This is just a quick patch to get better resolution receive timestamps from
the kernel. As far as I can tell, the timestamps are supposed to be using
the unix epoch. If not, I can switch it up from SO_TS_REALTIME to
SO_TS_MONOTONIC which does marginally less work but its epoch isn't January
1, 1970 - it's essentially the uptime.
Let me know if I missed anything.
Jeff.
>From a5a967a270233afcbdb7e5374ad9990362a884f8 Mon Sep 17 00:00:00 2001
From: Josef 'Jeff' Sipek <jef...@josefsipek.net>
Date: Wed, 9 Aug 2023 07:58:38 -0400
Subject: [PATCH] socket: enable nanosecond resolution receive timestamp on
FreeBSD
FreeBSD allows switching the receive timestamp format to struct timespec by
setting the SO_TS_CLOCK socket option to SO_TS_REALTIME after enabling
SO_TIMESTAMP. If successful, the kernel then starts adding SCM_REALTIME
control messages instead of SCM_TIMESTAMP.
---
socket.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/socket.c b/socket.c
index 8a5d046..f4bae6d 100644
--- a/socket.c
+++ b/socket.c
@@ -869,6 +869,11 @@ process_header(struct msghdr *msg, int msg_length, int sock_fd, int flags,
memcpy(&message->timestamp.kernel, CMSG_DATA(cmsg), sizeof (message->timestamp.kernel));
}
#endif
+#ifdef SCM_REALTIME
+ else if (match_cmsg(cmsg, SOL_SOCKET, SCM_REALTIME, sizeof (message->timestamp.kernel))) {
+ memcpy(&message->timestamp.kernel, CMSG_DATA(cmsg), sizeof (message->timestamp.kernel));
+ }
+#endif
#ifdef HAVE_LINUX_TIMESTAMPING
#ifdef HAVE_LINUX_TIMESTAMPING_OPT_PKTINFO
else if (match_cmsg(cmsg, SOL_SOCKET, SCM_TIMESTAMPING_PKTINFO,
@@ -1386,8 +1391,16 @@ SCK_EnableKernelRxTimestamping(int sock_fd)
return 1;
#endif
#ifdef SO_TIMESTAMP
- if (SCK_SetIntOption(sock_fd, SOL_SOCKET, SO_TIMESTAMP, 1))
+ if (SCK_SetIntOption(sock_fd, SOL_SOCKET, SO_TIMESTAMP, 1)) {
+#if defined(SO_TS_CLOCK) && defined(SO_TS_REALTIME)
+ /*
+ * We don't care about the return value - we'll get either a
+ * SCM_REALTIME (if we succeded) or a SCM_TIMESTAMP (if we failed).
+ */
+ SCK_SetIntOption(sock_fd, SOL_SOCKET, SO_TS_CLOCK, SO_TS_REALTIME);
+#endif
return 1;
+ }
#endif
return 0;
--
2.41.0
