Attempt both the v3 and r0 endpoints.

Author: clokep

synapse/federation/federation_client.py

@@ -21,6 +21,7 @@
     TYPE_CHECKING,
     AbstractSet,
     Awaitable,
+    BinaryIO,
     Callable,
     Collection,
     Container,
@@ -1862,6 +1863,41 @@ def filter_user_id(user_id: str) -> bool:
 
         return filtered_statuses, filtered_failures
 
+    async def download_media(
+        self,
+        destination: str,
+        media_id: str,
+        output_stream: BinaryIO,
+        max_size: int,
+        max_timeout_ms: int,
+    ) -> Tuple[int, Dict[bytes, List[bytes]]]:
+        try:
+            return await self.transport_layer.download_media_v3(
+                destination,
+                media_id,
+                output_stream=output_stream,
+                max_size=max_size,
+                max_timeout_ms=max_timeout_ms,
+            )
+        except HttpResponseException as e:
+            # If an error is received that is due to an unrecognised endpoint,
+            # fallback to the r0 endpoint. Otherwise, consider it a legitimate error
+            # and raise.
+            if not is_unknown_endpoint(e):
+                raise
+
+        logger.debug(
+            "Couldn't download media with the v3 API, falling back to the r0 API"
+        )
+
+        return await self.transport_layer.download_media_r0(
+            destination,
+            media_id,
+            output_stream=output_stream,
+            max_size=max_size,
+            max_timeout_ms=max_timeout_ms,
+        )
+
 
 @attr.s(frozen=True, slots=True, auto_attribs=True)
 class TimestampToEventResponse:

synapse/federation/transport/client.py

@@ -829,6 +829,30 @@ async def download_media_r0(
             },
         )
 
+    async def download_media_v3(
+        self,
+        destination: str,
+        media_id: str,
+        output_stream: BinaryIO,
+        max_size: int,
+        max_timeout_ms: int,
+    ) -> Tuple[int, Dict[bytes, List[bytes]]]:
+        path = f"/_matrix/media/v3/download/{destination}/{media_id}"
+
+        return await self.client.get_file(
+            destination,
+            path,
+            output_stream=output_stream,
+            max_size=max_size,
+            args={
+                # tell the remote server to 404 if it doesn't
+                # recognise the server_name, to make sure we don't
+                # end up with a routing loop.
+                "allow_remote": "false",
+                "timeout_ms": str(max_timeout_ms),
+            },
+        )
+
 
 def _create_path(federation_prefix: str, path: str, *args: str) -> str:
     """

synapse/media/media_repository.py

@@ -77,7 +77,7 @@ class MediaRepository:
     def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.auth = hs.get_auth()
-        self.client = hs.get_federation_transport_client()
+        self.client = hs.get_federation_client()
         self.clock = hs.get_clock()
         self.server_name = hs.hostname
         self.store = hs.get_datastores().main
@@ -645,7 +645,7 @@ async def _download_remote_file(
 
         with self.media_storage.store_into_file(file_info) as (f, fname, finish):
             try:
-                length, headers = await self.client.download_media_r0(
+                length, headers = await self.client.download_media(
                     server_name,
                     media_id,
                     output_stream=f,

tests/media/test_media_storage.py

@@ -27,10 +27,11 @@
 
 from twisted.internet import defer
 from twisted.internet.defer import Deferred
+from twisted.python.failure import Failure
 from twisted.test.proto_helpers import MemoryReactor
 from twisted.web.resource import Resource
 
-from synapse.api.errors import Codes
+from synapse.api.errors import Codes, HttpResponseException
 from synapse.events import EventBase
 from synapse.http.types import QueryParams
 from synapse.logging.context import make_deferred_yieldable
@@ -257,10 +258,15 @@ def write_to(
                 output_stream.write(data)
                 return response
 
+            def write_err(f: Failure) -> Failure:
+                f.trap(HttpResponseException)
+                output_stream.write(f.value.response)
+                return f
+
             d: Deferred[Tuple[bytes, Tuple[int, Dict[bytes, List[bytes]]]]] = Deferred()
             self.fetches.append((d, destination, path, args))
             # Note that this callback changes the value held by d.
-            d_after_callback = d.addCallback(write_to)
+            d_after_callback = d.addCallbacks(write_to, write_err)
             return make_deferred_yieldable(d_after_callback)
 
         # Mock out the homeserver's MatrixFederationHttpClient
@@ -316,7 +322,7 @@ def _req(
         self.assertEqual(len(self.fetches), 1)
         self.assertEqual(self.fetches[0][1], "example.com")
         self.assertEqual(
-            self.fetches[0][2], "/_matrix/media/r0/download/" + self.media_id
+            self.fetches[0][2], "/_matrix/media/v3/download/" + self.media_id
         )
         self.assertEqual(
             self.fetches[0][3], {"allow_remote": "false", "timeout_ms": "20000"}
@@ -671,6 +677,52 @@ def test_cross_origin_resource_policy_header(self) -> None:
             [b"cross-origin"],
         )
 
+    def test_unknown_v3_endpoint(self) -> None:
+        """
+        If the v3 endpoint fails, try the r0 one.
+        """
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/media/v3/download/{self.media_id}",
+            shorthand=False,
+            await_result=False,
+        )
+        self.pump()
+
+        # We've made one fetch, to example.com, using the media URL, and asking
+        # the other server not to do a remote fetch
+        self.assertEqual(len(self.fetches), 1)
+        self.assertEqual(self.fetches[0][1], "example.com")
+        self.assertEqual(
+            self.fetches[0][2], "/_matrix/media/v3/download/" + self.media_id
+        )
+
+        # The result which says the endpoint is unknown.
+        unknown_endpoint = b'{"errcode":"M_UNRECOGNIZED","error":"Unknown request"}'
+        self.fetches[0][0].errback(
+            HttpResponseException(404, "NOT FOUND", unknown_endpoint)
+        )
+
+        self.pump()
+
+        # There should now be another request to the r0 URL.
+        self.assertEqual(len(self.fetches), 2)
+        self.assertEqual(self.fetches[1][1], "example.com")
+        self.assertEqual(
+            self.fetches[1][2], f"/_matrix/media/r0/download/{self.media_id}"
+        )
+
+        headers = {
+            b"Content-Length": [b"%d" % (len(self.test_image.data))],
+        }
+
+        self.fetches[1][0].callback(
+            (self.test_image.data, (len(self.test_image.data), headers))
+        )
+
+        self.pump()
+        self.assertEqual(channel.code, 200)
+
 
 class TestSpamCheckerLegacy:
     """A spam checker module that rejects all media that includes the bytes