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authorOtto Moerbeek <otto@cvs.openbsd.org>2017-04-03 19:42:05 +0000
committerOtto Moerbeek <otto@cvs.openbsd.org>2017-04-03 19:42:05 +0000
commit2a18c7fd5d5f006405f1b816b94cb756cc608036 (patch)
treec0418d0797f4f0c640896a8f70d427b7a98151b9 /lib
parent8a49ee144a773180935ca993fc30fa63e028a515 (diff)
Add caveat telling it's better to always read a data byte when passing
control messages. Problem noted by Luke Small; ok deraadt@
Diffstat (limited to 'lib')
-rw-r--r--lib/libc/sys/recv.216
1 files changed, 14 insertions, 2 deletions
diff --git a/lib/libc/sys/recv.2 b/lib/libc/sys/recv.2
index 5f9c51fd7ef..7b312b2ba8d 100644
--- a/lib/libc/sys/recv.2
+++ b/lib/libc/sys/recv.2
@@ -1,4 +1,4 @@
-.\" $OpenBSD: recv.2,v 1.43 2015/02/16 16:20:15 tedu Exp $
+.\" $OpenBSD: recv.2,v 1.44 2017/04/03 19:42:04 otto Exp $
.\" $NetBSD: recv.2,v 1.6 1995/02/27 12:36:08 cgd Exp $
.\"
.\" Copyright (c) 1983, 1990, 1991, 1993
@@ -30,7 +30,7 @@
.\"
.\" @(#)recv.2 8.3 (Berkeley) 2/21/94
.\"
-.Dd $Mdocdate: February 16 2015 $
+.Dd $Mdocdate: April 3 2017 $
.Dt RECV 2
.Os
.Sh NAME
@@ -364,3 +364,15 @@ The
.Fn recv
function call appeared in
.Bx 4.2 .
+.Sh CAVEATS
+Calling
+.Fn recvmsg
+with a control message having no or an empty scatter/gather array
+exposes variations in implementations.
+To avoid these, always use an
+.Fa iovec
+with at least a one byte buffer and set
+.Fa msg_iov
+and an
+.Fa msg_iovlen
+to use this vector.