get rtt time differently

hbd/server/main.py

@@ -173,14 +173,20 @@ async def _run_async(config, config_path=None):
             f"Warning: Could not reset IPV6_V6ONLY not supported or dual-stack is unavailable. Error: {e}"
         )
 
-    # 3. Bind to all interfaces (::) on a specific port
-
-    # UDP server endpoint (handler wired to handle_datagram with context)
     bind_addr = ("::", config.get("hb_port", 50003))
     sock.bind(bind_addr)
     logger.info("Starting UDP server on %s:%s", *bind_addr)
 
-    def udp_handler(msg, addr, transport):
+    # Try to enable kernel receive timestamps (Linux SO_TIMESTAMPNS).
+    # If supported, read datagrams via recvmsg() so RTT uses the kernel
+    # timestamp rather than the time.time() call after asyncio scheduling.
+    use_kernel_ts = udp.enable_kernel_timestamps(sock)
+    if use_kernel_ts:
+        logger.info("SO_TIMESTAMPNS enabled: using kernel receive timestamps for RTT")
+    else:
+        logger.info("SO_TIMESTAMPNS not available: using time.time() for RTT")
+
+    def udp_handler(msg, addr, transport, recv_ts=None):
         ctx = dict(
             config=config,
             hbdclass=hbdclass,
@@ -190,13 +196,22 @@ async def _run_async(config, config_path=None):
             threshold_checker=threshold_checker,
             DEBUG=config.get("debug", 0),
             verbose=config.get("verbose", False),
+            recv_ts=recv_ts,
         )
         udp.handle_datagram(msg, addr, transport, ctx)
 
-    transport, protocol = await loop.create_datagram_endpoint(
-        lambda: udp.EchoServerProtocol(config=config, handler=udp_handler),
-        sock=sock,
-    )
+    if use_kernel_ts:
+        # recvmsg path: manage the socket ourselves with loop.add_reader()
+        sock.setblocking(False)
+        transport = udp.RecvmsgTransport(loop, sock)
+        reader = udp.make_recvmsg_reader(sock, udp_handler, transport)
+        loop.add_reader(sock.fileno(), reader)
+        protocol = None
+    else:
+        transport, protocol = await loop.create_datagram_endpoint(
+            lambda: udp.EchoServerProtocol(config=config, handler=udp_handler),
+            sock=sock,
+        )
 
     # Restore connection timers for hosts loaded from pickle
     restore_ctx = dict(