Faster joins: Support for calling `/federation/v1/state` (#12013)

This is an endpoint that we have server-side support for, but no client-side support. It's going to be useful for resyncing partial-stated rooms, so let's introduce it.

2 files changed, 170 insertions, 0 deletions

diff --git a/tests/federation/test_federation_client.py b/tests/federation/test_federation_client.py
new file mode 100644
index 0000000000..ec8864dafe
--- /dev/null
+++ b/tests/federation/test_federation_client.py
@@ -0,0 +1,149 @@
+# Copyright 2022 Matrix.org Federation C.I.C
+#
+# 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.
+
+import json
+from unittest import mock
+
+import twisted.web.client
+from twisted.internet import defer
+from twisted.internet.protocol import Protocol
+from twisted.python.failure import Failure
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.api.room_versions import RoomVersions
+from synapse.server import HomeServer
+from synapse.types import JsonDict
+from synapse.util import Clock
+
+from tests.unittest import FederatingHomeserverTestCase
+
+
+class FederationClientTest(FederatingHomeserverTestCase):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, homeserver: HomeServer):
+        super().prepare(reactor, clock, homeserver)
+
+        # mock out the Agent used by the federation client, which is easier than
+        # catching the HTTPS connection and do the TLS stuff.
+        self._mock_agent = mock.create_autospec(twisted.web.client.Agent, spec_set=True)
+        homeserver.get_federation_http_client().agent = self._mock_agent
+
+    def test_get_room_state(self):
+        creator = f"@creator:{self.OTHER_SERVER_NAME}"
+        test_room_id = "!room_id"
+
+        # mock up some events to use in the response.
+        # In real life, these would have things in `prev_events` and `auth_events`, but that's
+        # a bit annoying to mock up, and the code under test doesn't care, so we don't bother.
+        create_event_dict = self.add_hashes_and_signatures(
+            {
+                "room_id": test_room_id,
+                "type": "m.room.create",
+                "state_key": "",
+                "sender": creator,
+                "content": {"creator": creator},
+                "prev_events": [],
+                "auth_events": [],
+                "origin_server_ts": 500,
+            }
+        )
+        member_event_dict = self.add_hashes_and_signatures(
+            {
+                "room_id": test_room_id,
+                "type": "m.room.member",
+                "sender": creator,
+                "state_key": creator,
+                "content": {"membership": "join"},
+                "prev_events": [],
+                "auth_events": [],
+                "origin_server_ts": 600,
+            }
+        )
+        pl_event_dict = self.add_hashes_and_signatures(
+            {
+                "room_id": test_room_id,
+                "type": "m.room.power_levels",
+                "sender": creator,
+                "state_key": "",
+                "content": {},
+                "prev_events": [],
+                "auth_events": [],
+                "origin_server_ts": 700,
+            }
+        )
+
+        # mock up the response, and have the agent return it
+        self._mock_agent.request.return_value = defer.succeed(
+            _mock_response(
+                {
+                    "pdus": [
+                        create_event_dict,
+                        member_event_dict,
+                        pl_event_dict,
+                    ],
+                    "auth_chain": [
+                        create_event_dict,
+                        member_event_dict,
+                    ],
+                }
+            )
+        )
+
+        # now fire off the request
+        state_resp, auth_resp = self.get_success(
+            self.hs.get_federation_client().get_room_state(
+                "yet_another_server",
+                test_room_id,
+                "event_id",
+                RoomVersions.V9,
+            )
+        )
+
+        # check the right call got made to the agent
+        self._mock_agent.request.assert_called_once_with(
+            b"GET",
+            b"matrix://yet_another_server/_matrix/federation/v1/state/%21room_id?event_id=event_id",
+            headers=mock.ANY,
+            bodyProducer=None,
+        )
+
+        # ... and that the response is correct.
+
+        # the auth_resp should be empty because all the events are also in state
+        self.assertEqual(auth_resp, [])
+
+        # all of the events should be returned in state_resp, though not necessarily
+        # in the same order. We just check the type on the assumption that if the type
+        # is right, so is the rest of the event.
+        self.assertCountEqual(
+            [e.type for e in state_resp],
+            ["m.room.create", "m.room.member", "m.room.power_levels"],
+        )
+
+
+def _mock_response(resp: JsonDict):
+    body = json.dumps(resp).encode("utf-8")
+
+    def deliver_body(p: Protocol):
+        p.dataReceived(body)
+        p.connectionLost(Failure(twisted.web.client.ResponseDone()))
+
+    response = mock.Mock(
+        code=200,
+        phrase=b"OK",
+        headers=twisted.web.client.Headers({"content-Type": ["application/json"]}),
+        length=len(body),
+        deliverBody=deliver_body,
+    )
+    mock.seal(response)
+    return response
diff --git a/tests/unittest.py b/tests/unittest.py
index a71892cb9d..7983c1e8b8 100644
--- a/tests/unittest.py
+++ b/tests/unittest.py
@@ -51,7 +51,10 @@ from twisted.web.server import Request
 
 from synapse import events
 from synapse.api.constants import EventTypes, Membership
+from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
 from synapse.config.homeserver import HomeServerConfig
+from synapse.config.server import DEFAULT_ROOM_VERSION
+from synapse.crypto.event_signing import add_hashes_and_signatures
 from synapse.federation.transport.server import TransportLayerServer
 from synapse.http.server import JsonResource
 from synapse.http.site import SynapseRequest, SynapseSite
@@ -839,6 +842,24 @@ class FederatingHomeserverTestCase(HomeserverTestCase):
             client_ip=client_ip,
         )
 
+    def add_hashes_and_signatures(
+        self,
+        event_dict: JsonDict,
+        room_version: RoomVersion = KNOWN_ROOM_VERSIONS[DEFAULT_ROOM_VERSION],
+    ) -> JsonDict:
+        """Adds hashes and signatures to the given event dict
+
+        Returns:
+             The modified event dict, for convenience
+        """
+        add_hashes_and_signatures(
+            room_version,
+            event_dict,
+            signature_name=self.OTHER_SERVER_NAME,
+            signing_key=self.OTHER_SERVER_SIGNATURE_KEY,
+        )
+        return event_dict
+
 
 def _auth_header_for_request(
     origin: str,