svn commit: r352231 - head/lib/libc/sys
Ian Lepore
ian at freebsd.org
Wed Sep 11 21:50:14 UTC 2019
On Wed, 2019-09-11 at 19:48 +0000, Alan Somers wrote:
> Author: asomers
> Date: Wed Sep 11 19:48:32 2019
> New Revision: 352231
> URL: https://svnweb.freebsd.org/changeset/base/352231
>
> Log:
> getsockopt.2: clarify that SO_TIMESTAMP is not 100% reliable
>
> When SO_TIMESTAMP is set, the kernel will attempt to attach a timestamp as
> ancillary data to each IP datagram that is received on the socket. However,
> it may fail, for example due to insufficient memory. In that case the
> packet will still be received but not timestamp will be attached.
>
> Reviewed by: kib
> MFC after: 3 days
> Differential Revision: https://reviews.freebsd.org/D21607
>
> Modified:
> head/lib/libc/sys/getsockopt.2
>
> Modified: head/lib/libc/sys/getsockopt.2
> ==============================================================================
> --- head/lib/libc/sys/getsockopt.2 Wed Sep 11 19:29:40 2019 (r352230)
> +++ head/lib/libc/sys/getsockopt.2 Wed Sep 11 19:48:32 2019 (r352231)
> @@ -28,7 +28,7 @@
> .\" @(#)getsockopt.2 8.4 (Berkeley) 5/2/95
> .\" $FreeBSD$
> .\"
> -.Dd February 10, 2019
> +.Dd September 11, 2019
> .Dt GETSOCKOPT 2
> .Os
> .Sh NAME
> @@ -431,7 +431,8 @@ option is enabled on a
> .Dv SOCK_DGRAM
> socket, the
> .Xr recvmsg 2
> -call will return a timestamp corresponding to when the datagram was received.
> +call may return a timestamp corresponding to when the datagram was received.
> +However, it may not, for example due to a resource shortage.
> The
> .Va msg_control
> field in the
>
So I guess this actually happened to someone... is it a common thing
for the timestamp to fail? I ask because ntpd relies on SO_TIMESTAMP
and if this situation really happens and can persist for a long time,
ntpd would effectively stop working.
-- Ian
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