From 8d910a42823bf5d57e859949f355568657cc86dd Mon Sep 17 00:00:00 2001 From: Alan Somers Date: Wed, 11 Sep 2019 19:48:32 +0000 Subject: [PATCH] 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 --- lib/libc/sys/getsockopt.2 | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/lib/libc/sys/getsockopt.2 b/lib/libc/sys/getsockopt.2 index 942346cdd728..3f786e67793f 100644 --- a/lib/libc/sys/getsockopt.2 +++ b/lib/libc/sys/getsockopt.2 @@ -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