lookup_deferred = Deferred()
+        dns_client_mock = Mock()
+        dns_client_mock.lookupService.return_value = lookup_deferred
+        cache = {}
+
+        resolve_d = resolve_service(
+            service_name, dns_client=dns_client_mock, cache=cache
+        )
+        self.assertNoResult(resolve_d)
+
+        lookup_deferred.callback((
+            [
+                dns.RRHeader(type=dns.A, payload=dns.Record_A()),
+                dns.RRHeader(type=dns.SRV, payload=dns.Record_SRV(target=b"host")),
+            ],
+            None,
+            None,
+        ))
+
+        servers = self.successResultOf(resolve_d)
+
+        self.assertEquals(len(servers), 1)
+        self.assertEquals(servers, cache[service_name])
+        self.assertEquals(servers[0].host, b"host")