Add MSC4040 `matrix-fed` service lookups (#16137)

1 files changed, 24 insertions, 5 deletions

diff --git a/synapse/http/federation/matrix_federation_agent.py b/synapse/http/federation/matrix_federation_agent.py
index 91a24efcd0..a3a396bb37 100644
--- a/synapse/http/federation/matrix_federation_agent.py
+++ b/synapse/http/federation/matrix_federation_agent.py
@@ -399,15 +399,34 @@ class MatrixHostnameEndpoint:
         if port or _is_ip_literal(host):
             return [Server(host, port or 8448)]
 
+        # Check _matrix-fed._tcp SRV record.
         logger.debug("Looking up SRV record for %s", host.decode(errors="replace"))
+        server_list = await self._srv_resolver.resolve_service(
+            b"_matrix-fed._tcp." + host
+        )
+
+        if server_list:
+            if logger.isEnabledFor(logging.DEBUG):
+                logger.debug(
+                    "Got %s from SRV lookup for %s",
+                    ", ".join(map(str, server_list)),
+                    host.decode(errors="replace"),
+                )
+            return server_list
+
+        # No _matrix-fed._tcp SRV record, fallback to legacy _matrix._tcp SRV record.
+        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 SRV lookup for %s",
-                ", ".join(map(str, server_list)),
-                host.decode(errors="replace"),
-            )
+            if logger.isEnabledFor(logging.DEBUG):
+                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