Remove destinations from sending if not whitelisted

changelog.d/18484.bugfix

@@ -0,0 +1 @@
+Remove destinations from sending if not whitelisted.

synapse/federation/sender/__init__.py

@@ -342,6 +342,8 @@ async def _handle(self) -> None:
                 destination, _ = self.queue.popitem(last=False)
 
                 queue = self.sender._get_per_destination_queue(destination)
+                if queue is None:
+                    continue
 
                 if not queue._new_data_to_send:
                     # The per destination queue has already been woken up.
@@ -436,12 +438,24 @@ def __init__(self, hs: "HomeServer"):
             self._wake_destinations_needing_catchup,
         )
 
-    def _get_per_destination_queue(self, destination: str) -> PerDestinationQueue:
+    def _get_per_destination_queue(
+        self, destination: str
+    ) -> Optional[PerDestinationQueue]:
         """Get or create a PerDestinationQueue for the given destination
 
         Args:
             destination: server_name of remote server
+
+        Returns:
+            None if federation_domain_whitelist exists and destination not in
+            whitelist. Otherwise PerDestinationQueue for this destination.
         """
+        if (
+            self.hs.config.federation.federation_domain_whitelist is not None
+            and destination not in self.hs.config.federation.federation_domain_whitelist
+        ):
+            return None
+
         queue = self._per_destination_queues.get(destination)
         if not queue:
             queue = PerDestinationQueue(self.hs, self._transaction_manager, destination)
@@ -718,6 +732,15 @@ async def _send_pdu(self, pdu: EventBase, destinations: Iterable[str]) -> None:
         # track the fact that we have a PDU for these destinations,
         # to allow us to perform catch-up later on if the remote is unreachable
         # for a while.
+        # Filter out any destinations not present in the federation_domain_whitelist, if
+        # the whitelist exists. These destinations should not be sent to so let's not
+        # waste time or space keeping track of events destined for them.
+        destinations = [
+            d
+            for d in destinations
+            if self.hs.config.federation.federation_domain_whitelist is None
+            or d in self.hs.config.federation.federation_domain_whitelist
+        ]
         await self.store.store_destination_rooms_entries(
             destinations,
             pdu.room_id,
@@ -732,7 +755,9 @@ async def _send_pdu(self, pdu: EventBase, destinations: Iterable[str]) -> None:
         )
 
         for destination in destinations:
-            self._get_per_destination_queue(destination).send_pdu(pdu)
+            queue = self._get_per_destination_queue(destination)
+            if queue is not None:
+                queue.send_pdu(pdu)
 
     async def send_read_receipt(self, receipt: ReadReceipt) -> None:
         """Send a RR to any other servers in the room
@@ -841,12 +866,16 @@ async def send_read_receipt(self, receipt: ReadReceipt) -> None:
         for domain in immediate_domains:
             # Add to destination queue and wake the destination up
             queue = self._get_per_destination_queue(domain)
+            if queue is None:
+                continue
             queue.queue_read_receipt(receipt)
             queue.attempt_new_transaction()
 
         for domain in delay_domains:
             # Add to destination queue...
             queue = self._get_per_destination_queue(domain)
+            if queue is None:
+                continue
             queue.queue_read_receipt(receipt)
 
             # ... and schedule the destination to be woken up.
@@ -882,9 +911,10 @@ async def send_presence_to_destinations(
             if self.is_mine_server_name(destination):
                 continue
 
-            self._get_per_destination_queue(destination).send_presence(
-                states, start_loop=False
-            )
+            queue = self._get_per_destination_queue(destination)
+            if queue is None:
+                continue
+            queue.send_presence(states, start_loop=False)
 
             self._destination_wakeup_queue.add_to_queue(destination)
 
@@ -934,6 +964,8 @@ def send_edu(self, edu: Edu, key: Optional[Hashable]) -> None:
             return
 
         queue = self._get_per_destination_queue(edu.destination)
+        if queue is None:
+            return
         if key:
             queue.send_keyed_edu(edu, key)
         else:
@@ -958,9 +990,15 @@ async def send_device_messages(
 
         for destination in destinations:
             if immediate:
-                self._get_per_destination_queue(destination).attempt_new_transaction()
+                queue = self._get_per_destination_queue(destination)
+                if queue is None:
+                    continue
+                queue.attempt_new_transaction()
             else:
-                self._get_per_destination_queue(destination).mark_new_data()
+                queue = self._get_per_destination_queue(destination)
+                if queue is None:
+                    continue
+                queue.mark_new_data()
                 self._destination_wakeup_queue.add_to_queue(destination)
 
     def wake_destination(self, destination: str) -> None:
@@ -979,7 +1017,9 @@ def wake_destination(self, destination: str) -> None:
         ):
             return
 
-        self._get_per_destination_queue(destination).attempt_new_transaction()
+        queue = self._get_per_destination_queue(destination)
+        if queue is not None:
+            queue.attempt_new_transaction()
 
     @staticmethod
     def get_current_token() -> int:
@@ -1024,6 +1064,10 @@ async def _wake_destinations_needing_catchup(self) -> None:
                 d
                 for d in destinations_to_wake
                 if self._federation_shard_config.should_handle(self._instance_name, d)
+                and (
+                    self.hs.config.federation.federation_domain_whitelist is None
+                    or d in self.hs.config.federation.federation_domain_whitelist
+                )
             ]
 
             for destination in destinations_to_wake: