From af1c569e966ce947cc95f6aa553ea68cdb372a9a Mon Sep 17 00:00:00 2001 From: asomers 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 942346cdd72..3f786e67793 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 -- 2.39.5