2 files changed, 50 insertions, 0 deletions
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 90a7c16b62..8b247fe206 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -1177,6 +1177,28 @@ class TransportLayerClient:
             destination=destination, path=path, data=params
         )
 
+    async def get_room_hierarchy(
+        self,
+        destination: str,
+        room_id: str,
+        suggested_only: bool,
+    ) -> JsonDict:
+        """
+        Args:
+            destination: The remote server
+            room_id: The room ID to ask about.
+            suggested_only: if True, only suggested rooms will be returned
+        """
+        path = _create_path(
+            FEDERATION_UNSTABLE_PREFIX, "/org.matrix.msc2946/hierarchy/%s", room_id
+        )
+
+        return await self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"suggested_only": "true" if suggested_only else "false"},
+        )
+
 
 def _create_path(federation_prefix: str, path: str, *args: str) -> str:
     """
diff --git a/synapse/federation/transport/server.py b/synapse/federation/transport/server.py
index 640f46fff6..79a2e1afa0 100644
--- a/synapse/federation/transport/server.py
+++ b/synapse/federation/transport/server.py
@@ -1936,6 +1936,33 @@ class FederationSpaceSummaryServlet(BaseFederationServlet):
         )
 
 
+class FederationRoomHierarchyServlet(BaseFederationServlet):
+    PREFIX = FEDERATION_UNSTABLE_PREFIX + "/org.matrix.msc2946"
+    PATH = "/hierarchy/(?P<room_id>[^/]*)"
+
+    def __init__(
+        self,
+        hs: HomeServer,
+        authenticator: Authenticator,
+        ratelimiter: FederationRateLimiter,
+        server_name: str,
+    ):
+        super().__init__(hs, authenticator, ratelimiter, server_name)
+        self.handler = hs.get_space_summary_handler()
+
+    async def on_GET(
+        self,
+        origin: str,
+        content: Literal[None],
+        query: Mapping[bytes, Sequence[bytes]],
+        room_id: str,
+    ) -> Tuple[int, JsonDict]:
+        suggested_only = parse_boolean_from_args(query, "suggested_only", default=False)
+        return 200, await self.handler.get_federation_hierarchy(
+            origin, room_id, suggested_only
+        )
+
+
 class RoomComplexityServlet(BaseFederationServlet):
     """
     Indicates to other servers how complex (and therefore likely
@@ -1999,6 +2026,7 @@ FEDERATION_SERVLET_CLASSES: Tuple[Type[BaseFederationServlet], ...] = (
     FederationVersionServlet,
     RoomComplexityServlet,
     FederationSpaceSummaryServlet,
+    FederationRoomHierarchyServlet,
     FederationV1SendKnockServlet,
     FederationMakeKnockServlet,
 )