From 51f9bdc2b55ac2b73f6b6f1f94f947ecc50eece2 Mon Sep 17 00:00:00 2001
From: Andreas Wrede <aew.git@wrede.ca>
Date: Tue, 7 Apr 2026 10:46:54 -0400
Subject: [PATCH] use SO_TIMESTAMP, works on Linux, FreeBSD and macOS

---
 hbd/server/udp.py | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/hbd/server/udp.py b/hbd/server/udp.py
index 20cebef..1958e8e 100644
--- a/hbd/server/udp.py
+++ b/hbd/server/udp.py
@@ -14,22 +14,23 @@ from . import notify as notify_mod
 logger = logging.getLogger(__name__)
 eventlog = notify_mod.eventlog
 
-# SO_TIMESTAMPNS: kernel attaches a struct timespec to each received datagram.
-# The constant is not exposed by Python's socket module on all platforms,
-# so fall back to the Linux value (35) when absent.
-_SO_TIMESTAMPNS = getattr(socket, 'SO_TIMESTAMPNS', 35)
-# struct timespec uses two native C longs: tv_sec and tv_nsec
-_TIMESPEC = struct.Struct('@ll')
+# SO_TIMESTAMP: kernel attaches a struct timeval to each received datagram.
+# Supported on Linux, FreeBSD, and macOS.  The constant is not exposed by
+# Python's socket module on all platforms, so fall back to the Linux value (29)
+# when absent.
+_SO_TIMESTAMP = getattr(socket, 'SO_TIMESTAMP', 29)
+# struct timeval uses two native C longs: tv_sec and tv_usec
+_TIMEVAL = struct.Struct('@ll')
 
 
 def enable_kernel_timestamps(sock) -> bool:
-    """Try to enable SO_TIMESTAMPNS on *sock*.
+    """Try to enable SO_TIMESTAMP on *sock*.
 
     Returns True if the kernel will supply receive timestamps, False otherwise
-    (non-Linux, older kernel, or insufficient permissions).
+    (unsupported platform, older kernel, or insufficient permissions).
     """
     try:
-        sock.setsockopt(socket.SOL_SOCKET, _SO_TIMESTAMPNS, 1)
+        sock.setsockopt(socket.SOL_SOCKET, _SO_TIMESTAMP, 1)
         return True
     except OSError:
         return False
@@ -38,18 +39,18 @@ def enable_kernel_timestamps(sock) -> bool:
 def _extract_kernel_ts(ancdata) -> float | None:
     """Parse recvmsg ancillary data and return the kernel receive time.
 
-    Returns seconds as a float, or None if no SO_TIMESTAMPNS cmsg is present.
+    Returns seconds as a float, or None if no SO_TIMESTAMP cmsg is present.
     """
     for cmsg_level, cmsg_type, cmsg_data in ancdata:
-        if cmsg_level == socket.SOL_SOCKET and cmsg_type == _SO_TIMESTAMPNS:
-            if len(cmsg_data) >= _TIMESPEC.size:
-                sec, nsec = _TIMESPEC.unpack_from(cmsg_data)
-                return sec + nsec * 1e-9
+        if cmsg_level == socket.SOL_SOCKET and cmsg_type == _SO_TIMESTAMP:
+            if len(cmsg_data) >= _TIMEVAL.size:
+                sec, usec = _TIMEVAL.unpack_from(cmsg_data)
+                return sec + usec * 1e-6
     return None
 
 
 class RecvmsgTransport:
-    """Thin wrapper used when SO_TIMESTAMPNS is active (add_reader path).
+    """Thin wrapper used when SO_TIMESTAMP is active (add_reader path).
 
     Exposes the same sendto() / close() interface as asyncio's DatagramTransport
     so the rest of the code does not need to know which path is in use.
@@ -79,8 +80,8 @@ def make_recvmsg_reader(sock, handler, transport):
     """Return a callback suitable for loop.add_reader().
 
     Reads one datagram per call using recvmsg() so that kernel timestamps in
-    the ancillary data are accessible.  Falls back to time.time() gracefully
-    if the cmsg is missing.
+    the ancillary data are accessible.  Falls back to time.time() if the
+    cmsg is missing.
 
     handler(msg, addr, transport, kernel_ts) – same signature as udp_handler
     in main.py with the optional kernel_ts argument.