1 files changed, 33 insertions, 1 deletions
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index a3bb864bb2..9848534120 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -48,13 +48,14 @@ from synapse.crypto.event_signing import (
     compute_event_signature,
 )
 from synapse.events.validator import EventValidator
+from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.replication.http.federation import (
     ReplicationCleanRoomRestServlet,
     ReplicationFederationSendEventsRestServlet,
 )
 from synapse.replication.http.membership import ReplicationUserJoinedLeftRoomRestServlet
 from synapse.state import StateResolutionStore, resolve_events_with_store
-from synapse.types import UserID, get_domain_from_id
+from synapse.types import UserID, get_domain_from_id, create_requester
 from synapse.util import logcontext, unwrapFirstError
 from synapse.util.async_helpers import Linearizer
 from synapse.util.distributor import user_joined_room
@@ -105,6 +106,7 @@ class FederationHandler(BaseHandler):
 
         self.hs = hs
 
+        self.clock = hs.get_clock()
         self.store = hs.get_datastore()  # type: synapse.storage.DataStore
         self.federation_client = hs.get_federation_client()
         self.state_handler = hs.get_state_handler()
@@ -1300,9 +1302,39 @@ class FederationHandler(BaseHandler):
         context = yield self.state_handler.compute_event_context(event)
         yield self.persist_events_and_notify([(event, context)])
 
+        sender = UserID.from_string(event.sender)
+        target = UserID.from_string(event.state_key)
+        if (sender.localpart == target.localpart):
+            run_as_background_process(
+                "_auto_accept_invite",
+                self._auto_accept_invite,
+                sender, target, event.room_id,
+            )
+
         defer.returnValue(event)
 
     @defer.inlineCallbacks
+    def _auto_accept_invite(self, sender, target, room_id):
+        joined = False
+        for attempt in range(0, 10):
+            try:
+                yield self.hs.get_room_member_handler().update_membership(
+                    requester=create_requester(target.to_string()),
+                    target=target,
+                    room_id=room_id,
+                    action="join",
+                )
+                joined = True
+                break
+            except Exception:
+                # We're going to retry, but we should log the error
+                logger.exception("Error auto-accepting invite on attempt %d" % attempt)
+                yield self.clock.sleep(1)
+        if not joined:
+            logger.error("Giving up on trying to auto-accept invite: too many attempts")
+
+
+    @defer.inlineCallbacks
     def do_remotely_reject_invite(self, target_hosts, room_id, user_id):
         origin, event = yield self._make_and_verify_event(
             target_hosts,