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-rw-r--r--synapse/federation/federation_client.py328
-rw-r--r--synapse/federation/federation_server.py84
-rw-r--r--synapse/federation/transaction_queue.py14
-rw-r--r--synapse/federation/transport/client.py5
-rw-r--r--synapse/federation/transport/server.py79
5 files changed, 356 insertions, 154 deletions
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 62d7ed13cf..c9f3c2d352 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -25,7 +25,7 @@ from prometheus_client import Counter
 
 from twisted.internet import defer
 
-from synapse.api.constants import Membership
+from synapse.api.constants import KNOWN_ROOM_VERSIONS, EventTypes, Membership
 from synapse.api.errors import (
     CodeMessageException,
     FederationDeniedError,
@@ -48,6 +48,13 @@ sent_queries_counter = Counter("synapse_federation_client_sent_queries", "", ["t
 PDU_RETRY_TIME_MS = 1 * 60 * 1000
 
 
+class InvalidResponseError(RuntimeError):
+    """Helper for _try_destination_list: indicates that the server returned a response
+    we couldn't parse
+    """
+    pass
+
+
 class FederationClient(FederationBase):
     def __init__(self, hs):
         super(FederationClient, self).__init__(hs)
@@ -458,8 +465,63 @@ class FederationClient(FederationBase):
         defer.returnValue(signed_auth)
 
     @defer.inlineCallbacks
+    def _try_destination_list(self, description, destinations, callback):
+        """Try an operation on a series of servers, until it succeeds
+
+        Args:
+            description (unicode): description of the operation we're doing, for logging
+
+            destinations (Iterable[unicode]): list of server_names to try
+
+            callback (callable):  Function to run for each server. Passed a single
+                argument: the server_name to try. May return a deferred.
+
+                If the callback raises a CodeMessageException with a 300/400 code,
+                attempts to perform the operation stop immediately and the exception is
+                reraised.
+
+                Otherwise, if the callback raises an Exception the error is logged and the
+                next server tried. Normally the stacktrace is logged but this is
+                suppressed if the exception is an InvalidResponseError.
+
+        Returns:
+            The [Deferred] result of callback, if it succeeds
+
+        Raises:
+            SynapseError if the chosen remote server returns a 300/400 code.
+
+            RuntimeError if no servers were reachable.
+        """
+        for destination in destinations:
+            if destination == self.server_name:
+                continue
+
+            try:
+                res = yield callback(destination)
+                defer.returnValue(res)
+            except InvalidResponseError as e:
+                logger.warn(
+                    "Failed to %s via %s: %s",
+                    description, destination, e,
+                )
+            except HttpResponseException as e:
+                if not 500 <= e.code < 600:
+                    raise e.to_synapse_error()
+                else:
+                    logger.warn(
+                        "Failed to %s via %s: %i %s",
+                        description, destination, e.code, e.message,
+                    )
+            except Exception:
+                logger.warn(
+                    "Failed to %s via %s",
+                    description, destination, exc_info=1,
+                )
+
+        raise RuntimeError("Failed to %s via any server" % (description, ))
+
     def make_membership_event(self, destinations, room_id, user_id, membership,
-                              content={},):
+                              content, params):
         """
         Creates an m.room.member event, with context, without participating in the room.
 
@@ -475,13 +537,15 @@ class FederationClient(FederationBase):
             user_id (str): The user whose membership is being evented.
             membership (str): The "membership" property of the event. Must be
                 one of "join" or "leave".
-            content (object): Any additional data to put into the content field
+            content (dict): Any additional data to put into the content field
                 of the event.
+            params (dict[str, str|Iterable[str]]): Query parameters to include in the
+                request.
         Return:
             Deferred: resolves to a tuple of (origin (str), event (object))
             where origin is the remote homeserver which generated the event.
 
-            Fails with a ``CodeMessageException`` if the chosen remote server
+            Fails with a ``SynapseError`` if the chosen remote server
             returns a 300/400 code.
 
             Fails with a ``RuntimeError`` if no servers were reachable.
@@ -492,50 +556,37 @@ class FederationClient(FederationBase):
                 "make_membership_event called with membership='%s', must be one of %s" %
                 (membership, ",".join(valid_memberships))
             )
-        for destination in destinations:
-            if destination == self.server_name:
-                continue
 
-            try:
-                ret = yield self.transport_layer.make_membership_event(
-                    destination, room_id, user_id, membership
-                )
+        @defer.inlineCallbacks
+        def send_request(destination):
+            ret = yield self.transport_layer.make_membership_event(
+                destination, room_id, user_id, membership, params,
+            )
 
-                pdu_dict = ret["event"]
+            pdu_dict = ret.get("event", None)
+            if not isinstance(pdu_dict, dict):
+                raise InvalidResponseError("Bad 'event' field in response")
 
-                logger.debug("Got response to make_%s: %s", membership, pdu_dict)
+            logger.debug("Got response to make_%s: %s", membership, pdu_dict)
 
-                pdu_dict["content"].update(content)
+            pdu_dict["content"].update(content)
 
-                # The protoevent received over the JSON wire may not have all
-                # the required fields. Lets just gloss over that because
-                # there's some we never care about
-                if "prev_state" not in pdu_dict:
-                    pdu_dict["prev_state"] = []
+            # The protoevent received over the JSON wire may not have all
+            # the required fields. Lets just gloss over that because
+            # there's some we never care about
+            if "prev_state" not in pdu_dict:
+                pdu_dict["prev_state"] = []
 
-                ev = builder.EventBuilder(pdu_dict)
+            ev = builder.EventBuilder(pdu_dict)
 
-                defer.returnValue(
-                    (destination, ev)
-                )
-                break
-            except CodeMessageException as e:
-                if not 500 <= e.code < 600:
-                    raise
-                else:
-                    logger.warn(
-                        "Failed to make_%s via %s: %s",
-                        membership, destination, e.message
-                    )
-            except Exception as e:
-                logger.warn(
-                    "Failed to make_%s via %s: %s",
-                    membership, destination, e.message
-                )
+            defer.returnValue(
+                (destination, ev)
+            )
 
-        raise RuntimeError("Failed to send to any server.")
+        return self._try_destination_list(
+            "make_" + membership, destinations, send_request,
+        )
 
-    @defer.inlineCallbacks
     def send_join(self, destinations, pdu):
         """Sends a join event to one of a list of homeservers.
 
@@ -552,103 +603,111 @@ class FederationClient(FederationBase):
             giving the serer the event was sent to, ``state`` (?) and
             ``auth_chain``.
 
-            Fails with a ``CodeMessageException`` if the chosen remote server
+            Fails with a ``SynapseError`` if the chosen remote server
             returns a 300/400 code.
 
             Fails with a ``RuntimeError`` if no servers were reachable.
         """
 
-        for destination in destinations:
-            if destination == self.server_name:
-                continue
-
-            try:
-                time_now = self._clock.time_msec()
-                _, content = yield self.transport_layer.send_join(
-                    destination=destination,
-                    room_id=pdu.room_id,
-                    event_id=pdu.event_id,
-                    content=pdu.get_pdu_json(time_now),
+        def check_authchain_validity(signed_auth_chain):
+            for e in signed_auth_chain:
+                if e.type == EventTypes.Create:
+                    create_event = e
+                    break
+            else:
+                raise InvalidResponseError(
+                    "no %s in auth chain" % (EventTypes.Create,),
                 )
 
-                logger.debug("Got content: %s", content)
+            # the room version should be sane.
+            room_version = create_event.content.get("room_version", "1")
+            if room_version not in KNOWN_ROOM_VERSIONS:
+                # This shouldn't be possible, because the remote server should have
+                # rejected the join attempt during make_join.
+                raise InvalidResponseError(
+                    "room appears to have unsupported version %s" % (
+                        room_version,
+                    ))
+
+        @defer.inlineCallbacks
+        def send_request(destination):
+            time_now = self._clock.time_msec()
+            _, content = yield self.transport_layer.send_join(
+                destination=destination,
+                room_id=pdu.room_id,
+                event_id=pdu.event_id,
+                content=pdu.get_pdu_json(time_now),
+            )
 
-                state = [
-                    event_from_pdu_json(p, outlier=True)
-                    for p in content.get("state", [])
-                ]
+            logger.debug("Got content: %s", content)
 
-                auth_chain = [
-                    event_from_pdu_json(p, outlier=True)
-                    for p in content.get("auth_chain", [])
-                ]
+            state = [
+                event_from_pdu_json(p, outlier=True)
+                for p in content.get("state", [])
+            ]
 
-                pdus = {
-                    p.event_id: p
-                    for p in itertools.chain(state, auth_chain)
-                }
+            auth_chain = [
+                event_from_pdu_json(p, outlier=True)
+                for p in content.get("auth_chain", [])
+            ]
 
-                valid_pdus = yield self._check_sigs_and_hash_and_fetch(
-                    destination, list(pdus.values()),
-                    outlier=True,
-                )
+            pdus = {
+                p.event_id: p
+                for p in itertools.chain(state, auth_chain)
+            }
 
-                valid_pdus_map = {
-                    p.event_id: p
-                    for p in valid_pdus
-                }
-
-                # NB: We *need* to copy to ensure that we don't have multiple
-                # references being passed on, as that causes... issues.
-                signed_state = [
-                    copy.copy(valid_pdus_map[p.event_id])
-                    for p in state
-                    if p.event_id in valid_pdus_map
-                ]
+            valid_pdus = yield self._check_sigs_and_hash_and_fetch(
+                destination, list(pdus.values()),
+                outlier=True,
+            )
 
-                signed_auth = [
-                    valid_pdus_map[p.event_id]
-                    for p in auth_chain
-                    if p.event_id in valid_pdus_map
-                ]
+            valid_pdus_map = {
+                p.event_id: p
+                for p in valid_pdus
+            }
 
-                # NB: We *need* to copy to ensure that we don't have multiple
-                # references being passed on, as that causes... issues.
-                for s in signed_state:
-                    s.internal_metadata = copy.deepcopy(s.internal_metadata)
+            # NB: We *need* to copy to ensure that we don't have multiple
+            # references being passed on, as that causes... issues.
+            signed_state = [
+                copy.copy(valid_pdus_map[p.event_id])
+                for p in state
+                if p.event_id in valid_pdus_map
+            ]
 
-                auth_chain.sort(key=lambda e: e.depth)
+            signed_auth = [
+                valid_pdus_map[p.event_id]
+                for p in auth_chain
+                if p.event_id in valid_pdus_map
+            ]
 
-                defer.returnValue({
-                    "state": signed_state,
-                    "auth_chain": signed_auth,
-                    "origin": destination,
-                })
-            except CodeMessageException as e:
-                if not 500 <= e.code < 600:
-                    raise
-                else:
-                    logger.exception(
-                        "Failed to send_join via %s: %s",
-                        destination, e.message
-                    )
-            except Exception as e:
-                logger.exception(
-                    "Failed to send_join via %s: %s",
-                    destination, e.message
-                )
+            # NB: We *need* to copy to ensure that we don't have multiple
+            # references being passed on, as that causes... issues.
+            for s in signed_state:
+                s.internal_metadata = copy.deepcopy(s.internal_metadata)
 
-        raise RuntimeError("Failed to send to any server.")
+            check_authchain_validity(signed_auth)
+
+            defer.returnValue({
+                "state": signed_state,
+                "auth_chain": signed_auth,
+                "origin": destination,
+            })
+        return self._try_destination_list("send_join", destinations, send_request)
 
     @defer.inlineCallbacks
     def send_invite(self, destination, room_id, event_id, pdu):
         time_now = self._clock.time_msec()
-        code, content = yield self.transport_layer.send_invite(
-            destination=destination,
-            room_id=room_id,
-            event_id=event_id,
-            content=pdu.get_pdu_json(time_now),
-        )
+        try:
+            code, content = yield self.transport_layer.send_invite(
+                destination=destination,
+                room_id=room_id,
+                event_id=event_id,
+                content=pdu.get_pdu_json(time_now),
+            )
+        except HttpResponseException as e:
+            if e.code == 403:
+                raise e.to_synapse_error()
+            raise
 
         pdu_dict = content["event"]
 
@@ -663,7 +722,6 @@ class FederationClient(FederationBase):
 
         defer.returnValue(pdu)
 
-    @defer.inlineCallbacks
     def send_leave(self, destinations, pdu):
         """Sends a leave event to one of a list of homeservers.
 
@@ -680,35 +738,25 @@ class FederationClient(FederationBase):
         Return:
             Deferred: resolves to None.
 
-            Fails with a ``CodeMessageException`` if the chosen remote server
-            returns a non-200 code.
+            Fails with a ``SynapseError`` if the chosen remote server
+            returns a 300/400 code.
 
             Fails with a ``RuntimeError`` if no servers were reachable.
         """
-        for destination in destinations:
-            if destination == self.server_name:
-                continue
-
-            try:
-                time_now = self._clock.time_msec()
-                _, content = yield self.transport_layer.send_leave(
-                    destination=destination,
-                    room_id=pdu.room_id,
-                    event_id=pdu.event_id,
-                    content=pdu.get_pdu_json(time_now),
-                )
+        @defer.inlineCallbacks
+        def send_request(destination):
+            time_now = self._clock.time_msec()
+            _, content = yield self.transport_layer.send_leave(
+                destination=destination,
+                room_id=pdu.room_id,
+                event_id=pdu.event_id,
+                content=pdu.get_pdu_json(time_now),
+            )
 
-                logger.debug("Got content: %s", content)
-                defer.returnValue(None)
-            except CodeMessageException:
-                raise
-            except Exception as e:
-                logger.exception(
-                    "Failed to send_leave via %s: %s",
-                    destination, e.message
-                )
+            logger.debug("Got content: %s", content)
+            defer.returnValue(None)
 
-        raise RuntimeError("Failed to send to any server.")
+        return self._try_destination_list("send_leave", destinations, send_request)
 
     def get_public_rooms(self, destination, limit=None, since_token=None,
                          search_filter=None, include_all_networks=False,
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 657935d1ac..3e0cd294a1 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -27,14 +27,24 @@ from twisted.internet.abstract import isIPAddress
 from twisted.python import failure
 
 from synapse.api.constants import EventTypes
-from synapse.api.errors import AuthError, FederationError, NotFoundError, SynapseError
+from synapse.api.errors import (
+    AuthError,
+    FederationError,
+    IncompatibleRoomVersionError,
+    NotFoundError,
+    SynapseError,
+)
 from synapse.crypto.event_signing import compute_event_signature
 from synapse.federation.federation_base import FederationBase, event_from_pdu_json
 from synapse.federation.persistence import TransactionActions
 from synapse.federation.units import Edu, Transaction
 from synapse.http.endpoint import parse_server_name
+from synapse.replication.http.federation import (
+    ReplicationFederationSendEduRestServlet,
+    ReplicationGetQueryRestServlet,
+)
 from synapse.types import get_domain_from_id
-from synapse.util import async
+from synapse.util.async_helpers import Linearizer, concurrently_execute
 from synapse.util.caches.response_cache import ResponseCache
 from synapse.util.logutils import log_function
 
@@ -61,8 +71,8 @@ class FederationServer(FederationBase):
         self.auth = hs.get_auth()
         self.handler = hs.get_handlers().federation_handler
 
-        self._server_linearizer = async.Linearizer("fed_server")
-        self._transaction_linearizer = async.Linearizer("fed_txn_handler")
+        self._server_linearizer = Linearizer("fed_server")
+        self._transaction_linearizer = Linearizer("fed_txn_handler")
 
         self.transaction_actions = TransactionActions(self.store)
 
@@ -194,7 +204,7 @@ class FederationServer(FederationBase):
                         event_id, f.getTraceback().rstrip(),
                     )
 
-        yield async.concurrently_execute(
+        yield concurrently_execute(
             process_pdus_for_room, pdus_by_room.keys(),
             TRANSACTION_CONCURRENCY_LIMIT,
         )
@@ -323,12 +333,21 @@ class FederationServer(FederationBase):
         defer.returnValue((200, resp))
 
     @defer.inlineCallbacks
-    def on_make_join_request(self, origin, room_id, user_id):
+    def on_make_join_request(self, origin, room_id, user_id, supported_versions):
         origin_host, _ = parse_server_name(origin)
         yield self.check_server_matches_acl(origin_host, room_id)
+
+        room_version = yield self.store.get_room_version(room_id)
+        if room_version not in supported_versions:
+            logger.warn("Room version %s not in %s", room_version, supported_versions)
+            raise IncompatibleRoomVersionError(room_version=room_version)
+
         pdu = yield self.handler.on_make_join_request(room_id, user_id)
         time_now = self._clock.time_msec()
-        defer.returnValue({"event": pdu.get_pdu_json(time_now)})
+        defer.returnValue({
+            "event": pdu.get_pdu_json(time_now),
+            "room_version": room_version,
+        })
 
     @defer.inlineCallbacks
     def on_invite_request(self, origin, content):
@@ -426,6 +445,7 @@ class FederationServer(FederationBase):
             ret = yield self.handler.on_query_auth(
                 origin,
                 event_id,
+                room_id,
                 signed_auth,
                 content.get("rejects", []),
                 content.get("missing", []),
@@ -744,6 +764,8 @@ class FederationHandlerRegistry(object):
         if edu_type in self.edu_handlers:
             raise KeyError("Already have an EDU handler for %s" % (edu_type,))
 
+        logger.info("Registering federation EDU handler for %r", edu_type)
+
         self.edu_handlers[edu_type] = handler
 
     def register_query_handler(self, query_type, handler):
@@ -762,6 +784,8 @@ class FederationHandlerRegistry(object):
                 "Already have a Query handler for %s" % (query_type,)
             )
 
+        logger.info("Registering federation query handler for %r", query_type)
+
         self.query_handlers[query_type] = handler
 
     @defer.inlineCallbacks
@@ -784,3 +808,49 @@ class FederationHandlerRegistry(object):
             raise NotFoundError("No handler for Query type '%s'" % (query_type,))
 
         return handler(args)
+
+
+class ReplicationFederationHandlerRegistry(FederationHandlerRegistry):
+    """A FederationHandlerRegistry for worker processes.
+
+    When receiving EDU or queries it will check if an appropriate handler has
+    been registered on the worker, if there isn't one then it calls off to the
+    master process.
+    """
+
+    def __init__(self, hs):
+        self.config = hs.config
+        self.http_client = hs.get_simple_http_client()
+        self.clock = hs.get_clock()
+
+        self._get_query_client = ReplicationGetQueryRestServlet.make_client(hs)
+        self._send_edu = ReplicationFederationSendEduRestServlet.make_client(hs)
+
+        super(ReplicationFederationHandlerRegistry, self).__init__()
+
+    def on_edu(self, edu_type, origin, content):
+        """Overrides FederationHandlerRegistry
+        """
+        handler = self.edu_handlers.get(edu_type)
+        if handler:
+            return super(ReplicationFederationHandlerRegistry, self).on_edu(
+                edu_type, origin, content,
+            )
+
+        return self._send_edu(
+                edu_type=edu_type,
+                origin=origin,
+                content=content,
+        )
+
+    def on_query(self, query_type, args):
+        """Overrides FederationHandlerRegistry
+        """
+        handler = self.query_handlers.get(query_type)
+        if handler:
+            return handler(args)
+
+        return self._get_query_client(
+                query_type=query_type,
+                args=args,
+        )
diff --git a/synapse/federation/transaction_queue.py b/synapse/federation/transaction_queue.py
index 78f9d40a3a..94d7423d01 100644
--- a/synapse/federation/transaction_queue.py
+++ b/synapse/federation/transaction_queue.py
@@ -26,6 +26,8 @@ from synapse.api.errors import FederationDeniedError, HttpResponseException
 from synapse.handlers.presence import format_user_presence_state, get_interested_remotes
 from synapse.metrics import (
     LaterGauge,
+    event_processing_loop_counter,
+    event_processing_loop_room_count,
     events_processed_counter,
     sent_edus_counter,
     sent_transactions_counter,
@@ -56,6 +58,7 @@ class TransactionQueue(object):
     """
 
     def __init__(self, hs):
+        self.hs = hs
         self.server_name = hs.hostname
 
         self.store = hs.get_datastore()
@@ -253,7 +256,13 @@ class TransactionQueue(object):
                     synapse.metrics.event_processing_last_ts.labels(
                         "federation_sender").set(ts)
 
-                events_processed_counter.inc(len(events))
+                    events_processed_counter.inc(len(events))
+
+                    event_processing_loop_room_count.labels(
+                        "federation_sender"
+                    ).inc(len(events_by_room))
+
+                event_processing_loop_counter.labels("federation_sender").inc()
 
                 synapse.metrics.event_processing_positions.labels(
                     "federation_sender").set(next_token)
@@ -300,6 +309,9 @@ class TransactionQueue(object):
         Args:
             states (list(UserPresenceState))
         """
+        if not self.hs.config.use_presence:
+            # No-op if presence is disabled.
+            return
 
         # First we queue up the new presence by user ID, so multiple presence
         # updates in quick successtion are correctly handled
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 625b4def9b..1054441ca5 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -195,7 +195,7 @@ class TransportLayerClient(object):
 
     @defer.inlineCallbacks
     @log_function
-    def make_membership_event(self, destination, room_id, user_id, membership):
+    def make_membership_event(self, destination, room_id, user_id, membership, params):
         """Asks a remote server to build and sign us a membership event
 
         Note that this does not append any events to any graphs.
@@ -205,6 +205,8 @@ class TransportLayerClient(object):
             room_id (str): room to join/leave
             user_id (str): user to be joined/left
             membership (str): one of join/leave
+            params (dict[str, str|Iterable[str]]): Query parameters to include in the
+                request.
 
         Returns:
             Deferred: Succeeds when we get a 2xx HTTP response. The result
@@ -241,6 +243,7 @@ class TransportLayerClient(object):
         content = yield self.client.get_json(
             destination=destination,
             path=path,
+            args=params,
             retry_on_dns_fail=retry_on_dns_fail,
             timeout=20000,
             ignore_backoff=ignore_backoff,
diff --git a/synapse/federation/transport/server.py b/synapse/federation/transport/server.py
index 3b5ea9515a..7a993fd1cf 100644
--- a/synapse/federation/transport/server.py
+++ b/synapse/federation/transport/server.py
@@ -165,7 +165,7 @@ def _parse_auth_header(header_bytes):
         param_dict = dict(kv.split("=") for kv in params)
 
         def strip_quotes(value):
-            if value.startswith(b"\""):
+            if value.startswith("\""):
                 return value[1:-1]
             else:
                 return value
@@ -190,6 +190,41 @@ def _parse_auth_header(header_bytes):
 
 
 class BaseFederationServlet(object):
+    """Abstract base class for federation servlet classes.
+
+    The servlet object should have a PATH attribute which takes the form of a regexp to
+    match against the request path (excluding the /federation/v1 prefix).
+
+    The servlet should also implement one or more of on_GET, on_POST, on_PUT, to match
+    the appropriate HTTP method. These methods have the signature:
+
+        on_<METHOD>(self, origin, content, query, **kwargs)
+
+        With arguments:
+
+            origin (unicode|None): The authenticated server_name of the calling server,
+                unless REQUIRE_AUTH is set to False and authentication failed.
+
+            content (unicode|None): decoded json body of the request. None if the
+                request was a GET.
+
+            query (dict[bytes, list[bytes]]): Query params from the request. url-decoded
+                (ie, '+' and '%xx' are decoded) but note that it is *not* utf8-decoded
+                yet.
+
+            **kwargs (dict[unicode, unicode]): the dict mapping keys to path
+                components as specified in the path match regexp.
+
+        Returns:
+            Deferred[(int, object)|None]: either (response code, response object) to
+                 return a JSON response, or None if the request has already been handled.
+
+        Raises:
+            SynapseError: to return an error code
+
+            Exception: other exceptions will be caught, logged, and a 500 will be
+                returned.
+    """
     REQUIRE_AUTH = True
 
     def __init__(self, handler, authenticator, ratelimiter, server_name):
@@ -204,6 +239,18 @@ class BaseFederationServlet(object):
         @defer.inlineCallbacks
         @functools.wraps(func)
         def new_func(request, *args, **kwargs):
+            """ A callback which can be passed to HttpServer.RegisterPaths
+
+            Args:
+                request (twisted.web.http.Request):
+                *args: unused?
+                **kwargs (dict[unicode, unicode]): the dict mapping keys to path
+                    components as specified in the path match regexp.
+
+            Returns:
+                Deferred[(int, object)|None]: (response code, response object) as returned
+                    by the callback method. None if the request has already been handled.
+            """
             content = None
             if request.method in ["PUT", "POST"]:
                 # TODO: Handle other method types? other content types?
@@ -214,10 +261,10 @@ class BaseFederationServlet(object):
             except NoAuthenticationError:
                 origin = None
                 if self.REQUIRE_AUTH:
-                    logger.exception("authenticate_request failed")
+                    logger.warn("authenticate_request failed: missing authentication")
                     raise
-            except Exception:
-                logger.exception("authenticate_request failed")
+            except Exception as e:
+                logger.warn("authenticate_request failed: %s", e)
                 raise
 
             if origin:
@@ -384,9 +431,31 @@ class FederationMakeJoinServlet(BaseFederationServlet):
     PATH = "/make_join/(?P<context>[^/]*)/(?P<user_id>[^/]*)"
 
     @defer.inlineCallbacks
-    def on_GET(self, origin, content, query, context, user_id):
+    def on_GET(self, origin, _content, query, context, user_id):
+        """
+        Args:
+            origin (unicode): The authenticated server_name of the calling server
+
+            _content (None): (GETs don't have bodies)
+
+            query (dict[bytes, list[bytes]]): Query params from the request.
+
+            **kwargs (dict[unicode, unicode]): the dict mapping keys to path
+                components as specified in the path match regexp.
+
+        Returns:
+            Deferred[(int, object)|None]: either (response code, response object) to
+                 return a JSON response, or None if the request has already been handled.
+        """
+        versions = query.get(b'ver')
+        if versions is not None:
+            supported_versions = [v.decode("utf-8") for v in versions]
+        else:
+            supported_versions = ["1"]
+
         content = yield self.handler.on_make_join_request(
             origin, context, user_id,
+            supported_versions=supported_versions,
         )
         defer.returnValue((200, content))