Fix RES_USE_INET6 description

The previous wording implied this option does nothing, which is wrong.
This option does affect the way gethostbyname(3) works on OpenBSD
(return IPv6 addresses if available).  On some systems, it also
introduces IPv4-mapped IPv6 addresses, a "feature" that we don't
support.

ok deraadt@ eric@

1 files changed, 9 insertions, 7 deletions

diff --git a/src/lib/libc/net/res_init.3 b/src/lib/libc/net/res_init.3
index 01a6b8e0b3..f9f13cf4f9 100644
--- a/src/lib/libc/net/res_init.3
+++ b/src/lib/libc/net/res_init.3
@@ -1,4 +1,4 @@
-.\"     $OpenBSD: res_init.3,v 1.1 2019/08/30 18:33:17 deraadt Exp $
+.\"     $OpenBSD: res_init.3,v 1.2 2020/04/25 14:30:05 jca Exp $
 .\"
 .\" Copyright (c) 1985, 1991, 1993
 .\"     The Regents of the University of California.  All rights reserved.
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: August 30 2019 $
+.Dd $Mdocdate: April 25 2020 $
 .Dt RES_INIT 3
 .Os
 .Sh NAME
@@ -180,12 +180,14 @@ In the past, it turned off the legacy
 .Ev HOSTALIASES
 feature.
 .It Dv RES_USE_INET6
-Enables support for IPv6-only applications.
-This causes IPv4 addresses to be returned as an IPv4 mapped address.
+With this option
+.Xr gethostbyname 3
+will return IPv6 addresses if available.
+On some operating systems this option also causes IPv4 addresses to be
+returned as IPv4-mapped IPv6 addresses.
 For example, 10.1.1.1 will be returned as ::ffff:10.1.1.1.
-On
-.Ox
-this option does nothing.
+IPv4-mapped IPv6 addresses are not supported on
+.Ox .
 .It Dv RES_USE_EDNS0
 Attach an OPT pseudo-RR for the EDNS0 extension,
 as specified in RFC 2671.