From 6fadb560fcdc92466b0b5cac02551cb41ca9f148 Mon Sep 17 00:00:00 2001
From: "Olivier Wilkinson (reivilibre)" <olivier@librepush.net>
Date: Wed, 14 Aug 2019 13:30:36 +0100
Subject: [PATCH] Support MSC2197 outbound with unstable prefix

Signed-off-by: Olivier Wilkinson (reivilibre) <olivier@librepush.net>
---
 synapse/federation/transport/client.py | 40 ++++++++++++++++++--------
 synapse/handlers/room_list.py          | 29 ++++++++++++++++++-
 2 files changed, 56 insertions(+), 13 deletions(-)

diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 0cea0d2a1..2e99f77eb 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -327,21 +327,37 @@ class TransportLayerClient(object):
         include_all_networks=False,
         third_party_instance_id=None,
     ):
-        path = _create_v1_path("/publicRooms")
+        if search_filter:
+            # TODO(MSC2197): Move to V1 prefix
+            path = _create_path(FEDERATION_UNSTABLE_PREFIX, "/publicRooms")
 
-        args = {"include_all_networks": "true" if include_all_networks else "false"}
-        if third_party_instance_id:
-            args["third_party_instance_id"] = (third_party_instance_id,)
-        if limit:
-            args["limit"] = [str(limit)]
-        if since_token:
-            args["since"] = [since_token]
+            data = {"include_all_networks": "true" if include_all_networks else "false"}
+            if third_party_instance_id:
+                data["third_party_instance_id"] = third_party_instance_id
+            if limit:
+                data["limit"] = str(limit)
+            if since_token:
+                data["since"] = since_token
 
-        # TODO(erikj): Actually send the search_filter across federation.
+            data["filter"] = search_filter
 
-        response = yield self.client.get_json(
-            destination=remote_server, path=path, args=args, ignore_backoff=True
-        )
+            response = yield self.client.post_json(
+                destination=remote_server, path=path, data=data, ignore_backoff=True
+            )
+        else:
+            path = _create_v1_path("/publicRooms")
+
+            args = {"include_all_networks": "true" if include_all_networks else "false"}
+            if third_party_instance_id:
+                args["third_party_instance_id"] = (third_party_instance_id,)
+            if limit:
+                args["limit"] = [str(limit)]
+            if since_token:
+                args["since"] = [since_token]
+
+            response = yield self.client.get_json(
+                destination=remote_server, path=path, args=args, ignore_backoff=True
+            )
 
         return response
 
diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py
index e9094ad02..a7e55f00e 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -25,6 +25,7 @@ from unpaddedbase64 import decode_base64, encode_base64
 from twisted.internet import defer
 
 from synapse.api.constants import EventTypes, JoinRules
+from synapse.api.errors import Codes, HttpResponseException
 from synapse.types import ThirdPartyInstanceID
 from synapse.util.async_helpers import concurrently_execute
 from synapse.util.caches.descriptors import cachedInlineCallbacks
@@ -485,7 +486,33 @@ class RoomListHandler(BaseHandler):
             return {"chunk": [], "total_room_count_estimate": 0}
 
         if search_filter:
-            # We currently don't support searching across federation, so we have
+            # Searching across federation is defined in MSC2197.
+            # However, the remote homeserver may or may not actually support it.
+            # So we first try an MSC2197 remote-filtered search, then fall back
+            # to a locally-filtered search if we must.
+
+            try:
+                res = yield self._get_remote_list_cached(
+                    server_name,
+                    limit=limit,
+                    since_token=since_token,
+                    include_all_networks=include_all_networks,
+                    third_party_instance_id=third_party_instance_id,
+                    search_filter=search_filter,
+                )
+                return res
+            except HttpResponseException as hre:
+                syn_err = hre.to_synapse_error()
+                if hre.code in (404, 405) or syn_err.errcode in (
+                    Codes.UNRECOGNIZED,
+                    Codes.NOT_FOUND,
+                ):
+                    logger.debug("Falling back to locally-filtered /publicRooms")
+                else:
+                    raise  # Not an error that should trigger a fallback.
+
+            # if we reach this point, then we fall back to the situation where
+            # we currently don't support searching across federation, so we have
             # to do it manually without pagination
             limit = None
             since_token = None