fix: 当前的 relay 实现原来只记了一个“最后发包的下游客户端地址”

python/tests/test_sessions.py

@@ -56,7 +56,31 @@ def _run_server(binary_name: str, listen_addr: str):
             process.wait(timeout=2.0)
 
 
-def _connect_with_retry(session_cls, *, transport: str, server_addr: str, peer_id: str):
+@contextmanager
+def _run_relay(listen_addr: str, remote_addr: str):
+    binary = ROOT / 'bin' / 'kcpserver'
+    if not binary.exists():
+        pytest.skip(f'{binary} is not built')
+
+    process = subprocess.Popen(
+        [str(binary), '-mode', 'relay', '-listen', listen_addr, '-relay-remote', remote_addr],
+        cwd=str(ROOT),
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.DEVNULL,
+    )
+    try:
+        time.sleep(0.2)
+        yield process
+    finally:
+        process.terminate()
+        try:
+            process.wait(timeout=2.0)
+        except subprocess.TimeoutExpired:
+            process.kill()
+            process.wait(timeout=2.0)
+
+
+def _connect_with_retry(session_cls, *, transport: str, server_addr: str, peer_id: str, relay_via: str = ''):
     deadline = time.monotonic() + 3.0
     last_error: Exception | None = None
 
@@ -69,6 +93,8 @@ def _connect_with_retry(session_cls, *, transport: str, server_addr: str, peer_i
             }
             if transport == 'kcp':
                 kwargs.update(CONTROL_DEFAULTS)
+                if relay_via:
+                    kwargs['relay_via'] = relay_via
             else:
                 kwargs['enable_timestamping'] = False
             session.connect(**kwargs)
@@ -210,6 +236,36 @@ def test_kcp_peer_a_video_stale_receiver_is_evicted() -> None:
             receiver.close()
 
 
+def test_kcp_relay_routes_multiple_sessions_by_conv() -> None:
+    hub_port = _reserve_port()
+    relay_port = _reserve_port()
+    hub_addr = f'127.0.0.1:{hub_port}'
+    relay_addr = f'127.0.0.1:{relay_port}'
+
+    with _run_server('kcpserver', hub_addr):
+        with _run_relay(relay_addr, hub_addr):
+            sender = _connect_with_retry(Session, transport='kcp', server_addr=hub_addr, peer_id='pytest-relay-sender', relay_via=relay_addr)
+            receiver = _connect_with_retry(Session, transport='kcp', server_addr=hub_addr, peer_id='pytest-relay-receiver', relay_via=relay_addr)
+            chatter = _connect_with_retry(Session, transport='kcp', server_addr=hub_addr, peer_id='pytest-relay-chatter', relay_via=relay_addr)
+
+            try:
+                chatter.send(to='pytest-relay-sender', data=b'chatter-primes-last-client')
+                from_peer, msg_type, recv_payload = sender.recv(timeout_ms=1000)
+                assert from_peer == 'pytest-relay-chatter'
+                assert msg_type == MSG_TYPE_BINARY
+                assert recv_payload == b'chatter-primes-last-client'
+
+                sender.send(to='pytest-relay-receiver', data=b'relay-video-frame')
+                from_peer, msg_type, recv_payload = receiver.recv(timeout_ms=1000)
+                assert from_peer == 'pytest-relay-sender'
+                assert msg_type == MSG_TYPE_BINARY
+                assert recv_payload == b'relay-video-frame'
+            finally:
+                sender.close()
+                receiver.close()
+                chatter.close()
+
+
 def test_udp_session_close_interrupts_blocking_recv() -> None:
     port = _reserve_port()
     listen_addr = f'127.0.0.1:{port}'