From 61385846510ceed1bff571dde1233a70e02b4748 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Mon, 16 Feb 2015 14:08:02 +0000
Subject: [PATCH 1/2] Don't return anything from _handle_new_pdu, since we
 ignore the return value anyway

---
 synapse/federation/federation_server.py | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 9f5c98694c..7ca8d49c54 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -331,7 +331,6 @@ class FederationServer(FederationBase):
         )
         if already_seen:
             logger.debug("Already seen pdu %s", pdu.event_id)
-            defer.returnValue({})
             return
 
         # Check signature.
@@ -418,7 +417,7 @@ class FederationServer(FederationBase):
             except:
                 logger.warn("Failed to get state for event: %s", pdu.event_id)
 
-        ret = yield self.handler.on_receive_pdu(
+        yield self.handler.on_receive_pdu(
             origin,
             pdu,
             backfilled=False,
@@ -426,8 +425,6 @@ class FederationServer(FederationBase):
             auth_chain=auth_chain,
         )
 
-        defer.returnValue(ret)
-
     def __str__(self):
         return "<ReplicationLayer(%s)>" % self.server_name
 

From 91fc5eef1deb2f756d16f3d5ea20ede8d967f6df Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Mon, 16 Feb 2015 14:27:40 +0000
Subject: [PATCH 2/2] Mark old events as outliers.

This is to fix the issue where if a remote server sends an event
that references a really "old" event, then the local server will pull
that in and send to all clients.

We decide if an event is old if its depth is less than the minimum depth
of the room.
---
 synapse/federation/federation_server.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 7ca8d49c54..4391a60c02 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -366,7 +366,13 @@ class FederationServer(FederationBase):
                 pdu.room_id, min_depth
             )
 
-            if min_depth and pdu.depth > min_depth and max_recursion > 0:
+            if min_depth and pdu.depth < min_depth:
+                # This is so that we don't notify the user about this
+                # message, to work around the fact that some events will
+                # reference really really old events we really don't want to
+                # send to the clients.
+                pdu.internal_metadata.outlier = True
+            elif min_depth and pdu.depth > min_depth and max_recursion > 0:
                 for event_id, hashes in pdu.prev_events:
                     if event_id not in have_seen:
                         logger.debug(