fix: add WebSocket keepalive pings to prevent idle disconnects (#646) (#925)

proxy/bridge.py

@@ -266,6 +266,23 @@ async def _tcp_fallback(reader, writer, dst, port, relay_init, label, ctx: Crypt
     return True
 
 
+async def _ws_keepalive(ws, interval: float):
+    """Send periodic WS PING frames to keep the upstream flow warm.
+
+    A non-positive interval disables keepalive. The loop exits on send
+    failure so a dead upstream is detected promptly instead of lingering
+    until the next client packet (see issue #646).
+    """
+    if interval <= 0:
+        return
+    try:
+        while True:
+            await asyncio.sleep(interval)
+            await ws.send_ping()
+    except (asyncio.CancelledError, ConnectionError, OSError):
+        return
+
+
 async def bridge_ws_reencrypt(reader, writer, ws: RawWebSocket, label,
                                ctx: CryptoCtx,
                                dc=None, is_media=False,
@@ -337,12 +354,15 @@ async def bridge_ws_reencrypt(reader, writer, ws: RawWebSocket, label,
 
     tasks = [asyncio.create_task(tcp_to_ws()),
              asyncio.create_task(ws_to_tcp())]
+    keepalive = asyncio.ensure_future(
+        _ws_keepalive(ws, proxy_config.ws_keepalive_interval))
     try:
         await asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED)
     finally:
+        keepalive.cancel()
         for t in tasks:
             t.cancel()
-        for t in tasks:
+        for t in (*tasks, keepalive):
             try:
                 await t
             except BaseException: