From c5ffe9d3c50ebe266522132a268b5ba84efa00b7 Mon Sep 17 00:00:00 2001
From: Travis Ralston <travisr@matrix.org>
Date: Sat, 19 Aug 2023 17:25:01 -0600
Subject: [PATCH] Add MSC4040 `matrix-fed` service lookups

See https://github.com/matrix-org/matrix-spec/pull/1624
---
 scripts-dev/federation_client.py                | 17 ++++++++++++++---
 .../http/federation/matrix_federation_agent.py  | 13 ++++++++++++-
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/scripts-dev/federation_client.py b/scripts-dev/federation_client.py
index 5ad334b4d800..8d5d19d6d6c0 100755
--- a/scripts-dev/federation_client.py
+++ b/scripts-dev/federation_client.py
@@ -329,15 +329,26 @@ def _lookup(server_name: str) -> Tuple[str, int, str]:
                 raise ValueError("Invalid host:port '%s'" % (server_name,))
             return out[0], port, out[0]
 
+        # Look up SRV for Matrix 1.8 `matrix-fed` service first
         try:
-            srv = srvlookup.lookup("matrix", "tcp", server_name)[0]
+            srv = srvlookup.lookup("matrix-fed", "tcp", server_name)[0]
             print(
-                f"SRV lookup on _matrix._tcp.{server_name} gave {srv}",
+                f"SRV lookup on _matrix-fed._tcp.{server_name} gave {srv}",
                 file=sys.stderr,
             )
             return srv.host, srv.port, server_name
         except Exception:
-            return server_name, 8448, server_name
+            # Fall back to deprecated `matrix` service
+            try:
+                srv = srvlookup.lookup("matrix", "tcp", server_name)[0]
+                print(
+                    f"SRV lookup on _matrix._tcp.{server_name} gave {srv}",
+                    file=sys.stderr,
+                )
+                return srv.host, srv.port, server_name
+            except Exception:
+                # Fall even further back to just port 8448
+                return server_name, 8448, server_name
 
     @staticmethod
     def _get_well_known(server_name: str) -> Optional[str]:
diff --git a/synapse/http/federation/matrix_federation_agent.py b/synapse/http/federation/matrix_federation_agent.py
index 91a24efcd019..a3a5c0d8a1ff 100644
--- a/synapse/http/federation/matrix_federation_agent.py
+++ b/synapse/http/federation/matrix_federation_agent.py
@@ -400,7 +400,7 @@ async def _resolve_server(self) -> List[Server]:
             return [Server(host, port or 8448)]
 
         logger.debug("Looking up SRV record for %s", host.decode(errors="replace"))
-        server_list = await self._srv_resolver.resolve_service(b"_matrix._tcp." + host)
+        server_list = await self._srv_resolver.resolve_service(b"_matrix-fed._tcp." + host)
 
         if server_list:
             logger.debug(
@@ -410,6 +410,17 @@ async def _resolve_server(self) -> List[Server]:
             )
             return server_list
 
+        logger.debug("Looking up deprecated SRV record for %s", host.decode(errors="replace"))
+        server_list = await self._srv_resolver.resolve_service(b"_matrix._tcp." + host)
+
+        if server_list:
+            logger.debug(
+                "Got %s from deprecated SRV lookup for %s",
+                ", ".join(map(str, server_list)),
+                host.decode(errors="replace"),
+            )
+            return server_list
+
         # No SRV records, so we fallback to host and 8448
         logger.debug("No SRV records for %s", host.decode(errors="replace"))
         return [Server(host, 8448)]